Research On High Temperature Composting And Microbial Community Of Dairy Cow Dung And Pig Manure From Large-scale Farms

With the increasing modernization of agriculture and the rapid development of livestock breeding industry in China,poultry farm manure waste has become one of the important environmental pollution sources,seriously restricting the sustainable development of China’s agriculture.In view of the characteristic differences of various raw materials,cow dung,the pig manure and the wet pig manure were selected as the main materials,and the mushroom residue,the sawdust and the hulled bran were used as the auxiliary materials to carry out the high temperature composting experiments with different C/N ratios in order to explore the high-effiency composting technology,and to provide the theoretical basis for a moderate scale farm to produce organic fertilizer.Three C/N values(15,25 and 35)of raw materials constituted of cow manure and auxiliary materials(mushroom residue and rice husk)were arranged in the factory to investigate the effects of C/N values on variations of the physicochemical indexes including stack temperature,pH value,EC,C/N,and nutrients during the composting process.Results showed stack with C/N=25 reached the highest temperature in shortest time and kept the longest time with temperature above 65 ℃.Similar trends of variations of pH value,EC and C/N value during composting process were observed which decreased firstly and then increased for pH;increased with fluctuation at beginning,decreased after that,and remained stable at the end for EC;and gradually decreased for C/N value with 11.7,15.0 and 21.3 at last.Ammonium nitrogen contents of all treatments gradually decreased with the values decreased by 80.7%,36.6%and 46.7%,respectively,while nitrate nitrogen amounts increased with the values increased to 0.61 g kg-1,0.50 g kg-1,0.41 g kg-1,respectively,at the end of composting.The humic acids,fulvic acids and other substances became the main part of the DOM at the end of composting.Germination index of compost samples for stacks with C/N=10 and 35 were more than 50%but less than 85%,while highest germination index(more than 85%)was observed from compost samples for the stack with C/N=25.Moreover,total P and total K of all treatments increased.The high-temperature composting of cow manure and auxiliary materials can effectively transform this kind of waste to be organic fetilizer,especially when the C/N value is 25.Three treatments were arranged in the factory to investigate the effect of different additional amounts of pig slurry in the mixture of mushroom dregs,rice chaff and sawdust on the composting efficiency by monitoring the compost physicochemical indexes including stack temperature,pH value,EC,C/N,moisture content,ammonium nitrogen,nitrate nitrogen,germination index,lignin content,cellulose content,hemicellulose content,water-soluble carbon content and nutrients during composting process.The highest temperature was observed in stack Z3,temperature of which drops faster than stack Z1 and Z2.Similar trends of variations of pH value with decrease at beginning,decrease after that,then decrease to stabilization were observed during composting process.C/N of all treatments also showed a tendency with gradual decrease to remained stable.According to the ratio of the end C/N to the initial C/N,stack Z3 was basically mature at the end of composting.Contents of ammonium nitrogen and nitrate nitrogen decreased and increased gradually,respectively.Tyrosine,tryptophan and other substances from Z2 and Z3 disappeared,while the humic acids,fulvic acids and other substances became the main part of the DOM at the end of composting.Compared to Z1 and Z2,Z3 showed a greater degradation rate of hemicellulose during composting.Germination index of each treatment increased during composting process with Z1,Z2 and Z3 of the value of 72%,84%and 101%at the end of composting,respectively.Organic matter of all treatments decreased while total N,P and K increased.Two C/N values(10 and 20)of raw materials constituted of pig manure and auxiliary materials(mushroom residue and rice husk)were arranged in the factory to investigate the effects of C/N values on variations of the physicochemical indexes including stack temperature,pH value,EC,C/N,and nutrients during the composting process.Results showed stack with C/N=20 reached the highest temperature in shortest time and kept the longest time with temperature above 65 ℃.Similar trends of variations of pH value,EC and C/N value during composting process were observed which decreased for pH;increased with fluctuation at beginning,decreased after that,and remained stable at the end for EC.Ammonium nitrogen contents of all treatments gradually decreased with the values decreased by 78.78%and 23.31%,respectively,while nitrate nitrogen amounts increased with the values increased to 0.06 g kg-1 0.03 g kg-1,respectively,at the end of composting.Germination index of each treatment increased during composting process with Z1,and Z2 of the value of 82%and 90%at the end of composting,respectively.Moreover,total P and total K of all treatments increased.The high-temperature composting of pig manure and auxiliary materials can effectively transform this kind of waste to be organic fetilizer,especially when the C/N value is 20.The changes of microbial community during the high temperature composting were studied by high-throughput sequencing technology.During the composting process,the bacterial community changed mainly in Proteobacteria,Firmicutes,Deinococcus-Thermus,Bacteroidetes and Actinobacteria,and the nitrate nitrogen content of the reactor was positively correlated with the change of microbial community.The results of high temperature composting showed that high temperature composting could effectively deal with livestock fecal waste.Treatment of with C/N = 25 resulted in the highest efficiency composting for cow dung compared to treatments with C/N = 10,35;Treatment of with C/N = 20 resulted in higher efficiency composting for compared C/N=10;and addition of pig slurry,to mixture of mushroom residue,rice hulls and sawdust resulted in effective high-temperature composting.All research in the present study can provide a stratagem to deal with the huge amount of pig slurry from large-scale pig farms.