LAUSR

Abstract Natural phosphate rock reserves are limited to few geographical regions around the world requiring supply chains that are prone for geopolitical and natural disaster risks. Considering phosphorus (P) as a critical mineral, a strategic commodity P reserve from recycled P was explored at an urban scale representative of a large metropolitan area. Water resource recovery facilities (wastewater treatment facilities) are the ideal P sink where P can be recovered from wastewater. Using data collected in a metropolitan area, a Triple Bottom Line (TBL) sustainability analysis considering economic, social, and environmental impacts and benefits was conducted in comparing P recovery approaches including recovered as biosolids for land application; as fertilizers for immediate use; and recovered from sewage sludge ash (SSA) as P reserves. Evaluation criteria selected for the TBL analysis are: Economic category includes capital expenditures (CapEx) and operating expenses (OpEx); Social category includes public health and sustainable P supply; and Environmental category includes future regulations, air quality impacts, water quality impacts, and greenhouse gas (GHG) emissions. Recovering P from SSA of the study area would require a capital investment of approximately 760 M USGS (2019) which is the most expensive due to construction of a new centralized facility. However, recovery of P from SSA showed the best TBL benefits among the three scenarios. The principal reasons are: a sustainable P supply in the future from recovered P as well as a safer final sludge disposal option compared with land application option. The annual OpEx for Scenario 3 was estimated at 62 M USGS (2019) which is also more attractive than the other scenarios due to reduction in sludge truck hauling distance and improved efficiency by centralizing the operation. From a sustainable P supply and public health perspective, the benefits of storing recovered P as reserves far outweighs the benefits of land application or when recovered as fertilizers for immediate use. This research presents a novel approach to secure future P supply by centralization of P recovery from SSA. Researchers can follow the approach and conduct analyses using evaluation criteria that are most applicable to their own regions.