Here in the Pacific Northwest we are surrounded by an abundance of readily renewable carbon-neutral biomass, but we overlook this abundant fuel supply because we have been conditioned to assume that heating/cooking with wood-fire is laborious and creates atmospheric pollution. Such is not necessarily the case.
Pollution results when gases that are drawn (pyrolized) from the wood are not thereafter combusted into flame. This blue and black smoke rising into the sky is wasted fuel that poses health risks to everyone’s respiratory system. But to ban wood-firing on this basis would be akin to throwing the baby out with the bathwater.
Pollution-free combustion of wood is contingent upon three factors: Time, temperature and turbulence. When wood is burned hot (over 600 C) in a high-heat-duty fire chamber with an optimal rate of draft and fuel mixing conditions, combustion of wood gases is close to 100 per cent.
The fire is a bit smoky for the first few minutes as it warms up, but after that the exhaust is clear, with carbon-monoxide levels well under 500 parts per million, and particulate matter (1 micron range) around 2.5 grams per kilo of wood. This is as good as any pellet stove, and very close to the exhaust clarity of propane and natural gas, but of course, without the drawbacks of purchasing store-bought products and/or the environmental consequences of supporting the oil and gas industry.
As a long-time builder of cob masonry heaters, and rocket-fired cookstoves and ovens (including the outdoor kitchen in Centennial Park), I am aware that we North Americans are only beginning to realize the possibilities of high efficiency wood-burning.
The ancient know-how is available, and our grandchildren are calling us to seek it out. Key search words: rocket stove, rocket mass heater, masonry heater.
Patrick Amos
Glenora