With the abundance of wood in B.C. and our cold winters, many rural residents still rely on wood for space heating and some for cooking as well. I have had a number of wood furnaces and heaters, some which were not very efficient, so I can relate to new models which boast better conversion into heat from the wood they use.
In developing countries, millions still cook with open fires often inside their houses creating a very unhealthy environment. Author Barkhard Bilger in an article titled Hearth Surgery describes how millions of people in developing countries still cook and heat with wood and are suffering many smoke caused diseases.
Half of the world's population burns gas, kerosene or uses electricity for cooking, the other half burns wood, coal, dung or some other solid fuel. Open fires often contain a lot of contaminants that slowly kill you if you are continually exposed to them, products like benzene, butadiene, styrene, formaldehyde, dioxin and methyl chloride which can cause pneumonia, bronchitis, emphysema and a variety of cancers.
A number of inventors and scientists around the world have been trying to produce wood stoves that are more efficient and less polluting. For example a German aid agency GTZ and Aprovacho Research Agency have shown that a cooking fire produces as much CO2 as a car but the fire smoke produces more soot and black carbon which is 700 times more warming impact than auto fumes.
For example one gram of carbon black has 700 times more impact of global warming than running a 1,500 watt space heater for a week. With three billion people cooking on wood fire stoves it has been suggested that one way to reduce global warming is to make more efficient clean burning stoves available at a reasonable price.
While some stoves showed promise few met all six criteria for success which are 1) reduce fuel use by 50 per cent, 2) reduce black carbon by 50 per cent 3) reduce childhood pneumonia by 60 per cent 4) is affordable at $10 retail or less 5) cooks love to use it and 6) gets funded.
One group in Guatemala initiated a long-term study in San Lorenz that has lasted the longest and has impressive data on wood use and pollution products and collections of a wide variety of stove models. One example was the Lorana stove made from local materials (sand, clay and pumice) used less wood than similar ovens, but took a long time to warm up and used more wood that an open fire. Cooks loved it but it was outperformed by the smaller metal rocket stoves.
One of the best rocket stoves was mass produced in China, used half the wood and smoke as an open fire and only cost $8, but unfortunately only lasted two years.
A group of scientists from Oak Ridge, Tennessee came up with durable metal combustion chamber for $3 that could be incorporated into other models of rocket stoves that have lasted more than five years.
In a future article I will report on a recent United Nations study on wood stoves as well as some of the most promising stoves that have been developed and how they are being distributed throughout the developing world. The above article appeared in Best American Science and Nature Writing. Editor Freeman Dyson 2010.
