That might seem like a lot, but most of that urine is used to produce about 1 kg (2.2 lbs) of fertilizer as a byproduct. Randall called urine “liquid gold” because while it makes up less than 1% of domestic waste water by volume, within such water it accounts for 80% of the nitrogen and 63% of the potassium—essential fertilizer ingredients. And while regular bricks need to be kiln-fired at temperatures of 1,400°C (2,552°F) and produce carbon dioxide in the process, the urine bio-bricks don’t need heat.

“Given the progress made in the research here at UCT, creating a truly sustainable construction material is now a possibility,” Vukheta Mukhari, a student who worked with Lambert, told the Guardian.

Randall hopes that the human-urine project will change the way society views waste and the upcycling of waste, because the bio-bricks are hardy and practical, too. The strength of the brick will increase “the longer you allow the little bacteria to make the cement,” Randall said, exceeding even that of some limestone bricks (which are commonly used in masonry).

The only issue, Randall admitted to the BBC, is that the process is much smellier, and it takes 48 hours for the bricks to lose their ammonia smell. Still, these bio-bricks pose no health risks and the process turns pee into three useful products—nitrogen, potassium, bricks—with effectively zero waste.

📬 Sign up for the Daily Brief

Our free, fast, and fun briefing on the global economy, delivered every weekday morning.