What useful function did an engineer find for urine?

Mexican engineer Gabriel Luna-Sandoval was in the act of relieving himself one day, Phys.org reported, when he realized his precious bodily fluids were going to waste. Soon after, he developed a machine capable of transforming urine into a biogas that can power a household heater that can be used to heat shower or cooking water. The Mexican Space Agency called the invention a “great innovation” with "high viability to be considered in space technology and for space walks." Just a tablespoon of urine (give or take) is enough for a hot 15-minute shower.