An Overview of the Potential for Municipal Wastewater Treatment Plants to Be Integrated into Urban Biorefineries for the Production of Sustainable Bio-Based Fuels and Other Chemicals

Purpose of ReviewAn increase in the generation of waste within cities is unavoidable due to the increasing global population growth, particularly in urban areas. Municipal wastewater treatment plants (WWTPs) in these urban areas are being pushed to their design limits resulting in issues with WWTP residual management. This paper reviews potential applications of transitioning a municipal WWTP into an urban biorefinery for converting wastes into various value-added chemicals and energy.Recent FindingsPrimary WWTP-based residuals produced are waste-activated sludge, biosolids, grit, and effluent. These components are becoming viable feedstocks for producing many potential products and can be recovered for commercial purposes as opposed to simple disposal. Example products include chemicals, energy, and transportable biofuels. An advantage to biorefinery operations composed of WWTPs is that they provide greener solutions while posing little to no threat to the environment. There has also been an increasing interest in co-feedstocks to WWTPs, such as municipal solids, food wastes, agriculture wastes, and lignocellulosic biomass, which can enhance product yields while providing sustainable management solutions to these additional waste streams.SummaryMunicipal wastewater influents generated within the USA have a chemical energy potential of 1.3 MJ/person/day which represents about 4% of the total daily electricity consumed globally. The cost of waste management is expected to rise by 5.5% by 2027 which can be significantly lowered by having WWTPs integrated into biorefineries. This review found that there is great potential for converting WWTPs into true biorefineries that can effectively produce numerous value-added chemicals. Often, minor process changes can be applied which will yield the envisoned products. This paper provides the framework towards both commercialization opportunities and needed research.