COUNTY AG NEWS

Wood fuel for heating

Wood is a plentiful and accessible fuel for many in the Central and Northern parts of Wisconsin. It is relatively clean and comes from a renewable resource – the forest or wood lot. Wood, however, does have disadvantages for industrial or home heating. 

Wood takes up more storage space, and must be dry for best performance and should be cut and split a year ahead of use. There is a chimney-fire hazard because low pipe or flue temperatures cause tars and creosote to condense. The increased price of oil based fuels has raised the level of interest in renewable fuels which include wood. 

New efficient heating and fuel preparation systems also increase the popularity of wood as fuel. When wood burns, three things happen: water is removed by evaporation; chemically, the wood breaks down into charcoal, gas and volatile liquids, with carbon dioxide and water being the chief end products; the charcoal burns, forming carbon dioxide either directly or with an intermediate conversion to carbon monoxide.

 One pound of very dry (zero moisture content) wood of any species has a calorific value of approximately 8,600 BTU (British Thermal Unit, which equals the amount of heat required to raise the temperature of one pound of water one degree F). Any moisture in the wood reduces the recoverable heat by carrying heat up the chimney during vaporization.

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