Using urine to heat homes

URINE, THOUGH disdained by modern society, was once surprisingly useful stuff. Street-facing laundries in ancient Rome had pissoirs attached to them, to encourage passers-by in need of relief to provide, free of charge, a raw material which was then fermented into a degreasing agent. Urine also found employment as a mordant, to assist in the dying of cloth—Scottish tweed was once notorious for smelling of the stuff when it got wet. And urine was, too, a source of potassium nitrate, one of the ingredients of gunpowder.Now, Chen Wei-Shan of Wageningen University, in the Netherlands, thinks he has found yet another use for urine—and one relevant to today’s needs rather than yesterday’s. He plans to employ it to create heat without fire from waste wood.