The Influence Of Biomass Carbon To Low C/N In High Temperature Aerobic Composting

High temperature aerobic composting process is one of the most effective ways to deal with sewage sludge. However, the loss of nitrogen during composting process, low content of nutrients in compost products and too much straw addition hinder the application of high temperature aerobic compost process in dealing with sewage sludge. To solve these problems, we reduced C/N ratio to13and added three kinds of biochars derived from wheat straw(WB), shell of peanut(PB) and bamboo(BB), respectively) in compost pile. The following indexes including temperature, moisture content, pH, EC, transformation of organic carbon and nitrogen, and the activities of five kinds of enzymes were determined during compost process. The results are as follow:(1) The composting process is successfully conducted at C/N ratio of13. At this condition, the temperature of WSB-treated pile improved rapidly and reach the highest temperature of69.5℃at second day of composting. Addition of biochar promotes water of evaporating at earlier stage of composting, but is beneficial to keep water in the compost pile at the end of composting. Addition of biochar increases the values of pH in the compost pile, but there are no significant differences between biochar. The EC value in compost pile is increased by the addition of SSP and biochar.(2)Decreasing C/N ratio or adding biochar to compost pile decreases the contents of total organic carbon and water soluble organic carbon by10.37-22.61%and by21.62%～56.71%, respectively. Addition of SSP decrease the content of total organic carbon, but does not influence the content of water soluble organic carbon in compost pile.(3) Decreasing C/N ratio or addition of biochar also reduce the content of humic acid, and the addition of SSP also decrease the humic index(HI) of compost pile. The highest HI in the compost pile was obtained at the C/N ratio of20.(4) Compared with the initial nitrogen content, the total nitrogen at the end of composting increased by8.39%～27.70%, the phenomenon is most obvious when PB is added to the pile. However, when compared with the pile with C/N ratio of20, the loss of nitrogen increased. Addition of SSP or biochar alone or together can reduce nitrogen loss, the lowest nitrogen loss was obtained in the treatment of SSP+WB.(5) Compared with those in the treatment with C/N ratio of20, the NH4+-N and NO3--N in the compost pile with C/N ratio of13decreased. Addition of SSP and/or biochar is effective in remitting the degree of decrease, especially WB+SPP.(6) The acid hydrolysis nitrogen accounted57%～92%for the total nitrogen during compost. Amino nitrogen accounted30～40%for the acid hydrolysis nitrogen, and the non-identified nitrogen accounted about36.5%for acid hydrolysis nitrogen. The content of acid hydrolysis nitrogen increases at low C/N ratio. The content of organic nitrogen is slightly influenced by SSP application, but increases significantly by the addition of SSP and biochar, especially SSP+PB.(7) During the composting process, the activities of polyphenol oxidase, catalase, dehydrogenase and cellulose enzyme decreased, but the activities of urease increased. Addition of SSP can also increase the activities of oxidase and catalase, but reduce the activities of urease, and does not obviously influence the activities of polyphenol and cellulose enzyme. Addition of biochar only increase the activities of urease, suggesting that it is not beneficial to compost process.