Vermicomposting System Research Articles

Design of Manure Treatment Alternatives for Hillside Farms Pennsylvania, USA

An alternative treatment system for cow manure at The Lands at Hillside Farms, a 60 cow dairy farm located in Shavertown, Pennsylvania, was designed. The treatment system was sized for Hillside Farm’s 530,000 kg of annual manure production. The following systems were explored: lagoon, traditional composting, traditional anaerobic digester, anaerobic bag digester, and vermicomposting. The most practical manure treatment system was determined to be a vermicomposting system. The vermicomposting system employs Eisenia Fetida, a type of earth worm, to process the manure. The vermicomposting system consists of 12 units, each with a length and width of 4.6 m, and a depth of 0.3 m. To reduce costs and take advantage of Eisenia Fetida’s rapid reproduction ability, it was decided to initially purchase 5% of the total required worms. Each vermicomposting unit was estimated to cost $1,035, resulting in a total cost of $12,420. The primary concern for the treatment system is in regard to its performance during periods of low temperature. Eisenia Fetida’s manure processing rate declines with temperature. Hillside Farms should investigate the feasibility of installing a greenhouse or similar structure to insulate the vermicomposting units. The research paper herein contains valuable information that may assist other small farms exploring manure treatment options.

Dynamics of a vertical-flow windrow vermicomposting system.

Large-scale vermicomposting under outdoor conditions may differ from small-scale procedures in the laboratory. The present study evaluated changes in selected properties of a large-scale vertical-flow windrow vermicomposting system with continuous feeding with household biowaste. The windrow profile was divided into five layers of differing thickness and age after more than 12 months of vermicomposting. The top layer (0-30 cm, age <3 months) was characterised by partially decomposed organic matter with a high pH value and an elevated carbon/nitrogen (C/N) ratio. The earthworm biomass was 15 g kg-1 with a population density of 125 earthworms per kilogram predominantly found in clusters. The greatest amount of fungi (3.5 µg g-1 dw) and bacteria (62 µg g-1 dw) (expressed as phospholipid fatty acid analysis) was found in this layer. Thus, the top layer could be used for an additional cycle of windrow vermicomposting and for the preparation of aqueous extracts to protect plants against diseases. The lower layers (graduated by 30 cm and by 3 months of age) were mature as reflected by the low content of ammonia nitrogen, ratio of ammonia to nitrate nitrogen and dissolved organic carbon, and high ion-exchange capacity and its ratio to carbon. These layers were characterised by elevated values for electrical conductivity, total content of nutrients, available magnesium content, and a relatively large bacterial/fungal ratio. On the basis of the observed properties, the bottom layers were predetermined as effective fertilisers.

English

The present research evaluated the redox ability of Cr6+ in the earthworm Eisenia foetida, and its effects on growth and survival. An assay was conducted with an increasing doses of K2Cr2O7 (0, 200, 400, 800, 1000, and 1200 mg K2Cr2O7 kg-1 substrate) applied to a vermicomposting system which was inoculated with 30 earthworms per chamber. Earthworm growth, estimated by weight, showed a quadratic response (p = 0.03) with the lowest estimated growth at a dose of 435 mg K2Cr2O7 kg-1. Chromium (Cr) concentration increments were positively associated to mortality in adults and cocoons (p &lt; 0.01), and total Cr accumulation in earthworms (p &lt; 0.01). The accumulation of chromium in worms, is an indicator of the capacity of worms to resist different doses of potassium dichromate and, the effect on accumulation of Cr (VI) in vermicomposting was higher (p = 0.11). The difference of potassium dichromate in worms could indicate the oxide reduction in E. fetidae. &nbsp; Key words: Redox chromium, growth, survival, Eisenia foetida.

Earthworms as Organic Waste Managers and Biofertilizer Producers

Vermicomposting is the processing of organic materials by earthworms into homogeneous and humus-like material known as vermicompost. It is a complex mixture of fecal matter of earthworms and microorganisms. In vermicomposting system, earthworms act as voracious feeder, modifying composition of organic waste, gradually reducing its organic carbon and C:N ratio and retains more nutrients (nitrogen, potassium, phosphorus, calcium). The nutrient content is generally higher in vermicompost than in the traditional compost. Earthworm increases the surface area of any material and makes it more favorable for the activity of microbiota for further decomposition. Earthworms have the ability to consume various types of organic wastes such as livestock excreta, cattle dung, oil palm waste, agricultural residue, sewage sludge and other agro-industrial refuse. Studies suggested that organic wastes can be managed by the use of different species of earthworms and the production of vermicompost as a powerful biofertilizer in sustainable agriculture discouraging the use of chemical fertilizers. Vermicomposting accelerates the bioconversion process by two to five times as compared to traditional composting, thereby hastens the conversion of wastes into valuable biofertilizer. In the present review, earthworms are described as waste managers in utilizing and changing the physico-chemical properties of the organic wastes and highlight the need for the use of vermicomposting in organic waste recycling. Earthworm-microbe interaction and the nutrient status of final vermicompost are also discussed in detail.

Nutrient changes and biodynamics of Eisenia fetida during vermicomposting of water lettuce (Pistia sp.) biomass: a noxious weed of aquatic system.

This paper reports the results of vermicomposting of water lettuce biomass (WL) spiked with cow dung at ratios of 20, 40, 60, and 80% employing Eisenia fetida. A total of four treatments were established and changes in chemical properties of mixtures were observed. Vermicomposting caused a decrease in pH, TOC, volatile solids, and C/N ratio by 1.01-1.08-fold, 0.85-0.92-fold, 0.94-0.96-fold, 0.56-0.70-fold, respectively, but increase in EC, totN, totP, totK, totCa, totZn, totFe, and totCu, by 1.19-1.42-fold, 1.33-1.68-fold, 1.38-1.69-fold, 1.13-1.24-fold, 1.04-1.11-fold, 1.16-1.37-fold, 1.05-1.113-fold, 1.10-1.27-fold, respectively. Overall, the treatment with 60-80% of WL showed the maximum decomposition and mineralization rates. The earthworm showed the growth and reproduction rate in considerable ranges in all treatment setups but setups with 60-80% WL proportion exhibited the optimum results. Results reveal that biomass of water lettuce can be utilized effectively for production of valuable manure through vermicomposting system.

Assessing the Potential of Pomegranate Meal and Potato Waste as New Organic Amendments for Vermicompost

ABSTRACTWaste disposal has become one of the greatest global concerns, which has high operational costs and might cause environmental pollution. Due to the lack of the organic matter in most of the Iranian agro-ecosystem, recycling organic waste materials favors the environment by reducing chemical fertilizers as well as improving soil structure and fertility. A vermicomposting system using cow manure (CM), pomegranate meal (PM) + sawdust (S), CM + potato waste (PW), PM + PW, CM + PM, and CM + PM + PW was set up to find a viable alternative raw material for improving physico-chemical properties of vermicompost after 60 days. The amended vermicompost of PM + S and PM + PW markedly improved the electrical conductivity (EC), which were below the EC limit (by 1.01 and 2.27 dS m−1, respectively), pH (by 7.04 and 6.60, respectively), and water holding capacity (respectively 1.9 and 1.2 times higher than CM). Vermicompost amendment led to significant reduction of organic carbon (OC), but nonetheless, PM + S and PM + PW showed higher OC content in the final product probably due to the higher initial carbon to nitrogen (C:N) ratio, raw material origin, and lower decomposition rate. In regard to nutrient value, the total phosphorus content in the end-product of PM + S and PM + PW was, respectively, 19.3 and 7.9 times higher compared with the final product of CM. Additionally, the amended vermicompost of PM + PW markedly improved total nitrogen content as compared with CM. The findings suggested that the additional amounts of nitrogen and potassium to PM + S and also potassium to PM + PW would improve the physico-chemical properties and fertilization of the final vermicompost considerably higher than CM vermicompost. This amendment has the potential to mitigate the adverse effects of vermicompost of CM, for example, salinity and alkalinity; and chemical fertilizers, for example, soil pollution with heavy metals in phosphate fertilizers, as well as the potential for soil rehabilitation.

A metagenomic analysis displays the diverse microbial community of a vermicomposting system in Uganda

BackgroundVermicomposting is a mesophilic process using earthworms to efficiently and at low cost process large volumes of organic waste. It has been suggested to not only increase soil fertility but also increase biomass of beneficial bacteria while reducing harmful bacteria. The aim of this study was to set up a strategy to investigate and characterise the viral as well as the bacterial composition of a vermicomposting system.Material and methodsThe vermicomposting unit used in this study was placed at the Makerere University Agricultural Research Institute Kabanyolo on the outskirts of Kampala, Uganda, and was fed with 80% cattle manure and 20% food waste. On Day 172, the compost was terminated and compost samples were collected from three layers of the unit: the top, the middle and the bottom layer. A metagenomic approach was then applied to characterise the viral and bacterial composition of the vermicomposting system.Results and discussionA high abundance and diversity of bacteria were identified. Proteobacteria was the largest phyla in the compost (mainly Alpha-, Gamma- and Betaproteobacteria), constituting almost 65% of the bacterial reads in the data sets. DNA samples from several possible pathogenic bacteria, such as Salmonella spp., Escherichia coli, Enterobacter spp., Enterococcus spp. and Clostridium spp, were detected in the vermicompost, suggesting that there might still be harmful bacteria in the vermicast. Phages constituted the main viral group; apart from phages, mainly insect viruses were identified. The only animal or human virus identified was kobuvirus. In summary, metagenomic analysis was shown to be an efficient technology to characterise the microbial composition of vermicast. The data from this study contribute to a better understanding of the microbes present in this kind of composting system and can help determine measures necessary for safe manure handling.

Removal of Decachlorobiphenyl in Vermicomposting Process Amended with Rabbit Manure and Peat Moss

This study aimed to evaluate the removal of polychlorinated biphenyls, with a vermicomposting system, using the following as components: the earthworm Eisenia fetida, peat moss and rabbit excrement and a compound called decachlorobiphenyl, for a period of 91 days under non-sterile conditions. The results obtained were a removal of decachlorobiphenyl 79.6 % with an initial concentration of 100 mg L−1, 89.7 % with 150 mg L−1 and 95.38 % with 200 mg L−1; the earthworms bioaccumulated less than 5 mg L−1 in all concentrations of decachlorobiphenyl analysed without apparent toxic effect. Weight gain was observed in earthworms that assimilated contaminant during vermicomposting, as the number of cocoons produced in contrast to the control in which both the weight and the number of cocoons were lower. To our knowledge, this is the first study which suggests that vermicomposting may be a suitable mechanism for removal of decachlorobiphenyl with high recalcitrance from contaminated sediment or soils.

Vermiremediation of Water Treatment Plant Sludge employing Metaphire posthuma: A soil quality and metal solubility prediction approach

Water Treatment Plant Sludge (WTPS) is formed during sewage treatment and is extremely rich in nutrients (N, P and K) and toxic heavy metals. In this work, efficiency of vermicomposting technology was evaluated using an endogeic earthworm Metaphire posthuma, against aerobic composting in regard to stabilization of WTPS. Different combinations of WTPS and cow dung were utilized as feed stock. Low pH of WTPS changed towards neutrality under both the biocomposting systems. The contents of N (45–61%), P (50–80%) and K (83–88%) increased significantly under Metaphire vermicomposting system accompanied by substantial reduction in total organic C. Interestingly, improvement in soil quality and low accumulation of heavy metal (Cr and Cu) in soil under vermistabilized WTPS treatments was noteworthy. Moreover, the solubility pattern of non metal and metal ions in vermistabilized and crude WTPS was studied to understand their impacts on moist soil environment with the help of MINTEQ geochemical model. The model predicted decrement of metal solubility (Cr, Zn, Cu, and Mn) in WTPS+CD (1:1) and WTPS+CD (2:1) vermicompost as compared to untreated WTPS. The overall results suggest that Metaphire posthuma could be utilized as a successful candidate for bioprocessing toxic WTPS materials.

Vermicomposting as manure management strategy for urban small-holder animal farms – Kampala case study

Inadequate organic waste management can contribute to the spread of diseases and have negative impacts on the environment. Vermicomposting organic waste could have dual beneficial effects by generating an economically viable animal feed protein in the form of worm biomass, while alleviating the negative effects of poor organic waste management. In this study, a low-maintenance vermicomposting system was evaluated as manure and food waste management system for small-holder farmers. A vermicomposting system using the earthworm species Eudrilus eugeniae and treating cow manure and food waste was set up in Kampala, Uganda, and monitored for 172days. The material degradation and protein production rates were evaluated after 63days and at the end of the experiment. The material reduction was 45.9% and the waste-to-biomass conversion rate was 3.5% in the vermicomposting process on a total solids basis. A possible increase in the conversion rate could be achieved by increasing the frequency of worm harvesting. Vermicomposting was found to be a viable manure management method in small-scale urban animal agriculture; the return of investment was calculated to be 280% for treating the manure of a 450kg cow. The vermicompost was not sanitised, although hygiene quality could be improved by introducing a post-stabilisation step in which no fresh material is added. The value of the animal feed protein generated in the process can act as an incentive to improve current manure management strategies.

The Set-Up and Evaluation of a Vermicomposting System at a Hindu Temple in Order to Defer Food Waste from the Waste Stream

Participants will be able to defer a minimum of 500lbs of food waste from landfills with the use of vermicomposting.

Changes in chemical and microbiological properties of rabbit manure in a continuous-feeding vermicomposting system

In the present study the potential of the earthworm Eisenia fetida to process large amounts of waste was evaluated through continuous feeding reactors in which new layers of rabbit manure were added sequentially to form an age gradient inside the reactors. An optimal moisture level, ranging from 66% to 76%, was maintained throughout the process using an automatic watering system. The pH was close to 8.3, but decreased to 7.6 after 200d of vermicomposting. No changes in electrical conductivity through the profile of layers were detected. Based on comparisons of phospholipid fatty acid (PLFA) profiles and microbial activity measurements (basal respiration), a decrease in the levels of bacteria and fungi in layers corresponding to vermicomposting times of more than 200d occurred. This points to a higher degree of stabilisation in the final product, which is of utmost importance for its safe use as an organic amendment.

Qualitative analysis of the stability of a continuous vermicomposting system

A mathematical model was established to describe ecological relationships in a continuous vermicomposting system. The distributions of organic matter, microbes and earthworms on non-dimensional specific growth rates were simulated. The range of specific growth rates were visualized utilizing three-dimensional reconstruction technology. The stability of a vermicomposting system was not influenced by the initial concentrations of microbes and earthworms, only their species. The coordinates of the stable point depended on the dilution rate and initial amount of organic matter. The method described could be help for establishing a stable continuous vermicomposting system.

Earthworm production in cattle dung vermicomposting system under different stocking density loads

This work illustrates the productivity of composting earthworm Perionyx excavatus under different stocking density (in milligrams biomass per cubic centimeter vermibed space) gradients in cattle dung decomposing system. Earthworm biomass and reproduction performance was tested in vermibeds with five different stocking density loads: 0.0680 mg cm⁻³ (T₁), 0.1388 mg cm⁻³ (T₂), 0.205 mg cm⁻³ (T₃), 0.274 mg cm⁻³ (T₄), and 0.342 mg cm⁻³ (T₅). Results thus suggested the direct relationship between earthworm performance and stocking density load in vermicomposting system. P. excavatus showed the maximum individual biomass production in low-stocking density trials, while cocoon production rate was better in vermibeds with high-density trials. The statistical interrelationships between stocking density load and individual growth parameters of inoculated earthworms were also tested. The statistical interpretation also suggested the impact of stocking density load on earthworm growth and reproduction parameters in vermicomposting system, although further detailed studies are required to measure the earthworm growth behavior under the maximum carrying capacity load of a vermibed.

Industrial wastes and sludges management by vermicomposting

Vermicomposting has been arising as an innovative ecotechnology for the conversion of various types of wastes into vermicompost. Vermicompost is humus like, finely granulated and stabilized material which can be used as a soil conditioner to reintegrate the organic matter to the agricultural soils. Industrial wastes remain largely unutilized and often cause environmental problems like ground and surface water pollution, foul odours, occupying vast land areas etc. Non-toxic and organic industrial wastes could be potential raw material for vermitechnology. In the last two decades, vermitechnology has been applied for the management of industrial wastes and sludges and to convert them into vermicompost for land restoration practices. The success of the process depends upon several process parameters like quality of raw material, pH, temperature, moisture, aeration etc., type of vermicomposting system and earthworm species used. The review discusses the vermitechnology and the present state of research in the vermicomposting industrial sludges and wastes.

Sustainable Household Organic Waste Management via Vermicomposting

Increasing waste generation in developing countries has alarmed authorities on waste disposal issues. Therefore, various alternatives have been looked into to reduce waste disposed into landfill. Among others are the bioremediation options which may allow the conversion of putrescible wastes into value added products such as compost, biogas and others. This study was aimed to find optimal experimental set-up to conduct small scale vermicomposting suitable for households, since approximately 40-50% (wt) of the waste is putrescible component. The wastes were weighed and exposed to worms namely Eisenia foetida. Results indicated that household putrescible waste can easily undergo vermicomposting. However, factors such as high acidity and presence of certain materials in the waste can be detrimental to this process. Worms are very sensitive to pH changes and the vermicomposting process will reduce drastically when pH is lower than 5.0. Experimental set-up with the layering system proved to be the best method of conducting small scale vermicomposting. The layering set-up prevents worms from escaping the vermicomposting system and allows the gathering of the offspring in a safe environment. Different combinations of organic mixture resulted with different rate of vermicomposting completion. The fastest to degrade was the combination of kitchen waste with vermicompost, which come to completion within three weeks. Vermicompost provides the most suitable environment for the worms to flourish in addition to the availability of less complex components in kitchen waste. The average water holding capacity of the vermicompost was 25% (wt) while the total organic content was 12%. In conclusion, vermicomposting of organic components found in the MSW stream can be accomplished by taking into consideration crucial factors such as acidity and presence of hindering components. The identification of the most suitable conditions for vermicomposting will allow the implementation of this alternative biological remedy to reduce waste and tackle the problem in waste management, particularly in developing countries.Pertambahan penghasilan sisa di negara-negara membangun membimbangkan pihak berkuasa. Maka, pelbagai alternatif telah dipertimbangkan untuk mengurangkan jumlah sisa ke tapak pelupusan. Antara pilihan yang ada ialah bioremediasi yang membolehkan pertukaran sisa yang mudah terurai kepada produk bernilai seperti kompos, biogas dan lain-lain. Kajian ini bertujuan untuk mengetahui penyediaan eksperimen terbaik bagi menjalankan proses vermi-pengkomposan skala kecil yang sesuai bagi isirumah memandangkan hampir 40-50% (berat) sisa yang dihasilkan terdiri daripada bahan mudah terurai. Sisa ditimbang dan didedahkan kepada cacing jenis Eisenia foetida. Keputusan menunjukkan bahawa sisa mudah terurai yang dihasilkan sesuai menjalani proses vermi-pengkomposan. Walau bagaimanapun, faktor- faktor seperti keasidan yang tinggi dan kehadiran elemen-elemen tertentu di dalam sisa boleh membantutkan proses ini. Cacing-cacing ini sensitif kepada perubahan pH dan proses vermi-pengkomposan akan menurun dengan drastik apabila pH kurang dari 5.0. Persediaan eksperimen dengan sistem lapisan terbukti sebagai teknik terbaik bagi menjalankan vermi-pengkomposan skala kecil. Sistem lapisan menghalang cacing keluar dari sistem vermi-pengkomposan dan membolehkan penggumpulan anak-anak cacing dalam persekitaran yang selamat. Kombinasi-kombinasi yang berbeza dalam campuran organik lengkap diproses pada kadar yang berbeza. Campuran sisa dapur dan vermi-kompos paling cepat terurai iaitu selepas tiga minggu. Ini adalah kerana ia menyediakan persekitaran yang paling sesuai bagi cacing untuk membiak di samping terdapatnya komponen-komponen yang kurang kompleks. Secara purata kapasiti air tanah bagi vermi-kompos ialah 25% sementara kandungan organik total ialah 12%. Sebagai kesimpulan, vermi-pengkomposan komponen organik dalam sisa munisipal boleh dijalankan dengan mengambil kira beberapa faktor penting seperti asiditi dan kehadiran komponen penghalang tertentu. Pengenalpastian keadaan yang paling sesuai bagi vermi- pengkomposan membolehkan perlaksanaan rawatan biologi alternatif ini untuk mengurangkan sisa dan menyelesaikan masalah pengurusan sisa terutama di negara-negara membangun.

Effect of stocking density and food quality on the growth and fecundity of an epigeic earthworm (Eisenia fetida) during vermicomposting

Physico-chemical characteristics of the feed and optimum worm density are important parameters for the efficient working of a vermicomposting system. Overcrowding of worms can affect the efficiency of a vermicomposting system even if all other parameters have been optimized. This article reports the effect of stocking density and feed quality on the growth and fecundity of Eisenia fetida under laboratory conditions. The feed mixtures contained cow dung and textile mill wastewater sludge in different ratios. Three feed mixtures and five stocking rates (1, 2, 4, 8, and 12) were tested for 12 weeks. The results showed that E. fetida growth rate was faster at higher stocking densities; however, biomass gain per worm was faster at lower stocking densities. Sexual maturity was attained earlier at higher stocking densities. Growth rate was highest in 100% cow dung at all the stocking densities when compared to textile mill wastewater sludge containing feed mixtures. A worm population of 27–53 worms per kg of feed was found to be the most favorable stocking density.

VERMICOMPOSTING TECHNOLOGY FOR STABILIZING THE SEWAGE SLUDGE FROM RURAL WASTE WATER TREATMENT PLANTS

There are problems associated with sludge management in small treatment plants (&amp;lt;10 L/s) located in rural communities, due to costly conventional technology for sludge stabilization. Many of these plants have only sludge drying beds. Mexican Institute of Water Technology has proposed developing suitable low-cost technologies, one of which is vermicomposting a biodegradation system using earthworms of the species Eisenia foetida (earthworm) which stabilize sludge and reduce its pathogenicity. The objective of this work is to present two case studies where vermicomposting technology has been applied in Mexico. The first study corresponds to a plant where 4.8 m3/month of sludge are produced; for these wastes, a vermicomposting system was built and installed. The second study is a treatment plant where 9 m3/month of sludge are produced; experimental tests were conducted with sludge and water hyacinth and a vermicomposting system was designed. The vermicomposts were analyzed using parameters defined by Mexican standards. In regards to stabilization, TVS was reduced by 38% and the microbiological quality of the vermicompost was Class A and B, with a reduction in fecal coliforms and Helminth eggs according to NOM-004-SEMARNAT-2002. A CRETI (Corrosivity, Reactivity, Explosivity, Toxicity and Ignitability) analysis (NOM-052-SEMARNAT-2005) was used to show that the process reduced the concentration of releasable sulfides. The agronomic quality of the vermicompost exhibited a high content of organic matter comparable to many organic manures and high content of nutrients such as nitrogen and phosphorus. It is concluded that it is possible to improve the conditions of sewage sludge management in small plants of rural communities with a minimum investment (less than $10,000.00 USD) and with a requirement of a minimum area of 60 to 70 m2 for a production of less than 9 m3/month of dehydrated sludge (80% humidity).

CH 4 and N 2O from mechanically turned windrow and vermicomposting systems following in-vessel pre-treatment

Methane (CH 4) and nitrous oxide (N 2O) are included in the six greenhouse gases listed in the Kyoto protocol that require emission reduction. To meet reduced emission targets, governments need to first quantify their contribution to global warming. Composting has been identified as an important source of CH 4 and N 2O. With increasing divergence of biodegradable waste from landfill into the composting sector, it is important to quantify emissions of CH 4 and N 2O from all forms of composting and from all stages. This study focuses on the final phase of a two stage composting process and compares the generation and emission of CH 4 and N 2O associated with two differing composting methods: mechanically turned windrow and vermicomposting. The first stage was in-vessel pre-treatment. Source-segregated household waste was first pre-composted for seven days using an in-vessel system. The second stage of composting involved forming half of the pre-composted material into a windrow and applying half to vermicomposting beds. The duration of this stage was 85 days and CH 4 and N 2O emissions were monitored throughout for both systems. Waste samples were regularly subjected to respirometry analysis and both processes were found to be equally effective at stabilising the organic matter content. The mechanically turned windrow system was characterised by emissions of CH 4 and to a much lesser extent N 2O. However, the vermicomposting system emitted significant fluxes of N 2O and only trace amounts of CH 4. In-vessel pre-treatment removed considerable amounts of available C and N prior to the second stage of composting. This had the effect of reducing emissions of CH 4 and N 2O from the second stage compared to emissions from fresh waste found in other studies. The characteristics of each of the two composting processes are discussed in detail. Very different mechanisms for emission of CH 4 and N 2O are proposed for each system. For the windrow system, development of anaerobic zones were thought to be responsible for CH 4 release. High N 2O emission rates from vermicomposting were ascribed to strongly nitrifying conditions in the processing beds combined with the presence of de-nitrifying bacteria within the worm gut.

Large-scale vermicomposting: emission of nitrous oxide and effects of temperature on earthworm populationsThe 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

Summary A large-scale, outdoor vermicomposting system was monitored for 80 weeks. Earthworm populations were recorded for 60 weeks in unheated beds operating at ambient temperatures (34 weeks at 6.3 ± 2.3 °C) and in heated beds controlled at 13.7 ± 0.8 °C for 34 weeks. Both blocks of beds were at ambient temperatures for the remaining 26 weeks. Earthworm biomass and the numbers of hatchlings and cocoons produced for the heated beds were found to be significantly greater than for the unheated beds. Nitrous oxide fluxes in winter (week 60) were 3.2 ± 0.3 mg m –2 h –1 (unheated beds), 1.8 ± 0.3 mg m –2 h –1 (heated beds), and these were significantly different to the control beds (0.1 ± 0.0 mg m –2 h –1 ). Emissions during summer (week 80) were 20.1 ± 3.0 mg m –2 h –1 (unheated beds), 21.3 ± 2.8 mg m –2 h –1 (heated beds) and these were significantly different to the control beds 3.9 ± 1.7 mg m –2 h –1 . No relationship between earthworm density and nitrous oxide flux was found for the large-scale beds. However, in a subsequent laboratory experiment, nitrous oxide emissions were positively correlated with earthworm density (R 2 = 0.76). Maintaining moderate bed temperatures for vermicomposting systems during low ambient temperatures can significantly increase earthworm density. Vermicomposting systems have the capacity to emit high levels of nitrous oxide and earthworms appear to be primarily responsible for this. The environmental impact from nitrous oxide emissions appears to be comparable to other waste processing operations. Further research is required into ways of minimising emissions especially from vermicomposting systems operating at high earthworm densities and high waste processing rates.