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Firewood
Firewood is the oldest fuel of mankind and has been used for heat production for about 400,000 years. Decisive for the usefulness of firewood are the heat value, the combustion time and the environmental-friendliness. As to firewood suitable for open fireplaces we also have visual value, such as the appearance of the single pieces of wood, fire behaviour or
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flame pattern. The energetic use of wood is aimed at a high heat value. Decisive for it are
water content, raw density and resin content of the wood.
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Freshly chopped wood contains up to 50% water and, therefore, shows a very low heat value. Moreover, burning wood that is too moist leads to a soothing of the chimney or oven during combustion. Only with remaining moisture contents of approx. 15 - 20% (air-dry) the wood can be used effectively as firewood. In order to attain this degree of dryness, the wood should be dried at an airy but sheltered place for about 2 years.
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The density varies depending on the type of wood. Hardwood has got a higher density and with it a higher heat value per unit of volume. Softwood on the contrary has got more resin and with it a higher heat value per weight unit. Due to the high resin content there can be a higher formation of smoke and flying sparks. |
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Measures: Wood is traditionally traded in volume sizes although weight units, such as kilogram or ton, are gaining in importance with the increasing significance of compressed wood (briquettes, pellets). |
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1 stacked cubic metre (RM): one stacked cubic metre or stere corresponds to 1 m³ of stacked wood with clearances
1 bulk cubic metre (SRM): one bulk (or loose) cubic metre corresponds to 1 m³ of loosely dumped pieces of wood
1 solid cubic metre (FM): one solid cubic metre (or bank metre) corresponds to 1 m³ of pure wooden compound without clearances |
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