The Science of Composting

Simply stated, the role of composting in waste management is to be a productive option for the treatment and disposal of biodegradable waste. This paper focuses on two major categories of biodegradable wastes - they are: 1) the solid waste generated by households, businesses, and light industry (municipal solid waste (MSW)); and 2) settleable waste water solids, i.e., dewatered sewage sludge. Sewage sludge (‘biosolids’) is included because it is a major municipal waste which, if not managed properly, can very adversely affect environmental quality and public health. Because it is an option in solid waste management, the vicissitudes of composting mirror those of MSW management. This paper explores and attempts to explain and illustrate the role of composting as a waste management option. It does this by tracing the chronological status and development of waste management and composting and analyzes their interrelation. For purposes of this presentation, the chronology of this combination is somewhat arbitrarily divided into three broad, loosely defined periods; namely, 1930–1940, 1950–1960, and 1970-current.

The paper briefly presents the Community Energy Demonstration Programme (1978–1989), the THERMIE Programme (1990–1994) and the JOULE THERMIE Programme (1995–1998) of the Directorate General for Energy of the European Commission.More specific informations are given on the Energy from Biomass and Waste Sector, and on the ongoing and terminated project in the Composting sub-sector. The future perspectives of composting projects in the THERMIE and FAIR Programmes are briefly outlined.

Incineration, landfill and recycling are the three main strategies to face the problem of waste disposal, and they may co-exist. However, it is essential to encourage recycling, the only sustainable practice among the three above cited which avoids the existence itself of wastes by transforming possible waste materials in a series of products. Composting, as sustainable transformation of potential wastes in organic fertilizers, tunes up with sustainable agriculture, and must be optimized and encouraged. The importance of the use of compost in agriculture is a commonplace, and does not correspond to reality, particularly if rules and technical parameters for its application are not given by the proper professional and institutional competence, as is often happening. The use of compost in agriculture has much more than the importance of the application of an amendment to the soil. The three requisites needed in order that agriculture can be considered sustainable are discussed, and the use of compost is shown to enhance sustainability, not only of the agricultural activity, but in a more general context. Sustainable agriculture, and the use of compost in agriculture can be considered as essential activities for a sustainable society.

Solid waste management has moved to the forefront of the environmental agenda. The level of activity and concern by citizens and governments worldwide have reached unprecedented levels. Nations are considering restrictions on packaging and controls on products in order to reduce solid waste generation rates. Local and regional governments are requiring wastes to be separated for recycling, and some have even established mandatory recycling targets. There is considerable interest in composting and other forms of biological waste treatment in order to reduce disposal requirements and produce useful products. Concerns about emissions from incinerators and waste-to-energy plants have resulted in imposition of state-of-the-art air pollution controls. Landfills are being equipped with liners, impervious caps and liquid collection systems, and gas and groundwater is being routinely monitored. There is wide scale public opposition to the establishment of new solid waste treatment and disposal facilities. As a result, the costs of solid waste management are increasing rapidly.

The situation in Europe. in the aftermath of the second world war, was very poor. In most European countries the industrial infrastructure was either destroyed or looted. It is estimated that ca 15 Mio people in Western Europe were without a home, many more people were jobless. Food supplies were limited, both in quantity and variety. Common articles for consumption were in short supply and subject to rationing. People were undernourished, many people died prematurely due to combined effects of malnutrition and lack of proper medication.

A composting system consists of three parts:materials reception and pretreatment;the composting process; andcompost post-treatment. The first of these is where the materials are received, shredded and blended to give the optimum nutrient balance, mass structure and moisture content for successful composting. The post treatment is either for removing unwanted components (such as large particles by screening) or preparing the compost for a particular market. Both of these process areas have a profound influence on the overall composting installation, but for the purpose of this paper it is the composting process itself which will be the focus.

The modem composting plant is a biological processing facility designed to convert raw feedstocks to a usable, high quality end product. The desired end product is a stable, mature, and high quality compost which can be used for soil conditioning and fertilization. Many feedstocks can serve as starting substrates for the compo sting process. However, the characteristics of these feedstocks are most important to both design and operation of the composting plant and to the quality of the final product. The thermodynamic window of operation and the kinetic rates of reaction are determined largely by feedstock characteristics. This paper discusses the effect of feedstock characteristics on plant design and process management, describes the use of simulation models as design and operating tools, and presents several case studies where computer modeling helped resolve process problems.

We look into the past we see the history of composting as a history of problems. So, we have discussed: 1965 glass in compost1970 plastic in compost1975 heavy metals in compost1978 PCBs in compost1984 odour emissions from composting plants1989 dioxin in compost1990 micro-organisms in the exhaust air Every single problem mentioned above is enough to prevent composting. Especially odour is becoming an increasingly sensitive issue as people move closer to existing treatment plants. When sites for new facilities are proposed, the potential for odour is invariably one of the first concerns raised by local residents. Therefore, odours have been rated as the primary concern of the public relative to implementation of composting facilities. Designers must be conscious of this fact and be familiar with odour generation and odour control.

Planning to build a compo sting plant in Germany will almost surely provoke the emergence of an action group to prevent its erection. It is especially the odours emitted by a number of compost plants that effect the relations with the residents. Beside the odours we found some other possible emission like dust, noise, leakage water and micro-organisms.Environmental impacts of new and carefully planned plants are reduced to odours and germ-emissions, whereas the other emissions can be disregarded according to the closed buildings.Nevertheless the first main point of the paper will be the leakage water. If we believe in compost industry, new compo sting plants do not produce any waste water. This contention seems to be wrong. Actually the volume of leakage water often is higher than the low quantities we found in literature.Next main point of the paper will be new measuring dates of odour concentrations and odour flow rates. We will look to the problems of the authorities with this dates.The third main point is the description and valuation of investigations on germemissions. The loading of microorganisms - special fungi - on composting-workman seems to be dangerous. Opposite to this there are no risks for the neighbours of a composting plant.

Bacteria which can suppress the growth of the phytopathogen, Rhizoctonia solani K1 causing large patch disease of lawn grass, were isolated from compost products made of various organic wastes. Then, the bacterium which shows the largest suppressive effect on the pathogen was identified as Bacillus subtilis N4.A spontaneous streptomycin-resistant mutant, B. subtilis N4-1 was selected from B. subtilis N4 and was used for inoculum into lawn grass clippings as a composting raw material. This makes it possible to estimate the change in cell number of the strain N4-1 in the compo sting material.Optimum temperature for growth of the strain N4-1 in the compo sting material was found to be 40 C. And at 40 C composting, the lower the concentration of the other bacteria existed in the raw material, the higher the concentration of N4-1 became in the compost product. Then the feasibility of repeated use of compost product as a seed for the next composting was also examined. The concentration of N4-1 in the compost product decreased gradually with increasing in the number of repeated times. However, it can be ascertained by in vitro test on the agar plate that the compost product remained the suppressive effect to the phytopathogen until repeated times was 4 at which the concentration ratio of N4-1 to the total bacteria in the compost product was still higher than 1/105.

A ten-month study was carried out in an experimental farm in Hong Kong to investigate the changes in the forms and content of carbon, nitrogen, phosphorus and potassium of the pig manure under a pig-on-litter (POL) system. This system, known as in-situ composting, utilizes a mixture of sawdust and a commercial bacterial product as the bedding material on which pigs are kept and the pig excreta are decomposed within the bedding. The effects of the commercial bacterial product recommended by the POL system (the treated group) on nutrient transformation of the pig manure were evaluated and compared with the control group (without any bacterial product).It was found that there was no significant difference between the treated and the control groups in terms of the concentrations of organic carbon, total and extractable N, P and K of the sawdust pig manure litter samples. The patterns of how these nutrient changed with the experimental time were similar between the treated and the control groups. The concentrations of total N, NH4+-N, total and extractable P and K increased rapidly at the beginning of the experiment and the rate of these accumulations became slower towards the end of the study. On the other hand, total organic carbon content of the litter samples declined dramatically in the first few weeks, with C values dropped from an initial 40% to 31 % at week 10. Further decrease in total carbon concentration was observed as the experiment proceeded. A very drastic drop of the C:N ratio was found within the first few days, from an initial 175: 1 decreased to 40: 1 within one day then further dropped to 14: 1 at the end of week 1 in both treated and control groups. At the end of the experiment, the C:N ratio reached a very low value (10: 1). These results suggest that (1) the commercial bacterial product did not have any significant effect on nutrient transformation of pig manure under the POL system; (2) the nutrients released from pig excreta were rapidly assimilated and immobilized by microorganisms colonized within the bedding material, with an accumulation of total nutrients (N, P and K) but a decline in C throughout the experiment; and (3) the bedding material of the POL system appeared to become more stable and mature as the study continued, the samples collected at later stage of the experiment had a more constant nutrient level and a very narrow C:N ratio.

A physical model system was developed to permit measurement of heat evolved during the composting of sewage sludge, and to remove heat through ventilation and conduction in a manner realistically comparable to field scale systems. Heat evolutions of approximately 15,000 to 22,000 Joules per gram decomposed were observed, with peak outputs of almost 700 J/g initial sludge volatile per 12 hour period. Composting activity appeared to be enhanced by ventilation, independent of temperature or high interstitial oxygen concentration, but possibly related to particle surface turbulance factors improving oxygen transfer.

Effect of moisture levels and compactability (i.e. change in volume with load) were studied to determine their influence on aeration. Replicated experiments were conducted to measure pressure drop versus airflow using biosolids and cow manure composts at four moisture levels and loadings in the range of 0–43.2 kPa. Biosolids compost showed significant increase in compactability and pressure drops with increasing moisture levels. Cow manure compost behavior did not significantly change with increasing moisture. A generalized airflow model was developed based on the Kozeny Carman equation of permeability in porous media. The model successfully described the air permeability of the materials at all moisture and compaction levels. Data of moisture and temperature profiles during 21 days of compo sting are presented from a full scale invessel (6.1 × 3.0 × 220 m3) biosolids composting system. Based on this data and the air flow model it is quantitatively shown that management strategies using variable depth of compost can improve product uniformity and reduce operating costs. Maximum critical bed depth at different moisture levels and the potential for the formation of anaerobic conditions at different depths of the compost bed and at different moisture levels are described.

Compost must satisfy customers to secure reliable and sustainable markets. Proper management of feedstock and all phases of composting are essential for the production of marketable compost. The continuity of compost production and market supply also requires proper facility and environmental management. The basis to develop site- and technology-specific composting facility management strategies and control is provided by the Compost Facility Operating Guide. a guidance developed by the Standards and Practices Committee of The Compo sting Council (USA).The Operating Guide focus is on producing market quality compost from discarded compostable organics recovered from the Municipal Solid Waste stream. MSW contains a variety of biodegradable organics of which 30 to 60% can be returned to beneficial use by composting. This secondary resource from residential, institutional and commercial sources includes food waste, yard waste, and paper waste, especially soiled paper products and packaging. Compostable material can be source separated and recovered at curbside, or under exceptional conditions left mixed and recovered at central-sort facilities, transformed into compost. and marketed.Composting plant design and operation relies on a variety of processing and material handling technologies, but each must provide capability to prepare for and manage the biology of composting. Certain elements are common to all composting that are key to producing consistently marketable compost. These key elements are presented in the Compost Facility Operating Guide. The Operating Guide divides the composting process into seven basic unit operations. For each unit operation, the Operating Guide identifies operating parameters, and explains the principle, objectives, operating boundaries, control procedures, control monitoring, and control sample analytical test methods.

Asymbiotic nitrogen fixation by a free N₂-fixing strain has been followed in biofermentor during straw-sawdust mixtures composting added up or not in glucose. The physico-chemical and microbiological analyses have placed in prominent position different phases of microbiological activity during aerobic decomposition of these wastes, but especially proved the primordial part of a soluble carbon compound such as glucose, on the asymbiotic nitrogen fixation. In fact, with glucose, three nitrogen fixation phases have been observed. The first one, occured since the first days of composting, seems to be due to microorganisms both N2-fixers and cellulolytic. The nitrogen enrichment of the medium has reached value of 7.86g Kg_-1 initial dry matter(D.Mi). The two other phases have appeared on day 42 and day 97 with nitrogen gains of the medium of 2.37 and 1.29g Kg_-1DMi, and would be due as to Azotobacter. Without glucose, the nitrogen fixation which has only intervened on day 99 of fermentation with a N₂ enrichment of the medium of 2.96g Kg_-1D.Mi seems to be due to Azotobacter: During this experimentation, no phosphorus, an element necessary to free N₂-fixers was added. However, a relatively important nitrogen fixation has been registered and no effect of deficiency of phosphorus has been observed in the free living N₂-fixers.

A great variety and high numbers of aerobic thermophilic heterotrophic and/or autotrophic bacteria growing at temperatures between 60–80°C have been isolated from thermogenic (temperature 60–80°C) composts in several composting facilities in Switzerland. They include strains related to the genus Thermus (T. thermophilus. T. aquaticlls. and several other new strains). Bacillus schlegelii, Hydrogenohacter spp., and of course heterotrophic sporeforming Bacilli. This contrasts with the generally held belief that thermogenic composts (> 60°C) support only a very low diversity of heterotrophic thermophiles. This biodiversity suggests efficient decomposition of organic matter at temperatures above 60°C, and a good thermo-hygienization.During the terminal cooling or maturation phase of composts high numbers and a great metabolic diversity of mesophilic bacteria was observed, including nitrogen-fixers. sulfur-oxidizers. hydrogen-oxidizers, nitrifyiers. and producers of extracellular polysaccharides or bacterial humin. This microbial diversity plays an essential role for compost stabilization. It is suggested that mature compost application improves soil chemistry and microbiology, and can thus be regarded beneficial for agriculture.

My contribution aims at introducing you to a composting project developed after years of small scale trials and various researches on the best utilization of important organic matrices.

Production and application of compost from organic wastes can be the correct solution to the increasing lack of organic matter in soils and to the problem of organic waste disposal.

Recycling organic wastes in agriculture after appropriate biological treatment can produce organic matter resources and be of great interest in countries where soils are depleted. However the quality of end-products must be assessed. This paper deals with two main problems: the development of reliable, rapid and normalized procedures for the monitoring of organic matterthe evaluation of risks arising from the presence of micropollutants such as trace metals.Information provided by various analytical procedures is presented. Special attention is given to spectroscopic measurements for the monitoring of organic matter and, for trace metal speciation, to chemical sequential extraction and to gel exclusion chromatography coupled with a double detection (U.V. and atomic absorption spectrophotometry).

The principal scope of the compo sting process is to transform organic wastes of various origins and nature into a stable, mature, humus-like material suitable for use as soil amendment. The knowledge of the quality of humic acid-like and fulvic acid-like fractions formed during the composting process is of primary importance for the evaluation of the economic value, agronomic efficacy and environmental safety of the final product, the compost, which will be applied to soil. In this review paper, the chemical and physico-chemical analytical properties and data available for the evaluation on a molecular scale of the humic acid-like and fulvic acid-like constituents in composts are summarized and discussed in comparison with indigenous soil humic acids and fulvic acids. Discussed data include elemental and functional group composition, E₄/E₆ ratio, molecular weight distribution, isoelectrofocusing patterns, pyrolysis-gas chromatography-mass spectra, and infrared and Fourier transform infrared, nuclear magnetic resonance, electron spin resonance and fluorescence spectra. With respect to native soil humic and fulvic acids, humic and fulvic acid-like fractions in composted sewage sludges, municipal solid wastes, animal manures and plant wastes are generally characterized by (i) higher molecular heterogeneity; (ii) lower degree of aromaticity and structural polycondensation; (iii) higher aliphatic character; (iv) marked presence of incorporated proteinaceous materials, partially modified lignin moieties and polysaccharide-like structures; and (v) lower amounts of oxygen containing and acidic. especially carboxylic, functional groups. With composting, however, a loss of Ncontaining groups, alkyl chains and carbohydrates, and an increase in oxygenation, carboxyl groups and aromaticity generally occur in fulvic acids and. especially, humic acids. This is an important result which supports the validity of the compo sting process for organic wastes in approaching the quality of humuslike components to native soil humic substances.

Application of compost to soils is of considerable interest as means of maintaining a suitable soil structure as well as adding organic matter which is lost due to the practice of intensive agriculture. Among the possible negative effects of compost application to cropland is the potential release of toxic heavy metals into the environment, and the transfer to these elements from the soil into the food chain. A thorough evaluation of the effect of heavy metals following compost application may be supported by the knowledge of their behaviour in the soil environment. ‘Low metal compost’ deriving from source separated collection can be regarded as valuable resource in soil management practices because of their nutrient supply and organic matter content, particularly in Mediterranean soils which generally contain very low quantities of humified organic matter

The utilization of biowaste is an important factor for relief of the environment. But it should not be ignored that a variety of pathogens can be found in the raw material of biowaste. It is therefore necessary that by the composting technology the guarentee is given that these pathogens are inactivated during the composting process. The pathogens of importance in this respect belong to microbial groups of bacteria, fungi, viruses and parasites. The main role play salmonellas which reach the biowaste with kitchen waste of households, restaurants, canteens etc. Most of this material is of animal origin.The epidemiological importance of insufficiently treated food scraps and swill has been proved in Germany during the epizootic of European (Classical) Swine Fever in 1993/94. Since no sufficient experiences are available about the tenacity of viruses pathogenic for man and animals in the compos ted biowaste further investigations are necessary. But generally it can be said that the temperatures required for the inactivation of pathogens in compost which are stipulated in regulations of various countries do ensure that the health of humans and animals is not endangered when the compost facilities are operated in accordance with the relevant regulations.A further important factor of biowaste compo sting is the problem of occupational safety. The employees in composting plants are exposed to various harmful influences: dangerous substances, malodors, dust, microorganisms and their toxins, noise. Especially the problem of aerosolized microorganisms like Aspergillus fumigatus, other bacteria and viruses and their possible influence on the health of employees and of residents in the surroundings of composting plants are discussed. Recommendations are mentioned for a better outfit of workplaces to improve the protection of employees from microbial emissions. For the protection of the environment the use of biofilters for purification of waste air is recommended.

The majority of plant pathogens do not survive exposure to conditions prevailing during composting of infested plant residues. The most resistant pathogens are heat-resistant viruses and biotrophic root-infecting fungi. Most soil-borne viruses need nematodes or fungi for infection of the host plant. Since the vectors are destroyed during composting when properly performed, the product is not infectious. Apart from a few viruses, e.g. tobacco necrosis virus (TNV), virus particles in compost are not picked up by vectors that are resident in compost-amended field soil. Tobacco mosaic virus (TMV) is not completely inactivated. Since it can be directly transmitted to the plant root, i.e. without a vector, compost from infested residues should not be used in susceptible crops. Data on survival of other heat-resistant viruses that are mechanically transmitted are lackingSurvival of biotrophic fungal pathogens was only studied for Plasmodiophora brassicae and the virus vector Olpidium brassicae. Although the results are not consistent, it is tentatively concluded that these fungi are eliminated after exposure for one day to compost at 60 _C and a moisture content of 40%. Concerning trade of plants in compost-amended substrates within the EC countries, research on survival of composting by quarantine pathogens mentioned in Council Directive no 77/93/EEC is needed.Among the factors involved in inactivation, heat is considered to be the main factor in composting under predominantly aerobic conditions and toxic agents in decomposition under anaerobic conditions.The present sampling techniques and detection methods for plant pathogens in compost do not allow a reliable analysis for the evaluation of infestation of the finished product. An alternative is defining the conditions required for sanitation that should be maintained during the process for sanitation.

Canadians dispose of about 22 million tonnes of waste each year. Approximately 25% of this waste is leaf, yard and food waste that could be composted. Canada is committed to attaining its goal of 50% waste diversion by the year 2000 relative to a 1988 base year. In addition to reducing the amount of waste going to landfills, composting is one way to return nutrients and organic matter to soil. This makes compost a valuable product for landscaping, horticulture and agriculture. In light of these benefits, large scale composting facilities are being operated by industries and municipalities.

Three compost, from widely different composting processes (a garden compost and two municipal plants for solid waste treatment), were investigated for their biomass C and ninhydrin-N content at different stages of the compo sting period. Biomass C in all the 3 compost reached a maximum at the end of the thermophilic phase, maintained a high content throughout the mesophilic phase and then decreased with a trend that roughly parallels temperatureBiomass ninhydrin-N showed a regular decreasing trend during the whole composting period. A similar behaviour was observed for non fumigated ninhydrin-N. This parameter, reflecting the release of extracellular enzymes and the intensity of ammonification processes, could represent itself a useful parameter to evaluate compost stability.The ratio between biomass C and ninhydrin-N increased in the first month of the process and decreasing afterwards to values within the range normally found in soils (14–33), suggesting a change in the composition of microbial population during composting process.The percentage of biomass ninhydrin-N respect to total N, showed lower values in stabilized compost respect to compost in the early stage of decomposition. The trend observed in the 3 different composting processes, suggests that a low C_bio/nin-N_bio together with a ninhydrin-N_bio content about 1 % of the total N would indicate a well stabilized compost.

Three MSW-composts (C1, C2 and LC2) originating from separately collected organic household wastes were studied. C1 and C2 had undergone a traditional windrow composting with different maturation times. LC2 was a lumbricompost: the first 2 months of maturation had been replaced by an earthworm digestion. Composts organic matter was characterized at different levels. (1) Global carbon and nitrogen balances were determined in water or alkaline extracts and in acid hydrolysates. (2) Gross chemical fractionation was performed to estimate organic compounds like fats, resins, water soluble compounds, hemicellulose, cellulose, proteins and ‘lignin-humus’. (3) Biomolecules were more precisely analyzed with colorimetric methods: carbohydrates, amino acids and phenols. Some of the phenolic compounds were identified by HPLC. Organic matter characteristics were related to the degradability of the composts, assessed by carbon mineralization. In all the composts, a labile pool of organic matter could be characterized, as well as an important humified fraction. It appeared that maturation time (7 or 3 months) and lumbricomposting few influenced the studied organic matter properties.

Knowledge of the degree of organic matter decomposition (maturity or stability), both during the composting process and in the final, marketed product, is essential for; effective process control, beneficial use of composts, and the development of composting itself as a reliable waste management option. A wide range of parameters have been proposed to meet this need, but a simple, reliable and rapid test still remains to be found. The most promising parameter seems to be the change in microbial respiration which occurs during composting.In this study a respiration test is proposed, the SOUR (specific oxygen uptake rate) test, that utilises a dissolved oxygen (DO) meter to measure changes in the oxygen concentration of an aqueous compost suspension, at 30°C. The test takes advantage of the improved technology in the Clark-type polarographic DO probe routinely used in the wastewater field. A fully automated experimental procedure is described and the evolution of SOUR during composing of; sewage sludge, a poultry manure mixture and mechanically separated MSW is reported.The SOUR values correlated highly significantly (r=0.94) with results from another respiration test recently proposed by Iannotti et al., (1993), which also makes use of the DO meter, but measures the drop in oxygen concentration in the air space over a compost sample (solid phase) in a sealed container. Both tests indicated increasing stability with compost age. Analysis of other stability indicators confirmed the value of volatile solids in certain circumstances, while the information revealed following the optical density of compost water extracts was very limited.

The study of the molecular location of acid and alkaline phosphatases in a compost of urban refuse was initiated after their extraction using 0,05 M pyrophosphate at pH 9 and in the presence of 1 M KCl to modify its ionic strength. The extract was divided by ultrafiltration in cell-bound (UF₃ fraction with ϕ>0,45 μm) and exocellular enzymes: UF₂₃ with ϕ<0,45 μm and mol. wt.> 100 kD; UF₂₂ with 100<moi. wt.<30 kD; UF₂₁, with 30 <mol. wt.>l0 kD and UF₁, with mol. wt.<l0 kD. Thereafter UF₃ was divided by sonication in their intracellular (E_i) and membranebound components (E_m) and after solubilization with Triton X-100 in enzymes located outside (E_mp) and inside the membrane (E_ms)The highest activity of acid phosphatase appeared in the UF₃ fraction, its extraction being unaffected by the introduction of KCl in the extractant. The UF3 fractionation located the acid PA in the membrane-protein fractions (E_m). Alkaline phosphatase was predominant in the fraction UF23 showing 86% of the activity displayed by all the fractions; the increase in the ionic strength reduced this activity in UF₂₃ (-68%) increasing the activity in UF₂₂ (5,2% to 24,2%). In UF3, the alkaline phosphatase had an intracellular localization (E_i fraction) showing 90% of the activity displayed by UF₃Different mechanisms of stabilization for compost enzymes were postulated: acid phosphatases may be associated to membranous components of living or dead microbial cells with low solubility in the pyrophosphate extractant and alkaline phosphatase may form a soluble complex enzyme-organic matter of high mol. wt. dissociable at high ionic strength.

About 80 different biogenic waste composts were tested by new or modified conventional microbiological methods (oxygen-consumption, DMSO-reduction, Ehand pH-drop during anaerobic incubation, reference method: self-heating-capacity) to determine the state of maturity and the effect of composts on plant growth in pot-trials. The progress in ripening of composts could be proved well by oxygen- consumption, pH-drop and self-heating-capacity, while DMSO-reduction and Eh-drop reflected maturity only with restrictions. A satisfactory prediction of plant-growth (dry-matter-production of oats) after compost-application with the help of the biological parameters was scarcely possible, only pH-drop showed a somewhat higher correlation. It was found out, however, that the effect of compost on plants could be estimated well by making use both of the C/N-ratio and of biological parameters.

Efficient strategies for using composts in agriculture demand for parameters to estimate their nitrogen effect (mineralization, immobilization) in soil. To find such a parameter different extraction methods (water extract, K₂S0₄ extract, hot water extract) were carried out on 81 different biogenic waste composts. Besides this selfheating capacity, total organic carbon and total nitrogen were determined. The results of compost analysis were correlated with nitrogen uptake by oat in two pot trials. Selfheating capacity did not correlate with the nitrogen effect of the composts. The C/N ratio of the solid phase of composts was considerably well related to N uptake by oat and is therefore an important quality criterion of composts. But the correlation was found to depend on the similarity of law materials and management of composting. All in all the best correlation to N uptake by plants was given by the total organic carbon to total nitrogen ratio of K₂SO₄ extracts (C/N_K2SO4). The correlation coefficients were almost the same in both pot trials. C/N_K2SO4 is therefore proposed to be a good parameter to estimate the nitrogen effect of composts. This is further supported by results from field trials.

The paper presents several scenaria for heavy metal accumulation. The heavy metal balances are based on the average background levels in Austrian arable soils, the current limits for compost in Austria as well as the proposals discussed within the European commission on standardization ‘Soil Improvers and Growing Media’(CEN/TC223). Additionally balances are calculated based on Viennese biowaste composts. It is shown that, using the values discussed in CEN/TC223, the soil limits relevant in Austria and Germany (except for Zn) will be exceeded significantly after only 50–100 years.On the background of references for the ecotoxic significance of soil contamination the validity of the standards and upper limit values established in Austria or in Germany for universally utilizable soils [Cd 0.1 – 1.5; Cr 100; Cu 80 – 100; Hg 1.0; Ni 50 – 60; Pb 100; Zn 150 – 300 ppm d.m.l is prooved.This leads to the demand that the functionality of agricultural soils has to be maintained in the long run; specifically, the input of heavy metals stemming from organic fertilizer applications should be minimized. Based on the results, suggestions for a reasonable application of biowaste compost as soil improver in arable systems are made.

The mean level of PCDD/PCDF found in biowaste compost in Germany was found to be 14.8 ng I–TEQ/kg dm while the median value is 11.3 ng I–TEQ/kg dm – at a standardised content of organic matter (om) of 30%. The concentrations ranged between 2.5 and 79.2 ng I–TEQ/kg dm for the standardised om content (30%). The frequency distribution ranged from 7.49 to 17.5 ng I–TEQ/kg dm (upper and lower quartile).74% of the compost analysed hat PCDD/PCDF levels less than 17 ng I–TEQ/kg dm which is the limit value established in the Baden-Württemberg Compost Regulation. This limit value oft 17 ng TEQ/kg dm for compost is derived from the Germany Sewag Sludge Ordinance assuming an annual application of 10 Mg dm/ha (1 ha = 100 m * 100 m)Early results which reported an 8-fold increase of the TEQ in compost were not confirmed by later experiments. Laboratory as well as full-scale experiments for composting yard and biowaste showed an increase of hepta- and octa-PCDD during th composting process. As the HpCDD and OCDD only have very low toxicity equivalency factors (TEF) the increase of the overall toxicity equivalent (TEQ) ist not more than 2 ng I–TEQ/kg dm.It was demonstrated that the concentrations of the lower chlorinated PCDD/PCDF decreased during the composting process. The same experiments showed also that, generally, furans seem to be more susceptible for degradation.Laboratory experiments have shown that dioxins can be formed from chlorophenols as precursors.On the basis of current knowledge it does not seem to be necessary to study the formation of PCDD/PCDF during biological processing of yard and biowaste in more detail and to stop composting as a means for organic waste management and fertilization of agricultural soils.

Regarding the safety of waste management systems for composting the worst possible situation of non-marketability of large quantities of compost is often anticipated. First of all, it should be pointed out clearly that biogenic waste compost -produced from separately collected kitchen and garden waste – has a considerably higher standard concerning its quality than total solid waste compost, and problems in marketing as they occur in waste and waste/sludge compost can therefore not at all be applied to biogenic waste compost.

Composting is an excellent tool for stabilizing and facilitating the subsequent utilization of organic waste materials, (e.g., biosolids, municipal solid wastes (MSW), farm wastes and certain industrial wastes. Associated with compost production and utilization are various concerns. These concerns pertain to the ability, during processing and storage, to minimize odor and bioaerosols and to adequately destroy pathogens; and, prior to utilization, the ability to produce compost with sufficiently low pollutants contents, maturity and stability for intended end-uses.Rules and guidance can help assure good compost processing and the best and fullest use of these compost products. This paper will describe the approach the U.S. Environmental Protection Agency (EPA) took in developing its 40 CFR Part 503 biosolids rule which includes requirements for composting and use of biosolids-containing composts. The paper will also discuss the applicability of the Part 503 rule to composts that do not contain biosolids.

Composts offer unique opportunities to examine fundamental interactions between plant pathogens, biocontrol agents, soil organic matter and plant roots. These organic amendments can be prepared reproducibly and have the potential to provide consistent biological control of plant diseases. Foliar as well as root pathogens may be affected by composts. Unfortenately, many factors control these beneficial effects. Heat exposure during composting kills or inactivates pathogens if the process is monitored properly. Biocontrol agents with the exception of Bacillus spp. also are killed by this heat treatment, however. Thus, biocontrol agents largely must recolonize composts after peak heating. The raw feedstock, the composting environment, as well as conditions during curing and utilization affect the potential for recolonization of composts by biocontrol agents and the induction of disease suppression. In practice, controlled inoculation of compost with biocontrol agents has proved necessary to induce consistent levels of suppression.The stability of composts is another factor to be considered. Immature composts serve as food for pathogens. Their populations increase in fresh organic matter even if it is colonized by biocontrol agents. In mature composts, biocontrol agents inhibit or killl pathogens and induce suppression of disease. Excessively stabilized organic matter, on the other hand, does not support the activity of biocontrol agents. Disease develops in such highly mineralized organic matter. Finally, salinity and the rate of release of plant nutrients, particularly the amount of nitrogen released, affect suppressiveness. As a result, timing of compost application relative to planting of crops is another factor to be considered.

Composting enables a detailed evaluation of the humification process of various organic wastes within a short period of time (3 to 6 months). Humic substances (HS) constitute a large fraction of the organic matter (OM) in compost, and they are its most active fraction due to their effects on soil ecology, structure, fertility and metal complexes, and plant growth. The formation and properties of HS extracted from various composts such as municipal solid waste (MSW), grape marc (GM), composted separated cattle manure (CSM), sewage sludge (SS), wood compost (WC) and other organic wastes were studied. Degradative and non-degradative techniques (FTIR, DRIFT, 13C-NMR) were used to study the transformation of HS during composting of the various organic wastes. Time-course studies of composting some of these wastes showed an increase in the relative amount of humic acid (HA) (from 18% to 45% of OM in CSM compost and from 5% to 20% in MSW compost), whereas the formation rate of fulvic acid (FA) was inconsistent. A humification ratio (HR – the ratio of HA/FA) was used to evaluate compost maturity. Values of 0.9 to 3.4 and 3.0 to 9.2 were typical for immature and mature composts, respectively. Another humification index (HI) used to define compost maturity was calculated as the ratio between non-humified fraction (NHF) and the humified fraction (HA+FA). A HI decrease during composting represents the formation of HS. Elemental- and functional-group analyses indicated only minor differences between HA extracted from composts at various stages. Moreover, these values fell into a wide range, similar to that of soil HA. The 13C-NMR spectra of the HA exhibited strong bands representing aliphatic structures in various composts (50% of total C in CSM, 30% in MSW and 61% in GM) and a lower level of aromatic components (37% in CSM, 22% in MSW and 22% in GM). The FTIR spectra showed similar trends of strong aliphatic and carbohydrate components. Both techniques provided more qualitative information indicating that HA extracted from mature compost exhibits more aromatic structures and carboxyl groups and less carbohydrate components than that from immature compost.Studies on the effects of HS on plant growth showed stimulative effects. Typical response curves indicated enhanced growth with increasing HS concentration in solution, followed by decreases in growth at higher concentrations. In soils, the addition of composts was found to stimulate growth beyond that provided by mineral nutrients, presumably because of the effects of HS.

The agricultural and livestock sectors are of great significance in the region of Andalusia (South of Spain) (Table 1). Important quantities of agricultural and agroindustrial residues are generated by these activities, frequently causing environmental problems. These residues contain organic matter and nutrients and could therefore be recycled and used as fertilizers or amendments, with or without a previous treatment (composting, concentration). For some of these wastes, recipes for compost mixes, such as olive oil wastewater based compost, have been developed by private companies. Afterwards, laboratory and field experiments have been conducted to study the best conditions for their agricultural use and their degradation process in the soil (González-Vila et al., 1992, Martín-Olmedo et al., 1994). In other cases, such as those of the vinasse based composts, both the compost fabrication and its use have been studied previously to the marketing stage (Díaz et al., 1993, Madejón et al., 1994). Our first research projects at IRNAS dealt with the properties and reuse of municipal solid waste (MSW), and are still in progress.

An overview of the relationship involved between climate, vegetation and soil in the Mediterranean Basin is presented. According to the criteria established by the legend of the Soil Map of the World (FAO-UNESCO, 1974 & 1988), the main characteristics of dominant soils in the area are analyzed. As well, soil problems associated to actual land uses or land uses changes are considered.Low organic matter content is one of the common features of Mediterranean soils. Organic waste reuse through soil system for different land purposes seems to be the best way to improve soil organic matter contents. When organic wastes are composted these practices contribute to eliminate non polluted organic wastes with public health safety and environmental advantage.

Florida ranks fourth among states in the USA in population (about five percent of the total), but produces about one-tenth of the solid waste (about 18.4 million Mg annually in 1992). Perceived problems with landfills and incineration are encouraging composting as an environmentally benign way to recycle organics that cannot be reused in better ways. Potentially about 10 million Mg of organics could be composted to produce 3.6 to 5.4 million Mg of compost. Recycling this volume of material will occur only if research can demonstrate beneficial utilization. Thus, the University of Florida and several cooperators initiated a statewide research program to determine the benefits or problems with applying composts in the production of major crops grown in the state. Composts made from mixed municipal solid waste or source-separated wastes (e.g., yard trimmings, mixed waste paper, refuse derived fuel) with or sans biosolids were applied to soils planted to citrus, pines, various vegetables, turfgrass, sod and container grown woody ornamentals.Results indicate that metals in composts are not accumulated in plants at a level of concern to human health, nor do they occur at levels that exceed recommended soil loadings. The most serious problem identified is ‘nitrogen rob’ in plants immediately planted in soil treated with unstable and immature composts. Crops grown in soils with stable composts usually benefitted from the application—e.g., potato, tomato and watermelon yields increased 30% or more, water deficits delayed in turfgrass, expensive organics replaced in container media, nutrient and pesticide leaching attenuated, root density and extension increased, soil-borne root diseases reduced, soil water storage increased, corn silage yields increased. Data indicate that recycling waste resources has value associated with returning organics to soil, and it helps communities solve waste management.

Two growth chamber studies were conducted to determine whether compost-fertilizer combinations or blends were equal to or better than nitrogen (N) fertilizer alone for tall fescue (Festuca arundinacea) growth and N uptake. A sewage sludge compost(SC) or a compost made from both sewage sludge and municipal refuse (MC) was added on the basis of total N to Sassafras soil at rates equal to 17, 33 and 50% of the N requirement of fescue. The remaining N was supplied by NH₄NO₃ or urea. All combinations were compared to 50 to 100% fertilizer application rates and to each other. After approximately 150 days, fescue N uptake from the 83% NH₄NO₃:17% compost N blend equalled that from 100% NH₄NO₃ treatment which was not different from 83% NH₄NO₃. The 67% NH₄NO₃:33% MC blend equalled the 83 and 100% NH₄NO₃ alone treatments. The 67% urea:33% sewage sludge compost N blend equalled the 83 and 100% urea alone treatments. Because compost N is only partially mineralizable during the first year, the equality of compost:fertilizer blends to fertilizer alone suggests that ingredients other than N are benefitting the fescue. The studies presented herein suggest that the ability of compost in blends to substitute for a fraction of the fertilizer requirement is both compost and fertilizer dependent. The data suggest that blends with urea would be successful in substituting for one-third of the N fertilizer required by fescue.

Compost, liquid and dewatered sludge from a sewage purification plant were spread each year on a three-course rotation (maize- wheat and sugarbeet) at two rates, with or without an extra inorganic NP supply. Sludge application was compared with a mineral fertilisation based on 4 rates of urea. In the first 6 years no toxicity to plants grown in compost or sludge plots was observed, even at the highest application rate (15 t DM ha-1). Sludges gave crop yields similar to those obtained with the highest rate of urea; compost yielded as the best inorganic fertilisation, which often corresponded to the lowest inorganic fertilisation. Most of the results of the organic materials could be ascribed to their N-NH₄ content. The N in compost showed the lowest utilisation by crops (about 20% of urea-N), the highest in liquid sludge (30%) and intermediate values in dewatered material (27%). Because of negative effects of N relative to wheat lodging and quality of beet sugar, the disposal on agricultural land of liquid sludge requires particular care, whilst the application of dewatered sludge or compost appears much safer to crops.

Compost from selected organic waste (vegetable waste from fruit and vegetable market and pruning residues) was used alone and in mixture (25% of volume) with a substrate from straw-bedded horse manure, normally used in mushroom farms, for the cultivation of Agaricus bisporus (common white mushroom). The composting process lasted 20 days. After this period the mature material was transferred to the culture room. The substrate from straw-bedded horse manure was used as a control.The compost was found to be suitable for the cultivation of A. bisporus. The production of beds with the compost from selected organic waste alone was 18.34 kg/m2, the beds where this compost formed 25% of the volume was 23.21 kg/m2 and the beds with the compost from straw-bedded horse manure alone was 24.93 kg/m2. No differences were observed in the quality of the mushrooms from the three different substrates.

Composted organic wastes are increasingly pointed out as alternative to chemical fertilisers for crop production. This paper reports on a trial using sewage sludge compost and municipal solid waste compost at two rates (50 or 100 ton/ha) and two systems of application (incorporation to soil or as surface mulch) for the production of wheat (Triticum aestivum) in two consecutive growing seasons: spring (var. Canon) and winter (var. Mercia). Additional treatments were: Nitram (ammonium nitrate, 34.5% N) at 75 or 150 kg of N/ha and a null control. The different treatments were applied in a single dose, in the first season; the objective being the observation of possible residual effects in the second year. There was no statistical difference between the two compost, regarding release of nutrients to soil, biomass production, grain yield and grain quality. Composted societal wastes showed to be able to sustain crop production at levels of quantity and quality similar to those obtained from chemical fertiliser (Nitram, ammonium nitrate, 34.5% N). Results for rates of mineral nutrients at soil level throughout the experiment allow us to conclude that composted societal organic wastes provide nutrients to plants in a balanced way, providing high yields with low risks of soil and underground water pollution. Results for these trials indicate that the residual benefits from compost use for consecutive crops are minimal and, thus, compost should be used as a long term strategy for improving soil fertility, with applications of low doses –up to 50 ton/ha– prior to drilling of each crop or as surface mulch after that.

This paper summarises the results of six years application of compost and sewage sludge on the content of the heavy metals in crops and on the content of organic matter, total nitrogen, available phosphorus and extractable heavy metals in soil. The trial was carried out on a three course rotation including winter wheat, sugar beet, maize; all the crops in rotation were grown each year. The soil was a silt loam with an average pH of 7.8 and an average CEC of 13.8 meq/100 g.The experiment consists of treatments with compost from sewage sludge and straw, liquid and dewatered anaerobic digested sewage sludge, at two rates (7.5 and 15 t of dry matter ha-1 yea-1) and of four treatments with only mineral fertilizers.The application of organic materials determined an increase of the Zn content in grains and in root and an increase of Cu in sugarbeet root. The other investigated heavy metals (Cd, Cr, Ni, Pb) have not shown significant differences in crops. The increase of the application rate had no effect on the concentration of heavy metals in plants; the application of liquid sludge resulted, some years, in a higher accumulation compared to dewatered sludge and compost. After six years of sludge and compost application, the soil showed an increase in organic matter, total nitrogen, available phosphorus, in extractable Zn and Ni. This increase was higher with the higher rate of application and, for Zn and P, with liquid sludge dressing.

This paper describes the some of the results of a two experiment conducted to investigate the agronomy and environmental impact associated with the use of (i) co-composted municipal solid waste and sewage sludge (MSW) and (ii) composted greenwaste (GW) on forage maize. The experiment was conducted on a silty loam soil in South West England. In 1994 MSW and GW treatments of 15, 30 and 50 t ha-1 were compared with fertilizer and an untreated control. All treatments were replicated three times. The composts used were significantly different with respect to pH, loss-on-ignition, total potassium and calcium, but not mineral nitrogen or C:N ratio. No significant differences in soil nutrient status were observed between compost types or rates after drilling. The inorganic fertilizer treatment which showed significantly higher levels of mineral nitrogen but not P or K. Patterns of extractable nitrate-N recorded during the summer 1994 were very variable, and only the fertilizer treatment was significantly different from the compost or control treatments, and then not on every occasion. Post-harvest leaching on nitrate-N again showed no consistent pattern between compost types or application rates, while losses from the fertilized plots exceeded all other treatments. It is concluded that at the rates used in this experiment, the nutrients contained in composted MSW and GW can be considered environmentally benign.

The amount of compost originating from source separated organic household waste in Germany is increasing rapidly. According to estimates of the potential processing capacity based on current building activities and ongoing approval procedures, the biowaste composting capacity will double again within the next two years. This means that the 1996 annual output of bio- and yard waste compost in Germany will amount to some 2,5 million m3. With respect to this development it is necessary to use all sales potentials available to compost marketing. One potential field of compost application for high quality compost which has hardly been recognised so far is that of refined compost products, in particular potting soils, substratum and vegetation layers.Currently, bio- and yard waste compost is mainly used for soil improvement and fertilisation purposes. For this application quality criteria and plant production requirements have mostly been standardised and laid down in specific regulations (e.g. quality symbol RAL-GZ 251, revised LAGA information sheet M 10). In contrast, there is no complete set of quality criteria for compost use in the field of soils and growing media. yet. Some of the criteria have still to be developed while other parameter have to be differentiated more, or the limits have to be made more stringent. The requirements for compost application in such a sensitive area have been laid down in a list of preliminary quality criteria for substratum quality compost. Certain characteristics or contaminant limits for quality criteria applicable to compost which is used in growing media production are currently being established within a research and development project which has been underway since the end of 1993 and is funded by the German Federal Foundation for the Environment and the German Compost Trading Company.The effect of increasing contents of chloride, sodium, cadmium, copper and zinc on plant development have been evaluated in initial plant production trials using various ornamentals. At a compost application rate of 40 % (v/v) the ornamentals used showed no negative growth effects as long as the heavy metals tested did not exceed the tolerable level established in the preliminary quality standards for substratum quality compost (equivalent to RAL-GZ 251 limits). In contrast to the results above it was observed that 40 % (v/v) of compost which contained no more than 1.000 g chloride/l resulted already in severely retarded growth of Primula ohconica, the most sensitive test plant. With respect to the quality criteria ‘plant compatibility of compost’ it has been evaluated whether results obtained with summer barley (RAL-GZ 251 methodology) are also valid for horticultural production of ornamentals and plants used in landscaping. These initial trials indicated that growth inhibitors contained in compost show a stronger effect on some ornamentals than they do on barley.Further experiments which are necessary to verify the results obtained so far will facilitate the establishment of detailed standards for substratum quality compost meeting the requirements posed by horticulturists. A list of quality standards defining substratum quality compost and compost based products such as the one being compiled currently, will provide an expert basis for both producers and users of these products. These standards will also bring about the certainty sought after. Suitable raw materials required for the production of compost based media can be supplied by compo sting plants according to appropriate product diversification measures. Refining of bio- and yard waste compost is very interesting from a potential compost sales point of view and also with respect to the high prices that can be realised. Furthermore, a diverse range of high quality compost represents recycled raw material which is able to aid the reduction of peat contained in soils and growing media today. Hence, the use of compost facilitates active environmental protection in the field of plant production.The new compost based products can be mainly applied in the following areas: Hobby gardening (mainly potting media)Building industry (filling material)Melioration measures/establishment of green areas (e.g. exchange of contaminated soil)Garden- and landscaping industry (e.g. media for roof-gardens, filling material, substratum for tree planting, vegetation layers)Public institutions (corresponding to garden- and landscaping industry)Viticulture and fruit growing (substrata suitable for the establishment of new fruit plantations and vine yards)Commercial horticulture (substrata for seedlings and transplants as well as potting media suitable for vegetable production, growing of ornamentals and tree nurseries)It applies to all listed areas of use that an innovative development strategy, including quality assurance of the compost based products has to ensure the successful application of the new products in both, plant production and economic terms.

The design and implementation of a Pilot Program for compo sting organics from residential and commercial sources is discussed. This Pilot is perhaps unique in that it not only deals with various political and geographical entities, soliciting the cooperation of the organic material generators but also develops handling systems, a model compost facility, projections for utilization of the finished compost and provision for cost comparison with other waste handling methods.

Mantainance of private and public landscaping works produces heavy loads of vegetable materials which sizes, expecially in high social standing urban areas, to a major and cumbersome waste treatment and disposal problem. In these situations a ‘rural approach’ for a proper management of yard wastes is definitely lost; the farmer, who has often been called in rural areas to mantain landscape works, is no longer the subject that guides a more or less direct flow to agricolture of yard wastes both for crop uses (mulching, green plowing) and for bedding or animal feeding.

Numerous agronomic experiments were set up in fruit and vine growing, using both MSW compost (municipal solid waste not source separated) and BS compost (barks and sewage sludges). Both materials were compared with cattle manure in the field; in planting hole with peat; in mulches with usual under-plant soil management techniques. Compost affected soil porosity, softness, waterholding capacity, and availability of nutritive elements in a positive way. Compost generally improved plants themselves, positively influenced the growth of young apple-trees and vine cuttings, prevented weed development and supported an earlier production in young plants. In some trials with MSW compost, increased heavy metal content in the soil was observed, but that did not happen with BS compost.The BS compost proved a valid alternative to the soil and organic soil conditioners on the market in the recovery of degraded areas too. In the experiments, compost secured a rapid emergence and regular growth of herbaceous species covering degraded areas. Establishment of a grass sward allowed soil consolidation, reducing soil erosion. The thoroughly environmental safety of tested compost was proved: leaching water and soil tests showed no sign of pollution or eutrophication.

Composting is the solid state aerobic degradation of organic waste, principally of plant origin. This may be agricultural waste, garden waste or domestic refuse. The latter is included because of the large amount of paper used in packaging and in newspapers and magazines. The common factor with all of these is the high proportion of lignocellulosic material in them. Lignocellulose is the material of which plant cell walls are made and it is the most abundant organic material on Earth. It has been estimated that it represents approximately 50% of the annual global production of biomass, about 5 × 1010 tons (Goldstein, 1981). Composting can produce useful materials from lignocellulosic waste. It can also carry out desirable processes on waste itself and on other materials using the lignocellulosic waste. (Figure 1.)

The application of composting technology for the processing of agricultural wastes is reviewed. This paper covers the historical background of compo sting in agriculture and assesses the role of current composting technology and its relevance to farm wastes. The impact of ecological concerns over potentially polluting farm wastes is considered as more important a factor in promoting agricultural waste composting as the potential value of the compost end product.

In the early 1920’s, H. Clay Kellogg, Sr., a surveyor by profession, was working at a dry river bed in Santa Ana, California. He noticed luxuriant vegetation growing along the bank. Observing that this growth seemed to result from the sludge in which it was growing. he took some of the black material home to experiment.

Blue crab and calico scallop processing plant scraps have been landfilled, creating waste management problems. Alternative methods of in-plant compacting, anaerobic bioconversion potential, composting, compost marketing, compost crop applications and nematode control using compost were examined. It is feasible to compost blue crab and calico scallop processing plant scraps and there appears to be uses for the final compost products. Compo sting is a viable alternative to landfilling these processing scraps. Composting is being used sllccessfully to compost blue crab and scallop processing scraps.

A liquid dairy cattle slurry was composted using rice hull as absorbing matrix and bulking agent. The main results obtained were as follow: 1) The structure and size of rice hulls as well as their absorption capacity, made it possible to obtain a good compo sting mixture (moisture: 71.42 %; C/N ratio: 28.80 %; bulk density: 0.429 kg / dm3)2) The compost stability was reached after 56 days of composting, obtaining the follow data (% D.M.): ignition loss: 73.00: C/N: 18.36; TKN: 1.98; K: 1.84; P: 1.13; humified carbon: 4.60; respirometric index: 0.88 mg O₂/gVS x h; dry matter yield: 57.34 %; organic matter yield: 50.05 %, water losses: 56.99 %; airflow-rate: max: 2.96 m3/kg D.M. x day., min: 0.28 m3/kg D.M., men 0.75 m3/kg D.M.. 3) The curing phase determined as aspected the reaching of a high compost maturity degree. After 256 composting days the data obtained (% D.M.): ignition loss: 65.89; C/N: 13.52; TKN: 2.51; K: 2.00; P: 1.27; humified carbon: 10.81; dry matter yield: 46.36 %; organic matter yield: 36.91 %, water losses: 63.99 %. 4) As shown by the organic matter yield, the mixture presented high degradability, in contrast to the literature (Chino et al., 1983). This can be explained by the composting temperature obtained (30 –45 °C) wich permitted high cellulose-like material degradation. 5)The compost data obtained, suggests that two marketable products are obtained: the first after 56 composting days, utilizable in field applications, and the second after 254 days, as substitute for organic substrata (e.g., peat) in greenhouses and on sensitive plants.

Composting is fast becoming the primary disposal option for leaves and grass in the U.S. due to proposed bans on the land filling and incineration of these wastes. To date, few systematic field scale studies have been done to compare the effects of turning regime, pile size and feed stock mix ratios on the rate of compost production or the properties of finished compost. In this study, leaf, grass and brush mixtures of 4:1:1, 4:2:1, 4:3:1, as well as 4:2:1 and 4:3:1 with staged grass addition, were formed into windrows and piles and composted for 136 days. Using a windrow turner, one series of windrows (#1) was turned seven times every four weeks, while the second series of windrows (#2) was turned once every four weeks. The piles were turned using a front-end loader once every four weeks. Results showed that windrow temperatures rose to 55–62° C in 6 days and remained at this temperature through day 60 and then slowly declined to around 45° C by day 100. Pile temperatures rose to higher levels (68–74° C) and remained above 60° C for 100 days. Windrow oxygen concentrations ranged between 1 and 4% while the oxygen concentrations in the piles fluctuated greatly between 2 and 18%. Organic matter loss was fastest in windrows series #1 and slowest in the piles. The pH of all the treatments rose from neutral to slightly alkaline (pH>8). The bulk density increased by more than 400% for windrows in series #1 but by only 150%, and 100%, respectively, for windrows in series #2 and the piles. The results indicate that turning frequency has a significant effect on bulk density, a slight effect on the rate of organic matter loss, and an insignificant effect on temperature and oxygen concentration. The mix ratio of leaves to grass, on the other hand, had no significant effect on most measured parameters. The composts from all the treatments were stable after 60 days of compo sting as indicated by oxygen uptake rates of less than 0.1 mg O₂/g organic matter/hr. None of the composts inhibited seed germination or root elongation as measured by the Cress seed test.

The treatment of municipal wastewater in Australia results in the production of 250,000 dry tonnes of raw sewage sludge annually (Beavers, 1993). Two types of raw sewage sludge are produced. Primary sludge consists of settled organic matter from primary wastewater treatment. Secondary sludge is microbial matter produced from the activated sludge process in aeration tanks. In Western Australia, both types of raw sewage sludge are anaerobically digested to reduce pathogens, volatile solids and odour. The residual sludge is then blended for use in potting mixes, prior to land application.

The project on which this paper is based is sponsored by Wrekin Council and the work is carried out at Harper Adams Agricultural College in the Crop and Environmental Research Centre and the Agricultural Engineering Department. The aim of the project catalogued in this paper is to reduce the pollution problems associated with the direct application of agricultural slurries to land and the disposal of municipal organic waste to land-fill. Composting has the potential for reducing the levels of methane gas and harmful leachates produced in the landfill process and for reducing nitrate pollution from agricultural land.

This paper describes the progress of studies of the treatment of coal ash mixed with organic by-products by a compost process as a means of converting ash to a desirable commercial product. Mixtures of fly and bottom ash, broiler chicken litter manure, sawdust and pine bark were successfully composted during the winter of 1994. The recipes and compost procedures for production of the manufactured soils are described. The physical, biological and chemical properties of the manufactured soils are being studied and initial results are presented.

Waste disposal in the Netherlands has come under great pressure in recent years. The policy of the Dutch government is directed towards radically restricting on the domestic waste to be dumped on the basis of social, spatial and environmentalprotection considerations.At present, however, paper diapers are thrown into the rubbish bin (grey container) and then dumped or incinerated. The used paper diapers largely consist of pulp and are therefore in principle suitable for being composted together with normal Vegetable, Fruit and Garden (VFG) waste.Various studies on the compostability of a VFG waste/paper diaper mixture have demonstrated that a good-quality compost can be produced from it.However, the used paper diaper also contains approx. 15 wt. % plastic film in addition to the compostable material. This plastic diaper film must not end up in the final product. It is therefore anticipated that an adjusted process route will be necessary for composting VFG waste/diaper mixtures.The Department of Environmental Technology of the Institute of Environmental and Energy Technology (TNO-ME) in collaboration with the Research and Development Department of VAM has carried out a study to develop an adjusted process route for composting VFG waste/diaper mixtures. The point of departure for this adjusted process route is the composting process applied at VAM. The following process steps have been added to this VAM process and studied. Prior to composting: Screening of the VFG waste/diaper mixture over a 60 mm screen to remove all diapers from the VFG waste.Grinding of the screen fraction > 60 mm (mixture containing all paper diapers and coarse VFG waste).After composting: AircIassifying/screening of the screen fraction> 25 mm to remove the plastic>diaper film.The results of this study are as follows: Mixtures of VFG waste and used paper diapers can be composted without difficulty by introducing additional process steps. The quality of the agricultural compost produced from the VFG waste/diaper mixture via this adjusted process route is good, and the quantity of plastic diaper film in this final product is very low (0.04%) and not visually disturbing.The quantity by weight of used paper diaper waste to be dumped or incinerated is reduced by approx. 84% as a result of the composting of the used paper diapers. What remains as waste after compo sting of the used paper diaper is the plastic diaper film. This accounts for approximately 16% of the weight of the used paper diaper. The plastic diaper film can be separated out as residue to 98% as a result of the introduction of the additional process steps.In the context of integrated waste treatment in the Netherlands. the benefits resulting from the composting of used paper diapers can also be presented as reduced incineration costs. This can signify a cost saving of up to 10 million guilders per year on the waste treatment of used paper diapers, and a further increase in the future.

We have been able to successfully compost high C/N ratio materials such as grass straw. The straw composting was examined by using an on-farm windrow approach, different quality straw materials, and different number of turns. Temperatures typical of thermophilic composting (> 50°C) were commonly observed in the turned windrow treatments. The magnitude of culturable microorganisms varied little among treatments and windrow depth (30 cm and 100 cm). except that thermophile populations increased in the turned windrow treatments at all depths midway through the 200 day composting process. Hydrolytic enzyme activity showed no definable pattern for all treatments and windrow depths. The loss of lignin fraction C indicated that extensive lignin degradation occurred in all treatments including the control. The increased need for C and reduced requirement of N of the thermophilic biomass and the release of soluble N and ammonium during the mesophilic to thermophilic transition explains the extensive decomposition of high C to N ratio (50–60 to 1) grass straw during windrow composting. Upgrading of agricultural wastes through composting is a viable residue management alternative that may be important for developing sustainable cropping systems.

Olive-mill wastewaters (O.M.W.) were composted with wheat straw in a forced aereation static pile (7.5 × 2.5 × 1.8 m). To eliminate most of the liquid component and to degrade lignin, the thermophilic phase was prolonged for 5–6 weeks, adding O.M.W. every three days. At the end of the process, the ratio O.M.W./ solid substrate was about 10 litres per kg of straw. This paper discusses the bioremediation process from the standpoint of ligninolysis, humification, phenol degradation, phytotoxicity and agronomic value. The end product presented a degree of humification of 78%, and a residual lignin content of 30%. Soluble lignin fraction, made evident during the thermophilic phase, decreased during compost maturation. No phenols or phytotoxicity were detected in the end product. Pot and field experiments performed on maize, rye grass and horticultural plants indicated that bioremediated O.M.W. are able to support partially or totally the nutritional needs of cultures, at the same time improving soil properties.

Agricultural composting is expanding in the United States, with over 7,000 farms currently composting. Based on information collected from the 10 largest producing states for beef and dairy cattle, poultry, and swine, this is largely being driven by the need to find an alternative method to handle livestock mortalities. However, composting is also increasingly being used to recycle crop residues and to improve the handling, marketability, and/or quality of livestock manure. Factors affecting agricultural composting include the availability of land for application of manure or crop residues, proximity of farms to urban areas, environmental policies and regulations, and the support of industry and public agencies via research, education, and financial incentive programs.In the United States, more farms compost than municipalities, commercial/institutional establishments, and other private sector groups combined (Kashmanian, 1995). The move toward composting is particularly strong within the poultry industry, as many poultry farms have turned to composting to handle their mortalities. However, composting is also increasing among other livestock and crop farms. (In this paper, dry stacking is not considered a form of composting.) There are indications that agricultural composting is more prevalent in certain geographic regions or among certain types of farms. Critical environmental problems are probably a factor in the regional differences, although other contributing factors also seem to be responsible.To obtain an overview of agricultural composting in the United States, industry, government, and university representatives from the top 10 beef and dairy cattle, poultry, and swine producing states were contacted between January and April of 1995. The representatives provided information about the number of farms composting, the materials composted, composting methods, how the compost is used, and motivating and impeding factors for farms to compost. In addition, information was gathered concerning composting crop residues. In this case, specific applications of crop residue composting were identified and individuals knowledgeable about the applications were contacted for background information.The information collected provides insights into the status of composting in U.S. agriculture, including trends, motivating and impeding factors, and research and education needs.

Composting is considered as one of the most suitable ways of disposing unpleasant wastes and of increasing the amount of organic matter that can be used to restore and perserve the environment. The advantage of the Rutgers compsting system is that a stable compost can be obtained in a short period of time.Eight different composts were prepared by this method, using a wide variaty of wastes. Their evolutions were studied. Two of them were used as organic fertilizer. The results showed that there were not significant differences from the yields obtained with inorganic fertilizer. Other four composts were used as component of substrates for ornamental plants. The results indicated that they could be use sucessfully up to half of the whole volume of substrate. The third application was as substrates for seedling prodution. The preliminary results indicated that the yield depended mainly on the level of salts.

Approximately 1 million m3 of compost is produced in Finland annually. Sewage sludges and liquid animal manures are the major waste groups composted in windrows or smaller heaps. Owing to the severe odour and leachate water problems in wintertime, however, in the major cities and towns will probably shift towards closed processing in the near future. At present there are about 100 drum composters in use on Finnish farmes. With the new environmental legislation and targets set by the Ministry of the Environment, source separation of biowaste, and centralized composting as the most effective method of treating it, can be expected to expand rapidly. Approximately 3% of detached houses employ small composters and growth is likely to be small. Although many industrial waste fractions could be composted, this is only marginal in Finland.The composting process is an active area of research in Finland. Of particular interest are the compostability of different waste matrices and management of the process; quality aspects of composts, including the chemistry of biodegradation; the occupational hygiene of the process; and the composting of toxic waste fractions, particularly those containing organo chlorine aromatics.

The present French situation of waste management is the result of traditionnal treatment plants, sorting-composting MSW composting plants for instance, which are still running, and new perspectives coming from the achievement of the national policy (law n° 92–646 published in 1992). This transition period can be an opportunity for composting development if the three levels of analyze are correctly assessed as well as waste management alternative and as agricultural and ecological pertinence. For this assessment, better knowledge on impacts and new tools of management (including monitoring and control) are required. Up to now, we can consider that, in France all the conditions of composting development are present depending on a common will to do it. The Ademe will propose an adequate working scheme for the next 5 years, hoping that its partners will agree and correctly consider the effort that must be done.

An amount of at least 1.000 mio.tons of slurry from animal husbandry in Europe should, based upon environmental considerations, be subject to centralised treatment in order to recycle nitrogen and utilise the energy potential.The process technologies until now are lacking behind in order to fulfill ecological requirements to nitrogen recycling and utilisation for fertilising purposes, whereas the energetic utilisation by means of biological processes has been highly developed.The existing paradox, where costs of BOD reduction in urban areas are accepted to be over 100 times higher than what is allowed in the animal husbandry sector, even under very negative ecological impacts by denitrification and high consumption of fossil energy, can only be overcomed through sector integrated waste treatment allowing energy neutral operations etc..The NRS–SEABORNE technology should be a modern innovative mean to go for in urban/agricultural integration within waste treatment, ensuring ecological sustainability as well as clear advantages expressed in pure financial terms at the moment.

In this paper the existing composting plants in Italy, either in operation or that are about to come into operation in a short-to-medium time, are localized and the problems associated with two different approaches to composting are discussed: either from household waste that is not source separated or following the recovery and processing of sorted biomasses.A general overview shows a large number of ‘conventional’ plants (n° 42), most of which were designed in the late ‘70–80s’. These must undergo deep, albeit gradual, changes in their productive process or, alternatevely, the organic component is to be biologically stabilized before dumping. The existing processes will be mantained only if there is evidence of actual opportunities to profitably use the compost.Selected waste processing plants are rising fast (today they are at least 33) and some of them (at least the most efficient ones) have gained large market shares, due to their striking agronomic and environmental features.These advances, however, may be in vain, if the existing legislation, not encouraging the production of high-quality compost, remains in force. Although, however, this seems to be about to be amended, unacceptable restrictions are likely to be introduced by the Ministry for the Environment in terms of environmental criteria related to the building of plants and compost quality standards (with special regard to the levels of some heavy metals, such as copper, zinc and lead).

During the period from 1985 to 1995, the increased number of composting facilities in the United States of America was primarily motivated by high landfill tipping fees and bans that prevented the landfilling of vegetative organic residuals such as leaves and grass clippings. In the case of waste water biosolids, composting was part of a beneficial reuse strategy that kept sludge from being dumped in oceans and rivers as part of clean water programs. In the 1990s, increasing attention is being given to the Utilization of a high quality compost in sustainable agriculture and horticulture. Specifically, compost products are gaining recognition as an economical and environmental substitute for chemical inputs including toxic pesticides. More researchers are proving the relevance of compost applications in sustainable agriculture programs. While much progress has been made in the production and application of quality compost, there still remains great challenges if the potential widespread application of compost is to be realized.

Recycling of municipal wastes has been attracting attention and some practical recycling system has been established in Japan. The trend in disposal methods of municipal wastes in Japan will he explained. The garbage is an appropriate material for composting and thus, many composting plants have been constructed for the past ten years. The fever of the compost production by using garbage, however, is cooling down, mainly because of high construction and operation costs, quality change of municipal waste, contamination of plastics, ill-treatment of malodorous exhaust gas, etc. Characteristics and problems of a large-scale composting plant at Tokyo Metropolitan Government will be a typical example of the big city composting facility.At present, a small-scale home composter is getting popular especially in local areas. Some local governments prepare a subsidy system to promote the usage of such a composter at each house. The aim of this promotion by local governments is to reduce the amount of garbage disposed from each house.There are two types of composter. One is a simple plastic bin-type container which is placed in the outdoors. Another one is a new electric type equipped with mixing, heating, and amended with bulking agent to accelerate composting reaction rate. This electric one is also operated outdoors. Although there is a need of a lot of modification of the composters for further proliferation, this trend will be one possibility to loose burden of the waste treatment expenses in local governments.

The present reports on many aspects of composting in Brazil with particular emphasis on the main problems which contributed to the discredit of this important process in many areas of the country.Consideration, is made of the constant increase in the use of selective collection which can persuade facilities to increase the use of composting in waste management.Finally, aspects of solid waste composting in Brazil, related to its perspectives, the low cost techniques and recycling are considered.

Since mid-1993 an already existing conventional MSW (municipal solid waste) composting plant (serving 80.000 population) is being redesigned as a center for recycling and treatment. This comprises not only the construction of a biowaste composting plant according to the latest state the art in engineering for the recovery of reusable, separately collected organic components of domestic waste, but also the stabilization of residual waste according to the concept of ‘cold pretreatment’. The technical conception of the plant allows capacities for a texture-adapted treatment of sewage sludge, too.The domestic waste composting facility Sciaves/Alto Adige has been in use for more than 10 years and is processing approx. 20,000 tpa of MSW. The essential components of the plant are the mechanical treatment (comminution, homogenization, sieving), conditioning and landfilling of screen rejects (facultative production of RDF), and the controlled decomposition of the organic-rich fine fraction which will be deposited or used for remediation measures.The objective of the new conception and the technical adaption being carried out at present is to treat residual wastes to enable environmentally sound disposal and to treat and subsequently utilize source separated waste streams (compost, ‘dry recyclables’). The result will be a modem, integrated waste management center with several lines of processing.Most of the already existing equipment can be further used for the processing line ‘cold pretreatment’ and only few modifications of the process have to be carried out. Since the technical optimization of the process is mainly based on a simplification of the procedure it can also be regarded as a ‘low-cost-treatment’. It is envisaged to reduce degradable components of non-utilizable wastes (no incineration plant is projected medium term) by biologic treatment before landfilling and thus establish an inactive state of the material.On the basis of a preliminary study on the large-scale separation of organic wastes from industrial and domestic sources, an integrated composting facility was planned within the existing plant, which is destined for the sole production of well marketable quality compost. During the determination of the optimal treatment procedure two crucial settings were considered by the use of semimobile and modular enlargeable plant components: firstly the slowly raising amount of biowastes in the next years and secondly the need for a flexible adaptation on varying input materials. Thus it is also possible to selectively treat less contaminated sewage sludge as well as the organic fraction of domestic waste. The central part of the facility is an intensive rotting phase in an enclosed environment which guarantees an optimal process control and a minimization of emissions (especially odour).The presented project can be regarded as a model for the adaptation of existing, but technically not up-to-date biological waste treatment systems to facilities which are suitable to modern waste management strategies. It shows that realistic approaches for development are applicable to many disposal regions in Italy which are comparable to the described situation.In Alto Adige esiste l’ordine politico di riutilizzare i rifiuti urbani biogeni dopo averli adeguatamente preselezionati presso il produttore iniziale. L’idea fondamentale di questo modo di procedere viene seguito già da tempo dalle Comunità di Val d’lsarco e Alta Val d’ Isarco che gestiscono dal 1985 presso Sciaves un impianto di compostaggio. Le autorità competenti hanno dato ora l’autorizzazione per adattare questo impianto alle esigenze attuali. Sono ogetto della progettazione sia alcune modifiche nello schema d’impianto per facilitare la gestione (tra l’altro la sostituzione necessaria di alcuni blocchi logori) che la realizzazione di un centra di raccolta differenziata primario. Quest’ ultimo comprende una zona di trasbordo per materiale riciclabilie ed una semplice unità per la selezione dei rifiuti ingombranti ed industriali.

Partnerships with environmental groups, industry, and the public sector have proven to be a very effective way to advance source-separated composting of residential and commercial organic waste. The partnership concept has provided an opportunity to gather meaningful data and understanding needed to address key environmental, economic, and institutional questions that hinder broader acceptance and implementation of composting. In the United States, two innovative partnerships have shown that collaboration can achieve these goals. One partnership, ‘Compost for Earth’s Sake,’ involves the Grocery Industry and the environmental group, the National Audubon Society, working with local governments on pilot projects investigating source-separated composting. In addition to gathering data on collection performance, economics, and public acceptance, the team is investigating compost contamination from a multi-stakeholder perspective, both by measuring compost quality directly and by projecting long-term soil concentration levels that might result from sustained use. The second partnership, ‘Food for the Earth,’ is a partnership with representatives from the food service industry, the US Composting Council, and the National Audubon Society. In addition to testing the feasibility of behind-the-counter separation of organics, the food-service team is investigating the options for composting grease, which is an important disposal issue for the industry.

After illustrating the reasons behind the decision to support the development of composting plants and after enumerating the facilities already present in the Province of Forli’, the authors of this paper proceed to describe the main problems encountered in the operational phase of the plants and the solutions and legislature proposed, with a view to guaranteeing, in the future, an activity that conforms to the environment requirements of the population that resides close to the plants.

Household waste has been treated by digestion in city of Vaasa, Finland since 1990. The plant capacity is 25.000 t/a, which is corresponding to biowaste from 200.000 inhabitants.

Regulatory pressures are forcing major changes on the waste disposal industry. The proposed EU Directive on Landfilling of Waste, if implemented in its current form, will ban the co-disposal of industrial and municipal wastes in landfill. These developments indicate a likelihood that co-disposal will no longer be available as a disposal option for industrial wastes in the long term.Above-ground co-treatment of industrial wastes with sewage sludge and/or municipal solid waste prior to landfill is an approach to enhancing the efficiency of waste disposal to landfill and reducing reliance on incineration. It also provides an alternative to disposal to land where the wastes are considered too toxic. Degrading municipal waste and sewage sludge have been shown to promote the degradation of many toxic organic compounds and fix other organic and inorganic substances, for example as sulphides or into humic matter. These processes are used to justify the practice of co-disposal to landfill. Unfortunately, these processes are not optimised and cannot be controlled in landfill and hence co-disposal has come to be viewed unfavourably in many countries. Optimisation of these processes in an above-ground treatment system would have many advantages, including:1Stabilisation of environmentally damaging substances,2Reduction of waste volumes prior to landfill,3Generation of recoverable biogas ,4Detoxification of hazardous substances in a low temperature biological process, without the input of additional fossil fuel or the likelihood of generating dioxins and furans,5Generation of a benign stabilised residue,6Biological sanitisation of the treated waste stream,7.Disposal of a waste with a reduced capacity to generate landfill gas and possibly improved geotechnical performance.

The quality of compost produced from municipal solid waste or selected waste components therefrom is determined primarily by the characteristics of the waste components and by the processing methods. Consequently, a knowledge of the characteristics of the waste components and of the fundamentals of preprocessing and composting technologies is required in order to design a system to produce a compost to a desired set of specifications. The specifications can be a result of regulations, or market conditions, or both. The characteristics of the waste to be composted can be manipulated at the point of collection (e.g., by separate collection of the predominantly biodegradable waste components) and during subsequent processing. This paper focuses on the characteristics of various waste components and of mixtures thereof, the key fundamentals of processing relevant to composting, and the influence of waste characteristics on compost quality. Besides the discussion of applicable fundamentals, the characteristics of compost produced from mixed solid waste organics and from mixtures of source separated components are compared both on a theoretical basis and related to some actual data. The discussion provides information relevant to the determination of the advantages and disadvantages of using mixed solid waste organics or source separated wastes as compost feedstocks.

Biological treatment plays an important role in solid waste management since it can effectively treat a significant proportion of municipal solid waste, as well as certain industrial wastes. However, no one treatment method can manage all waste materials in an environmentally effective and affordable way. Biological treatment therefore needs to be part of an overall integrated waste management (IWM) system. Making such IWM systems both environmentally and economically sustainable requires that both their overall environmental burdens and economic costs can be predicted, and then optimised. This paper show how a Lifecycle Inventory (LCI) tool can be used to assess overall sustainability and optimise the role of biological treatment within integrated solid waste management. It suggests that further integration of both solid and water-borne CTwaste treatment can lead to additional environmental and economic improvements.

A comparative study was run during 13 months on two biowaste definitions involving both lab tests and field surveys. A narrow biowaste definition, allowing only biogenic wastes was compared to a broad biowaste definition, including compostable man-made products, such as non-recyclable wastepaper and diapers. Two similar real-life test areas with each about 425 inhabitants were defined in a semiurban area North of Antwerp. During the whole test period the amount of curbside waste, this is biowaste and restwaste (the ‘non-biowaste’), was continuously and precisely measured and also analysed regularly (twice per season) for composition. At the start, middle and end of the test, surveys were held with a questionnaire for the population of each test area. In each season of the year, bench-scale aerobic composting experiments were run to evaluate the influence of both biowaste definitions on the composting process and the compost end product.The introduction of source-separated waste collection resulted in an overall landfill diversion of 43% for the narrow biowaste definition and 46% for the broad biowaste definition. The contamination of biowaste (about 3%) was low for both definitions, the restwaste (or so-called grey waste) still contained a lot of organics (34 to 66%). Supposing that the collection and the appropiate disposal of organics could be improved to 95% efficiency (compared to about 60% currently), the landfill diversion could be increased to 59% for the narrow and 74% for the broad definition. Whereas the average efficiency of separate collection of organics is about 61%, it is 49% for non-recyclable paper and even about 20% only for certain categories of compostable, non-recyclable paper. Apparently some more education or a better system of recognition and identification is needed to improve the collection efficiency of man-made compostables.The acceptance and goodwill of the population was significantly higher for the broad biowaste definition, especially in the summer months. The yearly, overall composition of the total curbside waste (biowaste and restwaste combined) is 17% kitchen organics, 47% yard waste, 4% recyclable paper, 13% non-recyclable paper and 19% non-compostables. It must be mentioned that glass, paper and large yard waste are collected separately by a voluntary bring-system. The broad biowaste typically contained 16.0% paper (of which 2.9% was recyclable) versus 2% for the narrow (0.3% recyclable).The aerobic composting process was improved by expanding the biowaste definition through easier moisture control, better aeration and a more tempered pH evolution. A significant difference was seen for NH3 and corresponding odour emission, being much lower in the broad definition. The quality of the compost produced was similar and acceptable for both biowaste definitions.

Energy recovery of used materials can be performed as mixed municipal solid waste (MSW) incineration or as fuel recovery for co-combustion with conventional fuels. Recovered fuels are refuse derived fuel (RDF) which is mechanically separated and processed from MSW, as well as packaging derived fuel (PDF) which is the source separated, processed, dry combustible part of MSW.A one year long co-combustion test of RDF with peat and coal has been carried out in a 65 MW CFB power plant in Kauttua, Finland. The efficiency of the combustion process and corrosion behaviour of the boiler were of particular interest in this study. Five different PDFs were also tested. A wide analytical programme was carried out including solid and gaseous emission measurements.The results are encouraging, showing that RDF and PDFs are technically and economically feasible and environmentally friendly fuels for co-combustion. Low CO emissions showed clean and efficient combustion. SO₂ emissions decreased, because part of the coal was replaced by RDF and PDFs. HC1 emissions increased when the chlorine content of the fuel mixture increased. Heavy metals were concentrated to the fly ash in unleachable form. PCDD/F (dioxin) emissions were at the normal power plant level and far below the strictest incineration limit.Long-term co-combustion of 10% RDF did not cause any high temperature chlorine corrosion of the superheater (500°C) of the boiler. Soot blowing sequences did not change and no fouling was detected.The results show that it is useful, technically possible and environmentally friendly to combine resource and waste management in the form of fuel recovery for energy production in solid fuel fired power plants.

ERRA was established in 1989 by industries involved in the manufacture and sale of packaging. ERRAs mission is to ‘help organise economically efficient and environmentally effective packaging waste recovery and recycling’.

In this paper the Authors discuss the possible utilization of compost in landfills as cover material and biofilter. Compost can act as control layer of water inflow and perform a precious buffering function; contact with compost can remove some heavy metals from leachate under basic conditions. Well cured, unrefined composts can be suitable due to favourable size distribution, low compactability and high permeability.

Biological treatment of hazardous wastes is the application of microorganisms to break down the toxic compounds in the wastes into innocuous intermediates or end products. This paper discusses the basic requirements in order to use biological treatment to stabilize toxic compounds. In addition, the paper presents an overview of available types of treatment, including: in-situ remediation, treatment of liquid wastes, treatment of solid wastes, and the application of compost technology. Finally, a discussion is made of a case study in which oil refinery sludges were stabilized using a composting technology. In the case study, laboratory-scale experiments were first carried out to determine the viability of the composting process. The laboratory-scale experiments were followed by a series of pilot-scale tests, as well as extensive analyses of the gaseous and solid byproducts.

Biodegradable plastics are a new generation of materials, still at an early stage of development. Their development is tied to the growth of composting infrastructures, to the definition of severe standards for biodegradability and compostability, and to the marketing of effective and truly compostable products. The data reported in this paper, show that Mater-Bi Z grades comply with the compostability requirements. The biodegradation studies at laboratory scale, the full scale trials, and the toxicity and compost quality tests prove the compostability of Mater-Bi Z grades according to the scheme followed by the different International Committees (ISR/ASTM, CEN, DIN, ORCA). Moreover, experiments of separate collection of organic waste organized in several European Countries with Mater-Bi bags were fully satisfactory. These data indicate that biodegradable materials are mature for a real industrial development starting from specific applications such as composting bags.

Microbial strain capable of degraded complex polycyclic aromatic hydrocarbons are enought difficult to isolate becouse their scarcity in nature. With increasing PAHs contamination is possible to find sites where microrganisms had developed the mechanisms of adaptation in confront of these compounds. This is expecially true for the community present in soils or sediments that have been chronically exposed to PAHs.

Environmental contaminants such as the monocyclic aromatic group and polycyclic aromatic hydrocarbon (PAH) group can be found in practically all industrial areas. Pollution by these compounds are primarily associated with the processing, combustion, and disposal of fossil fuels. Industrial effluents from coal gasification and liquification processes, waste incineration, coke, carbon black, coal tar, and other petroleum-derived products are all major sources of contamination.

Biodegradation of PAH-contaminated soil was studied by a slurry reactor test and a soil column test. The initial total concentration 1000 ppm PAH soil was decreased to 50…100 ppm in the slurry reactor in 6 weeks. In the soil columns the concentration was decreased to 120…770 ppm in 4 weeks. Addition of coniferous tree bark enhanced degradation significantly in the soil column tests, but not in slurry reactor tests. Use of inoculants had only a slight positive effect in slurry tests; the effect was even negative in the degradation of 5–6 ring compounds in some soil column tests.The experiences were applied to practical scale by using a composting method where bark is used as a bulking agent. High moisture content is maintained in the heap and the leaching water is circulated until the target concentration is reached. The different functions of the bark addition is discussed.

Mature yard waste compost was mixed with pesticide-contaminated soil obtained from an agrichemical retail dealership to determine how much compost was needed to significantly stimulate plant growth, microbial activity, and pesticide degradation. The soil initially contained 1.6 mg kg-1 trifluralin, 1.7 mg kg-1 metolachlor, and 2.0 mg kg-1 pendimethalin. Proportions of the mixes were 0, 1, 5, 10, 20 and 40% compost (w/w). Mixtures were planted with sweet corn (Zea mays) and placed in a greenhouse for 4 weeks. Plant dry matter production, microbial activity (dehydrogenase), and pesticide content were determined. Maximal stimulation of plant growth was found at 20% compost, at which amount, plant growth was 154% of growth in only contaminated soil. Significant increases in soil dehydrogenase were seen at 20% and 40% compost with the activity being 18.8 times higher than it was in only contaminated soil. The soil was inhibitory to microbial activity at all rates of compost addition, with no stimulation in microbial activity at <20% compost. Degradation of trifluralin and pendamethalin was increased at compost rates of 20% or more. Only 40% compost significantly stimulated metolachlor degradation. Percentage degradation of the pesticides after 4 weeks of greenhouse incubation and 16 weeks of laboratory degradation was 85% (trifluralin), 100% (metolachlor), and 79% (pendimethalin). The results indicate that addition of relatively large amounts of compost to soils with phytotoxic and antimicrobial properties can significantly improve prospects for successful remediation, but smaller amounts have no significant benefit.

Within the programme of the Research Centre SFB 188 — entitled Treatment of Contaminated Soils‘ and funded by the DFG (German Research Foundation) since 1989 — one project has been investigating the fundamental principles of the biological treatment of contaminated soils in bioreactors. The aim is to optimize the processes of biological soil treatment so that the highest possible degree of degradation is reached within the shortest possible period of time. Pre-investigations using test systems on different scales will provide information on the potential for enhancement in decomposition processes. This is dependent upon various influencing factors such as milieu conditions, additives, etc., which must be known before remedial action can be taken.The investigations carried out so far have shown that it is beneficial to add compost during the biological treatment of oil-contaminated soils. The degradation of contaminants was enhanced by the addition of compost. This positive effect is attributed to various mechanisms. This paper presents the results from a variety of test systems on different scales.

The compost used, was produced in a pilot plant in which household refuse from Attica Region was treated. The composting took place in piles using forced aeration with air blow and suction. In compost, soil, and manure, that were used for the cultivation of pepper plants in pots and under greenhouse experimental conditions, the following metals were determined: Cd, Cr, Ni, Pb, Cu, Zn, Mn. There were also determined the metals fraction concentrations in compost. In part of the experimental cultivation, natural zeolite was used in various compositions with compost and soil. The natural zeolite used was the clinoptilolite. The removal of metals in compost and the compost-soil system were studied, and the metal contents in the leaves, body, crops, and roots of the plants were determined.The results showed that the plants contained lower quantities of metals when cultivated with zeolite and even lower when more zeolite was used.

Composting is a time-honored, worldwide practice as an inexpensive, effective means of enriching soil for crops and gardens. Over the past two decades, composting has become an increasingly common method for reducing the volume of organic materials – particularly yard waste – sent to landfills. In Europe, the entire organic portion of municipal solid waste (MSW) is often composted. Up until recently, that approach had been less common in the United States; however, as more states enact tougher landfill laws, diverting a higher percentage of organics found in MSW is attracting more interest.

In Austria the separate collection and treatment of municipal biowaste was introduced about 1989, and is now ordered by law since January 1995. From a population of about 7,8 Million, living in 3,1 million households, the expected total quantity of biowaste, coming from municipalities, parks and gardens, and the commercial sector is about 2 million tons per year. This quantity should be collected by the year 2000. At this time about 42% of the organic waste will be managed decentralised and composted by private people and farmers. About 58% of the biowaste is treated in composting plants with a capacity of more than 50t/a up to 100.000t/a. On the one hand in Austria a lot of new biowaste treatment plants have to be built, on the other hand existing co-composting plants have to be reconstructed and enlarged to convert biowaste with aerobic or anaerobic technologies into high a quality compost product.

This study offers an up-to-date picture of the basic processing technologies and composting plant design undertaken in Italy for the treatment of unselected MSW. Present trends in the field of the high quality compost production from preselected organic refuse are here analyzed in order to highlight the different components and sections of the composting plants. A special care was used in analyzing technologies proposed by the different firms for the management of the first phase of the biological process. This work integrates and concludes the state of the art and perspectives about the composting theme developed in a specific report presented in this symposium.

Our goal is to develop design procedures for passively aerated compost piles. In this system, piles are built on a base of porous material such as straw or peat moss. Perforated pipes are placed on this base, and the compost pile built over the base and pipes. The pipes are open to the atmosphere on the ends. As the warm moist air in the compost piles rises, the pipes increase the amount of fresh air drawn into the pile by free convection. The piles are not turned, nor is forced aeration equipment used, which significantly reduces the operating and capital expenses associated with these piles. The specific geometry considered here is that of a long windrow with pipes embedded in the porous base perpendicular to the length of the windrow. Currently, mathematical models are not available that describe these piles to aid in design, and optimum pile configurations and materials are worked out by trial and error.Models are difficult to develop for passively aerated piles because the air flow rate is not explicitly known, but coupled with pile temperature. In this paper, we develop a mathematical model to calculate the upward air flow velocity over a pipe, v_yo, and the fraction of that velocity <m:math display='block'> <m:mrow> <m:mfrac> <m:mrow> <m:msub> <m:mi>V</m:mi> <m:mi>y</m:mi> </m:msub> </m:mrow> <m:mrow> <m:msub> <m:mi>V</m:mi> <m:mrow> <m:mi>y</m:mi><m:mi>o</m:mi> </m:mrow> </m:msub> </m:mrow> </m:mfrac> </m:mrow> </m:math>$$\frac{{{V_y}}}{{{V_{yo}}}}$$ that is present as one moves away from the pipe. The temperature difference between ambient air and the pile is used to calculate the driving pressure drop. This model can be solved analytically, and contains one dimensioniess number <m:math display='block'> <m:mrow> <m:mi>&#x03B6;</m:mi><m:mo>=</m:mo><m:mfrac> <m:mrow> <m:mi>K</m:mi><m:msup> <m:mi>d</m:mi> <m:mn>2</m:mn> </m:msup> <m:mi>&#x03C1;</m:mi> </m:mrow> <m:mrow> <m:msub> <m:mi>K</m:mi> <m:mi>b</m:mi> </m:msub> <m:mi>H</m:mi><m:msub> <m:mi>H</m:mi> <m:mrow> <m:mi>b</m:mi><m:mi>&#x03C1;</m:mi><m:mi>b</m:mi> </m:mrow> </m:msub> <m:mo>,</m:mo> </m:mrow> </m:mfrac> </m:mrow> </m:math>$$\zeta = \frac{{K{d^2}\rho }}{{{K_b}H{H_{b\rho b}},}}$$, which characterizes <m:math display='block'> <m:mrow> <m:mfrac> <m:mrow> <m:msub> <m:mi>V</m:mi> <m:mi>y</m:mi> </m:msub> </m:mrow> <m:mrow> <m:msub> <m:mi>V</m:mi> <m:mrow> <m:mi>y</m:mi><m:mi>o</m:mi> </m:mrow> </m:msub> </m:mrow> </m:mfrac> </m:mrow> </m:math>$$\frac{{{V_y}}}{{{V_{yo}}}}$$ where K is the permeability of the composting material, d is the distance between the pipes, K_b is the permeability of the porous base, H is the height of the pile, and H_b is the height of the porous base. The results of these air flow calculations will serve as starting point to design passively aerated piles.

Odour control is identified as the critical technical issue for the success of composting projects. Tunnel composting has the advantages that the compost can be kept aerobic, all the excess air is collected for treatment and that building corrosion, that leads to fugitive emissions, is prevented. Data is given for the number of installations in Holland and USA. Rough costs indicate that tunnel composting has comparable costs to other s mechanised systems. Two types of tunnel system are described: batch and plug flow and their features compared.All compost projects are subject to the same pressures to a lesser or greater degree depending on the difficulty of composting the source material and local sensitivities. Compost projects fail for 3 major reasons: lack of proper project finance; poor community acceptance normally due to poor odour control and third, lack of product market. The first and the last come down to good management, but some systems are more prone to odour problems than others. Table 1 is a summary of technical factors to consider when choosing a composting system.There has been a gradual evolution and a wider range of wastes composted. In the US there was a large increase in composting following the USDA work at Beltsville in the late 70s. There was a dramatic increase in aerated static pile systems. Many of these early systems have had to be retrofitted with expensive leachate collection and odour control systems. The researchers did not take into account community acceptance as a key issue. This then led to upsurge so called invessel systems in the mid 80s. Some being true invessel built around a silo configuration and others being based on shed or hangar systems where aerated static pile, windrows or a combination has been carried out in a building. Many of the early silo systems had problems, primarily due to poor porosity and mechanical failure. The longitudinal or agitated bin system has proved to be the most robust system of the shed systems and has been widely adopted. There are still some inherent weaknesses due to the possibility of fugitive emissions and building corrosion for the more putrescible wastes which is coming to light for some of the earlier systems.

As programs are being implemented throughout the United States to divert wastes from landfill disposal, composting is continuing to increase in popularity as a means of treating organic wastes. As the number of composting facilities increases, the competition for markets and the importance of producing a high quality compost also increase. This paper provides an overview of composting in the United States, a discussion of compost markets and marketing efforts, and a presentation of factors that affect compost marketing. Trends in composting and compost marketing are discussed, including the use of source separated feedstocks, composting of segregated wastes, and governmental policies that affect composting.

In every major industry, the learning curve associated with the identification, quantification, and understanding of the markets is possibly the most limiting factor to total industry development. The faster the markets are identified, quantified, and understood, the faster the industry will grow. Where little information on the market is available, equally small market development seems to follow.

The qualified separated collection of organic residues from households, gardenand park areas is the actual technical standard in Germany and obligatory as to the regulations of the waste law. The former composting municipal solid wastes has not been proved to be successful.The German Ferderal Compost Quality Assurance Organisation (FCQAO) defined a general quality standard (RAL compost quality sign) and established a nation-wide system for external monitoring of composting plants and compost products. Today approximately 170 compost plants participate in the quality assurances of the FCQAO.The quality assurance programme contains the definition and continuation of quality requirements, the organisation and enforcement of quality monitoring, the punishment of regulation omissions and violations and the labelling of the quality standard.The type, extend and frequency of evaluations depends on the capacity of the composting plant. In order to guarantee an identical standard for the monitoring all over Germany, FCQAO established a central office where all results originated from external monitoring are evaluated.

Excessive cost of producing compost at many facilities through out the world continues to burden taxpayers. Observations on failed designs and management strategies in large scale facilities demonstrate operators have not clearly understood the interrelationship of the biological, physical and economic variables on the cost of production. This paper identifies the major variables under management control and their relationship on the cost of producing compost. Governing equations, based on energy and mass balances and the kinetics of composting, are presented and used to quantify the effects on cost and throughput capacity of in-vessel composting systems as operating practices are changed. Factors studied include air recycling, ambient air conditions, remix frequencies and moisture control, bed depths, fan management strategies (on/off, staged levels), temperature set points, and airflow paths. Data used in the analysis are from both pilot and full scale composting studies.The composting process transforms biodegradables into nonodorous, more stabilized materials. Today it is accomplished using systems identified as windrow with turning, static pile with forced aeration and in-vessel (Anomymous,1991). For the process to be used commercially, systems must be properly designed and operated (Hoitink et al., 1993).The process is governed by the basic principles of heat and mass transfer and biological constraints of living organisms (Keener et al., 1993a). Many researchers have studied such systems and determined operational data for the success of their particular configuration (Kuter et al., 1985; Nakasaki et al., 1987). Haug’s (1980, 1993) books details governing principles and reports on some of the systems that have been used for composting. Keener et al. (1993a) presented analytic expressions showing the interdependence between biological and physical factors. They used these expressions to derive the governing equations for optimizing the efficiency of the composting process. Later, Keener et al., (1993b, 1994) expanded those equations to aid in the efficient design and operation of the air handling system for compost facilities, to estimate remix times and to evaluate water requirements of a composting system.This paper presents data on composting parameters, as derived in controlled experiments, and uses that data to analyze the operation of the composting system.. The reader is referred to Keener et al. (1993a, 1993b, 1994, 1995) for specific details on development of the derived equations used in this paper.

In all a total of 12 papers were presented in this session covering the process aspects of composting on both the macro and the micro scale, and addressing some of the more frequently occurring process problems. The core feature which ran through these papers was the important of a relatively few process characteristics during composting itself. Essentially these are: the amount of aeration;the process operating temperature(s); andthe moisture content of the composting mass.

A wide range of waste materials used for composting – organic and inorganic – was reported in the fourteen paper presented in this session. From lignin containing materials through agricultural wastes including composting of whole pig and poultry mortalities), grass, sludges and even diapers from the urban sector to the use of bauwte and coal ash. Solid wastes such as these to the more intractable and problematical organic liquid wastes, such as cattie slurry and olive-mill wastewater were discussed. A session that proved once and all that if the substrate/waste is organic it can be composted; if the waste is inorganic it can be incorporated into the process.

The specific challenges and operational experiences were reported by the presenters who described the status of composting in Austria, Brazil, Denmark, Finland, France, Italy, Japan, Spain, and the United States of America. The specific challenges included the following themes which were cited by most presenters: The need to overcome legislative barriers and enhance economic incentives so private companies will assume a greater role in composting;The need to integrate waste management solutions into the framework of societal issues – and to explore the links between quality of life and recovery of organic residuals;The need to build on the awareness of the relevance of composting through research on critical issues, and to identify those issues and use research centers more effectively to develop solutions;The need to form new partnerships among the private sector, government agencies, nonprofits in order to expand the impact of composting projects. To achieve successful partnerships, it is necessary to aggressively show the common interests of environmentalists, industry associations, private corporations and public policy-makers;The need to develop the diversity of approaches in managing and recycling organic residuals. These approaches range from decentralized, backyard programs using home compost bins and regional ‘self-composting’ to curbside collection of source-separated residential organics and residuals from commercial generators where they are composted at centralized facilities. The diversity also relates to combinations of aerobic and anaerobic systems to produce energy in the form of biogas as well as soil-improving materials for application to farms and gardens.

The intention behind the session was to avoid the possible overfocussing on the specific composting/biogasification problem, and to avoid the kind of composting euphoria or megalomania that has caused very serious harm to the acceptance of biological treatment in the past.

In this session, a total of seven presentations were made. Five presentations dealt with bioremediation of contaminated materials, one covered the “removal” of heavy metals by the addition of a natural zeolite, and one discussed the application of starch-based biodegradable materials in the separate collection and composting of organic waste.

Six papers were presented in Session 5B, each addressing aspects of composting plant design. A brief summary of each paper is presented along with the moderator’s closing comments.

In the session on marketing and economy, live presentations were given: two dealing with the importance of marketing efforts and markets for composts; one dealing with the principles of the German quality assurance program; one on the activities of the Italian Composting Council; and one on economic modeling.

Olive press cake are solid agroindustrial residues produced during the extraction of olive oil, disposal of wastes produced during this process is a particularly pressing problem in Southern Spain and other mediterranean countries. We developed a pilot-scale windrow composting process for optimal transformation of this kind of substrate, characterized by a high lignocellulose content. We found that the 82% of lignocellulose degradation took place when temperatures were above 50°C. After three months temperature was still relatively high; this notwithstanding the phytotoxicity of the compost was almost nil as demosntrated by biological tests.

The amino acid composition of composts derives in part from the original amino-acid pool of the substrate and in part from extracellular enzymes and cells of the dead and living micro-organisms. Because of their high biodegradability, the relative molar distribution (RMD) of amino-acids in compost depends on a balance between re-synthesis and decomposition and should be related to changes in microbial community. The total amino-acid content increased sharply during the first days of composting fairly as a consequence of weight loss and remained fairly constant up to the 75th day of composting, decreasing thereafter during the curing period to about one half of the maximum value obtained (139 mmol/100g). The RMD shows a decrease in acidic amino-acids and particularly in the content of glutamic acid (11.19% at 7 days and 7.75% at 100 days), with a concomitant increase in cystine (6.85% at 7 days and 10.07% at 100 days) and methionine (8.45% at 7 days and 11.95% at 75 days). Comparison with previous work suggests that changes in RMD are related to process strategies.

In order to produce high quality composts it is necessary to start from selected organic wastes, non polluted by heavy metals and with limited inerts and unwanted materials. The source separation of municipal solid wastes and especially the separate collection of wastes from specific categories of producers, can help to supply good quality waste material s that can be composted together with yard wastes to advantage. This poster reports the most important results of a wide range of experiments, carried in Piedmont (Northern Italy), on separate collection of organics from specific categories of producers such as restaurants, canteens, and vegetable markets, foodstuff stores, and so on. Chemical characteristics and composition of these wastes were compared with those of mixed municipal wastes selected after collection.

Composting treatment reduce the volume of refuse to be dumped in landfills since household waste will thus lose a large portion of its organic components. Correctly implemented, composting is a reliable method of transforming the putrescible organic matter of wastes in to a soil conditioner.

The composting of organic wastes rich in easily biodegradable nitrogen compounds leads to, 1986). Mixing these organic wastes rich in nitrogen with lignocellulosic wastes which have high C/N ratio can result in partial incorporation of N into the organic fractions through immobilization (Bernal et al., 1993). Therefore, selecting the appropriate waste mixture may be an appropriate way of reducing ammonia losses during composting. Frequent turning of the pile may facilitate this NH3-volatilization (De Bertoldi et al., 1982). It might be possible to control NH3-volatilization by using the Rutgers static pile system which can also regulate the organic-N mineralization through controlling the pile’s ceiling temperature during composting.

Determination of the biomaturity of a compost is a critical point. It can be estimated by chemical analysis or optical measurements (Mathur et al. 1993). N-mineralization and N– immobilisation of composts can be assessed by the method of incubation and by germination tests. However, these methods are time consuming. We therefore compared facile and quick tests with those standard methods.

Composting is a process whereby organic matter is decomposed by a mixed population of microorganisms in a warm, moist, and aerobic environment. The process involves the interaction of several parameters which do not behave linearly with time and which have time constants varying between days and weeks. The complexity of the interactions between parameters produces several ecosystems which prohibit accurate modeling of the process in the form of differential mathematical equations. Physical modeling of composting [5] has been done but this imposes several constraints. Thermal balance analysis [6] may give a better insight of the process but performance prediction would not be possible because the equations might not be valid if the operating conditions change as is always the case in practice. On the other hand, engineers and scientists know the causes and effects of many parameters involve in composting. Since we know beforehand what effect (large, small, positive, negative etc.) different parameters have on one another, composting process can be treated as being ‘fuzzy’.

Composting is a self-heating, aerobic solid phase biodegradative process of organic waste materials, making possible its return to the environment as soil fertilizer and conditioner (Finstein & Morris, 1975; de Bertoldi & Zucconi, 1987; Finstein, 1992). Temperature increase involves a rapid transition from a mesophilic to a thermophilic microflora (65–75 °C) within a few hours, providing the pile is regularly aerated or frequently turned.

Commercial humic solutions are used in agriculture in order to enhance mineral nutrition of higher plants (Garcia et al. 1993), and especially P nutrition (Gaur 1969). The decisive effect on P dynamics (Rouquet 1988) has often been correlated with the complexing power towards di or trivalent ions, like calcium ions in calcareous soil. In the investigation reported, the effects of two commercial humic solutions on the phophorus exported by pot grown Italian rye-grass were compared after determining their caracteristics.

Each year during the period 1991 to 1994, three different types of input material (yard waste, biowaste and cattle manure) were composted and subsequently evaluated for their suppressiveness towards Pythium ultimum and Phytophtora parasitica spp.. This was achieved by means of bioassays conducted in a sterilised substratum (sand) employing the host-pathogen systems peas – P. ultimum and in non-sterilised substratum (commercial peat based potting mix) applying the host-pathogen systems peas or cucumber – P. ultimum and tomato – P. parasitica nicotianae. Amendment of P. ultimum inoculated sterilised sand with yard waste- and biowaste compost resulted in a significantly increased yield (fm). This was mainly due to pathogen suppressive biological mechanisms induced by compost. Composted cattle manure showed such an effect only occasionally. In experiments where 90% of control treatment plants were damped off, compost addition, apart from cattle manure compost, resulted in a reduction of the disease incidence by 30 to 50%. In bioassays with soils naturally infected with root-rot pathogens of red beet, however, we also observed some suppressive effects of cattle manure compost.Contrary to cattle manure compost, both yard waste- and biowaste compost show a high level of specific microbial activity, i.e. a high rate of Fluorescein diacetate-hydrolysis per unit microbial biomass. Therefore, micro-organisms originating from both waste composts are better competitors for easily available carbon sources. This results in a fungistatic effect towards pathogens since these organisms depend on the same carbon sources. This has been shown by the suppressive effects towards P. ultimum of a 50% yard waste compost amendment of a peat growing media in comparison to non-amended pure peat growing media. The two waste composts have been evaluated in non-sterilised container media in all other above mentioned host-pathogen systems. Yard waste compost application rates between 30% and 50% (v/v) resulted in a significant reduction of the disease incidence of at least 45% for cucumber, peas and also tomatoes. Due to a higher nutrient and salt content of composted biowaste, the application rate of this material was limited to 30% (v/v), resulting in a reduction of the disease incidence by 10–20%.With a St. Paulia – P.parasitica bioassay similar results were obtained during a cultivation period of 14 weeks. Compost amendment of 30 and 50% yard waste compost, respectively, to a non-sterilised peat growing media significantely prolonged the time until plants died.

The vermicomposting is a process widely employed for ecological recovery and transformation of biological sludges into ‘casting’ with a high fertilising value. While practical and scientific aspects of the process have been already studied and, for most part, understood both in laboratory and in pilot experiments, the legislative aspect is, still nowadays, very confused and lacunous. In fact, there are many national (Italian) laws which regulate the composting and vermicomposting and which overlap to regional legislation. Contrasts in defining the wastewaters origin (industrial, urban, municipal or assimilable to the municipal ones), in technical aspects of sludge processing, in finai classification and use of ‘stabilised’ product, are frequently encountered. In this work, attention has been focused on the technical aspects of sludge vermicomposting and on the legislative aspects to classify the product as a ‘compost’ according to the DPR 915/82.

Vast amounts of olive-mill wastewaters (OMW) are produced in Mediterranean countries causing very serious environmental problems either through spreading on agricultural land or storage in ponds. A wide variety of technological treatments are available to reduce their polluting effects and for their transformation into valuable products (Fiestas Ros de Ursinos and Borja Padilla,1992). However, very few data, if any, have been published on OMW composting. This paper reports a methodological approach for transforming these wastewaters into organic fertilizers by letting them be absorbed by plant waste materials which were later composted.

Composting of municipal solid waste (MSW) was studied in an attempt to better understand the composting process and define parameters of maturity. Composting was performed in l–m3 plastic boxes and the following parameters were measured: temperature, C/N ratio in solid and liquid phase (C/N(s) and C/N(w) respectively), humic substance fractions and contents, dissolved organic carbon (DOC). Spectroscopic method (DRIFT) was used to study the chemical composition of the bulk organic matter (OM). A bioassay based on cucumber plants growth was correlated to other parameters. C/N(w), C/N(s) and DOC showed high rates of change during the first 60 days, then stabilized. Humic acid (HA) content increased to a maximum at 110 days, corresponding to the highest plant dry weight and the highest 1650/1560 (cm–l/cm–1) peak ratios from DRIFT spectra. DRIFT spectra showed that the OM transformed to a more aromatic structure.

The stabilization level of the organic matter of compost from MSW has been monitored using the degree of humification (DH), the isoelectric focusing (IEF) and a Bimodal Gaussian Distribution (BGD) of pK of –COOH and phenolic –OH groups of HA. The results obtained show that these methods are able to monitor the processes.

Since 1985, the research section of Minoprio Foundation has been testing different composted materials of vegetable origin as components of growing media for ornamental pot plants. The study of the relationship between physical and chemical characteristics of composts and plant quality gave the opportunity to obtain good quality plants in cultivation trials, even by reducing the quantity of peat in the substrate until 1/3 of the total (Lamanna et al., 1991).

The European Directive on Packaging and Packaging Waste, recently promulgated, considers composting as a form of recycling of biodegradable packagings. To become effective the Directive must be endowed with technical tools such as definitions, criteria, and test methods. CEN (Comité Européen de Normalisation), the European Standardisation Committee has established on 1991 a subcommittee (TC261/SC4) named ‘Packaging and the Environment’ to provide the technical and standardization support to the Directive. Within this subcommittee the Working Group 2 (WG2: ‘Degradability’) is defining a test method to measure the biodegradability of packaging in composting conditions. Both this test and ASTM D5338–92 are derived from a proposal of Organic Waste Systems (Gent, B) and based on the measurement of CO₂ evolved by the test substance in conditions simulating the composting environment: aerobic fermentation, solid state, high temperature, and inoculum particularly rich in thermophilic microorganisms (mature compost). In order to verify the accuracy and precision of the method and gather useful data for the final standardization, the CEN TC261/SC4/WG2 has organized a ringtest at European level using cellulose, paper and Biopol, a polyhydroxyalcanoate, as test materials. In Italy NOVAMONT, a Company actively involved in the development of biodegradable materials, has taken part to the ringtest. A comprehensive description of the results of this testing activity will be soon published by the WG–2. In this presentation we describe the technical approach followed by us to set-up the test procedures and test apparatus.

Organic wastes from different sources determine the variation of several soil physico-chemical parameters such as pH, heavy metal content, redox potential, complexing activity and degree of humification, what may affect the soil fertility in a positive or negative way. The organic fraction of low molecular weight is involved in ionic mobilization and humification processes, its presence is particularly important in soils with a low level of organic matter and micronutrients.

Maize (Zea mays L.) is widely distributed in tropical and temperate regions, being an important cereal used for both human and animal consumption. Inorganic fertilizers can be too costly and out of reach for small producers, being unable to sustain soil fertility and also posing environmental risks of nitrate pollution of ground water table (Maynard 1994).

Mediterranean areas are specially affected by a soil organic matter decrease due to the drop of agricultural productivity and the deterioration of soil (desertization process, salinization, forest fire, etc.). On the same time, this waste may pollute the pedological environment because of its high contents of heavy metals and plant-damaging organic compounds.

Beet vinasse, a high density liquid waste from the sugar industry, and grape marc, a primary by-product of wine production, could be recycled as fertilizers due to their high OM and nutrient contents. The direct incorporation of grape marc into agricultural land, a common practice, has become a serious problem because degradation products inhibiting root growth are released (Inbar et al., 1991). Furthermore, the direct aplication of vinasse has also several shortcomings because of its high salinity (EC 250–300 dS m–1), low P content (P₂O₅ 0.012%) and liquid dense character (1.3 g cm–3). An alternative to overcome these disadvantages is the co-composting of vinasse with grape marc.

Increasing amounts of liquid and solid wastes are produced by the food and agricultural industries in Andalusia. However, the recycling of these residues is not always billed and their elimination, is, at times, an environmental problem. Beet vinasse, a high density liquid waste from the sugar industry, contains high levels of OM (35%), N (3%) and K (3%), which make the vinasse a potential fertilizer. However, the direct application of concentrated vinasse on agricultural land may lead to economical and environmental problems because of high salinity (EC 250–300 dS m–1), low P content (P2O5 0.012%) and its liquid dense character (1.3g cm– 3). The co-composting of vinasse with other agricultural residues could be used to overcome these disadvantages by producing a compost easily handled with higher P content and lower salinity.

The composting of town refuse is an interesting tool for waste management: compost is a major source of organic matter and fits completely into the framework of the recycling of organic waste. However, in order to be able to spread compost on different soils and to meet the various agricultural requirements, it is necessary to know perfectly the evolution of organic matter and the characteristics of the end-product. The composting process can be divided into two major stages: a rapid degradation of the easily degradable insoluble components into water-soluble compounds, and subsequently the metabolization by microorganisms of the latter and of the less degradable compounds. Many tests and criteria have been experimented for the long term monitoring of organic matter during the composting process as a whole whereas a less attention has been paid to monitoring merely the first stage of the process. Butyric, propionic and acetic acids are water-soluble intermediate compounds formed as organic matter are broken down. A better follow-up of the first stage of the process is necessary to avoid the presence of these phytotoxic compounds (DeVleeschauwer et al., 1981; Cocucci et al., 1989) in the end-product. Whereas volatile fatty acid (VFA) concentration is a parameter which has been widely used to monitor the anaerobic digestion (Azinari di San Marzano et al., 1981; Henson et al., 1986, Mata-Alvarez, 1990) of organic waste, it has rarely been used for the evaluation of the composting process evaluation (Saviozzi et al., 1992). In this work, it is proposed to use the VFA as the means to monitor organic matter during the first stage of composting while, for the characterization of the maturation level, a new index of maturity, based on rapid spectrophotometric measurements, has been proposed in previous works (Prudent et al., 1994, 1995).

The large amounts of slurry wastes produced in intensive farms cause serious disposal and pollution problems. Composting of slurries from animal waste offers an answer to odour nuisance and water pollution associated with their management. The aim of this research was to carry out a preliminar laboratory study trying to transform slurries into compost so they can be used as horticultural substrates, organic soil conditioners or fertilizers.

Landfillings restrictions and more stringent regulations on product spread on the fields oblige sludges and wastes producers to improve practices and quality.

Composting is proposed as a solution capable of meeting the twofold requirement of giving a correct solution to the disposing of waste biomasses and waste of different origins, pursuing recovery and valorization standards, while producing plenty of cheap organic fertilizer.

Compost can be used in floriculture and in horticulture within integrated and biological disease control programs (1–2–4). It is in fact well known that vegetables and ornamental plants are often damaged by pathogenous fungi causing damping off and root rot.

Olive mill waste waste (alpechfn) is a liquid agroindustrial residue produced during the extraction of olive oil. Disposal of waste water is a problem because of its phytotoxicity and difficulty of handling. We tried to eliminate the phytotoxicity of alpechfn by absorbing it on composted organic matter and posterior incubation. When this waste water was absorbed on compost, a great part of its phytotoxicity was chemically neutralized, and also had positive effects on plant growth. These effects increased with time of incubation of the alpechín/compost mixtures.

Modern crop production in Europe does not have sufficient farm animal waste byproducts to maintain crop yields at current levels and as a consequence relies heavily on the use of cheap easily available mineral fertilizers. A deterioration in soil organic matter and soil structure has been a consequence of intensive crop production and is especially evident with intensive cereal production. In the UK the area of cereal production has reduced slightly in the last 2 years due to CAP Reform measures and the introduction of set-aside policy but there has been a marked increase in the area of arable fodder crops grown particularly forage maize. Traditionally forage maize is grown in the UK without the use of much fertilizer but with the use of large quantities of farm animal waste particularly cow slurry. However, the expansion of the area of forage maize now exceeds cow slurry availability.

In Galicia (NW of Spain) there are wide extensions of forest destined to wood exploitation. Pteridium sp. and Ulex sp. are two common scrub species and they became into forestry wastes when cleaning works are made to minimise burning risks.

Composting is an aerob process. Aerob microorganismens need at least an oxygen-concentration of 3 Vol.–% to take part on the degradation of organic matter. If the oxygen-concentration is getting too low, anaerobic organismens become dominant. They produce oder and greenhouse gases. To avoid this effect all instruments must be used to increae the O₂–concentration in the plant.

Composting is Mother Nature’s original form of recycling. Simply, composting is the controlled biological decomposition and conversion of solid and liquid organic materials into a humus-like product. Managed composting, while somewhat limited in the U.S. since the green revolution, is a popular and successful animal waste and plant residue management option world-wide. It is more preferable to landfilling, incineration and roadside dumping. The benefits of the act of composting include a reduction in volume of compost inputs, destruction of pathogens, reduction in weed seeds, the degradation of many potentially harmful organic compounds, the binding-up of high-nitrogen materials such as manures, and the production of a useful soil amendment.

The field straw windrow composting study showed that a minimum of two turns and natural rainfall was required to reduce straw residue volume by 80% or greater in 16 to 21 wk. The decomposition of the high C:N ratio straw residue is contrary to established composting methodology where a C:N ratio of 30:1 or less is thought to be required to compost grass straw. The microbial biomass required more C and less N to function in the thermophilic treatment compared to the LT treatment. The microbial biomass N requirement was less than 4% of total straw residue N in both treatments. The low N requirement of the decomposer biomass indicates that the form or compartmentalization of N is more indicative of substrate quality than the concept of combined substrate C:N ratio. The increased requirement of the thermophilic biomass for C resulted in an increase in the decomposition of the lignin fraction compared to the LT treatment. The increased lignin fraction decomposition was detected through changes in the element composition of this fraction. For these reasons, the composting of grass straw residue is feasible without initially lowering the C:N ratio. Composting has value both as an avenue of straw disposal and for its potential for utilization in the cropping system. Volume reductions of straw windrows in this study were as high as 88% over 32 wk making in-field composting a viable straw disposal alternative to open field burning.

The following case study evaluates the development of a system of separate collection and composting of ‘greenwaste’(from garden— and park—areas) and ‘biowaste’(from the separate collection of municipal solid waste) in an Administrational District around the city of Kulmbach in Northern Bavaria/Germany. Greenwaste is brought by the citizens to decentralized, farmbased compost-sites. Biowaste is collected by the municipality in a separate ‘biobin’ and brought to biowaste-compost-places, which are connected to greenwaste-sites.Seven years after start 17.500 tons per year, or 170 kg per citizen are recycled on 14 compost-places and two biowaste-sites. Costs per input-ton are low, citizens accept the sites well, the system is modularly adaptable to changing requirements and can be directed by one central office.

During the process of composting, organic material is turned into the stable final product compost. It is performed by microorganisms causing the degradation and conversion of the organic material. Therefore, the main target of processing is to create optimal living conditions for the microorganisms.

For composting firms, compost producers and compost users it is very important to measure the compost maturity, cause of process control, process optimation, comparison of the process efficiency of different composting systems and application effects of the compost itself. Founded on experiments in aerated and non-aerated composting systems new aspects for the assessment of stabilization during biowaste composting have been achieved.It could be shown that the parameters respiratory activity and self heating rate are influenced by organic acids. This dependency seems to be the most important reason for the failures made in the measurement for compost maturity.Based on these results the suitability of the parameters to characterize the real rotting process can be shown. Also suggestions for improvement are given to minimize the failures and to increase the transferability and the quality of the results.

Gicom B.Y. is developing and design ing facilities for composting in tunnels. The composting process is fast, the system is closed, and the process control is optimized. The Gicom tunnel composting system is able to transform a variety of organic waste streams into compost, such as:biowaste (source separated domestic waste)municipal solid wastesewage sludgeindustrial sludgesmanureanaerobic digestion process residuescontaminated soil

Composting at industrial scale (installations treating. 100 tons per year) is increasingly used in Switzerland for the stabilization of organic waste and the recycling of humigenic materials. In 1992, 320.000 tons of garden and kitchen waste were treated in 150 composting sites, 80% thereof treating more than 1.000 t/a (1). Even if mature composts are generally of satisfactory quality, the process itself could often be considerably improved. Our research team is currently involved in a threeyear study that aims at optimizing the thermogenic phase of composting processes, in order to ensure a good thermo-hygienization (elimination of allergenic and pathogenic micro-organisms, e.g. the thermotolerant mold Aspergillus fumigatus) and to improve the number and diversity of the thermophilic micro-organisms. This will lead to a rapid degradation of the organic material. By this, phytotoxicity hazards can also be avoided.

The recycling of the organic wastes from different industries could satisfy the increasing demand for organic materials in agriculture and horticulture.

The CEC Directive 271/91 requires more stringent nitrogen and phosphorous standards in the wastewater discharged from treatment works. The reduction of the heavy euthropication problems in several European areas of the Mediterranean Sea (high Adriatic Sea) is a prioritary task, and the action is oriented at reducing the MSW (Municipal Solid Waste) addressed to land fills and /or incineration by increasing the performances of wastewater treatment plants.

The number of inhabitant s in Helsinki metropolitan area is 850000. They produce annually over 300000 tons of municipal waste, of which about one third is of rapidly decomposable biological origin. In April 1993, collection of source separated household waste and municipal biowaste was started in a large scale in the area by the the Helsinki Metropolitan Area Council (HMAC). This study is a part of the larger project conducted by the HMAC and the Technical Research Centre of Finland (VTT) which will find out ways to recycle the source separated biowaste. Theaim of the present study was to clarify the suitability of the biowaste for agriculture with the aid of physico-chemical analy ses and pot experiments which were carried out by the Agricultural Research Centre of Finland (MTT).

The use of compost for sustainable agriculture can suitably furnish the nutrients to plants and improve the soil fertility in terms of biological and chemical status. Effects of compost have been evaluated during the maize growth season as changes in the forage yield, the soil microbial biomass content, the soil metabolic quotient and the availability of nitrogen. Soil was analysed in correspondence of four different maize growth stages (lstsampling before compost and inorganic N application, 2nd sampling during stem elongation, 3th during flowering and 4th during milk maturity of maize).

Ascariasis effects approximately one quarter of the world’s population and is particularly prevalent in developing countries. As improvements in sanitation in most of these countries becomes more widespread, composting of human excreta and sewage sludge has become a popular and cost effective method for the disposal of these products, as well as offering a valuable source of organic fertiliser. If, however, the composting process is not properly controlled there may be a potential risk from pathogen and helminth infection to workers handling the compost and consumers of foodstuffs grown on land treated by the compost.The work carried out has examined the effect of compost on the development and the viability of ascarid embryos within their protective eggshell, in an attempt to establish any mechanisms which may be involved in the destruction of these eggs. Ascaridia galli eggs were used as a model for Ascaris lumbricoides eggs. These were suspended for a period of two to three weeks in compost and microorganism free compost extract, as well as in distilled water controls. In the first set of experiments, approximately four week old municipal waste compost was used, while in the following set of experiments approximately one week old compost was used. The results showed that both the one week old and the four week old compost extract retarded the development of the Ascaridia galli eggs suspended in them. This effect was seen to be more pronounced in the one week old compost extracts. No such delay in the development of the A. galli eggs was observed in the micro-organism free compost media. In spite of the observed delay in the development of the A. galli eggs suspended in the compost media, the viability of the eggs was unaffected. The observed delay in development was thought to have resulted from some form of microbial and/or fungal activity which would be present within the compost suspensions but not the micro-organisms free environments.

There is a growing emphasis on the composting of yard trimmings because of governmental bans on land-filling and incineration of leaves, grass and brush in many parts of the U.S. A primary concern with the composting of yard trimmings is the lack of knowledge about the fate of commonly used lawn care pesticides during composting. The purpose of this report is to summarize our recent findings on the fate of the most widely used lawn care pesticides 2,4–D (2,4–dichlorophenoxy acetic acid), Diazinon (O,O–diethyl O–[2-isopropyl–4–methyl–6–pyrimidinyl] phosphorothioate) and Pendimethalin (N–1–[ethylpropyl] 3,4–dimethyl 2,6–dini-trobenzamine) during the composting of yard trimmings.

Composting of food store organic wastes is an attractive alternative to incineration, or disposal of these wastes in land-fills. In this study, the total wastes as well as the organic wastes generated by individual departments in a typical U.S. food store were quantified and characterized and the organic fraction of the wastes was composted with leaves to determine the qualities of the finished compost.

Heavy metals (HM) are both hazard to human health and risk to the envinronment, the presence in composts has been estabilished as the main problem involved in the their use. The HM that are considered in italian legislation are As, Cd, Cr, Cu, Hg, Ni, Pb, Zn and limits are fixed for them in the compost and in soil (Ref. 1).

In the Perth metropolitan area, sludge from primary and secondary treatment is anaerobically digested in a two phase, mesophilic process, before being dewatered by belt press or centrifugation. Currently, all of the sludge produced is either stored on site, or composted by contractors and sold as a soil amendment. The composting processes and the quality of the marketed product are currently not subject to regulation. However, sludge use guidelines are expected to be released, which will specify a range of requirements for sludge based products intended for land application.

The main purpose of this work is to study the effect of sweet sorghum bagasse compost application on biomass production of sweet sorghum (Sorghum bicolor (L.) Moench cv Dale). Biomass production was studied in terms of dry matter and stalk sugar content, at the end of the crop cycle. The addition of compost to soil produced significant increases on sorghum productivity with regard to the control. Best results have been achieved with the composts obtained from a sweet sorghum bagasse and pig manure mixture (30t/ha). In this case, the aerial dry biomass increments with regard to the mineral fertilizer treatment was 37%, where the irrigation was 2/3 of the available water.

The composting plants for source separated household waste in Aarhus, Denmark, and Creusot-Montceau, France, are designed for the newly developed and patented Compodan process. The plant in Aarhus was put into operation in March 1995. The Compodan process features rapid process set-off, uniform process conditions and a built-in biofilter. In the reactor, the waste admitted on a daily basis is decomposed in 35 days.

Adsorption and desorption properties, of a magnesian vermiculite (VMg), have been used to follow the dynamic of the NH₄+ ion ,which has been produced during the ‘cellulotytic-diazotroph’ association appeared during the aerobic fermentation of a mixture of wheat straw and poplar sawdust.This fermentation has been regularly followed for three months in a mini digestor, and temperature, ventilation, pH, humidity, and C/N ratio of macro-elements were controlled. The same is done for the associative activity of cellulolytics and diazotrophes (NUNTAGIJ, et al., 1989). However, if fermentation is not carried out under optimal conditions, there is a loss of ammoniacal nitrogen, and that often occurs during large scale composting of organic residues (MARTIN, 1991). Clay properties can be used to control this loss. Four types of vermiculites are chosen to do so: a natural vermiculite (VMg), an NH₄+ saturated vermiculite (NH₄+), a calcium and ammonium-saturated vermiculite, only in exchangeable position (VCaNH₄+) and a vermiculite having exchangeable oligoelements (VMgCaCuCoMnZn).

Although technologies for making compost are well developed, index for assessing the quality of product is a difficult issue. There are several parameters in the literature and the subject have been reviewed several times. Some problems related with topic of compost quality or maturity are the wide diversity of substrates which can be composted, the wide number of index proposed and the lack of results of applying the index to compost from different origins and nature. In our point of view the main difficult is the lack of a patron.

The plant availability of municipal sewage sludge-borne phosphorus (MSS–P) and its effects on various soil P forms were investigated in a pot experiment using single superphosphate P (SSP–P) as the standard P source. Unlimed (control) and limed (pH 6.64, 7.19) samples of a silt loam soil [pH(H₂O) = 5.72] were mixed with 134 mg P kg–1 dry soil in the form of SSP or MSS, labelled with 32P tracer and gown with ryegrass (Lolium perenne L.). After harvesting the rye-grass plants at the earing stage, the soils were sampled and extracted sequentially with resin in the Cl– form followed by 0.5 M NaHCO3 (pH 8.5), 0.1 M NaOH and 1.0 M HCl solutions for P analysis. The sum of resin- and NaHC03–P levels as well as NaOH– and HCl–P levels were designated as the labile and nonlabile P pools, respectively. Relative MSS–P uptake established by 32P tracer averaged 8% (range 7.4–8.9), whereas the corresponding average MSS–P uptake established by the difference method was 7.5% (range 3.8–14.5), with lower values recorded in the limed soils. Liming and applications of SSP and MSS significantly (P = 0.05) increased soil levels of resin- and inorganic NaHC03‱P. Liming decreased organic NaOH‱P levels, whereas organic NaHC03–P and HCl–P levels did not significantly (P = 0.05) differ from that in the control treatment. MSS–treatments were, on average, less effective than the corresponding SSP–treatments at elevating the labile P pool sizes, whereas they were more effective than the latter at increasing nonlabile P pool sizes.

In the Mediterranean areas a great stream of liquid waste, roughly estimated in about 10 million tons, is yearly produced by olive mill industry in a short rainy season (November–February). In spite of the existing laws, olive mill wastewaters (O.M.W.) are often disposed of in the environment or collected in lagoons, with a consequent pollution linked to odours, insect proliferation and sludge production. To solve the problem, both clearing and recycling have been proposed (Fiestas Ros de Ursinos & Borja Padilla, 1992). At present, recycling rather than cleaning seems to be the most suitable solution. From the standpoint of the waste recycling for agronomical uses, the direct disposal onto soil has been taken into consideration (Andrich et al., 1992; Riffaldi et al., 1993).

The European Parliament and the Council of the European Union have recently finalized a Directive on Packaging and Packaging Waste. This foresees that, no later than five years from the date by which the Directive must be implemented in national law, between 50–65% by weight of the packaging waste should be recovered from the waste stream through recycling, reuse, or incineration with energy recovery. Recycling will cover the 25–15% of the totality of packaging materials contained in packaging waste. Composting is considered as a form of recycling of biodegradable packagings and it will have an important role in the rational management of waste. The definition of the criteria by which a material can be considered as compostable and recycled by composting is, therefore, a topical issue. International organisms such as the ISR/ASTM, CEN, ORCA have been constituted with the aim to define the compostability criteria. The fundamental requirements are: biodegradability, absence of negative effects on the quality of the compost, absence of negative effect on composting process. The first two conditions are determined at laboratory scale following the mineralisation of the test material and analysing the final compost quality. The laboratory data and the effect on the process should be verified in a composting plant.

Animal manure, with the exception of poultry, generally has a low fertilizer content. Consequently spreading cost is higher than chemical fertilizers. The organic matter content of animal manure is not good enough to raise its fertilizer value; in fact the low degree of humification helps little in raising the soil organic matter content. Composting is a good way of improving the fertilizer value of animal manure. This paper presents the results of a series of experiments performed by the C.R.P.A. and supported by funds from the Emilia-Romagna Region, Agricultural Department.

Untreated wastewater sludges have been successfully composted without the addition of bulking agents - straw, paper, green or municipal wastes - to form a stable soil conditioner.The advantages of this process are the minimal loss of nutrients, linked with a reduction in organic and volatile matter and moisture content. There are savings associated with construction, handling, transport and distribution costs.This material is one of a range of products manufactured by the company for beneficial reuse in agricultural land. If deregulation of current sludge legislation occurs, it is anticipated that this product will be in demand for other markets.Following successful trials at Horsham Wastewater Treatment Works, Sussex, Southern Water has formed a partnership with Sevar GmbH, Brackett Polcon and Tilbury Douglas Construction to build a pilot plant to 2000 tonnes of dry solids per annum of dewatered wastewater cake at the new Weatherlees Wastewater Treatment Plant on the East Kent Coast, at a cost of £3M.

The rooting response of three ornamental shrub species (Weigela florida, Deutzia gracilis, Kolkwitzia ‘Pink Cloud’) was tested in media made of pharmaceutical, village waste and farm yard manure composts.The properties of media were analyzed to investigate factors which are of most importance for the development of roots. Special attention was given to the measuring of the physical properties of the media due to their cruci al importance for root development.Farm yard manure compost and village waste compost have proved to be suitable materials for rooting media. Pharmaceutical compost is not suitable for wider use due to its physical properties and high electrical conductivity.

The trials were carried out by the CRPA on behalf of INALCA SpA at one of the biggest slaughter houses in Italy situated in Castelvetro, near Modena, where an average 500 head of beef cattle are slaughtered daily. They show a desire to introduce composting technology into a reality where a demand for quality is essential for the success of the technique.

Organic material has undeniable an influence on the soil ecosystem, including the population of soil nematodes. In this experiment, the influence of GFT-compost extracts on the motility of juveniles of H. schachtii is investigated. As reference Hoogmeerturf (a white peat) extract was taken, because there is no suppressive character against nematodes described for peat.A significant (p = 0,05) reduction of the motility of juveniles of H. schachtii was determinated from day 1 to day 4 after adding GFT-compost extract against as well the control (water) as the Hoogmeerturf extract (reference). The reduced motility couldn’t be explained by the concentration of organic acids.

There is a suppressive character described for several kinds of compost against soil borne pathogens (fungi). In this experiment there was a suppression of Penicillium digitatum in vitro after addition of extracts of GFT-compost or Hoogmeerturf (a white peat). Although there are only a few sources who reports a suppressive character of peat. The suppressive character of GFT-compostextract was a result of the high bacterial activity, while the great number of fungi (i.a. Trichoderma spp.) were responsible for the suppressive character of GFT-compost. The use of microfiltrations allowed to distinguish between the biotical and abiotical factors responsible for the suppression. The autoclavation of the Hoogmeerturfextract destroyed the suppressive character; in contrast the GFT-compostextract maintain his suppressive effect after autoclavating as a result of the allelochemicals.

Effective cation exchange capacity (ECEC) of mature manure-straw compost was determined by saturation-exchange method. Analysis was carried out on either fresh or dried and ground composts.Drying of the sample increased ECEC values, whereas drying accompanied with grinding did not seem to have any effect on ECEC, as compared with ECEC values analyzed from fresh compost.This study implies that ECEC determined of samples which are dried and ground describes well the actual cation exchange properties of the mature manurestraw compost, and that fresh compost can also be used for CEC determinations.

The treatment of wastewater generated through paper pulp production produces large amounts of sludges; management of these residues constitutes an important environmental problem for this industry. To date, most of these sludges were landfilled or incinerated, but this only constitutes a partial solution. Incineration in the biomass boiler produces toxics and ashes and requires energy supply from these factories, and landfilling is not reliable for a long time. Thus, this waste should be recycled and exploited like an important source of organic matter.

The degree of compost maturation has been widely studied in the water-soluble fraction (Chanyasak et al., 1982; Riffaldi et al., 1988; Garcia et al., 1991). Since it is there that the main biochemical transformations undergone by the microorganisms in organic matter take place. Therefore, phytotoxic substances, such as organic fatty acids of low molecular weight, ammonia and phenols and their degree of degradation during composting should be evaluated in this aqueous phase.

It is generally accepted that even with a source-separated feedstock, the presence of nuisance materials will result in a compromise between compost quality and yield. Plants will typically produce either a low yield of high quality compost, or large amounts of lower quality compost. This poster describes how refining by selective grinding can produce both maximum yield and top-quality compost.

Fresh and composted pea-nut shell microfloras qualitative and quantitative compositions were studied to accelerate the pea-nut shell aerobic composting by adding ‘starters’ stocks. The isolated germs are well suited to the Senegalese climatic conditions and many fungi have interesting cellulolytic possibilities. This work was completed by observations using a scanning electronic microscope.

In order to control the composting process, microbially generated heat must be removed from a pile. This is to prevent the temperature of the substrate, which is a good thermal insulator, from reaching levels inhibitive to the resident microbial population. A model of the heat transfer mechanisms responsible for the removal of any excess heat has been constructed. The heat transfer mechanisms involved are convection and conduction, with radiation effects being assumed negligible.An energy balance has been constructed for the energy transfers into, within and out of a composting system. These three components of the energy balance equate to the change in energy stored within the system, which dictates the temperature within the composting substrate. Separate equations have been developed for each of these components, leading to a complete mathematical energy balance for a composting system. This balance is taken over an instant in time and is expressed as rate equations, in J/s.

The disposal of compost on arable soils is expected to be an appropriate method for restoring a large quantity of compost. The potential climatic change as a result of the atmospheric increase of CO₂ and N₂O leads to the question, if mineralisation and humification due to the disposal of compost effects CO₂ and N₂O production and release into the atmosphere.

Improvement of composting efficiency is still an important research topic. Several authors have tried to define the optimal temperature for composting (Waksman et al., 1939; Jeris and Regan, 1973; Suler and Finstein, 1977). It is often assumed that thermophilic organisms are more efficient than mesophiles. Schulze (1962) showed that it is possible to maintain a composting process continuously in the thermophilic phase. Ventilation induced through temperature feedback system (Rutgers strategy) shows a higher decomposition rate than fixed ventilation (Beltsville strategy) (MacGregor et al., 1981). Blower operating either to pull or push air into the pile (Haug, 1980), drawing air from the base or the core of the pile (Mercedes et al., 1994) and the recirculation of the air in a reactor (Miller et al, 1990) have been tried to reduce the heterogeneous conditions common to piles. The aim of the present research is to compare the conversion of dry matter under self-heating conditions (with a preset temperature limit) with composting at the optimal temperature.

The 5/29/91 Italian Law by Decree foresees the source-separated collection and composting of MSW organic fraction. This implies the distribution of containers for the collection of the wet matter. The direct use of bins is not well accepted by the public because of aesthetic and hygienic problems. A specific composting bag i.e. waterproof, weight and tear resistant, easily tied after use to contain bad odours, and biodegradable is preferable. Paper bags show a poor resistance to wetting and tearing, are bulky and not easily tied. The normal polyethylene bags are not biodegradable. When torn by the bags-breakers before composting they form not sievable fragments which end up into the compost as not biodegradable inerts. Biodegradable plastic composting bags are supposed to be a solution because they combine the biodegradability of paper with the physical properties of plastics. Mater-Bi ZF03U film was specifically developed for the production of composting bags and its biodegradability well studied at laboratory scale. Biodegradation measured by the ASTM D 5338-92 test was 78% while cellulose (reference) was 85% (J.Boelens, 1992). Terrestrial toxicity tests and physical-chemical characterization of the compost showed the absence of negative effects due to Mater-Bi degradation (De Wilde and Boelens 1992). Biodegradation determined with a test described in the 12/7/1990 Italian Decree was higher than food-contact paper, in compliance with the prescriptions of the decree (Molinari, 1994).

In this work, oil-mill wastewater sludge composting has been carried out.Different lignocellulosic residues (straw, wine shoots, olive branches and olive husks) have been mixed with the sludge in order to obtain a suitable moisture and C/N ratio.In all cases, during composting an important organic matter degradation was observed. Results obtained showed a high extent of cellulose degradation indicating a very important microbial activity on the substrate, while the lignin attack was very light.

Tomato (Lycopersicon esculentum Mill.)(‘Sunny’) seeds were sown in Speedling trays filled with sugarcane filtercake (a waste byproduct of sugarcane processing), plug-mix, field soil (sandy), compost:soil mixture (1:1, v:v) under greenhouse conditions. Mean days to emergence, final percent emergence, or mean days to fully expanded cotyledons were not different among treatments. In a second study, tomato ‘Sunny’ transplants were placed in 3.7 L pots filled with compost, field soil, or compost:soil mixture (1:1, v:v) under greenhouse conditions. After 25 days, plant grown in compost, or compost:soil mixture had heavier shoots and roots, thicker stems, and taller plants than plants grown in field soil. In a field study, ‘Sunny’ plants were transplanted in plots without and with compost (224 mtha-1) at 0, 76.5N-67P-140K, or 153N-134P-280K fertilizer rates. Early and total marketable yields, shoot heights, diameters, and weights were higher in plots with compost than without compost, regardless of fertilizer rates. These results suggest that plots with incorporated sugarcane filtercake compost produced higher tomato yields and larger plants than plots without compost.

Production of Medium Density Fibreboard (MDF) from a mix of softwoods involves steam treatment and physical degradation of raw-materials to produce wood fibre for bonding. While the process is typically energy-efficient, using waste materials for steam generation, there may be an excess of wood wastes. In addition, effluent from washing and wood chips has to be treated. This involves a multistage process of filtration, Dissolved Air Flotation (DAF) and Activated Sludge processing. The mixed waste solids are typically belt-pressed and disposed to land-fill.

The pig-on-litter system, known as in-situ composting, has been developed as one of the recommended methods in Hong Kong to treat pig waste. The system utilizes a mixture of sawdust and a commercial bacterial product as the bedding material on which the pigs are raised, and the pig excreta are decomposed within the bedding material. After 10-13 weeks, the spent pig-manure sawdust litter is removed from the pig pens. This spent litter contains high concentrations of organic matter, nitrogen, phosphorus, potassium and trace elements, and also a significant amount of active microbial biomass, which is similar to an immature compost. In order to improve the quality of the spent litter, further composting to reach maturity is essential. Moisture is one of the most critical factors in controlling the rate of composting and the maturity of the product. Water provides a medium for the transport of dissolved nutrients for the metabolic and physiological activities of microorganisms. Very low initial moisture values would mean early dehydration of the pile which will arrest the biological process giving a physically stable but biologically unstable compost (Bertoldi et al., 1983). On the other hand, high moisture values may produce anaerobic conditions due to water logging. However, the effect of different moisture contents on composting of spent litter and their changes throughout the composting process are not yet understood. Therefore, the study aimed (1) to investigate the changes in the nutrients and organic matter of the spent litter at different stages of composting, and (2) to evaluate the effect of different initial moisture content of the spent litter on this composting process.

The influence of compost prepared from vegetable, fruit and garden waste (vfg compost) on disease incidence caused byPhytophthora cinnamomi and Rhizoctonia solani from woody ornamentals was assessed in bioassays with lupin and cucumber as test plants, respectively. Peat-perlite mixtures amended with vfg composts of different maturity levels and of two compost plants were suppressive to P. cinnamomi. Amendment of 20% long matured compost suppressed R. solani, whereas amendment of shortlty matured compost did not. In a radish bioassay damping-off by R. solani was even increased when 20% compost without additional maturation after delivery was added to potting soil. Availability of cellulose affected the suppression of R. solani by compost.

An important tool in reducing appreciably the flow of disposable refuses and landfilling problems is recycling by composting organic wastes collected by Municipalities, in order to obtain soil conditioners.

Pythium is a soil-borne fungus which causes root rot in several bulb crops. To reduce the use and dependence on fungicides, non-chemical control methods have to be developed.

The possibility of practical use of rock phosphate as a fertilizer has received significant interest in recent years. Unfortunatelly, rock phosphate is not plant available in soils with pH greater than 5.5–6 and even when conditions are optimal, yields are as a rule lower than those obtained with soluble phosphate (1). It has been repeatedly shown that low-molecular organic acids can strongly increase phosphorus solution concentration by mechanisms involving chelation and exchange reactions. Filamentous fungi are widely used as producers of organic acids and particularly Aspergillus niger and some Penicillium species have been experimented in fermentation systems or inoculated directly in soil in order to solubilize rock phosphate (2-5).

This paper presents the short-term results of a comparative study on language usage and terminology relating to the organic waste treatment method of composting. Approximately 210 tenns and their definitions regarding biology, process performance, composting techniques, engineering, starting materials and final product of composting as well as waste management in general are analysed and compared in three language systems.

Composting as a means of waste recycling in order to produce organic fertilizer has long been practised by farmers. Agronomic interest in compost is due to its elevated nutrient and organic matter content. However compost could have an adverse impact on account of its salinity or the presence of pathogens or toxic metals. Numerous studies on this last aspect have shown that heavy metal content in compost treated plant does not differ significantly from the control (Massantini et al., 1988; Stilwell, 1993). The agronomic trials carried out on compost have shown conflicting results for marked variability in composition, type of species grown and pedoclimatic characteristics of the trial area (Del Zan, 1989; Edwards et al., 1993; Paris et al., 1986). The purpose of the present research was to study the direct and residual agronomic effects of compost from treated municipal solid waste on horticultural species.

During composting, animal and plant debris is modified by mineralization and humification through a wide variety of biological and biochemical processes. Extracellular enzymes in composts are constituents of the biochemical decomposition, catalyzing reactions in which nutrients are released for later use.

Anaerobically digested primary sludge (ADPS) refers to the residue obtained after digestion of settled solids from primary wastewater treatment and contains significant levels of pathogens and heavy metals. Disposal of ADPS to land requires composting to reduce pathogens. Land disposal is restricted by total heavy metal content in the sludge. Total metal levels in the sludge can increase during composting as the associated organic matter is decomposed. Heavy metals in the sludge (eg copper), during anaerobic digestion are present in their insoluble reduced forms such as sulphides. During composting, the metals in the sludge become more soluble due to the oxidation of sulphides to sulphates. In addition, decomposition of organic matter and acidification as a result of sulphide oxidation during composting can increase metal mobility in the sludge (Qiao, In Progress). Land application of this compost could thus result in a significant mobilisation of metals into the soil from the compost. The accumulation of metals in soils may result in phytotoxic effects or harm consumers of the contaminated crops (Garcia et al., 1990). In addition, groundwater can also be contaminated by heavy metals leaching into the water table.

The physical, chemical and biological properties of four lombricomposts, obtained from cow dung, press-filter cake, coffe pulp and green residues, with the aid of the earthworm Eisenia fetida were studied.Except green residues, lombricomposts were produced with pH between 8.4 and 8.9, explained perhaps due to the lack of leaching during the process. The highest earthworm population was reached with coffee pulp and the best bacterial population was found in cow dung. The weight of aggregates retained for sieve No. 10 was high except in the case of green residues. The filter-press cake showed the best content of nutrients, followed by cow dung, coffee pulp and green residues.

Composting may be defined as the ‘aerobic biodegradation of organic material to form primarily CO₂ ’water and humus‘. It is a natural process which has been practised in our agricultural communities for many hundreds of years and by many of us in our own ’backyard‘ compost piles to generate a clean, valuable soil conditioner.