Fall 2012

Every good intention I had to get my firewood in early this year met an equally good excuse. First it was too cold then too hot, too wet then too dry, too many bugs, gas prices too high, too many huckleberries to pick, and then the fly fishing was way too good, and now it’s almost too late.

If you ignored all of those “good” excuses and have your firewood split and stacked, no need to read any further. Otherwise, keep reading.

Foresters often hear the question, “Which is the best species of wood to burn?” In our region, consisting of mixed conifer and deciduous forests, two species —western larch (tamarack) and western paper birch—are most often mentioned. Why is that?

Very simply, a pound of dry wood, regardless of species, produces a certain amount of BTUs (British Thermal Units) when burned.

We typically measure firewood in a unit called a cord, which consists of 128 cubic feet. For example, if you cut your firewood in two-foot lengths, then you will need to stack it eight feet high and eight feet wide to equal a cord (2’ x 8’ x 8’ = 128 cubic feet).

Further, the weight of a cord of seasoned firewood varies according to species. It should be no surprise that a cord of birch weighs more than a cord of aspen. Similarly, larch weighs more than grand fir (white fir). Therefore, the heavier the cord of wood, the more BTUs it will produce when burned.

A number of years ago, now-retired University of Idaho Extension Forester Don White developed a table comparing the fuel wood characteristics of our native tree species. A simplified version of that table illustrates several species commonly used in our area.

After looking over the table, you can readily see why larch and birch top the list for desirable species. That’s what I’ll be looking for as I head to the woods this fall to gather a few cords of firewood.

— Bill Love

Firewood Heat Values

(Based upon wood air-dried to a 20% moisture content)

Species BTU per Cord Pounds per Cord
Larch 26,825,000 3,300
Birch 24,490,000 3,040
Douglas-fir 23,925,000 2,970
Hemlock 21,750,000 2,700
Lodgepole pine 21,025,000 2,610
White pine 18,125,000 2,250
Ponderosa pine 18,045,000 2,240
Grand fir 17,400,000 2,160
Cottonwood 17,400,000 2,160
Aspen 17,400,000 2,160
Cedar 16,595,000 2,060