Comment by wiggler00m

"[Wood composted with urine could generate temperatures] high enough to be useful for heating buildings and, with a bit of a boost, perhaps for providing hot water as well. To commercialise the idea would mean designing a suitable reactor and heat exchanger, but the waste-wood fuel would be cheap. How you would go about gathering the necessary urine in bulk, given the expense of installing a network of suitably dedicated collection points, is not clear."