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LETTER: A reply to Andrew Bennett's comment on a previous letter regarding wood stoves
by Contributor on 16 Apr 2012
Thanks for your excellent comment to my letter in the Telegraph on wood smoke. I was very interested to read about your experiences with the Rocket Mass Heater.
I became interested in more efficient wood burning after staying in a house in Llamac in Peru in 2007 where the lady shown holding her grandchild in the upper photograph cooked us a fantastic typical Peruvian meal on the ‘wood stove’ she is sitting next to. We had hired her husband and his donkeys for a 12 day trek around the Huayhuash mountain range in the Cordillera Blanca and stayed in his house after finishing the trek. When I questioned them about a chimney (or lack of it) they just pointed to a hole in the roof.
In addition to spending a big part of her life next to this smoky “stove” she also spends a chunk of her life looking for scarce firewood. I thought that it was just “nuts” that she and her kids and grandkids should be exposed to so much wood smoke unnecessarily for most of their lives.
I thought that I could, and should, design something much more efficient in terms of efficiency...using less wood and improving heat transfer, which would really help people in this situation. After I got home I started thinking about it and “Doodled’ a few design concepts based on my engineering background. But then after “Googling” the topic I found that it had all been done decades before by various people.
I found information on the Rocket Stove design developed in 1982 by Dr Larry Winiarski (Aprovecho Research Centre) and read about how this had been developed and used in other countries such as by Dona Justa in Honduras to suit their local cooking methods etc. (Internet picture of her and her Rocket Stove in the lower picture shows a world of difference). The “icing on the cake”was that Aprovecho published a 40 page design manual in Spanish on the “Design Principles for Wood Burning Cook Stoves”. So I bought a copy and mailed it off to my hosts in Llamac, Peru with hopes that they would build one and spread the word in their village and surroundings. It would be interesting to go back there and see if it ever happened. Maybe one day!
The situation in Rossland and typically North America is very different to developing countries. You are right in that it is also a different situation in rural areas. The difference is that in rural areas neighbours are often far away from each other and wood smoke can disperse. Urban situations are very different from rural situations since the density of housing is much greater and ‘neighbours’ and neighbourhoods can be affected by wood smoke. Also, in cities and towns, a majority of people buy and operate wood stoves not out of need, but for the ‘aesthetics’ of having a “cozy” wood fire they can see through a glass fronted stove on a cold winter evening. This majority has little interest in spending the time and effort needed to attain efficient combustion conditions.
Wood can be burned efficiently but in a majority of domestic situations in North America it is not. The following is copied from a research paper on biomass burning which quotes various EPA documents:
Burning a kilogram of wood in a new stove will produce about 130 grams of carbon monoxide, 51 grams of hydrocarbons (including up to 10 grams of carcinogenic benzene), 21 grams of fine particulate, and about 0.3 grams of highly carcinogenic poly cyclic organic hydrocarbons(EPA 1984, Larson 1993). Wood burning also produces from 10 to 167 milligrams of highly carcinogenic dioxin per kilogram of fuel burning (Abelsen). Wood burning is responsible for about 3 percent of the total suspended particulates, 6 percent of the total carbon monoxide and 51 percent of the highly carcinogenic polycyclic organic matter produced by all U.S. sources (EPA 1986). Wood smoke is usually released near ground level in populated areas and thus is especially apt to hurt people. Wood burning pollution is often concentrated in certain areas of the country (USA) such as the Northwest and at specific times, such as winter evenings. Biomass smoke is generally heavier than air and tends to sink to the ground. It causes high concentrations of particulates where ever it is burned, from a food cart in New York City to a neighbour or restaurant near you.
When I look out of my windows I can see 6 out of 9 houses with wood stove chimneys all within about a hundred metres from my house. What has prompted me to change from “passive acceptance” and “become active” on this topic is a house below me in a state of re-construction where the City of Rossland has allowed a wood stove chimney that is only about 65 feet from my living room sliding doors and below the level of my bedroom windows. This is too close for comfort and smoke can, and does on occasions, drift directly to my house.
Unfortunately I don’t think anything will change as I’m sure many people consider that their right to burn wood supersedes the rights of others to breathe unpolluted air.