Microbial breakdown of fats through in-vessel Co-composting of agricultural and urban wastes

Abstract

The microbial degradation of the fats contained in various agricultural and urban wastes was investigated using an insulated and unheated stainless-steel reactor. The duration of the thermophilic stage was related to the initial fat content, irrespective of the peak temperatures reached. The thermophilic stage was characterized by a sharp increase in pH followed by a stabilization above pH 8, which corresponds to the maximum activity of thermostable lipases. The degradation rates of organic matter and lipids were not related to the initial fat content although the microbial activity was impaired by poorer physical conditions for the highest fat contents. In most cases, lipid degradation was in the range 85–95%. The upper limit for the input of fats appears to be ca 40% and the optimum values should not exceed 20–25%.