Optimization of biogas residue mixed with livestock manure co-composting using response surface methodology.

According to principal components analysis,a comprehensive evaluation function was built with WSC/WSN,E4/E6,NH4+-N/NO3--N,GI,and the comprehensive evaluation value F used for the assessment of co-compost maturity was obtained on the basis of this evaluation function.In order to get the optimal proportion of biogas residue mixed with livestock manure co-composting,choosing F value as the response value and amount of biogas residue,pig manure,and chicken manure as the three factors,fifteen composting experiments were designed using Box-Behnken,and a second order polynomial equation was established.The results showed,the significant differences between the response value F and livestock manure amount was as follows: chicken manure﹥biogas residue﹥pig manure.Linear term of chicken manure amount and quadratic term of anaerobic digestion residue amount both reached extremely significant level(P0.01).Interaction term of biogas residue amount,chicken manure amount and quadratic term of chicken manure amount reached significant level(P0.05).The optimized proportion of co-compost was: the biogas residue amount 5.83kg,the pig manure amount 7.95kg,and the chicken manure amount 7.54kg.Therefore,it is reasonable that response surface method was used for optimization of material proportion of co-compost.