Clean cookstoves displayed at an international meeting

(Updated 10/24/16: fixed broken links, changed photo)

If you were to list the top causes of death and sickness in the developing world, cooking would probably be in the top tier (I’d guess that lack of clean water is at the top). In villages and cities across the world, millions cook their food while engulfed in plumes of toxic gases and particulate matter (smoke and soot) from the fire underneath their cooking pots or in their cookstove. With women most often doing the cooking and children often nearby, they bear the brunt of the toxic cloud. Gathering the fuel can also be risky, exposing the gatherer to bandits and other nefarious people. A “Call to Action” on household air pollution in the Lancet states that household air pollution caused by burning of solid fuels results in 3.5 to 4 million premature deaths annually. (Inefficient cooking fires also leading to deforestation, erosion and other harm.)

This toxic burden has been receiving a lot of attention recently, including a long article in the December 21 & 28 issue of The New Yorker. When the issue arrived a few days ago, I made my usual scan of the table of contents to see what was inside. “A stove to transform the developing world”— the subtitle of an article called “Hearth Surgery” by Burkhard Bilger — caught my eye because I’ve long had an interest in domestic combustion devices.[1] So excited was I to see such an august publication covering something as humble as the cookstove that I immediately turned to the article and started reading.

In the first paragraph, I saw the name “Dale Andreatta” and just about fell over. Dale, it turns out, was one of my research colleagues during graduate school in the Department of Mechanical Engineering at the University of California, Berkeley. Even back then Dale had an interest in using engineering to solve difficult problems of the developing world. One project that I remember was solar water pasteurization with low-cost materials — some black trash bags, some sand, a hose, and a temperature switch.[2]  I helped out on a few occasions, but at that time in my life I hadn’t yet picked up experimental skills (I was into numerical modeling, the serious experimental work would come a few years later).

The Engineering Challenge of Clean Cookstoves

The New Yorker article picks up the story of cookstoves at “Stove Camp,” an annual event in Cottage Grove, Oregon at the Aprovecho Research Center. There, dozens of engineers, designers and others get together to tackle the technical problems of stove design and manufacturing. For example, how can a stove be designed so that Ethiopians can reliably cook their staple injera (a flat-bread/crepe made with fermented teff batter)? Cooking regional cuisines right is critical because if a stove doesn’t work for the end user, it will probably be discarded.

“The world is absolutely littered with failed stoves,” says Dean Still, the head of Aprovecho. And for good reason: “Building a stove is simple. Building a good stove is hard. Building a good cheap stove can drive an engineer crazy,” writes Bilger. The designer has to contend with a variety of inputs (small twigs, big sticks, wood chips, paper scraps, all with varying levels of moisture), a variety of conditions, and much more. And then, a perfect design can be foiled by slight adjustments. Bilger comments on this: “Too many stoves start out as marvels of efficiency, they said, and are gradually modified into obsolescence. Once the engineer is gone, the local builder may widen the stove’s mouth so it can burn larger sticks, only to draw in too much cold air. Or he’ll make the stove out of denser bricks, not realizing that the air pockets in the clay are its best insulation. The better the stove, the tighter its tolerances, the easier it is to ruin.”

With many past stove projects foiled by poor manufacturing quality or local stove builders who take liberties with the design, Aprovecho has decided to do what many other manufacturers do: go to China. Aprovecho has been collaborating with a manufacturing company in China to mass-produce stoves on a huge scale and with extremely high quality.

And, of course, cost is a major concern. In the article, Dean Still cites a retail price of $10 per stove as a target (this cost also assumes a lifetime for the stove, which wasn’t given in the article. A stove that lasts two years should cost much less than one that lasts five years.)

The Global Impact of Cookstoves

Although the human damage caused by cookstoves has been getting attention for decades from the public health community, non-profits and international development organizations, cookstoves’ role in climate change has brought them out of the haze and into the news. Although stove fires emit the main greenhouse gas (carbon dioxide, CO2), their smoke is the concern. Solid fuel fires emit a complicated mixture of particulate matter (PM). The darkest portion of this PM (the part known as “black carbon,” a sooty material that is nearly pure carbon) can cause warming in several ways, including these two: 1) when suspended in the atmosphere, it absorbs sunlight and causes local atmospheric heating; 2) when it settles on snow or ice, it increases the melting rate of the snow or ice (by reducing its reflectivity). Researchers are finding that black carbon’s climate influence had been underestimated previously. Many have suggested that control of black carbon and other agents with short atmospheric lifetimes (like methane) can slow climate change in the near term while we figure out what to do about CO2 (additional explanation is in an article in the L.A. Times).

The second effect is especially important to Asia because glaciers in the Himalayas are the source of fresh water for millions on the continent. Slow-melting glaciers act as storage units, keeping the winter’s precipitation ‘on ice’ and slowly releasing it during the warm season. Already, we are seeing changes in the glaciers on the Tibetan Plateau, as research from NASA shows.

It is unfortunate that the cookstove health crisis has festered for so long, killing and injuring millions, but perhaps the global focus on climate change will finally bring the resources and know-how to clear out the smoke that damages the world’s poorest and most vulnerable.

Photo Credit
Photo of Clean cookstoves from United States Mission Geneva’s Flickr collection, subject to a Creative Commons License

Notes
[1] Water heaters, industrial gas burners, radiant burners, and so on. (Return to text)
[2] The method of killing pathogens in water involved the following steps: In a sunny location, build a mesa-like platform using the sand, then hollow out the middle to make a well. Lay one sheet of plastic over the well and fill with water. Attach temperature switch to the hose, place hose in water. Cover water with another sheet of plastic. Given enough sun, the water will eventually reach temperatures that kill pathogens (given enough time – the hotter the water, the less time is required. Somewhere there is a table that shows the relationship but I don’t know where that is). (Return to text)