Effect Of Clay As Additive To Thechicken Manure Composting

Recycling of livestock and poultry manure is an important link to promote the sustainable development of livestock industry and environmental protection in China.Aerobic composting has been proved to be an effective and low-cost method to achieve this goal.However,traditional composting technology has several problems which can not be ignored such as nitrogen loss,greenhouse gas emissions,and pollutants such as antibiotics,resulting in low quality of compost products and secondary pollution to the environment.To assess the impact of clay as additive on chicken manure composting,six treatments with different dosages of clay were designed to conduct a chicken manure composting experiment for 50 days.The effects of clay as additive on the maturity of chicken manure compost,ammonia and greenhouse gas emissions,and the final quality of compost were systematically investigated.And the high-throughput sequencing was used to study the succession and variation of bacterial community during composting and the effect of clay on the relative abundance of antibiotic resistance genes and pathogenic bacteria?PB?,and study the mechanism of this kind of influence.The main results and conclusions are listed as below:?1?The clay amendment could prolong the thermophilic phase and reduced the maturity period of composting.In addition,the GHGs?N₂O and CH₄?and ammonia emission of clay added treatments were reduced by 25.3⁶3.4%,26.01⁵0.24%and 8.5⁷0.5%,respectively.But CO₂ emission was significantly higher in 10%clay amended treatment.Furthermore,the redundancy analysis showed that C/N ratio and total organic matter among all physiochemical properties had significant relationship with GHGs and ammonia emission.?2?The dominant phylum were Firmicutes,Proteobacteria,Actinobacteria and Bacteroidetes,while Bacillus,Paenibacillus,Virgibacillus,Oceanobacillus and Clostridium were the dominant genera in all the treatments.Correlation analyses provided useful tools for insight into the bacterial interactions with environmental factors and also extension of the compost maturation and resistance of bacteria.During the course of study,the diversity of bacteria similar but relative abundance variable in each treatments.However,the average and the normalized?to bacterial relative abundances?RAs?or copies of sequences?both remained greater in higher dosage of clay applied treatments.Finally,the RAs of various bacterial community composition was affected in chicken manure compost by the clay application.?3?In the initial raw chicken manure from the breeding farm,the antibiotics resistance genes?ARGs?concentrations were 1.7³.01 times higher than that after composting.High doses of the clay additive play an important role in reduction in the ARGs and are the main factor responsible for significant variations in ARGs abundance between the treatment groups.Therefore,we recommend adding high doses of clay?HDC?as an effective means to reduce the maximum percentage of ARGs in chicken manure compost.A heat map correlation study confirmed that HDC addition during the composting process reduced the bioavailable fractions of toxic metals originating from the chicken feed and significantly impacted ARGs dispersion.?4?85⁸7%of PB relative abundances were significantly reduced in lower dosages of applied clay?T2 and T3?.However,the maximum survival of PB was noticed in the T6 and T5 treatments,but most of the PB belong to Firmicutes,Actinobacteria and Proteobacteria phylum and their derivative bacterial species.The changes in PB during the composting were not only strongly influenced by clay amendment but also significantly associated with the succession of bacterial species in compost.Bacillus,Clostridium,Mycobacterium and Klebsiella were the dominant spore-forming bacteria identified in higher dosages of clay?i.e.,T4,T5 and T6?treatments,but very low abundance of these bacterial genus and its species were recovered from lower dosages of clay?T2 and T3?-applied treatments.Overall,without clay,amended-CM-derived compost contained a relatively higher PB abundance than other treatments,as the anaerobic bacterial species Clostridium_difficile_AA1,Vibrio_cholerae,andAcinetobacter_calcoaceticushadrelativelygreaterRAs,followedby Klebsiella_oxytoca₁0-5248,Paenibacillus_Bacillus_cereus and Bartonella_quintana_RM-11.In conclusion,clay as an additive can effectively reduce the greenhouse gases and ammonia emissions and the environmental risks of ARGs and PB during chicken manure composting as well as improve the quality of composting,which has a certain guinding significance for actural production.