Effects Of Red Mud On The Degradation Of Lignocellulose And Humus Formation And Succession Of Functional Microbial Communities During Composting

In China,large amounts of livestock manures and agricultural wastes are produced every year,which cause serious environmental pollution.Composting,as an eco-friendly technology for treating these hazardous wastes,has received widespread attention.During composting,organic matter(OM)is converted into stable humic substance(HS)by microbe.In traditional compost,lignocellulose is difficult to be biodegraded,which makes it a speed limit in the composting process.In this study,fresh cow manure and bagasse were used as the main composting materials,and the experimental group(T)with 10 % red mud and the control group(CK)were set up to conduct the composting experiment for 45 days.The physico-chemical properties,lignin and cellulose degradation,and the formation of HS were detected during composting,and the effects of red mud on the succession of β-glucosidase and laccase-producing microbial communities were investigated by high-throughput sequencing technology.The results showed that adding red mud could significantly enhance the activity of microbe,and increase the temperature of compost at high temperature(P < 0.05).In the thermophilic phase,the temperature of both CK and T lasted for 12 days,which reached the requirement of killing pathogenic microbe and ensured the safety of compost.The final degradation rates of OM in the T and CK were 25.74 % and 12.09 %,respectively.In addition,red mud can significantly accelerate the degradation of lignin and cellulose.The final degradation rates of lignin in the T and CK were 41.01 % and 22.34 %,respectively.The final cellulose degradation rates in the T and CK were 84.73 %and 74.71%,respectively.At the end of composting,the C/N values of both CK and T were less than 15,indicating that the compost had reached maturity.Red mud significantly increased the content of HS and the degree of humification during composting(P < 0.05).Compared with CK,the HA/FA value of the T was 2.12 on the days 21,which was greater than 1.9,indicating that the addition of red mud can accelerate the maturity of compost and promote the process of humification.Proteobacteria,Actinobacteria,Firmicutes and Ascomycota were the main dominant microbe producing β-glucosidase and laccase.RDA showed that temperature was the main factor driving the variation of β-glucosidase and laccase-producing microbial communities.Pearson correlation analysis showed that adding red mud could promote the degradation of lignocellulose and the formation of HS by β-glucosidase and laccase-producing microbe during composting.In summary,this study provides a new strategy for accelerating the degradation of lignocellulose and the formation of HS during composting,whichis of great significance for further understanding the composting process.