Evaluating inhibition conditions in high-solids anaerobic digestion of organic fraction of municipal solid waste

Abstract

High-solids anaerobic digestion (HSAD) processes, when applied to different types of organic fractions of municipal solid waste (OFMSW), may easily be subjected to inhibition due to organic overloading. In this study, a new approach for predicting these phenomena was proposed based on the estimation of the putrescibility (oxygen consumption in 20 h biodegradation, OD 20) of the organic mixtures undergoing the HSAD process. Different wastes exhibiting different putrescibility were subjected to lab-scale batch-HSAD. Measuring the organic loading (OL) as volatile solids (VS) was found unsuitable for predicting overload inhibition, because similar VS contents corresponded to both inhibited and successful trials. Instead, the OL calculated as OD 20 was a very good indicator of the inhibiting conditions (inhibition started for OD 20 > 17–18 g O 2 kg −1). This new method of predicting inhibition in the HSAD process of diverse OFMSW may be useful for developing a correct approach to the technology in very different contexts.