Three ‘T’s of wood-burning make it viable

If we are to stabilize our climate, we must make careful assessments of the pros and cons of various energy sources.

If we are to stabilize our climate, we must make careful assessments of the pros and cons of various energy sources. On the matter of combusting wood to produce heat: automatically equating wood-fire with atmospheric pollution is non-sensical. Centuries of empirical evidence clearly indicate that highly combustion-efficient wood fire is possible when we honour the three ‘T’s: time (appropriate draft), temperature (over 600 C), and turbulence (trajectory of gases).

The reason we struggle to achieve this real-world efficiency with metal box stoves is that the thin metal gives off too much heat too soon. The proliferation of metal box stoves in North America has much to do with pioneering days when folks were setting up homesteads. But the more energy efficient our houses have become, the harder it is to reduce the intensity of the fire without smouldering. A smouldering fire — not wood-fire per se — is the pollutant.

When we burn the wood very hot, then harvest the heat into earthen mass for a slow gradual release, we effectively decouple the generation of heat from its delivery into a living space. This is what masonry heaters and rocket mass heaters do very well. When only a small amount of heat is needed (say to take the chill off a spring or autumn morning), the size of the fire can be made smaller, but the fire always burns very hot.

The techniques are well-proven. During the 16th century wood-fuel shortage in northern Europe most every society developed a highly efficient masonry heater. The evolution of low-cost rocket mass heaters in North America over the past few decades, and the hybridization of the two via open source sharing, has made highly efficient wood-fired mass heaters a simple, sustainable and financially viable heating option.

Whether or not one chooses to explore this option, please, let us at least desist in equating wood-fire with pollution.

 

Patrick Amos

Glenora