Wood is a complex material made up of a number of organic compounds and chemicals. It’s no wonder that not all firewood is created equally; some varieties are much better in producing heat, burning longer, having a pleasant aroma, not producing soot etc.
We usually measure the heat value of firewood in BTUs, or British Thermal Units. A BTU is the amount of energy required to raise the temperature of one pound of water one degree Fahrenheit. Scientists have determined BTU values for a number of wood species, and as one might expect, the denser the wood, the more BTUs it puts out.
Some of the top varieties for BTU output are,
Osage Orange — 32.9 Million BTU/cord
Hickory — 27.7 Million BTU/cord
Locust — 26.8 Million BTU/cord
Apple — 25.8 Million BTU/cord
White Oak — 24 Million BTU/cord
Some of the woods on the lower end of heat output scale include lighter woods and evergreens. Evergreens have resins that initially burn hot but their heat does not sustain very long. Evergreens also produce a lot of soot that can clog up a chimney pretty quickly so they are not a good choice for firewood in conventional wood stoves and fireplaces.
Some woods at the lower end on the heat production scale are;
Soft Maple — 18.7 Million BTU/cord
White Pine — 14.3 Million BTU/cord
Basswood — 13.5 Million BTU/cord
Yellow Poplar — 12.7 Million BTU/cord
For maximum energy output, the wood must be well-cured. It is estimated that green firewood has 60 percent of the heat value of wood that is well-cured. To get the maximum BTU output of firewood, you should cut trees in the winter when the sap is down, split and stack the wood, and wait one year before burning it.
If you are lucky enough to own land you might be able to cut your own wood. Otherwise, you probably purchase your firewood. Firewood is always sold by the cord or in multiples of a cord since this is the only legal way to do so. A cord is 128 square feet of wood (4 x 4 x 8 feet). Besides advertising the amount in terms of a cord, a firewood vendor should also list whether the wood is cured or green.
If you need to burn the firewood immediately you should select cured firewood; if you can afford to let it cure for four to six months then green firewood is acceptable. The vendor should also list what type of firewood is for sale — oak, locust, or mixed firewood. You should ask the vendor how the material is delivered. Normally, the vendor will drop the wood at your residence. There will probably be an additional charge if you ask them to carry it onto a porch or deck, or stack the firewood.
How do you ascertain whether or not you got a good deal with your firewood? The first thing you can do is stack the wood and see how closely it resembles a “face” cord. You can also handle the wood before it is dumped to see if it is cured or still green. Green wood is heavier, has a dull sound when hit against another piece, has a cool or wet feel to it, and typically has distinctive colors or odors.
Cured wood on the other hand is lighter, drier to the touch, has a crisp sound when stuck (like a baseball bat) and usually is gray or dull in color with not much odor. You can also educate yourself in wood identification so you’ll know if you are getting the oak firewood you paid a premium for. If the wood does not look right you should not accept the delivery; just make sure you do so “before” the vendor unloads it. There are many good firewood vendors, so once you identify one you should continue to support them with your business.
Article by FCFCDB
Nature note for 11/20/21