Drying and storage of forest residues for energy production

doi:10.1016/0144-4565(85)90038-1

Biomass

Volume 7, Issue 2, 1985, Pages 125-134

https://doi.org/10.1016/0144-4565(85)90038-1 Get rights and content

Abstract

Since 1978 the Department of Forest Products has studied the drying and storage of forest energy logging residues of various types, ranging from unreduced material at the logging site to reduced material at the heating plant.

To be able to determine the energy changes in fuel during the storage period, we have analysed moisture content, matter loss and heat value before as well as after storing. If branches and tops are stored in piles for 6–9 months, no particular energy change takes place. While the logging residues are reduced into chiplike fractions, the energy loss varies between 7 and 21% during 6–9 months of pile storage. In connection with the energy change, heat was created which caused temperatures up to 90°C.

During storage great amounts of microfungi are formed, which can cause allergic reactions in those who handle the material. A heating plant's ability to pay for comminuted logging residues in relation to oil is between SEK 100 and 115 per m³ stacked, at the oilprice SEK 2000 per m³.

References (12)

T. Thörnqvist
Drying of fuel chips with solar panel warmed air (English summary)
Department of Forest Products, Swedish University of Agricultural Sciences, Uppsala, Report No. 126
(1982)
T. Thörnqvist
Storing of disintegrated logging residuals (English summary)
Department of Forest Products, Swedish University of Agricultural Sciences, Uppsala, Report No. 137
(1983)
T. Thörnqvist et al.
Factors affecting the occurrence of fungi in fuel chips for domestic consumption (English summary)
Department of Forest Products, Swedish University of Agricultural Sciences, Uppsala, Report No. 117
(1980)
T. Thörnqvist et al.
Health hazards caused by fungi in stored wood chips
Forest Products J.
(1982)
T. Thörnqvist
Storing of saplings of Salix spp. (English summary)
Department of Forest Products, Swedish University of Agricultural Sciences, Uppsala, Report No. 133
(1982)
T. Thörnqvist et al.
The importance of air drying for the storing property of fuel chips (English summary)
Department of Forest Products, Swedish University of Agricultural Sciences, Uppsala, Report No. 142
(1983)

There are more references available in the full text version of this article.

Cited by (78)

Long-term storage and fuel quality of residual Eucalyptus globulus biomass
2024, Industrial Crops and Products
Maximum energy demand (winter) and logging residue availability (spring and summer) occur at different times promnting the necessity of storage. Our aim was to analyse the effects of storage on baled logging residues from Eucalyptus globulus over a period of storage (TS_t) by measuring the moisture content (MC), net calorific value (NCV), and ash content, and by determining dry matter losses (DML) and the usable energy content of the residues. These analyses were performed six out 6 times over the course of 18 months for each component of the residues (leaves, branches and bark). The analysed samples were placed in different positions within stacks of cylindrical bales: 1) centrally placed and 2) surface (open-air).
MC decreased during the first 3 months of storage in all samples. From this point onwards, the surface samples’ MC varied significantly throughout the storage time (TS_t) because of precipitation influence, whereas it remained stable in the centrally placed samples. Significant differences in NCV (wet basis) were observed in the surface samples with respect to storage time, whereas in the centrally placed samples, these differences were not significant after 3 months of storage. Differences between surface and centrally placed samples for a given TS_t were more pronounced during periods of higher precipitation, reaching a value of 4.52 MJ kg⁻¹ after 6 months of storage. The influence of extractive content in the residues was reflected in the NCV (on a dry basis), which varied slightly with TS_t, peaking at 3 months with values of 17.60 and 18.34 MJ kg⁻¹, for the surface and centrally placed samples, respectively.
The ash content of the surface samples increased significantly (p < 0.05) with storage time, whereas the centrally placed samples did not exhibit this trend. The highest values were recorded in the following order: bark > leaves > branches. The maximum values obtained were 4.2% and 3.7% for the surface and centrally placed samples after 18 months of storage respectively. DMLs increased with storage time, reaching 16.5% and 4.9% for the surface and centrally placed samples after 18 months of storage, respectively. The usable energy content increased during the first 3 months, indicating a positive influence of storage time on the fuel quality. The shape of the top row of bales in a stack could help reduce rainwater penetration, resulting in a higher proportion of internal residues and therefore improving usable energy content.
Forest chip drying in self-heating piles during storage as affected by temperature and relative humidity conditions
2022, Fuel
Storing is an important part in the value chain of the energy use of forest chips as severe losses of dry mass and energy content and increases in greenhouse gas emissions may occur. During the storage the temperature in the biomass increases affecting the dry mass loss and the material drying. In a field-scale experiment, we monitored temperature inside two uncovered wood chip piles for 175 days and measured the chip gravimetric moisture content at the beginning and end of the experiment. In the laboratory the drying rate of the wood chips under different temperature and relative humidity conditions was determined. We constructed a new two-dimensional simulation model where water vapor diffusion within the pile, and chip moisture change was solved using a finite volume method. The determined chip drying rate was used as a source term in the simulation. The simulation model results were in close agreement with the experimental data in the middle sections of the pile, whereas the model was not able to describe the chip moisture redistribution in the pile tails. Modeling revealed that the pile size and porosity were important factors in determining the chip drying, which indicates that chip drying can be controlled by management, such as planning of pile dimensions and compaction.
Climate change mitigation potential of biochar from forestry residues under boreal condition
2022, Science of the Total Environment
Forest harvest residue is a low-competitive biomass feedstock that is usually left to decay on site after forestry operations. Its removal and pyrolytic conversion to biochar is seen as an opportunity to reduce terrestrial CO₂ emissions and mitigate climate change. The mitigation effect of biochar is, however, ultimately dependent on the availability of the biomass feedstock, thus CO₂ removal of biochar needs to be assessed in relation to the capacity to supply biochar systems with biomass feedstocks over prolonged time scales, relevant for climate mitigation. In the present study we used an assembly of empirical models to forecast the effects of harvest residue removal on soil C storage and the technical capacity of biochar to mitigate national-scale emissions over the century, using Norway as a case study for boreal conditions. We estimate the mitigation potential to vary between 0.41 and 0.78 Tg CO₂ equivalents yr⁻¹, of which 79% could be attributed to increased soil C stock, and 21% to the coproduction of bioenergy. These values correspond to 9–17% of the emissions of the Norwegian agricultural sector and to 0.8–1.5% of the total national emission. This illustrates that deployment of biochar from forest harvest residues in countries with a large forestry sector, relative to economy and population size, is likely to have a relatively small contribution to national emission reduction targets but may have a large effect on agricultural emission and commitments. Strategies for biochar deployment need to consider that biochar's mitigation effect is limited by the feedstock supply which needs to be critically assessed.
Influence of fuel quality and storage conditions on oxygen consumption in two different wood chip assortments – Determination of the storage-stable moisture content
2022, Fuel
Technical drying of wood chips by active ventilation is often applied, i. a. to reduce dry matter and energy losses due to decomposition during storage. However, wood chips are often dried to very low moisture contents (MC) of below 10–15 % (moisture mass fraction on wet basis), that might lead to a waste of drying energy. But the storage-stable MC has not been investigated intensively yet. Therefore, the purpose of our study was to determine as accurately as possible the threshold of MC where significant decomposition starts.
Outdoor-stored spruce wood chips were conditioned to different MC and filled into air-tight containers. The oxygen concentration inside the containers was measured after 48 h and the dry matter loss was stoichiometrically calculated. Two different assortments (high/low quality), two storage temperatures (cold/warm) and varying storage durations before sampling were examined.
The results showed that MC and oxygen consumption were significantly positively correlated for both assortments and storage temperatures. Even very low MC caused a slight decrease in oxygen concentration. A multiple linear regression model had a high predictive accuracy. For example, during a storage period of 6 months a dry matter loss of 1.1 % would be caused by a moisture content of 20 % for the low-quality assortment at a storage temperature of 21 °C.
In conclusion, this study shows that there is no absolute storage-stable MC for wood chips. The point of storage-stability rather depends on the definition of the acceptable dry matter loss. However, the results indicate, that it might not be efficient to dry wood chips below approximately 20 % MC.
Evaluation of an improved design for large-scale storage of wood chip and bark
2021, Biomass and Bioenergy
A developed bioeconomy needs better storage methods for wood chips and forest industry by-products, since increasing demands for more assortments, more storage will be necessary Today, solutions for coping with storage-related problems, such as dry matter losses and risk of self-ignition, are based on separating assortments into smaller piles and avoiding large-scale long-term storage of chips. A safe and efficient storage solution is needed to enable wood chip production all year round and not be limited to just-in-time production during the cold heating season when there is a large demand. This might result in a more robust system with larger buffer capacities, a less stressful working environment for chipping and transport contractors, and a better yearly machine utilisation.
This study evaluated storage outcomes for wood chips and bark when using an improved storage design that created assortment separation using concrete walls and a semipermeable sheet for cover. The new design enabled efficient area utilisation and increased fire safety. The storage outcome was also improved in terms of moisture content, dry matter losses and temperature development compared to conventional open-air piles.
Monitoring feedstock losses over five months storage of olive tree pruning hog fuel in piles. Comparison of covered vs. uncovered storage
2021, Biomass and Bioenergy
Citation Excerpt :
Several scientific articles are available regarding the storage of biomass and its impact on the quality and mass of the stored material. It has been shown that coniferous wood chips (e.g. spruce, pine) have monthly dry matter losses that range from 0.3% to 5.5% [20–26]. Whereas, storage trials of SRC chips (short rotation coppice), such as poplar, alder and willow, that were held in Central and Southern Europe, were reported to have monthly dry matter losses that range from 0.8% to 6.5% [25,27–31].
Aim of the current paper is the monitoring of feedstock losses during a five-month storage period of olive tree pruning (OTP) hog fuel, by comparing two storage solutions: i) uncovered, open-air storage and ii) fleece-covered open-air storage. For this task, two identical conical piles of harvested prunings were built and monitored for calculating the changes in dry matter and energy value of the stored material over time. One pile was left uncovered, while the other was covered with a breathable fleece. For each pile, net bags were used in order to obtain samples for analysis. Overall, the covered pile showed improved storage performance than the uncovered pile, which was much more influenced on weather conditions. The covered pile presented i) lower dry matter losses after five months of storage with an average value of 1.1% compared to 4.6% of the uncovered pile; ii) stable moisture content throughout the storage period at around 10% (as received), compared to the fluctuating moisture content of the uncovered pile from 11% to 24%; and finally, iii) recoverable energy gain with an average pile value of 12.1% compared to recoverable energy loss of 5.1% in the uncovered pile after the storage period.

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Biomass

Abstract

References (12)

Drying of fuel chips with solar panel warmed air (English summary)

Department of Forest Products, Swedish University of Agricultural Sciences, Uppsala, Report No. 126

Storing of disintegrated logging residuals (English summary)

Department of Forest Products, Swedish University of Agricultural Sciences, Uppsala, Report No. 137

Factors affecting the occurrence of fungi in fuel chips for domestic consumption (English summary)

Department of Forest Products, Swedish University of Agricultural Sciences, Uppsala, Report No. 117

Health hazards caused by fungi in stored wood chips

Forest Products J.

Storing of saplings of Salix spp. (English summary)

Department of Forest Products, Swedish University of Agricultural Sciences, Uppsala, Report No. 133

The importance of air drying for the storing property of fuel chips (English summary)

Department of Forest Products, Swedish University of Agricultural Sciences, Uppsala, Report No. 142

Cited by (78)

Long-term storage and fuel quality of residual Eucalyptus globulus biomass

Forest chip drying in self-heating piles during storage as affected by temperature and relative humidity conditions

Climate change mitigation potential of biochar from forestry residues under boreal condition

Influence of fuel quality and storage conditions on oxygen consumption in two different wood chip assortments – Determination of the storage-stable moisture content

Evaluation of an improved design for large-scale storage of wood chip and bark

Monitoring feedstock losses over five months storage of olive tree pruning hog fuel in piles. Comparison of covered vs. uncovered storage