Electrified Mineralization of Nutrients from Real Municipal Wastewater and the Energy Implications Thereof

Phosphorus and nitrogen are two of the three major nutrients required for plant and animal life and sustaining global population growth requires an anthropogenic impact on the natural cycles of these nutrients i.e., increased phosphorus mining and nitrogen fixation to sustain the per capita consumption of P and N availability, respectively.¹ However, this anthropogenic activity has also led decreased environmental sustainability: higher accumulation of N and P in water bodies due to nutrient runoff and leaching as well as higher greenhouse gas emissions from nutrient fixation, mining and transportation. Furthermore, the process energetics for solid P and N delivery are 4.0 and 5.7 GJ/t, respectively,¹ while the embodied energetics for P and N delivery are 10.4 and 55.5 GJ/t, respectively,² illustrating the key drivers for the associated GHG emissions.<br/>An alternative, yet sustainable, anthropogenic approach is the recovery and re-use of these nutrients from waste via an electrical driving force.^3,4 Although a chemical approach to recovery enhances the circular economy of nutrient use, an electrical approach using renewable electrons extends from materials conservation to significant process decarbonization. This electrified approach will be discussed in this invited talk, based on the combined efforts of researchers at Ohio University and Northeastern University.<br/>This presentation will describe an electrochemically-driven phosphorus and nitrogen recovery system using real wastewater from a municipal treatment plant as the substrate. Initial analyses consisted of 1-year of sampling from 3 different recycle streams at two different wastewater facilities: 4 million gallons per day and 100 million gallons per day throughput. Multivariate screening analyses of stream, design and operational variables on recovery efficiency and energy consumption from synthetic wastewater were conducted. These screening analyses were subsequently used to evaluate recovery efficiency and energetics with real wastewater as the treated substrate.<br/> <br/><u>References</u><br/>(1) Daramola, D. A.; Hatzell, M. C. Energy Demand of Nitrogen and Phosphorus Based Fertilizers and Approaches to Circularity. <i>ACS Energy Letters</i> <b>2023</b>, <i>8</i>, 1493–1501.<br/>(2) Bhat, M. G.; English, B. C.; Turhollow, A. F.; Nyangito, H. O. <i>Energy in Synthetic Fertilizers and Pesticides: Revisited</i>; ORNL/Sub-90-99732/2; Oak Ridge National Lab., TN (United States); Tennessee Univ., Knoxville, TN (United States). Dept. of Agricultural Economics and Rural Sociology, 1994. https://doi.org/10.2172/10120269.<br/>(3) Belarbi, Z.; Daramola, D. A.; Trembly, J. P. Bench-Scale Demonstration and Thermodynamic Simulations of Electrochemical Nutrient Reduction in Wastewater via Recovery as Struvite. <i>J. Electrochem. Soc.</i> <b>2020</b>, <i>167</i> (15), 155524. https://doi.org/10.1149/1945-7111/abc58f.<br/>(4) Kékedy-Nagy, L.; Abolhassani, M.; Perez Bakovic, S. I.; Anari, Z.; Moore II, J. P.; Pollet, B. G.; Greenlee, L. F. Electroless Production of Fertilizer (Struvite) and Hydrogen from Synthetic Agricultural Wastewaters. <i>J. Am. Chem. Soc.</i> <b>2020</b>, <i>142</i> (44), 18844–18858. https://doi.org/10.1021/jacs.0c07916.