Forest
Stewardship News Release
November
22 , 2005- For Immediate Release
Contact: Allyson
Muth , Phone: 814-863-0401 E-mail: abm173@psu.edu
Burning 20-Proof Wood
Written by: Jim Finley, 814-863-0401, fj4@psu.edu
This winter may seem to cast back to the early 1970s, when the energy crisis drew many people back to the practicality of burning wood. This winter, I expect many calls and emails about what species to burn in the woodstove and how dry should it be to burn most efficiently. The answers are relatively simple. Generally, burn whatever species you have; but it should be dry - hopefully at least 20 proof.
What is 20 proof wood?
We measure wood moisture content on an oven-dried basis, expressed as
the percentage moisture content. That is,
Percentage Moisture Content = ((Green Weight - Dried Weight) / Dried Weight)
X 100.
Firewood should have a moisture content of 20 percent. To achieve this in Pennsylvania, you should cut, split, and stack wood under shelter up off the ground for nine months to a year. By burning wood that is not 20 percent moisture, you waste heat through inefficient burning, and risk accumulating creosote in your stovepipe and chimney.
In a fire burning wood that is too wet, heat from the fire must first drive off the excess moisture - essentially lots of steam travels up the chimney. This steam robs heat available from the fuel. The fire burns cooler, perhaps at temperatures where the volatile gases that would normally burn, do not. If this is the case, these gases condense in the stovepipe and chimney, coating these surfaces with tar and creosote.
Besides losing heat, making steam, and not burning the gases efficiently, your stovepipe and chimney actually becomes increasingly constricted from the build up of tar and creosote. Eventually this stored waste may start to burn and when it does, the intensity is amazing. The resulting chimney fire is both scary and potentially very dangerous.
The lesson is - burn properly dried wood. Try to get your firewood moisture content to 20-proof.
The following adage is one way to guide wood selection. "Poplar gives a bitter smoke, fills your eyes and makes you choke. Apple wood will scent your room, with incense like perfume. Oaken logs, if dry and old, keep away the winter's cold. But ash wet or ash dry, a king shall warm his slippers by."
It is fun to study your firewood. There is excitement and recreation in splitting, stacking, and burning firewood when you know what you have. A woodshed filled with a mix of species is even fun. Black cherry provides a cheery flame, pops, and snaps, and outside your home a rich pleasant smoke wafting in the air.
If you want a long-lasting heating wood, choose the highest-density species, like hickory and ironwood. Other top-shelf species are beech, oak, black locust, sugar maples or the fruitwoods. Second-string are red maple or ash, and the lowest-density woods are aspen, basswood, elm, and black cherry.
Base your wood choice on its use. On a brisk autumn morning or cool spring evening, a warming fire is exactly what you want. Lighter woods, like aspen, red maple, elm, and even pine are easier to ignite than higher-density wood, and the fire does not linger, providing heat when you no longer want it. Wood density is a major factor in predicting a species' ability to warm your home. Even the densest woods give off smoke that gets in your eyes and makes you choke.
Lighter woods often have higher water content. Because of moisture content, we do not buy wood by the weight. Standing green ash, for example, is 45 percent moisture. Green aspen is 120 percent. That is 45-proof and 120-proof wood. Moisture content is a lot like alcohol proof, determined by the weight of water lost.
There is no need to moan the thought of splitting wood. Make it fun when you do this chore. If you study the wood as you split it, you can see that red oak and ash are easy to split; there are no interlocking grain fibers. White oak hangs together. You can recognize it by the way the fibers hang off the split edge. Red maple splits nice if it is not too limby. Black birch is nasty. It has a very tight grain.
If you chose to heat with wood, almost whatever tree species you use, when it is properly dried, has a place in your woodstack.
The Pennsylvania Forest Stewardship Program provides publications on a variety of topics related to woodland management for private landowners. For a list of free publications, call 1-800-235-WISE (toll-free), send e-mail to , or write to: Forest Stewardship Program, Forest Resources Extension, The Pennsylvania State University, 320 Forest Resources Building, University Park, PA 16802. The Pennsylvania Bureau of Forestry and USDA Forest Service, in partnership with the Penn State's Forest Resources Extension, sponsor the Forest Stewardship Program in Pennsylvania.
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