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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% or less moisture content.
The burning of wood results in about 6–10% ashes on average. [2] The residue ash of 0.43 and 1.82 percent of the original mass of burned wood (assuming dry basis, meaning that H 2 O is driven off) is produced for certain woods if it is pyrolized until all volatiles disappear and it is burned at 350 °C (662 °F) for 8 hours.
Wood drying (also seasoning lumber or wood seasoning) reduces the moisture content of wood before its use. When the drying is done in a kiln , the product is known as kiln-dried timber or lumber , whereas air drying is the more traditional method.
In the last decade concerns were raised that the chemicals may leach from the wood into surrounding soil, resulting in concentrations higher than naturally occurring background levels. A study cited in Forest Products Journal found 12–13% of the chromated copper arsenate leached from treated wood buried in compost during a 12-month period.
Today, burning of wood is the largest use of energy derived from a solid fuel biomass. Wood fuel can be used for cooking and heating, and occasionally for fueling steam engines and steam turbines that generate electricity. Wood may be used indoors in a furnace, stove, or fireplace, or outdoors in furnace, campfire, or bonfire.
Green wood is considered to have 100% moisture content relative to air-dried or seasoned wood, which is considered to be 20%. Energy density charts for wood fuels tend to use air dried wood as their reference, thus oven dried or 0% moisture content can reflect 103.4% energy content.
There are no binders involved in this process. The natural lignin in the wood binds the particles of wood together to form a solid. Burning a wood briquette is far more efficient than burning firewood. Moisture content of a briquette can be as low as 4%, whereas green firewood may be as high as 65%.
Pyrolysis liquids from slow pyrolysis of bark and hemp have been tested for their antifungal activity against wood decaying fungi, showing potential to substitute the current wood preservatives [99] while further tests are still required. However, their ecotoxicity is very variable and while some are less toxic than current wood preservatives ...