New, greener electrochemical process turns urine into plant fuel Premium

A new electrochemical technique published in the journal Nature Catalysis now proposes to separate urea from urine in its solid form via a greener, less energy-consuming process. This method converts urea, a nitrogen-rich compound in urine, into a crystalline peroxide derivative called percarbamide.

In the 17th-century, a German alchemist named Hennig Brandt was on a quest to find the “philosopher’s stone”, a mysterious object that could turn any ordinary metal into gold. When he realised the golden colour of urine, he believed it contained tiny particles of the precious metal.

Brand then collected urine from himself, his family, and beer drinkers at his local pub and began distilling it in the hope of finding gold at the end. There was no gold, alas, but the silver lining was that Brandt discovered the element phosphorus.

In fact, some call urine “liquid gold” because it is loaded with elements that plants desire. The waste product is packed with phosphorus, potassium, and nitrogen in the form of urea, the “Big Three” nutrients that fuel plant growth and form the backbone of commercial fertilisers.

A new electrochemical technique published in the journal Nature Catalysis now proposes to separate urea from urine in its solid form via a greener, less energy-consuming process. This method converts urea, a nitrogen-rich compound in urine, into a crystalline peroxide derivative called percarbamide.

Thus it strikes two targets at once: enabling the treatment of urine in urban wastewater and transforming it into a useful resource.

Humans obtain nitrogen from food, convert it into urea, and excrete it through urine. Since urea is rich in nitrogen, it has the potential to be a natural fertiliser. In theory, returning the nutrients to the soil could complete the nitrogen cycle, but scientists currently lack efficient methods to extract urea directly from urine, leaving a crucial gap in this cycle, Xinjian Shi, a researcher at Henan University, China, and the first author of the new study, said.

“Our team’s research fills this gap.”