Firewood

Firewood 

sawn and usually split trees intended for use as fuel. In the USSR it is customary to measure firewood by volume, for which purpose it is stacked in piles, the value (wood content) of which depends on the way it is stacked: the stacking is considered normal if the firewood totals 70 percent of the volume. The mass of 1 cubic meter (with wood occupying 100 percent of the volume) with a relative moisture content of 20 percent weighs approximately 730 kg for oak, 670 kg for birch, 525 kg for pine, 470 kg for fir, and 500 kg for aspen. The wood of all species of trees in the USSR has a similar chemical composition and contains about 50 percent carbon. Hence the heat of combustion of wood of various species in absolutely dry condition in terms of 1 kilogram is the same: about 18,800 kilojoules (4,500 kcal), with a variation of not more than 3 to 5 percent. However, the heat of combustion of wood per cubic decimeter is different and is on the average, in kilojoules (kcals), 12,500 (3,000) for oak, 10,900 (2,600) for birch, 8,400 (2,000) for black alder, 7,500 (1,800) for pine, and 7,100 (1,700) for fir and aspen. In terms of heat of combustion 100 kg of dry wood corresponds to 31 kg of oil residues, 43 kg of coal, 50 kg of dry peat, and 120 kg of semidry peat. The proportion of wood in the fuel balance of the USSR is negligible and steadily diminishing.