Municipal wastewater sludge as a renewable, cost-effective feedstock for transportation biofuels using hydrothermal liquefaction. (15th September 2020)

• Record Type: Journal Article
• Authors: Seiple, Timothy E.; Skaggs, Richard L.; Fillmore, Lauren; Coleman, André M.
• Is Part Of: Journal of environmental management. Volume 270(2020)
• Publication Date: 2020-09-15
• Subjects: Waste to energy -- Energy recovery -- Wastewater -- Sewage sludge -- Biosolids -- Biofuels; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2020.110852
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: U.S. municipal wastewater contains approximately 160 trillion Btu/y of influent chemical energy, but very little is recovered and utilized nationwide. Hydrothermal liquefaction (HTL) is a thermochemical process that converts biomass into a biocrude intermediate that can be upgraded to a variety of liquid fuels. HTL provides an opportunity to enhance energy recovery at wastewater treatment plants by transforming underutilized municipal wastewater solids into a renewable, cost-effective feedstock for transportation biofuels. In this study, we estimate total national economic sludge feedstock supply by performing discounted cash flow analyses at >15, 000 U.S. wastewater treatment facilities to assess the net present value of 30-year HTL investments, with comparison to wider adoption of anaerobic digestion (AD). This analysis is the first to model HTL technology deployment across the real-world fleet of wastewater treatment plants. Analyses indicate treatment facilities ≥17 ML/d (4.6 million gal/d) could supply 9.77 Tg/y of dry solids feedstock to economically produce 3.67 GL/y of biocrude intermediate, thereby increasing energy, environmental, and financial sustainability of sludge treatment while reducing disposal costs and operational and environmental risk. Highlights: Assess the economic feasibility of HTL at 15, 000 U.S. wastewater treatment facilities. HTL is feasible at wastewater facilities with flows ≥17 ML/d (4.6 million gal/d). 9.77 Tg/y (79%) of sludge supply could economically produce 3.67 GL/y of biocrude. Economic HTL projects could eliminate USD 3.29 B/y in disposal costs. HTL could help increase energy recovery by 188% and lower disposal costs by 43%.