The Science of Composting

Inhaltsverzeichnis

1. Frontmatter

2. Plenary Section

   1. Frontmatter

   2. Historical Review of Composting and its Role in Municipal Waste Management

      C. G. Golueke, L. F. Diaz

      Abstract

      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.

   3. The Thermie Programme and Composting Projects in the Energy from Biomass and Waste Sector

      G. L. Ferrero

      Abstract

      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.

   4. The Role of Composting in Sustainable Agriculture

      Paolo Sequi

      Abstract

      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.

   5. I.S.W.A. Policy in the Regard of Composting as an Integrated System of Waste Management

      John H. Skinner

      Abstract

      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.

   6. Waste Management and Legislation

      W. A. Van Belle

      Abstract

      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.

3. Composting Process

   1. Frontmatter

   2. Composting Control: Principles and Practice

      E. I. Stentiford

      Abstract

      A composting system consists of three parts:

      • materials reception and pretreatment;
      • the composting process; and
      • compost 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.

   3. Composting Plant Design and Process Management

      Roger T. Haug

      Abstract

      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.

   4. Odour Emissions from Composting Plants

      W. Bidlingmaier

      Abstract

      We look into the past we see the history of composting as a history of problems. So, we have discussed:

      • 1965 glass in compost
      • 1970 plastic in compost
      • 1975 heavy metals in compost
      • 1978 PCBs in compost
      • 1984 odour emissions from composting plants
      • 1989 dioxin in compost
      • 1990 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.

   5. Environmental Impact of Composting Plants

      Klaus Fischer

      Abstract

      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.

   6. Production of functional compost which can suppress phytopathogenic fungi of lawn grass by inoculating Bacillus subtilis into grass clippings

      Kiyohiko Nakasaki, Masahiro Kubo, Hiroshi Kubota

      Abstract

      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.

   7. Nutrient transformation of pig manure under pig-on-litter system

      N. F. Y. Tam, S. M. Tiquia, L. L. P. Vrijmoed

      Abstract

      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.

   8. Heat Evolution During Composting of Sewage Sludge

      Frederick C. Miller

      Abstract

      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.

   9. Process Control based on Dynamic Properties in Composting: Moisture and Compaction considerations

      K. Das, H. M. Keener

      Abstract

      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.

   10. Compost Facility Operating Guide

       Philip B. Leege

       Abstract

       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.

   11. Glucose Influence on the Asymbiotic Nitrogen Fixation During Lignocellulsic Waste Composting

       K. Ezelin, G. Brun, M. Kaemmerer, J. C. Revel

       Abstract

       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.

   12. Taxonomic and Metabolic Microbial Diversity During Composting

       Trello Beffa, Michel Blanc, Laurent Marilley, Johanna Lott Fischer, Pierre-François Lyon, Michel Aragno

       Summary

       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.

   13. A new composting plant realized within the THERMIE program of the European Commission

       T. Papi, G. Marani, R. Mannironi, M. de Bertoldi

       Abstract

       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.