Rice-powered stove ignites new hope for poor farmers
Once thought to be waste, rice husks now can be used as clean, cheap fuel for developing countries.
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“I saw rice mills throw husks into the rivers,” says the agricultural engineer. “I started thinking about using them as fuel.”
Mr. Belonio was already an accomplished inventor, having designed over 30 devices ranging from paddy dryers to water pumps for poor Filipino farmers. So his thinking led him to the cooking stove, an item fraught with expense and danger in the developing world.
More than a third of the world’s population can’t afford propane or other petroleum-based cooking fuels, relying instead on biomass such as wood or charcoal. Most biomass is burned in inefficient stoves that emit soot, smoke, and toxic fumes.
Belonio envisioned a safer, cleaner, and less-expensive way to cook. Working largely in isolation and with little funding, he turned rice husks – an inedible byproduct of milling rice for food – into a bright blue flame.
Inventing the impossible
Turning rice husks into fuel isn’t a new idea: Several cooking stoves invented for the developing world, such as the Lo Trau (Vietnamese for “rice husk stove”), can use the agricultural waste. But husks are messy. They tend to make a smoky, unstable fire and leave a tar-like residue, says Kirk R. Smith, an environmental health scientist at the University of California, Berkeley, who specializes in indoor air quality and frequently tests cooking stoves.
Burning husks cleanly enough to rival a propane or butane stove at low cost was deemed impossible by many stove developers.
Mr. Anderson worked on his designs with Tom Reed, a former Massachusetts Institute of Technology chemist. Mr. Reed invented the top-lit updraft (T-LUD) biomass stove, one of a class of stoves that can “gasify” its fuel. In gasifier stoves, biomass burns until only charcoal and burnable gases remain; the gases are separated and ignited, producing a smokeless blue flame like that of a natural gas stove, leaving only charcoal behind.
In traditional wood fires, these two processes happen together, creating the familiar yellow, smoky flames. Separating the stages makes for a cleaner, more controlled burn that has made the technology popular worldwide.
Reed and Anderson burned wood in their T-LUD stoves, but neither succeeded in gasifying finer agricultural waste. Then, after seeing a Reed T-LUD stove demonstration at a conference in Thailand, Belonio started imagining a husk gasifier.