The adaptation of waste-to-energy technologies: towards the conversion of municipal solid waste into a renewable energy resource

Currently, there are an estimated 1.3 billion tonnes of municipal solid waste (MSW) generated per year globally, and this quantity is predicted to increase to 2.2 billion tonnes annually by 2025. If not well treated, this rapid growth of waste products can lead to socio-economic and environmental problems. Waste is potentially a misplaced valuable resource that can be converted and utilized in different ways such as renewable energy resources for the realization of sustainable development. Presently, waste-to-energy technologies (WtETs) are considered to be an encouraging advanced technology that is applied to convert MSW into a renewable energy resource (methane, biogas, biofuels or biodiesel, ethanol, syngas, or alcohol). WtETs can be biochemical (fermentation, anaerobic digestion, landfill with gas capture, and microbial fuel cell), thermochemical (incineration, thermal gasification, and pyrolysis), or chemical (esterification). This review mainly aims to provide an overview of the applications of these technologies by focusing on anaerobic digestion as biological (nonthermal) treatment technologies, and incineration, pyrolysis, and gasification processes as thermal treatment processes. Landfill gas utilization technologies, biological hydrogen production processes, and microbial fuel cells also are assessed. In addition, the contemporary risks and challenges of WtETs are reviewed.