On multiple environmental measures, “peecycling” almost always comes out ahead
December 22, 2020
Manufacturing the fertilizer on which much of modern agriculture depends takes a heavy environmental toll. The phosphorus in commercial fertilizer comes from phosphate rock, a non-renewable resource, while nitrogen comes from natural gas and requires a lot of energy to produce.
But there’s an endless stream of renewable phosphorus and nitrogen available: yes, we’re talking about urine. And meanwhile, lots of energy and expense goes to removing nutrients like nitrogen and phosphorus from municipal wastewater.
“Both conventional wastewater treatment and fertilizer production are carbon intensive processes,” says Gregory Keoleian, director of the Center for Sustainable Systems at the University of Michigan in Ann Arbor. “Flushing urine with its valuable nutrients down toilets for processing in energy intensive wastewater treatment plants makes no sense.”
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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 new University of Michigan-led study.
The study, published online Dec. 15 in the journal
Environmental Science & Technology, modeled large-scale, centralized urine-diversion and fertilizer-processing systems none of which currently exist and compared their expected environmental impacts to conventional wastewater treatment and fertilizer production methods.
The researchers 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% to 64%, depending on the impact category.
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