Use of Avoidance Tests for Investigating Potential of the Earthworm Eisenia fetida to Improve Composting of Grass Clippings

The earthworm Eisenia fetida is the most commonly used worm for worm-supported composting of organic residues. Within the present study, the potential of E. fetida for decomposing grass clippings, an organic waste which usually causes anoxic conditions and thus insufficient degradation in the course of common composting, was investigated. To enable a thorough investigation, the substrate-related requirements of E. fetida were studied using so-called avoidance tests. These tests provide a sensitive method for evaluating the preferences and aversions of soil animals related to substrate ingredients in a sublethal range. E. fetida favored relatively moist soil with about 70% of the WHC_max and the most preferred concentration of fresh grass clippings within soil was 15% (v/v). Pretreatments of the grass clippings like silage, precomposting or inoculation with the fungi Trichoderma viride and Geotrichum klebahnii were investigated and point to an increased tolerance of the worms against pre-composted and inoculated grass whereas ensiled grass and remoistened hay was avoided. The optimum concentration of ammonium for E. fetida was 18 μg NH₄⁺-N g^?1 DW soil although the worms could withstand much higher concentrations. Lactic and acetic acid, intermediates that are quickly released from fresh lawn clippings under oxygen lacking conditions, were indicated to be the most important factors for preventing worms from tolerating higher concentrations of grass clippings.     

Evaluation of Compost Activators for Composting Grass Clippings

The effects of seven manufactured commercially available activators were evaluated for their efficiency in the composting of yard trimmings (grass clippings/wood chip mixture). Two naturally available additives, and a control (absence of activator) were also evaluated. Four measures of composting efficiency were used to compare the overall decomposition response for each activator: weight loss, volume reduction, volatile solids decrease, and oxygen uptake rate. Four experimental blocks were set up in the field, and two experimental blocks were set up in the laboratory. The physical/chemical characteristics of the compost material were monitored as a function of time for each additive. Interrelationships between measures of composting efficiency were also evaluated. Results showed that grass clippings can be composted as efficiently with naturally available materials such as topsoil or mature compost, as with commercially available compost activators, or an unactivated control. The cost of commercially available activators was $1.37 to $9.36 per cubic yard of compostable grass clippings. Naturally available materials such as topsoil and mature compost are available in needed quantities at no cost to backyard composters.     

Clopyralid and Compost: Formulation and Mowing Effects on Herbicide Content of Grass Clippings

The presence of clopyralid, a selective broadleaf herbicide, in compost near Spokane, Washington in 2000 was attributed to grass clippings collected from area lawns and subsequently used as compost feedstock. A field study was conducted in 2001 to evaluate the effects of herbicide formulation and mowing practice on the clopyralid content of grass clippings. The objective was to develop guidelines that would limit the concentration of clopyralid in clippings, thereby reducing the amount of clopyralid entering the compost production stream. Clopyralid was applied to turfgrass as either a sprayable (S) or granular (G) formulation. Grass clippings were either collected in a bagging lawn mower and removed from the plots or returned into the plant canopy using a mulching mower designed to finely chop and disperse the leaf blades. Clippings were sampled for a period of ten weeks after application, and again in the summer of 2002, and analyzed for clopyralid content. Mowing treatment had no significant effect on clopyralid content of grass clippings. The S formulation resulted in higher concentration than the G at 4 hours after treatment (193 mg kg^?1 and 53 mg kg^?1, respectively). At 10 weeks after treatment (WAT), clopyralid concentration averaged 0.9 mg kg^?1, and cumulative recovery of clopyralid in grass clippings was 35% and 29% of the amount applied for the S and G formulations, respectively. By 56 and 98 WAT, clopyralid concentration in clippings was 0.06 and 0.02 mg kg^?1, respectively. Based on these results, and depending on feedstock dilution and composting conditions, a waiting period of up to one year after application of clopyralid could be necessary for treated grass clippings to be safely used as compost feedstock.     

Chemical and microbiological parameters for the characterisation of the stability and maturity of pruning waste compost

Composting of pruning waste, leaves and grass clippings was monitored by different parameters. A windrow composting pile, having the dimensions 2.5 m (height) x 30 m (length) was establish. The maturation of pruning waste compost was accompanied by a decline in NH₄ ⁺-N concentration, water soluble C (WSC) and an increase in NO₃ ^–-N content. Both organic matter (OM) content and total N (TN) losses during composting followed a first-order kinetic equation. These results were in agreement with the microbiological activity measured either by the CO₂ respiration or dehydrogenase (DH-ase) activity during the process. Statistically significant correlations were found between DH-ase activity, easily biodegradable organic C forms, NH₄ ⁺-N and NO₃ ^–-N concentrations and organic matter content and N losses. For this reason, DH-ase activity and the CO₂ evolution could be used as good indicators of pruning waste compost maturity. In contrast, humification parameters data from the organic matter fractionation did not agree with the initially expected values and did not contribute to the assessment of compost maturity. Neither the cation exchange capacity nor the germination index showed a clear tendency during the composting time, suggesting that these parameters are not suitable for evaluating the dynamics of the process.     

Nitrogen Mineralization of Grass Clippings — A Case Study in Fall Cabbage Production

In this three-year field study, grass clippings were applied to fall cabbage to determine the effectiveness of using this common yard waste as a nutrient supplement for crops. Objectives of this research were: 1) To determine the characteristics of grass clippings used in this study; 2) To monitor soil NH₄-N and NO₃-N dynamics in the upper 30-cm soil layer over time; and 3) To determine fall cabbage yield at various grass clippings application rates. The grass clippings used were heterogeneous in their chemical and physical characteristics. Even at the same application rate, soil NH₄-N and NO₃-N concentrations and yields were very different for each year. To avoid over- and underfertilization, targeted N supply from grass clippings should be less than necessary to grow fall cabbage. Additional N fertilizer can be applied based on the PSNT (pre-sidedress soil nitrate test).     

两种微生物菌剂对烟草废弃物高温堆肥腐熟进程的影响

以烟草废弃物为主要原料,添加合适比例猪粪进行高温堆肥试验,研究了烟草废弃物堆肥体系中加入两种微生物菌剂（NNY、FB）后的温度、总氮（T-N）、NH4＋-N、C/N、种子发芽指数（GI）的动态变化及其对烟草废弃物堆肥产品品质的影响。结果表明,添加微生物菌剂缩短了烟草废弃物堆肥达到高温的时间,延长了高温分解持续时间,增加全氮含量,加快物料NH4＋-N和C/N比的降低速率,提高种子发芽指数（GI）,加快了烟草废弃物堆肥腐熟化进程。纯烟草废弃物单独堆肥,最高温度为43℃,GI最高为78.4%。添加微生物菌剂NNY、FB的堆肥处理都在堆肥2d后进入高温分解阶段（〉50℃）,高温持续时间分别为15、12d,较仅添加合适猪粪比例处理进入高温分解阶段时间提前2d,高温持续时间分别延长5、2d。至堆肥11d,添加微生物菌剂NNY和FB的堆肥处理种子发芽指数较纯烟草废弃物处理分别增加了185.5%和117.7%,较仅添加合适比例猪粪处理分别增加了41.4%和7.6%。添加NNY、FB微生物菌剂的处理可以显著增加烟草废弃物堆肥产品的N、P、K养分含量,降低堆肥容重,提高堆肥总孔隙度和持水孔隙度,改善了堆肥产品的品质。两种微生物菌剂对烟草废弃物高温腐熟效果较优。     

Composting Process Optimization – Using On/Off Controls

Despite the commercialization of a variety of different composting systems, the design and operation of composting systems to minimize the cost of producing compost remains a major goal. Evaluation of how system design and management affects the time required to stabilize compost is critical to optimizing the process. In this study, analytical equations relating biological and physical factors and compost temperature, moisture, oxygen level and decomposition rates for aerobic composting are developed. The study focused on the effects of intermittent aeration on the composting operation. A multi-parameter kinetic model in conjunction with heat and mass balance equations were used to predict and optimize the performance of composting systems. Equations evaluating airflow and on/off fan cycle times on composting temperature, oxygen and moisture were developed. Kinetic data from pilot scale experiments using three different feedstocks: municipal solid waste, biosolids/woodchips, and grass/leaves/brush were used in the derived equations to evaluate the composting systems operation.     

Assessing How the Ratio of Barley Mash to Wood Chips in Compost Affects Rates of Microbial Processing and Subsequent Vegetable Yield

The composting of food waste coupled with urban agriculture presents an opportunity to increase nutrient recycling in urban ecosystems. One potential constraint limiting the expansion of aerobic food waste composting is the availability of carbon-rich recalcitrant materials, such as wood chips. We measured the differences in nutrient retention throughout the compost life cycle for different mixtures of barley mash to wood chips, to assess whether composting using proportionally less wood chips would lead to higher nutrient recycling rates. Nine compost piles (1 m³) were constructed at varying ratios barley mash to wood chips, ranging from 10:90 to 90:10. During the composting process, the 50:50 mixture maintained internal temperatures above 55°C for 30 days, with drop-offs as mixtures diverged in either direction. Food waste content was positively related to internal moisture and CO₂, and negatively related to internal O₂, throughout the ensuing 3 months. The finished compost was used in raised-bed garden plots during the following summer. Yields of arugula and tomatoes increased with compost barley mash content, saturating at high levels. Across all treatments, <5% of N and <2% of P were recycled from barley mash into new vegetable production. Although the maximum amount of nutrients was recycled using high barley mash compost, these treatments also had lower nutrient recycling efficiency compared to intermediate mixtures. These results indicate that the use of wood chips in composting increases the efficiency nutrient retention from food waste and in turn enhances nutrient recycling in urban environments.     

Evaluation of Organic Wastes for Composting

Management of organic wastes is essential to reduce environmental pollution and increase resources of plane nutrients for crop production. This study was undertaken to evaluate major organic wastes produced in northwestern Pakistan for characteristics that are useful for composting. Organic wastes such as manures, municipal wastes (MW), crop residues, fruit/vegetable wastes, and yard wastes contained large reserves of nutrients. Manures had high nitrogen (N) and crop residues had low N. Crop residues were relatively dry (7–12% moisture); MW, poultry manure, sheep manure, leaves, and city garbage were moderately moist (27–47% moisture), whereas cattle manure (CM), fruit and vegetable wastes, and grass clippings were wet (62–89% moisture). The compost developed from mixing MW with CM matured early and had low C/N ratio compared with either source alone. These results suggested that MW could be converted into compost when mixed with CM. The inoculation of wastes with effective microbes (EM) was ineffective in expediting the process of composting.     

Influence of Different Nitrogen Sources on Composting Of Miscanthus in Open and Closed Systems

Composting of Miscanthus straw was compared in two different, insulated systems, one constructed from four open boxes and one of four closed reactor vessels. Composting of Miscanthus supplemented with either ammonium sulfate, urea, liquid pig manure or brown sap from grass was studied. Hygienization of composts was evaluated by integrations of heat developments. Mixtures of Miscanthus and ammonium sulfate or liquid pig manure lead to high heat development in beginning of composting period while composting of mixtures of Miscanthus and brown sap or urea progressed later in composting period. The period of high microbial activity during composting may therefore be extended using mixtures of manure and brown sap or ammonium sulfate and urea as nitrogen source.     

Cocomposting Separated MSW And Poultry Manure in Morocco

Separated municipal solid waste (SMSW) was composted using poultry manure (PM), to lower moisture content and the C/N ratio. Two different mixtures (3:2 and 2:3, SMSW:PM w.w. ratio) and two particle biomass sizes (1 cm and 0.2 cm) were studied to assess the final compost quality and the feasibility of composting. Results suggest that the 3:2 SMSW:PM starting mixture ratio gave less compost yield than the 2:3 ratio, although the compost characteristics were very similar for both mixtures. Results also showed that a smaller particle size (0.2 cm) increased the degradation rate of the waste matter and the degree of evolution to the final products, but only slightly. The final compost products, regardless of the initial mixture ratios and particle size, appear very similar and of good quality, suggesting composting to be a useful biotechnology for processing waste matter produced in Morocco.     

In-Vessel Cocomposting of Green Waste With Biosolids and Paper Waste

In comparison to traditional windrow composting, in-vessel composting techniques often represent more effective waste management options due to the reduced production of bioaerosols and leachate and the potential for better process control. Chemical processes occurring during the cocomposting of three common wastes (green waste, biosolids and paper processing waste) were studied using the forced aeration, static pile, in-vessel EcoPOD® composting system. Since no turning of the compost occurs within the static piles, spatial differences in the vessel were also monitored. These measurements revealed significant spatial gradients in temperature; however, this did not result in spatial differences in nutrients within the composting vessel. Significant differences in soluble N production were observed during the composting process following the series: green plus paper waste < green waste < green waste plus biosolids. After the active compost phase was over, and the compost was removed from the vessel and matured outside, we demonstrated that covering the compost was essential to preserve compost quality. Our study clearly shows that cocomposting of common waste feedstocks can be used to successfully manipulate the chemistry of the final compost making it suitable for multiple end uses. In addition, our study demonstrated that careful management of the compost maturing phase is also required to maximise quality and minimize pollution.     

MSW Compost Reduces Nitrogen Volatilization During Dairy Manure Composting

Manures lose N through volatilization almost immediately after deposit. Attempts to control losses include the addition of a C source to stimulate nitrogen immobilization. Composting is a treatment process that recommends the addition of carbonaceous materials to achieve a C:N ratio of 30:1 to stimulate degradation and immobilize nitrogen. Dairies near cities may be able to reduce N loss from manures by composting with urban carbonaceous residues such as municipal solid waste (MSW) or MSW compost that, by themselves, have little agronomic value. Studies were conducted using a self-heating laboratory composter where dairy solids were mixed with MSW compost to determine the reduction of N loss during composting. One-to-one mixtures (v/v) of dairy manure solids and MSW compost were composted and NH₃ volatilization, CO₂ evolution and temperatures were compared to composting of manure alone. Addition of MSW compost resulted in increased CO₂ evolution and reduced N loss. Nitrogen loss from composting dairy manure alone was four to ten times greater than that from composting dairy manure mixed with MSW compost. Adjustment of the C:N ratio to 25 by adding MSW compost to manure appeared to be the major factor in reducing N losses.     

Effect of Feeding Regime on Composting in Bins

Composting in bins is one of the most practical home composting methods. There is currently a need for greater information to improve the management of the composting process and to create home composting programs, which ensure sustainable production of high quality compost. This study investigates how two aspects of the bin feeding regime—the feeding frequency and the amount of waste applied at each feed—influence the process's evolution and the quality of the compost. Compost bins were assayed after introducing the same amount of kitchen and garden waste according to three different frequencies: in a single batch, weekly, or every 3 weeks. A fourth treatment was applied to calculate the potential waste reduction achieved by the composting process, filling the bins to the brim on a weekly basis. Temperature, mass, and volume changes; the microbial diversity (by Biolog); and gas emissions (CO₂, CH₄, N₂O, and NH₃) were all determined during the process. At the end of the experiment, all of the composts were weighed and characterized. Results show that the main differences were very dependent on the quantity of waste provided. Large amounts of waste were added increasing the compost's temperature and maturity during the process, while slightly affecting the salinity and phytotoxicity of the final compost but without any clear effects on microbial diversity and gas emission. Therefore, from a technical point of view, the shared use of compost bins among several households (community composting) is preferable to individual use.     

盐含量对餐厨垃圾好氧堆肥腐殖化过程及微生物演变的影响

含盐量过高会对堆肥有机质腐殖化过程产生抑制作用,但作用规律仍不清楚。该研究以餐厨垃圾为研究对象,以不添加盐分的处理为对照,设置添加食用盐的处理作为试验组（添加质量分数分别为0.5%、1%和1.5%）,进行好氧堆肥,研究不同盐分含量对基本腐熟度指标、有机质组成、腐殖质（Humus,HS）的影响,并结合微生物群落结构和相关性统计分析阐明其作用规律。结果表明,4个处理温度、碳氮比（C/N）、有机质组成等达到腐熟要求,但盐分添加提高了堆体电导率（Electrical Conductivity,EC）,添加比例达到1.5%时,高温期缩短至13 d,种子发芽指数（seed Germination Index,GI）降低至65.5%,总有机物降解率降低6.5%,有机质腐殖化过程受到限制。高通量测序和相关性分析的结果表明,添加1.5%盐分主要通过抑制高温双岐菌（Thermobifida）、糖单孢菌（Saccharomonospora）和曲霉（Aspergillus）、毛孢子菌（Trichosporon）的活性,降低总糖、木质纤维素等有机物质的降解和后续HS形成,从而限制餐厨垃圾堆肥过程中腐殖化效果的提升。本研究将为餐厨垃圾等农村有机废弃物处理技术应用提供理论指导。     

Yard Waste Composting: Studies Using Different Mixes of Leaves and Grass in a Laboratory Scale System

Composting has become a widely used method of recycling yard wastes such as leaves and grass. However, very little information is available on the chemical changes that occur during the composting of different mixtures of leaves and grass. In this study, three different mixes of leaves and grass were composted at approximately 60% moisture in a temperature controlled laboratory scale system. The mixes, which consisted of all leaves (Mix 1); 2/3 leaves + 1/3 grass (Mix 2); and 1/3 leaves + 2/3 grass (Mix 3), had initial C:N ratios of 48, 30 and 22, respectively. The compost process was monitored by measuring the rate of CO₂ evolution, pH, stability, the degree of humification and changes in polysaccharide, carbon, nitrogen and organic matter content. Results showed that the greater the grass content of the mix, the higher the initial pH and the faster the rate of CO₂ evolution, organic matter loss and nitrogen loss. After 43 days of composting, Mixes 1, 2 and 3, lost, respectively 61%, 74% and 78% of the cellulose, 57%, 79% and 82% of the hemicellulose and 40%, 49% and 42% of the acid-insoluble organic matter. Humification indices and stability tests indicated that composts produced from the three mixes were well humified and stable.     

Windrow Composting of Waste Paint Sludge Containing Melamine Resins

ABSTRACT

Melamine resins (MR), widely used in various industries, are thermosetting plastics that have hard and durable properties. These resins can be introduced into the environment as components of waste products or via industrial effluents. It is important to seek environmentally friendly means to recycle, remove, or degrade melamine resins before they are released to the environment. Waste paint sludge containing MR has been shown to be efficiently composted under bench-scale conditions. In this study, the impacts of C/N ratios on windrow composting of waste paint sludge containing MR were evaluated. As composting proceeded, temperature, concentrations of MR and melamine degradation products (i.e., ammeline, ammelide, and cyanuric acid) were determined. After 98 days of composting, 87.5, 83.3, 80.9, and 70.1% of the initial MR were degraded under the treatments with C/N ratios of 30, 33, 35, and 37, respectively. Degradation of MR was enhanced by relatively low C/N ratios. Significant amounts of plant nutrients were found in the final composts, while heavy metals were well below values considered to be of concern regarding surface water quality or crop production. We conclude that adjusting C/N ratio to approximately 30 in the initial mixtures with oat and hay straws can increase the degradation of MR and its derivatives during windrow composting of waste paint sludge containing MR and produce a good quality compost product.     

Changes in Chemical,Physical and Biological Properties Of Passively-Aerated Cocomposted Poultry Litter And Municipal Solid Waste Compost

Cocomposting of poultry litter with municipal solid waste compost (MSW) was evaluated as a means to stabilize nitrogen and phosphorus in poultry litter and to produce a stable organic soil amendment. Four passively aerated compost piles were established by mixing fixed weight ratios of MSW and composted poultry litter (21:1, 6:1, 3:1, 1:1); moisture was adjusted to 50 percent by weight at pile establishment. These ratios represented a range of initial C:N (26-12) and C:P (150-50) ratios. Composting process parameters monitored over eight months included temperature, oxygen and moisture contents, pH, electrical conductivity, C:N:P ratios, microbial respiration and diversity. Initial feedstock ratios had no significant effect on temperature in the thermophilic phase of composting. After one year of composting, microbial respiration in 21:1 and 6:1 mixtures was high relative to 3:1 and 1:1 mixtures suggesting slow maturation in piles with high MSW content. Salmonella sp. and coliform organisms were detectable for up to 47 days. Results suggest that MSW has potential as a carbon feedstock for poultry litter composting when used in moderate amounts.     

Wood Ash as an Amendment in Municipal Sludge And Yard Waste Composting Processes

Wood ash from a wood-fired, electrical generating plant was examined as a potential amendment in municipal biosolids and yard waste composting applications. The rate of composting and the final compost quality (chemical, physical, and plant growth characteristics) were examined. Yard waste (leaves, grass, and wood chips) and a municipal biosolids-chip mixture were either not amended or amended with wood ash at eight percent or five percent by weight, respectively, and then composted outdoors in insulated, 1700L, aerated reactors. Yard waste piles heated rapidly to 60°C within six to seven days, whereas biosolid piles heated more slowly to a maximum of 52 to 57°C within nine to 11 days. Ash had little, if any, effect on the time-temperature response. In general, ash-amended compost had higher pi I, plant nutrient, and salt contents. Tomato plants (Lycopersicum esculentum) produced 100 percent more shoot biomass in biosolids than in yard waste compost media. Poor plant growth in the yard waste compost was likely due to the high initial pH and salt content of the growth medium. In yard waste media, tomato plants germinated and produced more shoot biomass in the control compost than in the ash-amended compost.

A pH neutralization study indicated that wood fly ash could be used as an economical substitute for lime which is commonly used to stabilize municipal biosolids prior to land filling or land application. Wood fly ash (pH = 13.2-13.4), when added to biosolids at a 2 to 1 ratio by weight, raised the pH of the mixture to 12.0.     

SE—Structures and Environment: Compost Airflow Resistance

Four bulking agents, pine shavings, mixed (long and chopped) grass hay, chopped grass hay and long (whole) wheat straw, were each mixed with pig slurry and tap water to obtain three moisture contents (MC) of 60, 65 and 70%. Quadruplets of each treatment were placed in laboratory composting vessels with a capacity of 105 l and a composting depth of 0·95 m. Using the air plenum at the bottom of each vessel, air was forced at apparent velocities of 0–0·002 m s⁻¹ through each compost mass to measure the air static pressure drop across the compost mass as a function of apparent air velocity. Airflow resistance values were measured for compost depths ranging from 0·55 to 0·85 m. Following this test, all mixtures were aerated for 21 days of composting without overturning. The static pressure measurement procedure was then repeated on all quadruplet mixtures.The air static pressure drop was found with respect to a packed bed under laminar flow, defined using the particle size distribution, porosity, depth and airflow channel characteristics of the compost material. Although MC affected the value of the airflow channel characteristics of the compost material, both the hay and straw demonstrated similar values, while shavings demonstrated values more variable and wider values for MC between 60 and 70%.There was a significant increase in airflow resistance after 21 days of composting, which supports the need for compost overturning to reestablish the material's structure and to restore the airflow channels or pores.