Human urine might seem like an unlikely ingredient for making chemicals used in energy storage.
But researchers in Australia have developed a new method that could one day turn urea, a major component of urine, into a valuable chemical used in batteries, fuel cells and even rocket fuels.
A team from the University of Adelaide’s School of Chemical Engineering has found a way to use electricity to convert urea into hydrazine.
Hydrazine is an important industrial chemical with applications ranging from pharmaceuticals and aerospace technology to emerging energy-storage systems, including some technologies being explored for electric vehicles.
Today, hydrazine is usually manufactured through industrial processes involving ammonia or chemicals derived from urea.
These methods have been used for decades, but they can require hazardous chemicals and large amounts of energy. That makes hydrazine relatively expensive to produce and raises environmental concerns.
The Adelaide researchers wanted to find a simpler and potentially greener alternative. Their new approach, reported in Nature Synthesis, uses an electrochemical process involving urea, electricity and sodium chloride, better known as ordinary salt.
During the process, sodium chloride helps produce reactive forms of chlorine on the surface of an electrode. These chlorine-containing substances then react with urea to create an intermediate chemical called N-chlorourea. Through another relatively simple reaction involving water, this intermediate can then be converted into hydrazine.
Importantly, the researchers showed that the process works with more than laboratory-grade urea. They successfully produced hydrazine from several sources, including pure urea, wastewater rich in urea and human urine.
That could eventually turn a common waste product into a useful raw material. Human urine contains abundant urea, and wastewater treatment facilities already handle large quantities of it. Recovering that urea and converting it into valuable chemicals could potentially reduce waste while creating materials for energy applications.
The researchers suggest that hydrazine produced this way could have uses in fuel cells and other energy systems. It could also be particularly interesting for long-duration space missions, where recycling waste and producing useful resources from limited supplies can be extremely valuable.
However, the technology is still at the research stage. Several challenges must be solved before urine-derived hydrazine could be produced economically on a large scale. These include preventing salt from building up in the system, reducing energy use during purification, lowering costs and designing reactors that can operate continuously.
The researchers now plan to improve the process and make it more practical. If these challenges can be overcome, renewable electricity could eventually help transform urea from wastewater—and perhaps even human urine—into a valuable chemical for cleaner energy and other industries.
