A Toilet Flush Away from Powering your Car

Listen to the Story

A trip to the bathroom usually sounds like this. [BITE: Sound of toilet flush]. But a study from Ohio University suggests it might soon sound like this [BITE: Sound of car starting]. Professor Gerry Botte discovered a method to convert urea – the main component of urine – into hydrogen fuel. “We are machines making fuels basically,” says Botte. The method is known as urea-electrolysis. Botte says she could produce hydrogen fuel by dipping two nickel electrodes into urine and applying an electric current across them. The voltage causes the urea molecule to break and release its primary chemical building blocks. Nitrogen and Potassium Carbonate go to one side. Hydrogen goes to the other. “What I’m providing is an on-board source of hydrogen. So you store urea and therefore you produce your hydrogen on demand,” says Botte. The method is similar to another method to get hydrogen: water electrolysis. This method uses electricity to break down the water molecule and release hydrogen. But Botte says electrolysis in water is inefficient because it requires a lot of energy. “With water the amount of energy that you will require to break the molecule will be more than what you can get from the combustion,” says Botte. Botte says urea is a better starting point than water for hydrogen production. “It contains more hydrogen than water. The other thing is that it’s 95% lower energy consumption than water electrolysis,” says Botte. The technology would be quite attractive if an infinite source of urea existed. But it doesn’t. No matter how much coffee we drink, we can produce only so much. And animals can only produce so much. “Obviously we cannot power completely a car with urine because we don’t make enough,” says Botte. At the end of the day, it’s a matter of numbers. One human produces about 30 grams of urea every day sometimes more, sometimes less depending on what we eat. On a good’ day, one person’s urine could not power a car for more than half a mile of highway driving. Therefore it’s apparent that powering all of America’s cars would require a lot of toilet flushes or a lot of cows [BITE: cows]. However some researchers are skeptical. “I’m not convinced that there are practical applications of the technology,” says Bruce Logan, Bruce Logan is a professor of Environmental Engineering at Penn State. He doubts the economic practicality of converting urea to hydrogen. Logan suspects there would be a better way to make money from urine. “If you had a solution with high concentrations of urea, you’d have a pretty valuable fertilizer. The value of the fertilizer might be more useful than the economic value of the hydrogen you make by that process,” says Logan. This could be true for solutions with large concentrations of urea. But urine – or waste water in general – is only a diluted stream of the substance. Jason Ganley is a member of the Ammonia Fuel Network. He says the challenge to using urea as a fertilizer is it would require concentrating the wastewater first. “It’s a question of not only where can you find the fuel but how easy is it to concentrate it. It would take a lot of energy and effort to collect it out of the wastewater stream,” says Ganley. On the other hand, Ganley says Botte’s idea to use urea as fuel does not depend on concentration. Hydrogen fuel could come out of any stream of wastewater – dilute or not. “She could take a waste stream and as it flows by, apply a voltage to it and immediately gather a hydrogen product,” says Ganley. Ganley acknowledges the innovation will not replace standard combustion engines in vehicles anytime soon. But he says Botte’s research could yield bigger picture benefits.

“Anytime we could take a waste stream, something that we would have normally thrown away – and turn it into something useful, you’ve done something good,” says Ganley.

Comments