But biogas could become an extremely useful fuel source. “It’s a multi-solution,” says Nora Goldstein, a council board member and the editor of Biocycle, a trade publication. By being both a waste-disposal and energy-production system, she says, “it addresses multiple urban and rural infrastructure challenges.” It uses an overlooked fuel source, it localizes the production of energy, it produces useful by-products such as fertilizer, and it doesn’t require new, purpose-built facilities. “When you just look at the potential energy output,” she says, “that kind of gets lost.”
Culhane is not the only biogas evangelist in Kenya. Dominic Wanjihia designed his first biogas system while working as an auto mechanic more than a decade ago. And now, at the Jamhuri Renewable Energy Centre in Nairobi, he shows Culhane his latest prototype.
Wanjihia, increasingly concerned about the pollution and deforestation caused by firewood use, has come up with a flexible PVC “balloon” digester that runs on manure. To generate biogas, a farmer shovels manure into the tube and closes it with a sort of zipper made from a hose. Then he adds water through a pipe. It takes about three days to get rolling, but after that, the system will produce a constant supply as long as it’s fed. The system can produce enough gas for a typical household, using about 25 pounds of cow manure per day (less than the daily output of a single cow).
Wanjihia’s new company, Simply Logic, sells the digesters for about $525 as part of a package that includes installation and training. Wanjihia imagines selling the systems in supermarkets to customers who then have a local handyman install them, the same way we might acquire a new washing machine in the U.S. For biogas to succeed, he says, it must become a profession. “People will become skilled in a trade, and they will then find customers, get a commission on the sale, and do the maintenance,” he says.
Culhane is obviously delighted by Wanjihia’s design. Oblivious to the midday sun, they chat excitedly about ultraviolet-resistant PVC and a new plastic joint Wanjihia has installed. Culhane mentions that his own biogas systems are designed to run on kitchen waste. Wanjihia looks dismayed. People won’t chop the food, he tells Culhane. It will never work. Culhane reaches into his bag and hands his fellow evangelist some literature. As Wanjihia reads, he begins to nod. He smiles and taps on the glossy brochure. It’s the promotional material for an InSinkErator Evolution 200, a garbage disposal—the perfect high-powered tool for turning kitchen scraps into raw pulp for biogas.
The InSinkErator costs $400, far too much for the average Kenyan. But a single garbage disposal could band several families together into one energy-producing unit. Wanjihia puts down the manual. “I could design a version we could manufacture in Kenya,” he says. And if two or three households share one to produce enough useful fuel, Culhane adds, their neighbors will see the flame, and might even be willing to chop food waste by hand to have a flame of their own.
The next day, at the Mukuru school kitchen, Culhane zeroes in on a disconnected metal sink that no one’s been using, an ideal site for installing an InSinkErator that just arrived by plane. He and the school’s art teacher, David Redmond, spend half a day hunting down beat-up tools and frayed extension cords and drilling out the drain opening to hold the disposal. Another teacher, Henry Okeyo, lends a hand, and when the work is finally done, a pipe feeds the InSinkErator waste straight from the kitchen into the digester. Another pipe brings fuel into a biogas-ready stove bought from the Jamhuri Energy Centre.
It will take a small amount of electricity to run the InSinkErator, and if it breaks down, someone will have to order the parts and crawl under the sink to fix it. But it’s otherwise a seamless system, very nearly a closed loop. All it takes, Culhane says, is bacteria and garbage. Thousands of miles from any sort of reliable energy infrastructure, Kenyans have improvised a system that is almost as reliable as that in any U.S. kitchen. Culhane turns the knob. Out comes gas.
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Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.