The Business Of Pee
British startup NPK Recovery parks a mobile unit outside music festivals and sports events. Inside: waterless urinals that collect human urine. The system processes the liquid on-site, turning it into bottled fertilizer within hours. The company’s name comes from the three elements plants need most — nitrogen, phosphorus, potassium — and all three are abundant in human urine.
This isn’t performance art. It’s closing a loop we broke a century ago.
Why Plants Need Nitrogen
Plants build proteins from nitrogen. But atmospheric nitrogen — the gas that makes up 78% of the air — is triple-bonded and chemically inert. Plants can’t use it. They need nitrogen in a reactive form: ammonia, nitrate, compounds they can absorb through roots.
In nature, certain bacteria perform this conversion. Legumes host nitrogen-fixing bacteria in root nodules. Lightning strikes also split nitrogen molecules, allowing them to react with oxygen and dissolve into soil as nitrate. For most of human history, farming depended on these slow natural processes, plus animal manure and crop rotation.
Then in 1909, German chemist Fritz Haber figured out how to synthesize ammonia from atmospheric nitrogen and hydrogen. The Haber-Bosch process — scaled up by engineer Carl Bosch — uses high pressure, high temperature, and an iron catalyst to force nitrogen and hydrogen together. It gave humanity synthetic fertilizer. It also consumes roughly 2% of global energy supply today.
What Urine Contains
An adult produces roughly 1.5 litres of urine per day. That urine carries nitrogen the body didn’t use — nitrogen extracted from food that was fertilized using the Haber-Bosch process. Urine also contains phosphorus and potassium, the other two elements in NPK fertilizers.
In cities, we flush this nitrogen into sewage systems. Treatment plants either release it into waterways (causing algal blooms) or strip it out using energy-intensive denitrification processes that convert it back into atmospheric nitrogen. Either way, the nitrogen extracted from the air at high energy cost ends up wasted.
NPK Recovery’s system short-circuits this waste. The startup’s units stabilize the urine using natural processes, concentrating the nutrients into a form plants can use. No high-temperature synthesis. No pressure vessels. No natural gas input.
The Scale Question
One human produces enough urine annually to fertilize roughly 400 square meters of cropland. The UK produces approximately 6.5 billion litres of urine per year — enough to replace a meaningful fraction of imported synthetic fertilizer.
But collection is the bottleneck. Urine must be stored separately from feces (which carry pathogens requiring different treatment). This requires either source-separating toilets in buildings or mobile collection units at events. NPK Recovery targets festivals because they concentrate thousands of people in temporary locations where installing specialized toilets is practical.
The company sells the resulting fertilizer to farms and gardens. Early trials show crop yields comparable to synthetic fertilizer. The nitrogen is in urea form — the same compound synthetic fertilizers often use, but produced by human metabolism rather than industrial chemistry.
Why This Matters Now
The Haber-Bosch process turns natural gas into food. As long as natural gas stays cheap, synthetic fertilizer stays cheap, and urine recycling struggles to compete on price. But three forces are shifting the economics:
First, natural gas prices are volatile. Europe’s energy crisis showed how quickly fertilizer costs can spike when gas supplies tighten.
Second, agriculture faces pressure to reduce emissions. Synthetic fertilizer production and the nitrous oxide released when farmers overapply it together account for roughly 5% of global greenhouse gases.
Third, phosphorus — the P in NPK — comes from mining finite rock deposits. Unlike nitrogen, phosphorus has no atmospheric reservoir. Peak phosphorus projections vary, but known reserves could deplete within this century. Urine contains phosphorus. Flushing it away is flushing a non-renewable resource.
The Pee Cycle
NPK Recovery calls its system “pee-cycling.” The term is cheeky but accurate. The nitrogen cycle on Earth runs through every living thing — air to soil to plant to animal and back. Industrial agriculture broke that cycle in one direction: we extract nitrogen from the air but dump the nitrogen in our waste rather than returning it to soil.
Before sewers, human waste returned to fields. Night soil collection was standard in agricultural societies. Cities shipped their waste to farms. The practice ended not because it was inefficient but because it was unsafe — human waste carries pathogens. Modern sanitation protected public health by separating waste from water supplies.
Urine, stored alone for a few weeks, self-sanitizes. Ammonia concentrations rise as urea breaks down, killing most pathogens. This makes urine simpler to recycle safely than feces, which require composting or other treatment to neutralize disease risk.
The question is whether we can rebuild the return loop at scale — whether “pee-cycling” can graduate from festival toilets to urban infrastructure.
What Closing The Loop Requires
Sweden has installed source-separating toilets in several housing developments. Switzerland is piloting urine collection in urban buildings. China has studied phosphorus recovery from urine at city scale. But none have moved beyond demonstration projects.
The barrier isn’t technical. It’s economic and cultural. Toilets built for mixed waste disposal are standard. Retrofitting buildings costs money. Convincing people to use urine-diverting toilets requires overcoming disgust — even though urine from a healthy person is sterile when fresh and poses lower disease risk than soil.
NPK Recovery sidesteps both problems by targeting events, where temporary infrastructure is already required and participants are primed to accept novel experiences. Whether the model scales to cities depends on whether energy costs make Haber-Bosch fertilizer expensive enough that urine becomes worth collecting — and whether societies decide that recycling nutrients matters more than flushing them away.
The nitrogen is already there. We extracted it once. The question is whether we’ll use it twice.