Quick Answer
Hardwood firewood generally produces more heat output and burns longer than softwood due to its higher density and moisture content.
Moisture Content and Burning Efficiency
Hardwood typically has a lower moisture content than softwood, which affects its burning efficiency. For example, dry hardwood can have a moisture content of 20% or less, whereas softwood often contains 30% or more moisture. When wood burns, the moisture content affects its heat output and duration of burn. Hardwood’s lower moisture content allows for a more complete combustion process, releasing more heat.
Calorific Value and Heat Output
The calorific value of a fuel is a measure of its energy content per unit of weight. Hardwood generally has a higher calorific value than softwood, which translates to more heat output per unit of weight. For instance, dry oak (hardwood) has a calorific value of around 20.3 megajoules per kilogram (MJ/kg), while dry pine (softwood) has a calorific value of around 18.3 MJ/kg. This difference in calorific value results in hardwood producing more heat when burned.
Practical Considerations for Burning Hardwood
When burning hardwood, it’s essential to ensure the wood is properly seasoned to achieve optimal heat output. Seasoning involves allowing the wood to dry for at least six months to a year, reducing its moisture content and increasing its burning efficiency. Additionally, hardwood often requires a longer time to reach its optimal burn temperature, but the extra patience results in a more efficient and longer-lasting burn.
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