Microbial C and N dynamics during composting process of urban solid waste

Abstract

Microbial characterization of composting is of importance for the optimization of the process and the quality of the end product. The aim of this work was to follow microbial biomass C and N dynamics during the composting process of urban solid waste. Microbial biomass C ( BC) ranged from 4.06 to 1 μg kg-1 of dry compost from day 5 to day 62 and decreased to reach 0.44 mg kg-1 in mature compost. Microbial biomass N ( BN) showed the same trend as BC, ranging from 1.472 to 0.443 μg kg-1 of dry compost from day 5 to day 62. This behaviour is probably related to the decreasing availability of readily decomposable substrates with the ongoing of the process. BC and BN showed a strong correlation ( r = 0.78). The dynamics of the BC/ BN ratio, index of the chemical composition of the whole microbial population suggested a shift in the composition of microbial populations during the process from prevailing bacteria and actinomycetes to prevailing fungi.