Hydrogen fuel cell cars could help solve the global warming crisis, but nobody wants to buy them. Yoshikazu Tanaka, chief engineer of the Toyota Mirai, Toyota’s hydrogen fuel cell car, calls it a “chicken or the egg” problem: no one wants to purchase hydrogen cars because there are no hydrogen fuel stations, and nobody wants to build hydrogen fuel stations because there are no hydrogen cars.
But Toyota thinks it may have found a solution. For unlimited clean energy, it’s turning to one of the dirtiest places there is: the toilet.
In Fukuoka, Japan, the automaker is converting human waste into hydrogen to fuel the Mirai. The process is pretty simple. At a wastewater treatment plant, like the Fukuoka City Central Water Processing Plant, sewage is separated into liquid and solid waste. The solid waste, called sewage sludge, is exactly what it sounds like: a foul-smelling, brown lump. Most sewage sludge is thrown in landfills.
But in Fukuoka, microorganisms are added to the mix. These microorganisms break down the solid waste, creating biogas, about 60% methane and 40% carbon dioxide. Then, workers filter out the CO₂ and add water vapor, which creates hydrogen and more CO₂. They extract the CO₂ again, and voila: pure hydrogen.
“It’s not a new or advanced technology,” says Marc Melaina, a senior engineer at the National Renewable Energy Laboratory in Denver. “In India, they have loads of biogas plants in villages and such that are just part of their energy infrastructure.”
If Tanaka has his way, Japan and the U.S. will soon follow suit. Currently, the Fukuoka plant produces 300 kilograms of hydrogen per day, enough to fuel 65 Mirai vehicles, Tanaka says. If all the biogas produced by the plant were converted to hydrogen, that number would jump to 600 cars per day. It’s a far cry from enough to achieve his goal of a “hydrogen society” that has no need whatsoever for fossil fuels, but it’s a good first step. Ideally, the process would be implemented in a scaled-up fashion at the wastewater processing plants of the world’s biggest cities.
