Prospect of anaerobic co-digestion of dairy manure: a review

Abstract

Dairy manure is an abundant waste in dairy farming and poses handling, storage and disposal challenges. With poor management, dairy manure produces odour, ammonia and releases greenhouse gases that contribute to global warming. Anaerobic digestion (AD) is a means to produce renewable energy and to reduce environmental impacts resulting from improper management of dairy manure. Dairy manure AD suffers from low biogas production per unit mass, hence it is costly per unit volume. To improve biogas production per unit volume, anaerobic co-digestion of dairy manure is one of the methods used to enhance biogas production. This article reviews various approaches and challenges of co-digestion to enhance biogas production and methane yield that have been used in the last decade. Substrate selection and prediction of biogas production based on chemical oxygen demand are the main areas of focus. Process inhibition by co-substrates is also examined.