Heating Value of Firewood
The moisture content of firewood determines how it burns and how much heat is released. Unseasoned (green) wood moisture content varies by the species; green wood may weigh 70 to 100 percent more than seasoned wood due to water content. Typically, seasoned (dry) wood has 20% to 25% moisture content. Use of the lower heating value is advised as a reasonable standard way of reporting this data.
The energy content of a measure of wood depends on the tree species. For example, it can range from 15.5 to 32 million British thermal units (16.4 to 34 GJ) per cord. The higher the moisture content, the more energy that must be used to evaporate (boil) the water in the wood before it will burn. Dry wood delivers more energy for heating than green wood of the same species.
Here are some examples of energy content of several species of wood:
| Wood Species | Heat Value per Cord |
|---|---|
| Tamarack | 22.3 MMBtu (23.5 GJ) |
| Birch | 21.3 MMBtu (22.5 GJ) |
| Red Fir | 20.6 MMBtu (21.7 GJ) |
| White Fir | 16.7 MMBtu (17.6 GJ) |
The Sustainable Energy Development Office (SEDO), part of the Government of Western Australia states that the energy content of wood is 4.5 kWh/kg or 16.2 gigajoules/tonne (GJ/t).
Read more about this topic: Firewood
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—Julia Child (b. 1912)