Exploring Nutrient-Energy-Water Cycles

Ann Arbor, Michigan, and Brattleboro, Vermont, USA

As the infrastructure in the United States ages, it serves as an opportune time to rethink use and reuse of natural resources. Urine contains nitrogen, phosphorus, and potassium--nutrients that are essential for plants to grow. Therefore, Professor Nancy Love, her team, and collaborating institutions have explored the technology, risks, and regulations associated with urine separation, concentration, sanitization, and preparation for re-use as fertilizer.

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About the Project

Every year, 1.2 trillion gallons of drinkable water are flushed down toilets. Additionally, on average, every five out of six flushes of a toilet are for urine only. Human urine contains important nutrients such as Nitrogen, Phosphorus, and Potassium that are crucial for plant growth. The project team is exploring how humans, as a society, can rethink and reuse our resources in a way that could save energy, drinking water, and reuse limited nutrients in a way that reduces pollution of lakes and waterways. In doing so, we can go beyond resource recovery to achieving resource efficiency in communities.

For the past several years, the University of Michigan research team has been collaborating with the Rich Earth Institute, a non-profit research institute in Brattleboro, VT. Rich Earth has been using urine and its products as fertilizer since 2012. Working together, the Michigan and Vermont teams are studying the effectiveness and safety of using urine-derived products as fertilizer for all kinds of crops. In order to do so, researchers have developed several different processing methods with the goal of removing trace pharmaceuticals and pathogens.

Normally, when urine enters the wastewater stream, it carries with it the majority of the nitrogen, phosphorus, and potassium that people take in when they eat. Many wastewater treatment plants do what they can to remove these nutrients before the wastewater effluent reaches water bodies since these nutrients, though important for plant growth, can cause eutrophication, harmful algal blooms and fish kills when they reach bodies of water in high concentrations. Unfortunately, the processes used to remove nutrients can be costly and energy-intensive. Further, not all treatment plants are equipped to remove nutrients, and would need significant (and expensive) upgrades to meet environmental protection needs.

The project team is assessing if diverting urine will be a less energy intensive and more cost-effective way to reduce the nutrient loads in wastewater effluents and create fertilizer for agriculture.

Special bathrooms were installed at U-M, including a urine-diverting toilet and a urine-diverting urinal, where the urine flows through a series of pipes into the Urine Processing Room in the basement of the building. The urine goes through a series of processing steps that serve to concentrate it, sanitize it, and prepare it for re-use as fertilizer. This small scale system is a prototype for how urine separation for processing can be done in larger buildings.

In 2018, the team compared several different urine-derived fertilizers to conventional fertilizers. Using lettuce, carrots, and hay as test crops, they compared the efficacy, safety and environmental impacts of urine-derived fertilizers and conventional fertilizers. Additionally, they are engaging in social research and market research to understand how the public and relevant stakeholders such as farmers, regulators, wastewater treatment plant personnel, and legislators perceive urine-derived fertilizers.

To learn more about this project, please contact Nancy Love, Principal Investigator, at nglove@umich.edu.

Funding Source

$3 million grant from the National Science Foundation

Other Contributors

  • Joe Arvai, University of Michigan
  • Alexandra Cohen, University of Michigan
  • Kensey Dahlquist, University of Michigan
  • Rebecca Dickman, University of Buffalo
  • Lucina Li, University of Michigan
  • Kim Nace, Rich Earth Institute
  • Julia Raneses, University of Michigan
  • Enrique Rodriguez, Rich Earth Institute
  • Tatiana Schreiber, Rich Earth Institute
  • Harrison Suchyta, University of Michigan

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