(186a) Techno-Economic Analysis of Renewable Transportation Fuel from Wastewater Treatment Sludge

For several decades, the Department of Energy Bioenergy Technologies Office (BETO) has supported research and development for the advancement of bioenergy pathways for terrestrial and algal feedstocks. More recently, BETO has begun to explore the potential of wet wastes for biofuel production, and estimates that 77 million dry tons per year of wastewater residuals, manure, food waste, and fats, oils and greases are generated annually, 65% of which are underutilized for any beneficial purpose, such as for fertilizer, biodiesel or compost. Conversion of this resource into transportation fuels could significantly contribute to the nation’s renewable energy goals and provide an economically and environmentally sustainable alternative for current waste disposal practices.

Hydrothermal liquefaction (HTL) is a process that uses hot, pressurized water in the condensed phase to convert wet biomass to an oil product. As such, it is particularly well suited for processing wet waste feedstocks and eliminates the need for drying that is required for other biomass conversion technologies. The oil product, also known as “biocrude”, is analogous to petroleum crude in that it contains a mixture of hydrocarbons with carbon numbers in the gasoline/jet/diesel range. However, it contains higher oxygen and nitrogen than petroleum and therefore must be hydrotreated to improve compatibility with petroleum fuels. This talk presents the conceptual process design, economics and supporting data for a sludge-to-hydrocarbon fuel blendstocks pathway through HTL and biocrude upgrading. The design and techno-economic analysis represents a goal case for the pathway, targeting performance that is anticipated to be achievable by 2022 (BETO’s target year for verification of biofuel hydrocarbon pathways) with further development. The relevance of this work reaches beyond sludge to lay the groundwork for application to other distributed wet wastes and blends that together represent a substantial resource of underutilized biomass.