Effect of turning frequency on co-composting pig manure and fungus residue

Composting of agricultural wastes not only can reduce environmental pollution caused by improper disposal, but also can recycle agricultural wastes and transform them into highly valuable products, such as fertilizers or soil conditioners, for agricultural applications. However, the composting process and final product are easily affected by the limited oxygen supply that results from insufficient aeration, especially in the center of a large-scale windrow. Hence, a pilot-scale experiment was conducted to investigate the effects of the turning frequency on the composting efficiency and compost quality of used pig manure and fungus residue. Physical and chemical characteristics were measured over the course of 63 days of composting. The data indicate that higher temperatures and more rapid moisture removal generally result from a turning treatment of once every 2–4 days than in fewer, or no, turning treatments. The total nitrogen, total phosphorus, and total potassium contents increased in all windrows as the organic matter content decreased, but both the increases and decrease were greater in windrows that were turned more frequently. The reduction of the organic matter mass by 53.7–66.0% for a turning of once every 2–8 days is significantly higher than that for the static windrow (39.1%). Although there is an increase in nitrogen mass loss with an increased turning frequency, lower nitrogen mass losses (12.7–25.7%) in all treatments were noted compared with previous studies. A final compost product with less moisture, less weight, higher nutrient content (N, P, and K), and greater stability was obtained in windrows with turning frequencies of once every 2–4 days, which is recommended when composting pig manure and fungus residue.

Implications: Composting of agricultural wastes not only can reduce environmental pollution caused by improper disposal, but recycling of agricultural wastes transforms them into highly valuable products, such as fertilizers or soil conditioners, for agricultural applications. However, the composting process and final product are easily affected by the limited oxygen supply that results from insufficient aeration, especially in the center of a large-scale windrow. Hence, a pilot-scale experiment was conducted to investigate the effects of the turning frequency on the composting efficiency and compost quality of used pig manure and fungus residue, so as to capture an operational technique suitable for the effective co-composting pig manure and edible fungi residue for a large-scale composting plant.     

Composting of spent pig litter in turned and forced-aerated piles

A study was carried out to compare the compositing efficiency of spent litter (a mixture of partially decomposed pig manure and sawdust) in turned and forced-aerated piles. Duplicate piles were built with manual turning (every 4 days) during composting, and duplicate piles were set up with forced aeration using an air pump. The present study demonstrated that the efficiency of composting in the turned and forced-aerated piles was similar. Spent litter in these piles reached maturity at the same time (60 days). The forced-aerated piles went through similar physical, chemical, and microbial changes with the turned piles during composting. The forced-aerated composting system was also as effective as the turned system in eliminating Salmonella sp. in the spent litter. These results suggest that a forced-aerated composting system could be used as an alternative method in composting spent litter. The similarities in temporal changes in temperature, chemical, and microbiological properties of the forced-aerated piles, compared with the turned piles, indicate that addition of a bulking agent under forced aerated composting of spent litter is not necessary. The partially decomposed sawdust in the spent litter provided enough free air space, allowing the delivery of oxygen for the microorganisms in the spent litter piles.     

Composting of spent pig litter at different seasonal temperatures in subtropical climate

To investigate the effects of seasonal temperatures on the composting of spent pig-manure sawdust litter (spent litter), two sets of experiments were carried out: one during winter, the other during summer. Physicochemical and microbial parameters including temperature, pH, inorganic N, humification indicators (HA and FA), heavy metals (Cu and Zn), total aerobic heterotrophs, ATP content and dehydrogenase activity were measured to understand changes in the spent litter during composting. Results demonstrated that the composting was faster during summer than winter. The spent litter during the summer trial reached maturity at day 56 whereas that of the winter trial was still immature at the end of composting (days 91). Microbial activities during the thermophilic stage of composting were much lower in the winter trial. Values began to increase during the latter part of composting, indicating that the spent litter in this winter trial was biologically unstable and must be further composted to reach full maturity. The changes in the microbial activities of the spent litter during summer or winter reflected the changes in their temperatures and chemical properties. The maturation of the spent litter during summer was accompanied by stabilization of the microbial and chemical properties and a drop in temperature to ambient level. Results of correlation analysis showed that temperature correlated not only with the microbial parameters but also with most of the chemical parameters. These parameters also correlated with each other. Among all the parameters measured, the trend of temperature changes is the simplest and most rapid parameter that can be used to evaluate the maturity of spent litter.     

Effects of composting on phytotoxicity of spent pig-manure sawdust litter

The phytotoxicity of spent pig-manure sawdust litter (spent litter) was evaluated during further composting. Aqueous extracts of the spent litter were prepared by shaking the sample with water (1:10 w/v), and the toxicity of these extracts was determined on relative seed germination, relative root elongation and germination index (GI, a factor of relative seed germination and relative root elongation). The sensitivity of six plant species, namely Brassica parachinensis (Chinese cabbage), Brassica albogalera (Chinese kale), Allium sativum (onion), Cucumis sativus (cucumber), Amaranthus espinosus (Chinese spinach), and Lycopersicon esculentum (tomato) were compared. The effect of different moisture levels during composting on the phytotoxicity of the spent litter was also examined. Phytotoxicity of the spent litter was only evident during the earlier stage of composting (first 14 days) and, that seed germination and root elongation reached 100% (same as the control) towards the end of the composting. The concentrations of the major inhibitors, water-extractable Cu and Zn, and NH4(+)-N of the spent litter, declined during composting, indicating that these inhibitors were gradually eliminated as composting proceeded. Multiple regression analysis showed that the NH4(+)-N content of the spent litter was the most important chemical factor affecting phytotoxicity of the plant species selected for this study. Relative root elongation and GI were more sensitive indicators of phytotoxicity than seed germination. In the present study, the GI's of all plant species were >80% at day 60, indicating that the spent litter had reached its maturation by day 60. The responses of different plant species to the water-extracts of the spent litter were different. Among the six species, Chinese cabbage and Chinese spinach were the most sensitive species, and tomato and cucumber were the least sensitive species to indicate phytotoxicity of the spent litter. Moisture adjustment during the composting process did not affect the results of the phytotoxicity test.     

土霉素残留对猪粪堆肥过程中理化性质的影响

为探讨土霉素残留对猪粪堆肥过程的影响,以猪粪和锯末为原料,设置土霉素初始残留质量浓度分别为0、10、50、100、150 mg/kg的5个处理,进行为期30 d的好氧堆肥,研究土霉素对堆肥过程中温度、含水率、水溶性NH4+-N、水溶性NO3- -N、水溶性有机碳(DOC)的变化影响.结果表明:(1)土霉素残留加速了温度的下降,不利于温度的上升.(2)土霉素初始残留质量浓度为100、150 mg/kg不利于堆肥过程中水分的散失,并且会造成堆肥结束后堆体的高含水率.(3)土霉素抑制了堆肥过程中微生物对有机氮的分解及硝化细菌的硝化作用,其中150mg/kg处理的土霉素抑制作用最显著.(4)堆肥结束后,0、10、50、100、150 mg/kg处理的DOC分别为3 815.65、3 461.88、3 429.28、3 231.18、2 782.09mg/kg.0 mg/kg处理的DOC高于其他4个处理,且与150 mg/kg处理之间差异显著,表明土霉素抑制了堆肥过程中微生物对有机碳的利用,其中150 mg/kg处理的土霉素抑制作用最显著.     

Fate of nitrogen during composting of chicken litter

Chicken litter (a mixture of chicken manure, wood shavings, waste feed, and feathers) was composted in forced-aeration piles to understand the changes and losses of nitrogen (N) during composting. During the composting process, the chemical [different N fractions, organic matter (OM), organic carbon (C), and C:N ratio], physical, and microbial properties of the chicken litter were examined. Cumulative losses and mass balances of N and organic matter were also quantified to determine actual losses during composting. The changes in total N concentration of the chicken litter piles were essentially equal to those of the organic N. The inorganic N concentrations were low, and that organic N was the major nitrogenous constituent. The ammonium (NH(4)(+))-N concentration decreased dramatically during first 35 days of composting. However, the rapid decrease in NH(4)(+)-N during composting did not coincide with a rapid increase in (NO(3)(-)+NO(2)(-))-N concentration. The concentration of (NO(3)(-)+NO(2)(-))-N was very low (<0.5 g kg(-1)) at day 0, and this level remained unchanged during the first 35 days of composting suggesting that N was lost during composting. Losses of N in this composting process were governed mainly by volatilization of ammonia (NH(3)) as the pile temperatures were high and the pH values were above 7. The narrow C:N ratio (<20:1) have also contributed to losses of N in the chicken litter. The OM and total organic C mass decreased with composting time. About 42 kg of the organic C was converted to CO(2). On the other hand, 18 kg was lost during composting. This loss was more than half (59%) of the initial N mass of the piles. Such a finding demonstrates that composting reduced the value of the chicken litter as N fertilizer. However, the composted chicken contained a more humified (stabilized) OM compared with the uncomposted chicken litter, which would enhance its value as a soil conditioner.     

Degradation of aldrin and endosulfan in rotary drum and windrow composting

Removal efficiencies, kinetics and degradation pathways of aldrin, endosulfan α and endosulfan β in vegetable waste were evaluated during rotary drum and conventional windrow composting. The highest percentage removal of aldrin, endosulfan α and endosulfan β in rotary drum composting was 86.8, 83.3 and 85.3% respectively, whereas in windrow composting, it was 66.6%, 77.7% and 67.2% respectively. The rate constant of degradation of aldrin, endosulfan α and endosulfan β during rotary drum composting ranged from 0.410–0.778, 0.057–0.076 and 0.009–0.061 day^?1 respectively. The pathways of degradation of these pesticides in composting process were proposed. Metabolites dieldrin and 1 hydroxychlorodene formed during composting of aldrin in the vegetable waste indicated the occurrence of epoxidation reaction and oxidation of bridge carbon of aldrin containing the methylene group. Formation of chloroendic acid and chloroendic anhydride during composting of endosulfan containing vegetable waste support the occurrence of endosulfan sulfate and dehydration reaction respectively.     

添加小麦秸秆对猪粪高温堆肥腐熟进程的影响

选用猪粪与小麦秸秆为堆肥原料进行高温好氧堆肥实验,研究添加小麦秸秆对猪粪高温好氧堆肥过程中堆体温度、pH值、种子发芽指数、碳氮比和养分等理化指标的影响,寻求猪粪高温堆肥时的最佳秸秆配比,旨在为猪粪快速资源化利用提供科学依据。结果表明,猪粪高温堆肥时添加小麦秸秆可以缩短进入高温发酵阶段的时间,减少氮素损失,加快C/N的降低速率,加速有毒有害物质分解。其中猪粪和小麦秸秆6∶4处理各层温度在2~5 d内上升至50℃,并持续37~46 d,在堆肥结束时,有机质和速效氮含量较堆肥初期下降幅度最小,分别为33.90%和23.76%,全氮、全磷、全钾、速效磷和速效钾含量较堆肥初期提高幅度最大,分别为13.34%、20.24%、53.19%、41.53%和16.57%。若以种子发芽指数80%作为堆肥腐熟的评价指标,猪粪和小麦秸秆6∶4配比堆肥的腐熟速度比纯猪粪快18 d,36 d即可腐熟。综合判断,实际应用中,猪粪与小麦秸秆按体积6∶4进行堆肥较为适宜。     

Composting duck excreta enriched wood shavings: C and N transformations and bacterial pathogen reductions

Composting of agricultural and domestic wastes is used increasingly to reduce weight, volume, and odor; destroy animal and plant pathogens; and improve the quality of end-products to be used as soil amendments and growth substrates. The objective of this study was to investigate the transformation of C and N and the survival of bacterial populations and pathogenic bacteria during in-vessel composting of duck excreta enriched wood shavings. Two feedstocks, collected on different dates, were composted (C1 and C2) in an enclosed hall system equipped with an electromechanical turner. Temperature was continuously recorded, whereas moisture content and bacterial counts were determined twice a week. Data showed that, although the N content of C2 was only half of that of C1, both materials were fully biostabilized at the end of the composting period as indicated by extractable lipid ratios. In the compost with the low C/N ratio (C1), all bacterial populations were eliminated, whereas fecal streptococci, total coliforms, and gram-negative bacteria were still present in C2 at the end of the composting period. Our results emphasize that the composting of manures and other organic wastes needs to be properly managed to stabilize C and N and to eliminate or reduce bacterial populations.     

不同生物炭对猪粪堆肥过程中抗生素及抗生素抗性基因的削减规律研究

为探讨不同类型生物炭对猪粪堆肥过程中抗生素和抗生素抗性基因(ARGs)的削减规律,分别将玉米秸秆生物炭、竹炭和猪粪生物炭添加到猪粪中进行好氧堆肥,解析不同类型生物炭添加对猪粪堆肥过程中抗生素浓度和ARGs丰度的影响.研究发现,添加竹炭堆肥对抗生素的平均去除率最高(97％),其中对四环素类抗生素的去除率高达98％;添加玉...     

固体废弃物的堆肥化处理技术

固体废弃物已成为限制城市发展的重要环境问题.堆肥化处理是固体废弃物资源化利用的一种方式,已逐渐被国内外所重视.本文综述了现有的三种堆肥化系统:条垛式系统、通气静态垛式系统和发酵仓式系统,介绍了三种系统的优缺点.     

When is a soil remediated? Comparison of biopiled and windrowed soils contaminated with bunker-fuel in a full-scale trial

A six month field scale study was carried out to compare windrow turning and biopile techniques for the remediation of soil contaminated with bunker C fuel oil. End-point clean-up targets were defined by human risk assessment and ecotoxicological hazard assessment approaches. Replicate windrows and biopiles were amended with either nutrients and inocula, nutrients alone or no amendment. In addition to fractionated hydrocarbon analysis, culturable microbial characterisation and soil ecotoxicological assays were performed. This particular soil, heavy in texture and historically contaminated with bunker fuel was more effectively remediated by windrowing, but coarser textures may be more amendable to biopiling. This trial reveals the benefit of developing risk and hazard based approaches in defining end-point bioremediation of heavy hydrocarbons when engineered biopile or windrow are proposed as treatment option.     

Integrated waste management through producers and consumers education: composting of vegetable crop residues for reuse in cultivation

As part of the design of an integrated waste management scheme through the use of the PRECEDE/PROCEED model in the area of Crete, data concerning the applicability of composting in various agricultural wastes was considered as necessary. Vegetable residues from tomato, cucumber, eggplant, and pepper crops were collected, shredded and composted either alone or with the use of olive press cake, olive tree leaves, and branches and vine branches as bulking agents. Seven random combinations--mixtures of the above materials were composted using windrows, where additional four similar windrows were made up by approximately 10 m3 of the above mentioned vegetable crop residues. All windrows were turned four times during the eight weeks thermophylic phase, with the help of a mechanical turner. A large number of physiochemical parameters were monitored in the raw materials, at the end of the thermophylic phase and at the end of the maturation phase. The temperature which was monitored daily, recorded the highest values (above 55 degrees C) in the windrows where bulking agents were used. All raw vegetable crop residues and their mixtures presented increased electrical conductivity values (above 5 mS/cm and up to 9.7 mS/cm) resulting to end products with respectively high EC values (above 3 mS/cm and up to 15 mS/cm) probably due to the presence of large amounts of soil, rich in fertilisers, attached to the roots of the plants. There was no detection of any remains of the 13 pesticides for which all 11 composts were tested for. The accuracy of the results was tested through a recovery test of the pesticides in mature compost, resulting to acceptable recovery values.     

The use of elemental sulphur as organic alternative to control pH during composting of olive mill wastes

High values of pH may represent a limitation for the agricultural use of the composts, not only when used as soil-less substrate but also as soil amendment in high pH soils. The addition of elemental S during the maturation phase of the composting process was evaluated as suitable method to reduce pH of the composts under the organic agriculture regulations. A compost prepared with two phase olive mill waste (OMW) and sheep litter (SL) was used to study the effect of elemental sulphur addition on the pH of the composting mixture. Initially, different bench scale experiments were designed in order to study the influence of moisture, sulphur concentration, and incubation temperature on the sulphur oxidation rate and thus on the pH of the compost. A concentration of 0.5% in sulphur (dry weight basis) and moisture of 40% were proposed as the optimum conditions to decrease the compost pH by 1.1 units without increasing in EC to levels that may suppose a limitation for its agricultural use. Finally, these optimum experimental conditions found at bench scale were tested at full scale in a commercial composting plant treating the same organic materials by windrowing. The pH values of the composting mixture were reduced by one unit after 2 weeks following the addition of elemental S causing no negative effects on the final compost quality.     

Preventive control of odor emissions through manipulation of operational parameters during the active phase of composting

Better understanding of the effects of key operational parameters or environmental factors on odor emission is of critical importance for minimizing the generation of composting odors. A series of laboratory experiments was conducted to examine the effects of various operating conditions on odor emissions. The results revealed that airflow rates that were too high or too low could result in higher total odor emissions. An optimal flowrate for odor control would be approximately 0.6 L/min.kg dry matter with intermittent aeration and a duty cycle of 33%. Temperature setpoint at 60°C appeared to be a turning point for odor emission. Below this point, odor emissions increased with increasing temperature setpoint; conversely, odor emissions decreased with increasing temperature setpoint above this point. With regard to the composting material properties, odor emissions were greatly affected by the initial moisture content of feedstock. Both peak odor concentration and emission rate generally increased with higher initial moisture content. Odor emission was significant only at moisture levels higher than 65%. An initial moisture level below 45% is not recommended due to concern with the resulting lower degree of biodegradation. Biodegradable volatile solids content (BVS) of feedstock had pronounced effect on odor emissions. Peak odor concentration and emission rate increased dramatically as BVS increased from 45% to 65%, thus, total odor emission increased exponentially with BVS.     

Impact of drying and composting procedures on the concentrations of 4-nonylphenols, di-(2-ethylhexyl)phthalate and polychlorinated biphenyls in anaerobically digested sewage sludge

Enhanced treatments of sewage sludge produce a more manageable product for agricultural use by stabilizing the material, removing water, and reducing the possibility of pathogen transfer. We investigated the impact of pilot-scale composting and drying of sludge on physicochemical characteristics and on the concentrations of some organic contaminants. During the 143 day composting procedure, organic matter fell 22% and moisture by half. Concentrations of 4-nonylphenols (4-NPs) fell by 88% and di-(2-ethylhexyl) phthalate (DEHP) by 60%; losses continued throughout the procedure. Losses of total polychlorinated biphenyls (PCBs) were 11%, mostly from the lower molecular weight congeners, suggesting volatilization as the most likely loss mechanism. The drying process was much shorter, 40 days, yet organic matter content decreased by 27% and moisture by 85%. Losses of 4-NPs (39%) and DEHP (22%) were less than in composting and stopped when moisture content became constant. There were no losses of PCBs. Both treatments are simple, practical procedures that reduce the volume of waste and are applicable in situ on farms. Composting would be the method of choice for reducing organic contaminants but requires much longer times than drying.     

Effects of different ratios of pig manure to fungus residue on physicochemical parameters during composting

This study examined physicochemical parameters to assess their effectiveness as stability and maturity indicators during the process of composting pig manure and fungus residue at different ratios. The results showed that composting mixtures with all ratios of pig manure to fungus residue maintained a temperature exceeding 50 °C for more than 10 days during composting and met the requirement for pathogen destruction. The treatment containing mainly pig manure showed higher nitrogen loss and a shorter thermophilic phase and maturity time than the treatment containing mainly fungus residue. The germination index (GI) values indicated that compost maturity was achieved in the final compost with initial ratios of pig manure to fungus residue of 9:1–7:3 (GIs of 101.4%, 91.2%, and 81.3%); the ratio of 6:4 did not reach compost maturity (GI of 63.8%) and had an inhibitory effect on seed germination. The results of this study suggest that a ratio of pig manure to fungus residue of approximately 8:2 can be considered suitable for the efficient and quality composting of pig manure and fungus residue.

Implications: Co-composting of pig manure and edible fungi residue with appropriate proportion can effectively reduce the risk of environmental pollution caused by agricultural wastes, as well as achieve a safer and high-quality organic fertilizer, which can be used to improve physical and chemical properties of the soil, increase crop yields, and promote agricultural sustainable development. Therefore, technique of co-composting of pig manure and edible fungi residue has a wide prospect of application in practical production all over the world.     

Wastes of multilayer containers as substrate in composting processes

An evaluation of the influence and degradation of ground multilayer containers, such as Tetra Brik Aseptic (TBA), in the composting process of municipal solid wastes (MSW) is presented. Two composting piles were formed by mixing, in different proportions, an organic fraction of MSW and TBA material ground as flakes or stripes. Piles were periodically aerated by mechanical mixing. Evolution of the composting was followed by frequent measurements of suitable parameters such as temperature, moisture, ashes, total organic carbon (TOC), nitrogen, C/N ratio, pH, conductivity, nutrients, and heavy metals. As expected, aluminum and polyethylene films from TBA were not degraded during the processes, but the cardboard fraction of TBA showed a partial decomposition that was more intense in the material ground as flakes. After two months of curing, the composts were refined and analyzed to determine their nutrient and heavy-metals contents. Despite their poor aesthetic properties, mainly resulting from the presence of little pieces of plastic and aluminum films, the composts contained the required amounts of nutrients; furthermore, their heavy-metals content was below the limits proposed by some official European organizations.     

垃圾堆肥工艺过程动态模拟及优化研究

选取通气量、含水率、温度、底物浓度等作为堆肥控制因子,在堆肥生物反应动力学的基础上,根据堆肥反应过程的物料平衡和能量平衡,以及微生物比生长速度与含水率、堆肥温度的依存关系,结合翻转式堆肥反应装置操作运行条件,对厨房垃圾好氧堆肥过程中堆温、含水率、有机物、微生物量及氧气消耗量等变化进行计算机模拟计算,并将模拟结果与堆肥实验结果进行对比。结果证明,除了由于反应装置保温不理想引起堆温和含水率二者有偏差外,总体模拟计算结果与实际堆肥结果基本吻合。另外还开展了利用所开发的模型进行堆肥通气优化的应用研究。模型计算结果表明当出口氧气控制在10%～18%时,采用间歇供氧,不仅能提高堆肥效率,而且可以使供氧时间减少40%以上。经过堆肥实验验证模拟结果是正确的。由此可见,利用模型模拟堆肥过程,快速优化堆肥方案是可行与有效的。     

Measurement of biosolids compost odor emissions from a windrow, static pile, and biofilter.

A pilot study was conducted to compare odor emissions from a windrow process and an aerated static pile and to determine the odor reduction efficiency of a pilot two-phase biofilter for odor control of biosolids composting. Chemical compounds identified as responsible for odors from biosolids composting include ammonia, dimethyl disulfide, carbon disulfide, formic acid, acetic acid, and sulfur dioxide (or carbonyl sulfide). Aeration was found to reduce the concentration of ammonia, formic acid, and acetic acid by 72, 57, and 11%, respectively, compared with a nearby windrow, while dimethyl sulfide, carbon disulfide, and sulfur dioxide (or carbonyl sulfide) concentrations were below detection limits. Using dilution-to-threshold olfactometry, aeration followed by biofiltration was found to reduce the odor from biosolids composting by 98%. Biofiltration also altered the character of odor emissions from biosolids composting, producing a less offensive odor with an earthy character. Biofiltration was found to reduce the concentration of ammonia, dimethyl disulfide, carbon disulfide, formic acid, acetic acid, and sulfur dioxide (or carbonyl sulfide) by 99, 90, 32, 100, 34, and 100%, respectively. The concentrations of those odorants were estimated to be 3700, 110000, 26,37,5, and 1.2 times reported human detection limits before the two-phase biofilter, respectively, and 42,9600,18,0,3, and 0 times human detection limits after the biofilter, respectively.