Life Cycle Assessment of Urine Diversion and Conversion to Fertilizer Products at the City Scale

Abstract

Separate collection of urine to recover nitrogen and phosphorus has been advocated to enhance the sustainability of water management and food production. Urine could provide a renewable source of nitrogen and phosphorus, which are currently extracted from nonrenewable resources. Urine diversion also has the potential to prevent nutrients from entering water bodies and to reduce the amount of energy and chemicals needed to treat wastewater. However, urine diversion would require systems to collect urine, produce urine-derived fertilizers, and to ship them, all of which have their own environmental impacts. This thesis explores the greenhouse gas emissions, cumulative energy demand, freshwater use, eutrophication potential, and acidification potential of systems that recover urine compared to those that do not. It evaluates the importance of location-specific factors by focusing on three locations, and then by conducting further sensitivity analysis. This work has been submitted to the journal Environmental Science & Technology (currently in review). v TABLE OF CONTENTS

The potential contribution of urine source separation to the SDG agenda – a review of the progress so far and future development options

“…This also makes sense from an environmental point of view. Whereas a number of life cycle assessments have consistently shown that urine source separation is environmentally beneficial, [45][46][47][48][49] this is strongly dependent on the ability to off-set synthetic fertilizer 45 and the ability to produce a fertilizer product with low nitrogen emissions during spreading. 50 We thus observe three positive aspects of urine source separation with respect to the SDGs.…”

Root-Associated Bacterial Community Shifts in Hydroponic Lettuce Cultured with Urine-Derived Fertilizer

“…Human excreta are the primary source of essential nutrients in domestic wastewater. Urine contains an estimated 50% of P and 80% of N present in domestic wastewater while accounting for less than 1% of wastewater volume [ 7 ]. Source-separation of urine for fertilizer production can reduce the environmental impact compared to synthetic fertilizers [ 7 , 8 ].…”

“…Urine contains an estimated 50% of P and 80% of N present in domestic wastewater while accounting for less than 1% of wastewater volume [ 7 ]. Source-separation of urine for fertilizer production can reduce the environmental impact compared to synthetic fertilizers [ 7 , 8 ]. Hilton et al [ 7 ] assessed that fertilizer production from source-separated urine could reduce greenhouse gas emissions by 47%, energy consumption by 41%, eutrophication potential by 64%, and freshwater use by 50% compared to synthetic fertilizer use.…”

Nested risks and responsibilities: Perspectives on fertilizer from human urine in two U.S. regions

“…Conducting our study in the New England and the Upper Midwest regions enabled us to consider how both geographic location and scale of implementation will influence patterns of adoption. Several recent studies have addressed the value of urine reclamation to achieve sustainability goals, including completing nutrient cycles and reducing greenhouse gas emissions (see Hilton et al, 2021;Legrand et al, 2020;Simha & Ganesapillai, 2017). Other site-specific social studies conducted across the globe on urine diversion have emphasized different facets of the complex risks and understandings caught up in both the technological implementation and agricultural reuse of human urine.…”

“…The wider project of which our work is part explores how human urine has the potential to complete the nutrient cycle (preventing nutrient pollution and supporting sustainable agriculture) while also reducing greenhouse gas emissions (Hilton et al, 2021). 1 From the wastewater perspective, urine contributes approximately 75% of the nitrogen and 50% of the phosphorus in domestic wastewater (Vinnerås, 2006), nutrients which are rarely removed before their discharge into waterways, resulting in nutrient pollution that contributes to harmful algal blooms.…”