Hydrogen is seen as one of the most promising clean energy sources of the future. It burns cleanly, produces only water as a by-product, and offers a versatile way to decarbonize sectors where electrification falls short—like heavy industry, aviation, and shipping.
It can also serve as long-term energy storage, making it a key pillar in the global push to phase out fossil fuels.
But there’s a catch: producing hydrogen cleanly and affordably remains a major challenge.
Most of today’s hydrogen is made from fossil fuels, known as gray hydrogen, which releases large amounts of CO₂.
The cleaner alternative, water electrolysis, avoids emissions but requires enormous amounts of electricity, making it cost-prohibitive in many regions. That trade-off has kept green hydrogen from scaling up fast enough.
Scientists turn to an unlikely source: urine
Now, researchers from the University of Adelaide and the ARC Centre of Excellence for Carbon Science and Innovation (COE-CSI) have developed two innovative electrolysis systems that use urea in human urine and wastewater to produce hydrogen more efficiently.
Their systems cut electricity use by 20–27% compared to water splitting and eliminate toxic by-products in the process.
“While we haven’t solved all the problems, should these systems be scaled up, our systems produce harmless nitrogen gas instead of the toxic nitrates and nitrites, and either system will use between 20–27 per cent less electricity than water splitting systems,” said Professor Yao Zheng, COE-CSI Chief Investigator.
From lab-made urea to real human waste
In their first study, the team used a novel membrane-free system powered by a copper-based catalyst and pure urea.
However, pure urea is typically produced via the Haber-Bosch process, which is energy-intensive and carbon-emitting.
To address this, the second system was designed to run on actual urine, a more sustainable and readily available source.
“We need to reduce the cost of making hydrogen, but in a carbon-neutral way,” said Zheng. “The system in our first paper, while using a unique membrane-free system and novel copper-based catalyst, used pure urea, which is produced through the Haber-Bosch ammonia synthesis process that is energy intensive and releases lots of CO₂. We solved this by using a green source of urea—human urine—which is the basis of the system examined in our second paper.”
Dealing with chlorine corrosion in urine
Urine, while a promising source of urea, brings its own challenge. It contains chloride ions, which can trigger unwanted chemical reactions during electrolysis.
These reactions produce chlorine gas, which corrodes the system’s anode and damages the setup over time.
To address this, the researchers developed a chlorine-mediated oxidation mechanism. Instead of letting the chloride ions cause corrosion, the new system redirects the reaction pathway using platinum-based catalysts supported on carbon.
This approach not only protects the anode but also maintains efficient hydrogen production from urine.
Toward sustainable, low-cost hydrogen
While platinum works, it’s expensive and scarce. That’s why the next step is developing carbon-supported, non-precious metal catalysts to further cut costs and improve scalability.
The team is now working toward building full membrane-free systems that both recover green hydrogen and remediate nitrogen-rich wastewater.
The research is published across Angewandte Chemie International Edition and Nature Communications.
