Getting the most from your Firewood
September 24, 2006
By Clare NunamakerIf you're relying on firewood for heating this winter, you're probably already aware of the importance of burning seasoned (dried) wood. Basically, the drier the wood, the more heat value you will get out of it.
Green wood, or wood that is freshly cut, has a high moisture content. Depending on the species, as much as about 65% of the weight of the wood may be water. Air-drying wood for several months can reduce the moisture levels down to 12-25%.
When you burn your wood, some of the energy goes into heating and evaporating the moisture in it. So the greener, or wetter it is, the more energy is wasted. Well-seasoned firewood may provide 5500-7500 BTUs per pound, whereas green wood can provide as little as 1100 BTUs per pound.
Of course, there's more to the equation than simply reducing moisture levels, as different tree species have different densities, meaning different weights per cord. A cord of seasoned white oak, for example, will weigh much more and produce much more heat than a cord of seasoned Ponderosa pine. But regardless of species, the drier the wood, the better it will burn.
If you find yourself without seasoned wood this winter (or if your tarp blows off the woodpile and some of it gets soaked), you can increase the amount of heat given off in your woodstove by pre- heating your wood. Keep the wood you're about to burn near enough the fire to heat it, letting some of the moisture evaporate. You won't get well-seasoned wood this way, but you will get a little more heat out of it.
You can now view Tree Tips on the web. Go to www.nwwg.org, click on Resources and click on Tree Tips.
You can contact Clare Nunamaker at forestry@nunamaker.com. Clare is a California Registered Professional Forester currently living near Edinburgh, Scotland.