Like many of her neighbors in Amubri, an indigenous community at the southern tip of Costa Rica, Gloria Torress Buitrago relied for years on a fogón for cooking. The traditional open-fire stove is common in Amubri (map), and so are the dire health effects. "It was hard to look around and just breathe without feeling the smoke burning the eyes or throat," Buitrago said. One cousin suffered from asthma, and everyone in her family was constantly tearing up from the wood fire's smoke.

Buitrago was just one of three billion people worldwide who rely on such open-fire cookstoves. A recent global health study found that the fumes from those stoves was the largest environmental health threat in the world today, killing 3.5 million people a year—more deaths than caused by malaria and HIV/AIDS combined. (See related blog post: "Cookstove Smoke Is 'Largest Environmental Threat,' Global Health Study Finds.") Cookstoves that burn cleaner can help fight this epidemic, but they can do even more than that when configured to produce biochar, a dark, fine-grained residue that can become a prized asset for rural communities.

In regions as diverse as the high mountain valleys of Costa Rica and the agricultural fields of western Kenya, biochar cookstoves are being used to simultaneously clear the air and enrich the soil. Biochar, a type of charcoal produced when biomass burns in an oxygen-free environment, can boost water and nutrients in dry, depleted soil while serving as a vehicle for burying the carbon that contributes to global warming.

View Images Cookstoves that can produce biochar, like the one pictured above in western Kenya, can be a key tool in fighting respiratory disease and boosting agricultural production. Photograph courtesy ACON

Breathing Easier

Groups like Seattle, Washington-based SeaChar, the recipient of a $72,000 grant from National Geographic's Great Energy Challenge initiative, have been testing new variations on clean cookstoves. SeaChar's Estufa Finca ("Farm Stove" in Spanish) burns biomass cleanly while turning it into biochar. It's not a fancy apparatus: Fashioned from local materials, its components include a five-gallon steel paint bucket, some corrugated steel roofing material, and half of a one-gallon tomato sauce can.

Gloria Torres Buitrago's family is one of 110 households that acquired one of the stoves last year through SeaChar's Estufa Finca program in Costa Rica's Talamanca region. Buitrago says the stove has relieved not only the smoke problem in her home, but also the effort required to keep fires burning. "The time and money it takes to get wood has been reduced a lot," Buitrago said in an interview with a SeaChar staff member, who then translated and emailed her responses. "This time can be used to share with family or just do other things in the garden." (See related story: "Protecting Health and the Planet With Clean Cookstoves.")

In addition to wood, the stove burns garden debris, dried animal dung, and food material such as dried corncobs and coconut husks. A family cooking a pot of beans will use 40 percent less wood with the Estufa Finca than with an open-fire stove, said SeaChar President Art Donnelly, who designed the stove. "Those are trees you do not have to cut down."

Donnelly said tests conducted by SeaChar show a significant reduction in exposure to harmful smoke. "In laboratory testing, these stoves reduced particulate matter emissions by 92 percent and the carbon monoxide emissions by 87 percent as compared to an open cooking fire," he said in an email. "These two are the big drivers of respiratory disease."

Another grantee of the Great Energy Challenge, the African Christians Organization Network (ACON), has been working since 2004 with local farmers to reduce deforestation and improve soil conditions in western Kenya. Introducing innovative cookstoves to local families is part of that effort, and ACON's Salim Mayeki Shaban said that feedback on the stoves has been positive.

"[Women] reported that the reduction of smoke in the house decreased irritation of their and their children's eyes, runny noses, coughing, chest discomfort, and difficulties in breathing, along with cost savings due to fewer hospital visits," Shaban said in an email.

Table-to-Farm Cooking

In Costa Rica, Donnelly said, many local families initially expressed interest in the new stove because it is smoke-free. "The real hook though, is the biochar," he said.

SeaChar offers a biochar buyback program, through which households can earn an extra $15-20 per month by selling the biochar produced by their cookstoves. Currently 22 households regularly participate in the program, and SeaChar has collected 273 feed sacks of biochar, paying families about $5 per sack.

The biochar is buried in the ground for research and demonstration projects, and used at locations such as cacao farms, large organic nurseries, and school garden projects, according to Donnelly.

A recent field study in Costa Rica on the effects of adding biochar and chicken manure to soil showed an increased crop yield of cacao. Juliano Hojah da Silva, a second-year graduate student at the Center for Tropical Agricultural Investigation and Education (CATIE) who led the study, said in an email that the biochar improved the soil's chemical and physical quality.

"All the applications made of biochar increased total soil carbon amounts, as well as soil organic matter, gains which were stable even after one year of implementation," Hojah da Silva said. "These gains are expected to be a persistent beneficial long-term effect." SeaChar will continue to study the effects of biochar on soil in the coming year, Donnelly said.

ACON also has observed benefits for crops treated with biochar. In 2009, it trained farmers in the use of biochar as a soil supplement to help with water and nutrient retention in the western Kenya region of Bungoma (map), which often experiences periods of drought. In subsequent field trials, ACON found that vegetable and cereal crops fared better in plots that were fertilized with biochar and a 15 percent solution of human urine.

In the process of researching biochar, ACON also has found a way to target an aquatic pest while easing resource strain on forests. The group harvests water hyacinth, an invasive species in nearby Lake Victoria that can be dried and converted into fuel briquettes for the cookstoves.

Buried Treasure?

Biochar enthusiasts say that in addition to helping boost crop production, it can be a powerful tool to fight global warming. The International Biochar Initiative, a nonprofit organization that promotes biochar applications, estimates that biochar could help store 2.2 gigatons of carbon annually by 2050.

Kurt Spokas, a research soil scientist with the USDA Agricultural Research Service in St. Paul, Minnesota, agrees that biochar can reduce atmospheric carbon dioxide concentrations, and he says there is scientific evidence that the carbon remains stable in the soil. "The difficulty is in extrapolating to the future," he said.

Projecting carbon sequestration over the long term, especially to the levels of multiple gigatons, would require infrastructure that is not currently in place, Spokas said. "In order to get to that scale, we would have to have industrial plants that are converting biomass into the biochar," he said. "When you look at those numbers, it's scientifically, technologically feasible, but we just don't have that type of infrastructure developed yet."

Spokas noted that the production of charcoal has historically evoked an economic conflict over its value as both a fuel and a soil enhancer. "The cookstoves are a very good model of a system where biochar can work," he says. "They need to burn biomass to produce energy for cooking, so they are not trying to wedge into a new economic scheme. Instead, they are modifying the stoves to simultaneously cook food and produce biochar for soil application."

In the coming year, SeaChar and ACON both plan to expand their projects. SeaChar is developing an Urban Stove for use in homeless encampments in the Seattle area, and is working to educate local farmers, gardeners, landscapers, and kids on the benefits of biochar. ACON's Shaban hopes to scale up his program to other parts of Kenya and to other regions around the world.

While some environmental benefits of biochar stoves may take time to materialize, the health impact remains immediate for the home cooks, so many of them women with children nearby, who finally can prepare meals without suffering devastating health consequences. (See related blog post: "Time to Clear the Smoke.") "The difference that a smoke-free stove makes in the household is very evident," said Gloria Torress Buitrago. "It is even better for the cook."