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Use the following calculator to help you determine the energy content, or calorific value, of your woody biomass fuel. For more details about the effects of moisture content on the calorific value of biomass see below. A more advanced calculator allows for the specification of the moisture/water content
Oven-dry woody biomass typically has a calorific value of 18-21 MJ per kg on a dry basis (this is the gross calorific value).
Most fuels are not oven dry when burnt and the water in the wood must be evaporated, detracting from the extractable energy* (or net calorific value). Moisture or water content is the single biggest factor in the variability in combustion behaviour of woody biomass (for more information follow this link). The following figure shows the dependence of net calorific value on moisture content (dry basis) and water content (wet basis)
The water content of green wood that has not undergone any pre-treatment is typically 60%, whereas a high-quality fuel like wood pellets has a moisture content of 10%.
*Note, however, that the use of a condensing boiler enables one to recover much of the heat in the water vapour escaping up the flue, and the calorific value of the biomass will approach the gross calorific value.
The theory behind this calculator is described here.
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Last modified: Mon Dec 17 10:34:18 New Zealand Daylight Time 2007