From the backseat of a beat-up Toyota taxi, Thomas Taha Rassam Culhane points out the passing sights. Fraying sacks of charcoal cut from nearby forests wait beside makeshift shops. Corrugated metal, cardboard and other scrap make up the ramshackle huts. A stream of dirty water, stained red by runoff from a nearby factory, runs down the alley. Garbage is everywhere. The ingredients of life here in Mukuru, one of Nairobi’s largest slums, are raw. Yet Culhane leans forward in his seat, excited by the possibilities they present.
The taxi stops at the Mukuru Skills Training Center, an art and vocational school. A guard emerges from a small concrete shack to open the front gate. The Mukuru neighborhood is dirty and chaotic, but inside the compound, tidy bits of improvisation are everywhere: An art studio opens onto a small garden filled with herbs and saplings. Three composting toilets turn waste into fertilizer. And outside a bare-bones kitchen, a 500-gallon tank full of old beans and banana peels is slowly generating cooking gas.
Culhane, a 49-year-old American, designed the fuel system. It’s not providing as much gas as it should, so he’s here to make a few improvements. The first step is pretty simple. One tube delivers food waste to the tank, another tube delivers gas back to the kitchen, and right now the food tube is clogged. Culhane grabs a mop handle and works it into the tube, giving it a vigorous declogging. He then takes a container of goopy kitchen scraps and, using a sawed-off plastic water jug as a funnel, feeds them into the system. As he works, a crowd of children, having just finished a free Sunday meal at the school, wanders over to watch.
Culhane must work quickly. The sun is going to set soon, and it won’t be safe to travel through the slum, even by taxi. But he can’t resist the opportunity to explain his project. The kids crowd closer. Some of the smaller ones climb whatever they can for a better view. Culhane points to the tank. “There are bacteria living in here, but vigidudu sivya magonjwa,” he says, using the Swahili phrase for germs that are not diseased. “If we grind up all our food waste and put it in here, the bacteria will eat it and make cooking gas.”
Culhane asks a boy watching from the front row if he is a good climber. The boy nods. “Come up here,” Culhane says, gesturing toward the tank. “But don’t ever do this if there are no teachers around.” The boy climbs on the tank and then, at Culhane’s request, jumps up and down on the lid. The pressure pushes the gas against a valve on the side of the tank. Culhane turns the tap, flicks a pocket lighter, and an orange flame spurts from a valve. “Aha!” Culhane cries. “You see that? Biogas!”
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.