Putting the P(ee) in perennial agriculture: Reflections on a workplace urine reclamation project
Publication: Journal of Agriculture, Food Systems, and Community Development
Land Institute researchers Madeline DuBois, Laura van der Pol, Aubrey Streit Krug, and Timothy Crews share findings from a human urine nutrient reclamation project conducted in the workplace and research fields at The Land Institute to explore opportunities and barriers to restoring the nutrient circularity in perennial agroecosystems.
Abstract
Phosphorus (P) is a finite resource essential for food production currently lost from fields at an unsustainable rate via runoff and crop harvests. These losses could be addressed by pairing perennial crops, which reduce runoff with their deep roots that stabilize the soil, with recovering nutrients from human excreta. Urine contains the majority of P and other nutrients that humans excrete and therefore has been the focus of recent nutrient reclamation efforts. Urine fertilizer has yet to be explored for perennials, however, and understanding the biophysical effects of urine fertilizer on soil nutrients and biomass in perennial crops could inform the design of a more circular food system. To that end, we started the first known workplace urine nutrient reclamation project in the state of Kansas, U.S., to test the feasibility of supplying available soil P from urine to alfalfa (Medicago sativa), a perennial legume forage crop. After one growing season, urine fertilizer had no effect on aboveground biomass but did increase available soil P which otherwise decreased in the control treatments. Urine also increased soil nitrate and sodium compared to the water-only controls. The field study was coupled with a survey of staff members who participated in urine collection to identify opportunities and potential barriers to urine diversion in the U.S. The survey revealed a lack of awareness of both unsustainable P management and urine recovery as a potential solution, underscoring the need for increased education. Regulatory challenges faced in the second field season also highlighted the need for policy that explicitly defines urine separately from wastewater in the U.S. We hope that results from this project will make it more feasible to conduct additional studies and circular food system community-based projects on a larger scale going forward.