Human urine usually ends up in septic tanks and later, in costly water treatment facilities. However, several studies have made an interesting suggestion: Use human urine as agricultural fertilizer.
H. Kirchmann and S. Pettersson in 1994 made a bold move to understand the chemical composition of human urine in an attempt to compare it with commercial organic fertilizer. They initially mentioned the absence of literatures exploring the use of urine as fertilizers, except for earlier studies that probed the agricultural value of urine along with feces.
Understanding the literatures
In their study published by Fertilizer Research, Kirchmann and Pettersson found out that stored human urine contained critical constituents similar to commercial fertilizers. These include nitrogen, potassium, calcium, and phosphorus. The study also revealed urine has lower heavy metal concentrations than organic fertilizers.
Several relatively recent studies subsequently contributed to the growing body of literature about the use of urine as fertilizer. For instance, H. Heinonen-Tanski, S. K. Pradhan, and P. Karinen in 2010 reviewed related studies detailing the effectiveness of urine in cereal and vegetable yields.
Published by the journal Sustainability, the review suggested plants fertilized with human urine might have produced higher, similar, or slightly lower yields than plants fertilized with commercially available minerals. Still, urine-fertilized plants had higher yields than non-fertilized plants.
Researcher and resource-recycling specialist Carol Steinfeld authored the book Liquid Gold: The Lore and Logic of Using Urine to Grow Plants. It essentially provides not only a definitive guide to using urine to grow plants for domestic or commercial use but also an extensive discussion about the valuable applications of urine throughout history and across several purposes.
Commercial application of urine
According to the World Health Organization, although human urine comprises less than 1% of domestic wastewater, it still contains a substantial amount of nitrogen and phosphorous—about 80% and 55% respectively. Urine contamination of rivers and streams runs the risk of algal blooms that can choke off aquatic life.
Rich Earth Institute, meanwhile, has initiated the collection of urine instead of letting it go in septic tanks and water treatment facilities.
Founded in 2011, the people behind Rich Earth Institute have dedicated themselves to advancing and promoting the use of human waste as a resource. Their goal is to bring together sanitary engineers, farmers, water quality advocates, businesspeople, agricultural scientists, and regulators. Together, they would demonstrate the valuable uses of human waste. The Urine Project is their first flagship initiative.
“Since 2012, we have been collecting urine from over 170 volunteer participants in and around Brattleboro, Vermont. After sanitizing the urine, we apply it to farmland that is producing hay. Throughout the process, we collect detailed data on the effect of urine fertilizer on the quantity and quality of the hay harvest and on the properties of the soil,” said Rich Earth Institute.
The Netherlands, especially the city of Amsterdam, had also ventured into a similar undertaking. Dubbed as the Green Urine Campaign that ran during the International Water Week in 2014, the city government placed public urinals that served as urine collection sites. The goal of the campaign was to raise awareness of the benefits of using urine as fertilizer.
Waternet, the water company of Amsterdam, is currently on the process of building a facility that would create 1,000 tons of fertilizers from the wastewater of 1 million people.
Researchers H. Heinonen-Tanski, S. K. Pradhan, and P. Karinen have also come up with a suggestion for better integrating domestic sewage system with urine collection. In their paper, they suggested installment of separate or exclusive toilets for urinating, especially in poor rural areas or farm communities.