Wood and Combustion Heat Values

Combustion heat values for Pine, Elm, Hickory and many more species

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The type of wood burned, whether hardwood or softwood, is important for the heat value and the energy efficiency.

Hardwoods have less resin and burn slower and longer. Softwoods burn quickly. In addition to the type of wood, the seasoned length of the wood influence on the fuel efficiency. Seasoning the wood refers to the allowed drying time before burning.

Moisture reduces the woods fuel value and wood need to be dried at least 4 to 6 months before used.

Wood Species	Density (lbs per cubic ft)	Weight Per Cord (lbs)	BTU's Per Cord (millions)	Recoverable BTU's per Cord (Millions)	Units needed to produce 1 Million BTU's
Apple	48.7	4,100	26.5	18.55	0.054
Aspen	27	2,290	14.7	10.29	0.097
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
Black Ash	35.2	2,992	19.1	13.37	0.075
Black Spruce	29.2	2,482	15.9	11.13	0.090
Box elder	32.9	2,797	17.9	12.53	0.080
Cherry	36.7	3,121	20	14	0.071
Cottonwood	24.8	2,108	13.5	9.45	0.106
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
Jack Pine	31.4	2,669	17.1	11.97	0.084
Norway Pine	31.4	2,669	17.1	11.97	0.084
Paper Birch	37.4	3,179	20.3	14.21	0.070
Ponderosa Pine	28	2,380	15.2	10.64	0.094
Red Oak	44.2	3,757	24	16.8	0.060
Red Maple	34.4	2,924	18.7	13.09	0.076
Sugar Maple	44.2	3,757	24	16.8	0.060
Tamarack	38.2	3,247	20.8	14.56	0.069
Yellow Birch	43.4	3,689	23.6	16.52	0.061
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

The Combustion Process of Burning Wood

At first wood heats up to approximately 212 ^oF evaporating the moisture in it. There is no heating from the wood at this point.
Then the wood solids starts to break down converting the fuel gases (near 575 ^oF).
From 575 ^oF to 1100 ^oF the main energy is released when the fuel vapors containing 40% to 60% of the heat burn.
After the fuel gases have burned off and the moisture is evaporated, only charcoal remains burning at temperatures higher than 1100^o F.

Wood and BioMass Heat Combustion value of wet and dry wood in btu/pounds, kJ/kg and kcal/kg
Unit Converter with the Most Used Units

T(^oC) = 5/9[T(^oF) - 32]
1 m (meter) = 3.2808 ft
1 lb = 0.4536 kg
1 kWh = 3.6x10⁶ J = 3.671x10⁵ kpm = 859.9 kcal = 2.656x10⁶ ft lbf = 3.412x10³ Btu

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