The shortage of fertiliser, worsened by the war in Ukraine, and sky-high prices is getting people in a part of the United States to revive an almost forgotten practice. Plants feed us, so why not feed them? they ask. They are talking about peecycling or using human urine to fertigate plants. A report in the New York Times says people in Vermont, have been persuaded by a local nonprofit group called Rich Earth Institute to donate their pee for use in farms since 2013. The institute says on its website that it has saved 1.8 lakh gallons of water since then. (One gallon is 3.78 litres).
Urine is rich in nitrogen, potassium and phosphorous – nutrients that plants need. The production of ammonia, a chemical fertiliser, is energy intensive. Energy is needed to crack hydrocarbons to yield hydrogen. Energy is again needed to combine hydrogen with nitrogen under intense heat to produce ammonia.
A visit to Rich Earth Institute’s website is quite educative. It says nine billion pounds (4.05 billion kg) is the amount of chemical fertiliser that could be replaced with urine Americans produce each year. Eighty percent of nitrogen and phosphorous pollution in wastewater is caused by human waste. It says 125 gallons (473 litres) is the approximate volume of urine an adult produces each year. An adult human could save 4,000 gallons (15,140) of water per year by diverting urine for fertiliser.
Recycling urine on an industrial scale would need a change in urban plumbing systems. Transporting urine over long distances for use in farms does not make sense as it is mostly water. The Rich Earth Institute says nitrogen in stored urine is in the form of ammonia, which is prone to evaporation and requires special handling during fertiliser application. To counter these challenges, it is experimenting with innovative methods for stabilising the nitrogen in urine, as well as adapting reverse osmosis equipment for use in producing a concentrated fertiliser product.
The institute says in association with the University of Michigan, University at Buffalo and the Hampton Road Sanitation District it is studying the presence and persistence of a wide variety of pharmaceuticals when urine-derived fertiliser is used for growing fresh vegetables.
Another area of research involves social acceptance and overcoming the stigma attached to the use of human waste.
You can read the NYT article here.