Wood Density and Heat of Combustion Values

With the cost of heating oil, gas, and electricity increasing, a lot more people are installing indoor wood stoves and outdoor wood burners to help offset the utility bills.

Unfortunately for a many of those who live within city limits, restrictions are being placed on what kinds of fireplaces - if any - are allowed. Some ordinances ban all forms of wood heating while others allow only compressed wood pellets.

Benjamin Franklin famously said, "He who cuts his own wood warms himself twice." Anyone who has done gone into the forest to cut down a big maple or oak tree, cut it into fireplace size logs to pile into a truck bed, then take it home and split and stack it knows what he means. I did so often as a teenager. In the last few years I have cut down a lot of trees, but it has been to clear land of clutter; sometimes I even managed to sell the logs.

Here is a table of wood properties that includes BTU values. Pretty much the exact same table is reproduced all over the Web, so here it is again here. The information has not been verified against a reputable source, so be forewarned. Presenting a single value (especially to 3 significant figures), as opposed to a range of values, is unrealistic since wood typically varies widely in density based on water/sap content, growing conditions, and processing. Therefore, numbers should be regarded as an average value.

In the following table, 1 cord = 85 ft3 (the standard cord is defined as a densely stacked 4' x 4' x 8' = 128  pile ft3, so 85 ft3 assumes 65% wood and 35% air space) is used to convert between the "Density" and "Weight of Cord" column. Be aware that the densities used for the wood species varies significantly. The densities used above is for natural dried wood where the average moisture content is approximately 20%.

Heat values of Cords with dry wood can be estimated by adding the green wood cords values with approximately 10%.

 WoodSpecies Density of Dry Wood (lb/ft3) Weight of Dry Cord (lb/cord) Heat Value of Cord (Green Wood)(MBtu/cord) Recoverable Heat Value of Cord (Dry Wood)(MBtu/cord) Units Needed to Produce1 Million (cord/Btu's) Apple 48.7 4,100 26.5 18.55 0.054 Ash 22.3 Aspen 27 2,290 14.7 10.29 0.097 Balsa 4 - 12 Balsam Fir 26.3 2,236 14.3 10.01 0.10 Basswood 24.8 2,108 13.5 9.45 0.106 Beech 44.2 3,757 24 16.8 0.060 Birch 21.7 Black Ash 35.2 2,992 19.1 13.37 0.075 Black Spruce 29.2 2,482 15.9 11.13 0.090 Boxelder 32.9 2,797 17.9 12.53 0.080 Buckeye 13.4 Butternut 15.4 Catalpa 16.4 Cherry 36.7 3,121 20 14 0.071 Chestnut 12.9 Coffeetree 21.6 Cottonwood 24.8 2,108 13.5 9.45 0.106 Dogwood 27.0 Douglas Fir 26.4 East Hop hornbeam 50.2 4,267 27.3 19.11 0.052 Elm 35.9 3,052 19.5 13.65 0.073 Hackberry 38.2 3,247 20.8 14.56 0.069 Hemlock 29.2 2,482 15.9 11.13 0.090 Hickory 50.9 4,327 27.7 19.39 0.052 Ironwood 26.0 Jack Pine 31.4 2,669 17.1 11.97 0.084 Larch - Eastern 18.7 Locust 27.3 Lodgepole pine 19.3 Maple 21.6 Mulberry 25.8 Norway Pine 31.4 2,669 17.1 11.97 0.084 Osage Orange 32.9 Paper Birch 37.4 3,179 20.3 14.21 0.070 Pinon Pine 33.5 Ponderosa Pine 28 2,380 15.2 10.64 0.094 Redcedar - east 19.8 Red Oak 44.2 3,757 24 16.8 0.060 Red Maple 34.4 2,924 18.7 13.09 0.076 Spruce 16.0 Sucamore 19.5 Sugar Maple 44.2 3,757 24 16.8 0.060 Tamarack 38.2 3,247 20.8 14.56 0.069 Tanarack pine 21.2 Yellow Birch 43.4 3,689 23.6 16.52 0.061 Yellow pine 22.0 Walnut - black 21.5 White Ash 43.4 3,689 23.6 16.52 0.061 White Oak 47.2 4,012 25.7 17.99 0.056 White Pine 26.3 2,236 14.3 10.01 0.100 Willow 13.2

1 ft (foot) = 0.3048 m
1 lb = 0.4536 kg
1 Btu (British thermal unit) = 1,055.06 J = 2.931x10-4 kWh = 1.055x1010 ergs = 252 cal = 0.293 watt hour

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