CHICAGO, Dec. 16 (Xinhua) -- Diverting urine away from municipal wastewater treatment plants and recycling the nutrient-rich liquid to make crop fertilizer would result in multiple environmental benefits when used at city scale, according to a study led by the University of Michigan (UM).
Using a technique called life-cycle assessment, which provides a comprehensive evaluation of multiple environmental impacts, the researchers compared the performance of large-scale, centralized urine-diversion and fertilizer-production facilities to conventional wastewater treatment plants and the production of synthetic fertilizers using non-renewable resources.
They found that urine diversion and recycling led to significant reductions in greenhouse gas emissions, energy use, freshwater consumption and the potential to fuel algal blooms in lakes and other water bodies. The reductions ranged from 26 percent to 64 percent, depending on the impact category.
"Urine diversion consistently had lower environmental impacts than conventional systems," said lead author Stephen Hilton, who conducted the study at UM's School for Environment and Sustainability. "Our analyses clearly indicate that the well-defined benefits: reduced wastewater management requirements and avoided synthetic fertilizer production, exceed the environmental impacts of urine collection, processing and transport, suggesting that further efforts to develop such systems are warranted."
The UM study is the first to include detailed modeling of wastewater treatment processes, allowing the researchers to compare the amount of energy and chemicals used in each method.
"This is the first in-depth analysis of the environmental performance and benefits of large-scale urine recycling relative to conventional wastewater treatment and fertilizer production," said Greg Keoleian, senior author of the paper and director of the Center for Sustainable Systems at the UM School for Environment and Sustainability.
Diversion of urine to recover and recycle nitrogen and phosphorus has been advocated as a way to improve the sustainability of both water management and food production. It has the potential to reduce the amount of energy and chemicals needed to treat wastewater while decreasing the flow of nutrients that fuel harmful algal blooms in lakes.
Urine contains the essential nutrients nitrogen, phosphorus and potassium and has been used as a crop fertilizer for thousands of years. In recent years, urine recycling has been studied as a way to produce renewable fertilizers while reducing the amount of energy and chemicals needed to treat wastewater.
The study was published Tuesday online in the journal Environmental Science & Technology. Enditem