Water Reuse in Sustainable Aviation Fuel Production

Introduction. Water recycling is essential in advancing low-carbon and renewable energy solutions contributing significantly to the global initiative to combat climate change. The integration of non-traditional water sources specifically reclaimed municipal wastewater, into the low-carbon liquid fuel production process is crucial for reducing dependence on freshwater sources. The successful implementation of emerging technologies demands a holistic approach that considers various resource and technology factors at the regional level. However, obtaining region-specific data on available reclaimed water sources is challenging but vital for making informed decisions regarding the siting of fuel production facilities. Recognizing this need, and with the support of the Department of Energy, Office of Bioenergy Technologies (BETO), we undertook an extensive multi-year survey on water recycling. The primary goal was to create a comprehensive county-level dataset for the United States, capturing information on water reuse and untapped reclaimed municipal water flow from 2019 to 2021. This dataset was then utilized to analyze various CO2 reduction and utilization (CO2RU) technologies for sustainable aviation fuels (SAF). These pathways are currently under evaluation by BETO's CO2RU consortium. Through this research, we aim to contribute valuable insights that can guide decision-making processes and promote the environmentally responsible development of low-carbon energy solutions. Methodology. The project comprises three main components: a Reclaimed Municipal Wastewater (RW) survey, an estimation of untapped RW, and an analysis of RW utilization for Sustainable Aviation Fuels (SAF) through various technology pathways in select market regions. A comprehensive, multiple-level survey, encompassing state, county, and facility levels, was conducted for each state. Secondary and tertiary effluent flow data from municipal water resource reclamation facilities spanning the years 2019-2021 were collected from the ECHO database and cross-verified with state and local data when available, with aggregation performed at the county level. Additionally, a state-level survey was executed to gather and analyze current water reuse practices, informing the estimation of untapped RW effluent-net available flow for further use-with data aggregated at the county level. The resulting dataset was then applied to evaluate three CO2RU technology pathways. A baseline scenario was established, assuming the production facility utilizes groundwater as a primary source. Water sustainability was assessed using the Water Availability Index (WAI) from https://Water.es.anl.gov, which considers the fraction of annual renewable water supply available for other economic sectors in a region after meeting specific production demands (range 0-1), with a recommended level greater than 0.8. Further analysis compared the potential of water recycling when RW replaces cooling water, process water, and water for hydrogen production. The study focused on four key fuel production states: Texas, Louisiana, Iowa, and California. Results. Our analysis reveals that water demand for the fuel production facility varies with the technology and ranges from 44-70 million gallons per year, resulting in the production of 24 to 29 million gallons per year of Sustainable Aviation Fuel (SAF). On average, it requires 1.5 to 2.9 gallons of water to produce a gallon of SAF. Integrating RW recycling into the CO2RU SAF production facility can lead to a reduction in water demand for production across all counties in Iowa, 70% of counties in Louisiana, 98% of counties in California, and 47% of counties in Texas, assuming a refinery facility is constructed in these regions. In counties with available untapped RW, up to 100% of the water demand (44-70 Mgal) could be avoided, with a four-state average of 65-66%. The recycling of RW in SAF production has the added benefit of enhancing freshwater availability for other economic sectors. When compared to scenarios with no water recycling, the Water Availability Index experiences a substantial increase with recycling in place, reaching its highest level in Scenario 2, where RW is utilized for both refinery and hydrogen production (Figure 1). Our assessment highlights Iowa as the most favorable location for constructing a SAF facility from a water resource standpoint. Conversely, the impact on water resources in Texas could be substantial, particularly in regions facing water stress. Although TX has ample supply of CO2 sources and electricity grid to support SAF production several counties in Texas may not be suitable for a SAF due to low renewable groundwater availability. The datasets and insights derived from our study offer valuable quantitative information for stakeholders in the energy sector and those at federal, state, and local government levels. This information serves to improve decision-making processes concerning regional water resource management, energy project deployment, and the formulation of environmental policies. Ultimately, our work contributes to fostering a more sustainable and water-conscious approach to energy production in a low-carbon economy.