Diverting urine away from municipal wastewater remedy vegetation and recycling the nutrient-rich liquid to make crop fertilizer would lead to a number of environmental advantages when used at metropolis scale, based on a brand new College of Michigan-led research.
The research, printed on-line Dec. 15 within the journal Environmental Science & Know-how, modeled large-scale, centralized urine-diversion and fertilizer-processing techniques — none of which presently exist — and in contrast their anticipated environmental impacts to traditional wastewater remedy and fertilizer manufacturing strategies.
The researchers discovered that urine diversion and recycling led to important reductions in greenhouse gasoline emissions, power use, freshwater consumption and the potential to gasoline algal blooms in lakes and different water our bodies. The reductions ranged from 26% to 64%, relying on the affect class.
“Urine diversion persistently had decrease environmental impacts than standard techniques,” mentioned lead creator Stephen Hilton, who performed the research for his grasp’s thesis at U-M’s College for Atmosphere and Sustainability.
“Our analyses clearly point out that the well-defined advantages — decreased wastewater administration necessities and prevented artificial fertilizer manufacturing — exceed the environmental impacts of urine assortment, processing and transport, suggesting that additional efforts to develop such techniques are warranted.”
Urine incorporates the important vitamins nitrogen, phosphorus and potassium and has been used as a crop fertilizer for hundreds of years. In recent times, urine recycling has been studied as a strategy to produce renewable fertilizers whereas decreasing the quantity of power and chemical compounds wanted to deal with wastewater.
Whereas no city-scale urine-diversion and recycling techniques exist, a number of small-scale demonstration tasks are underway, together with one at U-M and a Vermont challenge led by the Wealthy Earth Institute. Hilton used knowledge from each tasks to mannequin the probably environmental impacts of city-scale urine diversion and recycling.
Wastewater remedy was a serious focus of the research, and knowledge from remedy vegetation in Michigan, Vermont and Virginia have been used within the evaluation. The Virginia plant is positioned within the Chesapeake Bay area and served for example of remedy vegetation with strict necessities for nitrogen and phosphorus removing.
Utilizing a method known as life-cycle evaluation, which supplies a complete analysis of a number of environmental impacts, Hilton and his colleagues in contrast the efficiency of large-scale, centralized urine-diversion and fertilizer-production amenities to traditional wastewater remedy vegetation and the manufacturing of artificial fertilizers utilizing non-renewable sources.
Urine diversion and recycling was the clear winner in most classes and in some instances eradicated the necessity for sure wastewater-treatment chemical compounds. On the draw back, one technique for making urine-derived fertilizer led to constant will increase in acidification.
A couple of earlier life-cycle assessments have in contrast the environmental impacts of urine recycling to traditional techniques. However the brand new U-M research is the primary to incorporate detailed modeling of wastewater remedy processes, permitting the researchers to check the quantity of power and chemical compounds utilized in every technique.
“That is the primary in-depth evaluation of the environmental efficiency and advantages of large-scale urine recycling relative to traditional wastewater remedy and fertilizer manufacturing,” mentioned Greg Keoleian, senior creator of the ES&T paper and director of the Middle for Sustainable Techniques on the U-M College for Atmosphere and Sustainability. He additionally chaired Hilton’s thesis committee.
About half of the world’s meals provide relies on artificial fertilizers produced from nonrenewable sources. Phosphate rock is mined and processed to make phosphate fertilizer. The manufacturing of nitrogen fertilizer is an energy-intensive course of that makes use of pure gasoline and is answerable for 1.2% of world power use and related greenhouse gasoline emissions.
On the similar time, water and wastewater techniques devour 2% of U.S. electrical energy, with nutrient removing being probably the most energy-intensive processes.
Diversion of urine to recuperate and recycle nitrogen and phosphorus has been advocated as a method to enhance the sustainability of each water administration and meals manufacturing. It has the potential to cut back the quantity of power and chemical compounds wanted to deal with wastewater whereas reducing the circulation of vitamins that gasoline dangerous algal blooms in lakes.
Nonetheless, large-scale diversion and recycling would require techniques to gather and transport urine, course of it into fertilizer, then ship the top product to prospects. Every of these steps has environmental impacts.
In 2016, U-M researchers have been awarded a $3 million grant from the Nationwide Science Basis to check the potential of changing human urine into protected crop fertilizer. The challenge is led by Nancy Love and Krista Wiggington of the U-M Division of Civil and Environmental Engineering and includes testing superior urine-treatment strategies and investigating attitudes folks maintain about the usage of urine-derived fertilizers. Love can be a co-author of the brand new Environmental Science & Know-how paper.
As a part of the NSF-funded effort, urine-diverting demonstration bathrooms have been put in on U-M’s North Campus, together with a lab the place the urine is transformed to fertilizer. Hilton, who was a dual-degree grasp’s pupil on the U-M College for Atmosphere and Sustainability and the Division of Civil and Environmental Engineering, used knowledge from the challenge to assist mannequin a large-scale system that diverts urine to make fertilizer.
“These new findings are encouraging as a result of they exhibit the potential environmental advantages of large-scale urine-diversion and recycling techniques, suggesting that we’re heading in the right direction and will proceed to develop these applied sciences,” mentioned research co-author Glen Daigger, a U-M professor of civil and environmental engineering and a member of Hilton’s thesis committee.
Bowen Zhou, a former member of the U-M analysis crew who’s now on the College of Waterloo, can be an creator of the ES&T paper. The analysis was supported by the Nationwide Science Basis and the Water Analysis Basis.