Anaerobic Conversion of Biodegradable Municipal Solid Waste to Biogas: A Review

Abstract

Huge quantity of Municipal Solid Waste (MSW) is generated daily. This waste comprises a biodegradable portion which can be converted into biogas (bioenergy) by anaerobic digestion (AD). This study reviews MSW and its management, AD feedstock and their characteristics, factors affecting biogas production in a biodigester and anaerobic co-digestion of Organic Fraction of MSW (OFMSW) with other substrates. Municipal solid waste is managed through waste diversion (reduction, reuse, recycling and recovery) and waste disposal (controlled incineration, landfilling and controlled dumping). AD feedstock includes agricultural waste/residues, animal wastes, energy crops, food waste, forestry crops and residues, organic industrial waste and wastewater, weeds, aquatic algae, sewage and OFMSW. The essential factors that influence the production of biogas are temperature, pH, mixing rate, carbon/nitrogen ratio, organic loading rate, micro and macro-nutrient availability, retention time, nature of the feedstock and digester type. Anaerobic co-digestion of OFMSW with other substrates results in improved AD process stability, enhanced biogas productivity, maximization of the capacity of available feedstock for anaerobic digestion. It is also a cost-effective and improved technique to optimize anaerobic digestion process via the increase in nutrients and bacterial variety in substrates. The generation rate and composition of MSW, as well as the characteristics of OFMSW feedstock for anaerobic digestion, are required for the design of a full-scale biodigester for municipal use. The information provided in this review is invaluable to researchers, governments, industries and other stakeholders interested in anaerobic conversion of biodegradable solids to bioenergy.