| China is the largest pig breeding country in the world,with an annual output of more than500 million pigs,2 billion tons of fecal pollution and 50 million dead pigs.These dead pigs represent economic losses,are also the source of disease infection,and threaten environmental safety.They must be properly handled.Burial and incineration are easy to cause disease transmission,groundwater pollution,air pollution and carbon emission increase,which is not in line with sustainable agricultural development and environmental ecological construction.Composting is recognized as the most environmentally friendly method to realize harmless and resource-based livestock and poultry breeding waste treatment in the world.According to the team’s previous research experience,the biggest challenge faced by the technical route is the heterogeneity of the pile and low C/N ratio.In order to overcome the above problems,this study adopts: 1)increasing the C/N ratio of fecal waste pile by adding crushed corn straw;2)Screening and adding compound microbial agents suitable for maintaining high temperature duration of low C/N ratio reactor,so as to realize synchronous harmless treatment and fertilizer application of dead pigs and fecal sewage.This study intends to use the static composting technology route of in-situ dissolution of fecal sewage from pig farms to realize the synchronous harmless treatment and resource utilization of dead pigs and fecal sewage.(1)The C/N ratio of fresh pig manure collected from intensive pig farms was adjusted by corn straw and set at 14:1(raw manure),16:1,18:1,20:1,22:1,24:1 and 26:1,respectively.The effects of C/N ratio on composting of pig carcass tissues(excluding viscera)were studied.The experiment was conducted for 35 days.The raw manure experiment group failed to start.In the C/N ratio 14:1(raw manure)group,the maximum heap temperature only reached34.5°C,and never reached the national standard for harmless treatment of fecal pollution with50°C for 10 days or 60°C for 5 days.The experimental groups with temperature above 60°C were 18:1,20:1,22:1,24:1 and 26:1,lasting for 6,13,10,9 and 9 days respectively.The experimental group with low C/N ratio(20:1)had significantly higher lasting-days of high temperature than other experimental groups when the temperature of composting pile exceeded60°C.Based on the chemical and biological indexes of compost maturity,the end products with no difference in maturity and stability between the experimental group with low C / N ratio(20:1)and other experimental groups with high C/N ratio can be obtained.The degradation rates of the experimental groups with the C/N ratios of 20:1,22:1,24:1 and 26:1 were 75.7%,77.4%,74.4% and 78.0%,and the relative degradation rates were 30.6%,33.6%,28.4% and 34.5%,respectively.There was no significant difference about these two indexes between the low C/N ratio(20:1)experiment group and the other high C/N ratio groups.(2)High temperature strains were isolated and screened from the experimental group with C/N ratio of 20:1.The effects of culture conditions on the growth of high temperature strains were studied.The basic gene characteristics were analyzed by the whole genome sequence of the strain.A total of 10 thermophilic strains were screened.According to the standard of harmless composting temperature,one strain of 50 °C,55 °C and 70 °C strains were selected,who were identified as Bacillus amyloliquefaciens,Bacillus subtilis and Geobacillus thermodenitrificans They were named by B.amyloliquefaciens scc500-1,B.subtilis scc550-1 and G.thermodenitrificans scc700,respectively.All the three strains were gram positive whose optimum growth temperature was 50 °C,55 °C and 70 °C,respectively.The optimum p H range of the three thermophilic strains was 7.0-8.0.The adaptation range of Na Cl concentration was concentrated in 0-2%.The growth curves of the three thermophilic strains all reached the peak in 20-24 h.The results of whole genome sequencing showed that the percentage of GC in G.thermodenitrificans scc700 was 49.3%,which was 2.7% and 5.7% higher than that in B.amyloliquefaciens scc500-1 and B.subtilis scc550-1,respectively.The results of whole gene sequence annotation showed that the three strains had similar gene abundance values for carbohydrate and protein transport and metabolism.G.Thermodenitrificans scc700 had better lipid metabolism and related coenzyme expression than the other two high temperature strains.(3)The fermentation broth of B.amyloliquefaciens scc500-1,B.subtilis scc550-1 and G.thermodenitrificans scc700 strains were mixed at a ratio of 1:1:1(v/v)and solidified by corn cob powder to form a special microbial agent for pig carcass compost.The evaluation results of bacterial agent application showed that the inoculation bacterial agent had a significant effect on improving the temperature of experiment group with C/N ratio of 20:1 over 60°C.The degradation rate of microbial agent to the experimental group with C/N ratio of 20:1 increased by 15.4%,and the degradation rate of this group was 89.5%,which was significantly different from that of other C/N ratio experimental groups.The results of residue rate showed that the non degradable part of this group was significantly less than that of other C/N ratio experimental groups.(4)The results of resource utilization of pig carcasses compost showed that compared with chemical fertilizer,organic fertilizer had more significant growth promoting effect on Chinese Pakchoi and Cayenne pepper.The effect of organic fertilizer on the content of material components of Chinese Pakchoi was significantly higher than that of chemical fertilizer,and the activity of PPO,CAT and NR enzyme was significantly improved.The results of Cayenne pepper yield showed that the yield of organic fertilizer group increased by 11% compared with that of chemical fertilizer group.The yield increase effect was improved significantly. |
