It turns out that the nitrogen in human urine can be used in fertilizer. However, humanity’s use of nitrogen is everything but efficient, according to a pair of siblings who founded the Swiss start-up company, VunaNexus. In fact, the space technology that also reuses nutrients from human wastewater inspired the idea, which originated from a collaboration with the ESA’s MELiSSA project. However, back here on Earth, “nitrogen pollution from human urine is a significant, mostly overlooked environmental problem. “Our vision is that in the future, most large constructions in dense city centres will have technologies to recycle nutrients from urine,” David said.