Effects of Biochar on Substrate Degradation and Ammonia Emission during Aerobic Composting of Chicken Manure

In this study, chicken manure and Caragana korshinskii Kom powder were used as the main raw materials with different amounts of biochar added to test four aerobic composting treatment groups A, B, C and D with laboratory composting fermenters and testing apparatus, and new insight into biochar’s nitrogen conservation mechanism was gotten, based on the experimental data and related exploration such as the physical and chemical properties of the final products, the changing interactions among nutrient elements and other elements, and the relationship between substrate degradation and the amount of biochar used as well as the best formula for reducing ammonia emission. The results showed that the proper proportion of the added biochar to the other elements was conducive to less ammonia emission and nitrogen loss during the aerobic composting. The composting effect of Treatment C （biochar at 20%） was the optimal in the test, where in the composting temperature rose the most rapid and the earliest to the maximum temperature 52.5℃, with the least nitrogen loss. An effective, safe and high-quality resource utilization of chicken manure was established through the aerobic composting with reasonable material mixture proportion.

Static aerobic composting of municipal sewage sludge with forced ventilation:Using matured compost as bulking conditioner

Static aerobic composting of municipal sewage sludge with forced ventilation or air ventilation using matured compost as bulking conditioner was investigated. Physical and chemical parame ,eters, e.g., temperature, moisture content, VSS, CODcr, pH, and germination index （GI）, were analyzed to characterize the composting process. Fermentation starts quickly in both forced and air ventilation compost heaps and reaches high-temperature stage after 2 d, owing to the bulking function of matured compost. Compared to air ventilation, however, forced ventilation enables the high-temperature stage to last longer for approximately 7 d. The moisture content of both compost bodies decreases from 62% to about 50% as a result of evaporation, and it decreases slightly faster in forced ventilation compost heap after 13 d due to the higher temperature and better ventilation condition. Although no obvious differences of VSS and pH are observed between both compost heaps, the soluble CODcr and GI show differences during the second half period of fermentation. In forced ventilation compost, the soluble CODcr has a small rebound after 13 d, and GI decreases from 46% to 35% but then increases. These results show that in general, the matured compost is a good conditioner and force ventilation with a proper air supply strategy can be more efficient than air ventilation.

Phosphate rock reduces the bioavailability of heavy metals by influencing the bacterial communities during aerobic composting

Available information on the microbial mechanisms associated with heavy metal(HM)passivation during co-composting amended with phosphate rock(PR)remains limited.Thus,this study investigated the dynamic changes in bacterial communities and HM-fractions(Zn,Cu,Cd,Cr and Pb)during swine manure composting with maize straw,and ascertained the bacterial influence on HM-passivation.The results demonstrated that the addition of PR improved HM-passivation,especially for Zn and Cd,with their bioavailability factors(BFs)reduced by 247.41 and 176.25%,respectively.As for bacterial communities,the proportion of Firmicutes decreased,while the proportions of Proteobacteria,Bacteroidetes,DeinococcusThermus and Gemmatimonadetes increased in all treatments.PR significantly changed the primary bacterial phyla in the thermophilic phase.Bacteroidetes were the main bacterial component controlling the passivation of Zn,Cu and Cr,while Deinococcus-Thermus mainly regulated the mobility of Zn and Pb,and Proteobacteria only dominated the transformation among Cd-fractions.These results may provide a reference for the use of HM-passivation techniques during composting.

Formation of Struvite Crystals in a Simulated Food Waste Aerobic Composting Process

Bench-scale treatments with three mixtures of Mg and P salts, including K3PO4＋MgSO4, K2HPO4＋MgSO4, and KH2PO4＋MgSO4 as additives in a simulated food waste aerobic composting process, were conducted to test the magnesium ammonium phosphate（MAP） formation, and the compost products were analyzed by X-ray diffraction（XRD）, Scanning electron microscopy（SEM）, and Energy dispersive X-ray spectroscopy（EDS） analyses. The comparison results between XRD, SEM, and EDS analyses of MAPs in the dried compost and synthesized MAPs confirm the formation of MAP crystals in the simulated food waste aerobic composting process. The analysis of the compost also indicates that the addition of all the three mixtures of Mg and P salts in the aerobic composting process can increase nitrogen conservation and decrease nitrogen loss because of the formation of MAPs. The mechanism of MAP formation was verified as the reaction of ammonium（NH4＋） with magnesium（Mg^2＋） and phosphate[HnPO4^（3-n） , n=0, 1, and 2）.

Aerobic composting of paper mill sludge and the reuse of compost in agriculture

Paper mill sludge （PMS） is a kind of bio-solid waste. The technology of aerobic composting of PMS was investigated. The ratio of the material components was as follows, sludge：chicken dung：spill=6kg：2kg：4kg, which could attain 55% moisture content （MC） and 25 the ration of carbon to nitrogen （C/N）. The aeration rule of fan was controlled by single chip microcomputer （SCM）. During composting, the system temperature more than 55℃ lasted for 3 days, pH changed in the range of 6.5-8.5 and MC changed between 53% to 60%. PMS became mature on the 20th day. The germination index （GI） of compost attained 95% or so and coliform was 23/100 ml volatile solid （VS） and organic carbon （OC） were stable at the content of 60% and 30%, respectively. The result showed that this technology could make the sludge stable and innocuous. A pot experiment with latosolic red soil mixed with paper mill sludge compost （PMSC） was carried on. The result showed that PMSC could increase the crop biomass, the soil nutrients and the physical characteristics of the soil, such as OC, total nitrogen （TN）, total phosphorus （TP）. The total amount of heavy metals in the soil was measured to be lower than the Environmental standard for soil in China （GB15618-1995）. So PMSC was a good and safe soil amendment.

Effects of Different Microbial Agents on Aerobic Composting of Cow Manure

For the control of environment pollution caused by livestock and poultry manure, four microbial strains conducive to aerobic composting were selected and mixed into four compound microbial agents, and effects of different compound microbial agents on aerobic composting of cow manure were studied from aspects of changes in temperature, pH, water content and C/N during the composting process. The results show that microbial agent M2 has the best effect for aerobic composting of cow manure, so microbial agent M2 has broad popularization and application prospect in livestock and poultry farms in low-temperature areas of Northeast China.

Study on Aerobic Composting of Mixed Municipal Sludge, Kitchen Waste and Water Hyacinth

In this study, a in vessel aerobic composting method is adopted to investigate the variation rules of various evaluation parameters （temperature, moisture content, pH, organic matter, water soluble ammonia nitrogen, water soluble nitrate nitrogen and germination index） in cocomposting of municipal sludge, kitchen waste and water hyacinth at different proportions. The results show that, in composting, the parameters of moisture content, pH, water soluble ammonia nitrogen and water soluble nitrate nitrogen demonstrate marked dynamic change rules during composting process; the temperature of three groups of compost materials rapidly rise to above 55 ~C within 96h, and last for 3 - 7d, meeting the harmless requirements, and their organic matter degradation rate excess 30%, the GI index is higher than 83%, in line with the requirements on maturity, which proves that the co-composting of municipal sludge, kitchen waste and water hyacinth can realize harmlessness and resource reutilization after composting.

Use of additive and pretreatment to control odors in municipal kitchen waste during aerobic composting

The effects of adding a bulking agent and chemically pretreating municipal kitchen waste before aerobic composting were studied using a laboratory-scale system. The system used20-L reactors and each test lasted 28 days. The objective was to decrease NH3 and H2S emissions during composting. The bulking agent, dry cornstalks, was mixed with the kitchen waste to give a mixture containing 15%（wet weight） bulking agent. A combined treatment was also conducted, in which kitchen waste mixed with the bulking agent was pretreated with ferric chloride（FeC l3）. Less leachate was produced by the composted kitchen waste mixed with bulking agent than by the kitchen waste alone, when the materials had reached the required maturity. The presence of cornstalks also caused less H2 S to be emitted, but had little impact on the amount of NH3 emitted. The FeC l3 was found to act as an effective chemical flocculant,and its presence significantly decreased the amounts of NH3 and H2S emitted. Kitchen waste mixed with cornstalks and treated with FeC l3 emitted 42% less NH3 and 76% less H2 S during composting than did pure kitchen waste.

Environmental effects and risk control of antibiotic resistance genes in the organic solid waste aerobic composting system: A review

Antibiotic resistance genes(ARGs)have been diffusely detected in several kinds of organic solid waste,such as livestock manure,sludge,antibiotic fermentation residues,and food waste,thus attracting great attention.Aerobic composting,which is an effective,harmless treatment method for organic solid waste to promote recycling,has been identified to also aid in ARG reduction.However,the effect of composting in removing ARGs from organic solid waste has recently become controversial.Thus,this article summarizes and reviews the research on ARGs in relation to composting in the past 5 years.ARGs in organic solid waste could spread in different environmental media,including soil and the atmosphere,which could widen environmental risks.However,the conventional composting technology had limited effect on ARGs removal from organic solid waste.Improved composting processes,such as hyperthermophilic temperature composting,could effectively remove ARGs,and the HGT of ARGs and the microbial communities are identified as vital influencing factors.Currently,during the composting process,ARGs were mainly affected by three response pathways,(Ⅰ)“Microenvironment-ARGs”;(Ⅱ)“Microenvironment-microorganisms-ARGs”;(Ⅲ)“Microorganisms-horizontal gene transfer-ARGs”,respectively.Response pathway Ⅱ had been studied the most which was believed that microbial community was an important factor affecting ARGs.In response pathway Ⅲ,mainly believed that MGEs played an important role and paid less attention to eARGs.Further research on the role and impact of eARGs in ARGs may be considered in the future.It aims to provide support for further research on environmental risk control of ARGs in organic solid waste.

Influence of dissolved organic matter on methylmercury transformation during aerobic composting of municipal sewage sludge under different C/N ratios

Current knowledge about the transformation of total mercury and methylmercury(Me Hg) in aerobic composting process is limited. In this study, the composition and transformation of mercury and dissovled organic matter(DOM) in aerobic composting process of municipal sewage sludge were were comprehensively characterized, and the differences among the three C/N ratio(20, 26 and 30) were investigated. The main form of mercury in C/N 20 and 26 was organo-chelated Hg(F3, 46%-60%);while the main form of mercury in C/N 30 was mercuric sulfide(F5, 64%-70%). The main component of DOM in C/N 20 and 26 were tyrosine-like substance(C1, 53%-76%) while the main fractions in C/N 30 were tyrosine-like substance(C1, 28%-37%) and fulvic-like substance(C2, 17%-39%). The mercury and DOM varied significantly during the 9 days composting process. Compared to C/N 20 and 26, C/N 30 produced the less Me Hg after aerobic composting process, with values of 658%(C/N 20), 1400%(C/N 26) and 139%(C/N 30) of the initial, respectively. Meanwhile, C/N 30 produced the best compost showed greater degree of DOM molecular condensation and humification. Hg fraction had been altered by DOM, as indicated by a significant correlation between mercury species and DOM components. Notably, C/N 30 should be used as an appropriate C/N ratio to control the methylation processes of mercury and degration of DOM.

Effects of adding chicken manure to cattle manure on aerobic compost process parameters at low temperature

The research was aimed at studying the effect of adding certain proportion chicken manure to cattle manure on compost below 0℃ with aerobic compost method, which was suitable for northern cold climate. The results indicated that the mixed compost completed 3 days earlier than the single compost, the temperature of the mixed compost rose to 50.7℃ at the 1st day,and achieved its highest temperature 74.4℃ at the 3rd day. The temperature of the single compost rose to 40.0℃ at the 1st day,rose to 55.6℃ at the 3rd day,and achieved its highest temperature 70.1℃ at the 5th day. Adding chicken manure had no impact on the variety trend of the process parameters such as moisture content, pH and C/N ratio, hut increased the variety range of these parameters.

Study on Characteristics of a Strain of Penicillium sp.Capable of Heterotrophic Ammonium Oxidation

An ammonia-oxidizing strain of Penicillium sp., M25-22 which was isolated from chicken feces compost, was studied to make clear its characteristics of ammonium oxidation and provide references for its application in aerobic composting. In media containing （NH4）2SO4 at a concentration of 0.5 g 100 mL^-1, mycelium weight and utilization ratio of ammonium nitrogen increased markedly during the 1st 5 d, concentration of nitrate increased markedly from the 3rd to the 5th d and concentration of nitrite remained at a low level. The strain showed the ability to oxidize ammonium nitrogen growing in media containing glucose, sucrose, starch, or cellulose as the sole carbon source and to oxidize the negative trivalent nitrogen of ammonium sulfate, peptone, acetamide, urea, or L-aspartate. Slowly available carbon or nitrogen sources such as starch, cellulose, and peptone were beneficial to ammonium oxidation. In media containing sucrose as the sole carbon source and ammonium sulfate as the sole nitrogen source, nitrate formation was the most pronounced with sucrose present at a concentration of 12 g L^-1 and ammonium nitrogen present at a concentration of 2.438 mg mL% at the initial pH level of 7.5 and at 30℃.

Characteristics of night soil and leaf co-composting using aerobic static method

The main purpose of this work is to investigate the characteristics of night soil and leaf co-composting using aerobic static composting method. Three influencing factors, including proportion of night soil and leaf, aeration rate and aeration pattern, were investigated through the evolution of the principal physicochemical properties, i.e., temperature, oxygen consumption rate, organic matters, moisture content, carbon, nitrogen, carbon-to-nitrogen ratio and Germination index （GI）. It was found that the 3：1 （w：w） mixture of night soil and leaf was capable of achieving the highest composting temperature, longest retention time of high temperature （55℃）, and fastest organic matter degradation. The 0.14 m3. min-1. m-3 aeration rate was most beneficial to composting, and the mixture of night soil and leaf maintained the highest temperature for the longest duration and achieved the highest CO2 content and GI. The continuous aeration pattern during composting was superior to an intermittent aeration pattern, since the latter delayed the composting process.

Feasible strategy for the nitrogen fixation and humification quality improvement by spent mushroom substrate as conditioning agent

There is an overlooked problem which increasing microbial abundance while reducing nitrogen loss during composting.This study investigated the viability of spent mushroom substrate(SMS)as conditioners in the aerobic composting of kitchen waste(KW)with cattle manure(CM).The variation of temperature,pH,C/N,organic matter,cellulose,hemicelluloses,germination index(GI),and microflora structure were explored to evaluate the potential in accelerating maturity and nitrogen fixation by SMS addition.The results showed that the addition of SMS accelerated the heating rate,prolonged the high temperature time,and decreased organic matter,hemicellulose,and cellulose by 17.49%,23.61%,and 18.62%,respectively.The GI reached 105.86%with SMS addition,while 74.17%was found in control treatment after composting.SMS changed the microbial community composition and increased the species abundance.Proteiniclasticum,Clostridium XI and Azomonas were dominant bacteria,which increased the retention of nitrogen,promoted organic matter degradation and reduce compost time.The study can provide a feasible strategy for nitrogen fixation in the field of organic waste recycling.

Succession of bacterial community during composting:dissimilarity between compost mixture and biochar additive

Previous research showed that biochar addition facilitated composting and elevated nutrient retention.However,few of these studies explored bacterial structure and abundance in the compost mixture and biochar additive.Thus,this study aims to distinguish bacterial communities in both compost and bamboo biochar(BB)additive.Results indicated that the dynamics of nutrient contents in compost and BB samples were in a similar pattern,although there were lower levels of nutrients and metals(i.e.,Cu and Zn)in BB additives.The total number of operational taxonomic units(OTUs)in both compost and BB additives peaked on day 7 and then gradually reduced during composting.There was more abundance of bacteria in compost,whereas the diversity of bacteria was more in BB additives.Furthermore,the dominant bacteria in compost and BB samples were distinct at the different stages of composting.The Firmicutes steadily decreased in compost samples(from 34.78%to 7.65%),while it was the dominant phylum in BB additives during the whole composting period.Furthermore,Ruminofilibacter,Pseudoxanthomonas,and Actinomadura were the most abundant genera in compost samples than Pseudoxanthomonas,Azoarcus,and Paenibacillus in BB additives at the final stage of composting.Results from this study could provide a theoretical reference for the sound performance of biochar-added composting.

Life cycle assessment on the environmental impacts of different pig manure management techniques

The management of livestock waste is an effective way to achieve emission reduction and carbon fixation in agriculture and rural areas.At present,aerobic composting and anaerobic fermentation are widely used in livestock waste treatment technology.In this study,pig manure management was taken as an example,a comprehensive environmental load index was constructed to quantitatively evaluate the environmental impacts of global warming,environmental acidification,eutrophication,and photochemical ozone synthesis during aerobic composting and anaerobic fermentation based on the life cycle assessment.The results showed that the potential values of aerobic composting and anaerobic fermentation were similar,and the order was global warming,environmental acidification,eutrophication,and photochemical ozone synthesis.Anaerobic fermentation contributed more to global warming,while aerobic composting contributed more to environmental acidification,eutrophication,and photochemical ozone synthesis.In addition,the environmental load index of aerobic composting was significantly higher than that of anaerobic fermentation.There were certainly regional differences in the environmental load index,and the environmental impact effect of anaerobic fermentation was low and more environmentally friendly.These findings provided a technical basis for livestock manure management in different regions of China,which was conducive to promoting animal husbandry emission reduction and carbon sequestration.