Permaculture

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Wood is attractive as an alternative to dwindling and increasingly expensive gas supplies. Wood is a renewable resource – Sustainable re-growth of woodfuel captures the CO2 back from the atmosphere. The net effect on the global atmosphere is zero, unlike that of fossil fuels and the people who depend on woodfuel maintain the trees that provide it, they don’t cut them down.

However, the way most wood is burned is both wasteful, unhealthy and even dangerous.

If wood is burned properly, the only products that will be formed are a gas called carbon dioxide, water vapour and a small amount of ash, which cannot burn. However, often wood does not burn completely and the products of incomplete combustion can be a lot of smoke with hundreds of different chemicals. Incomplete combustion is also wasted fuel.

Any kind of stove is cleaner-burning and more efficient than a fireplace and a well designed stove can even burn the carbon particles in the smoke; a heavy stove with lots of thermic mass can even act as a storage heater.

For camping or outdoors again, a tin-can “hobo” stove or any kind of container with air holes in is cleaner-burning and more efficient than an open fire, but there are plenty of free plans for woodgas stoves, or “inverted downdraft gasifier” stoves, operating on natural convection or with a solar-powered fan, where wood is gasified pyrolytically by heating to >400 C, which can also yield charcoal. (N.B. the stage where this charcoal burns produces a high level of carbon monoxide, so ventilation is necessary.) Wood gas stoves are a healthier alternative to the majority of indoor fireplaces used in developing countries, where indoor air pollution is responsible for nearly half of the more than 2 million deaths each year that are caused by acute respiratory infections.

Wood smoke might smell nice, but it contains fine particulate matter, carbon monoxide, formaldehyde, sulfur dioxide and various irritant gases such as nitrogen oxides that can scar the lungs. Wood smoke also contains chemicals known to be carcinogens, such as polycyclic aromatic hydrocarbons (PAHs) and dioxin.
Fine Particulate Matter can stay airborne for weeks and travel upto a thousand kilometres.

The particles of wood smoke are extremely small – so small that windows and doors cannot keep it out and even the newer energy-efficient weather-tight homes cannot prevent wood smoke from entering homes that are not burning wood. Particles are not filtered out by the nose or the upper respiratory system. Instead, they end up deep in the lungs, where they remain for months, causing structural damage and chemical changes. Wood smoke’s carcinogenic chemicals adhere to these tiny particles, deep inside the lungs, increasing the risk of heart attacks and strokes. For people with heart disease, short- term exposures have been linked to heart attacks and arrhythmias. If you have heart disease, these tiny particles may cause you to experience chest pain, palpitations, shortness of breath, and fatigue.

So don’t smoke out your neighbour:
Fireplace and wood stove chimneys should be high enough to protect neighbours from exposure.
Use a clean-burning and fuel efficient stove.

Solid Fuel Advisory Service
http://www.woodgas.com/gasification.htm
http://www.woodgas.com/cookstoves.htm
http://journeytoforever.org/at_woodfire.html#woodgasstoves

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