Configuring municipal solid and liquid waste treatment plants into bio-refinery to achieve sustainable development goals

Increased population and per capita consumption have resulted in an increase in resource depletion and waste generation, thus necessitating the reuse of generated waste for resource recovery to ensure sustainability and circular economy. Municipal solid waste (MSW) and municipal liquid waste (MLW) generated are abundant and inexhaustible biomass resources. The efficacy of wet waste to energy technologies, viz. hydrothermal liquefaction (HTL), anaerobic digestion (AD) and microbial electrolysis cell (MEC), and the influence of the process parameters in the treatment of MSW and MLW have been reviewed in this study. Solid-state anaerobic digestion (SSAD) in a continuous stirred tank reactor or plug flow reactor and thermophilic high-solids anaerobic digestion are the best systems, respectively, for energy recovery from organic fraction of municipal solid waste (OFMSW) and municipal sewage sludge generated in municipal wastewater treatment plants. A conceptual bio-refinery by deploying HTL, AD and MEC to process MLW alone and an integrated MSW and MLW treatment are proposed to produce biochar, biooil, biogas, biohydrogen and reusable water. This reduces the reliance on coal, oil, natural gas and fresh water and thus provides energy independence to nations and helps to achieve the United Nation’s sustainable development goals 11, 7 and 13.