| | Planning on using wood as a heat source this winter? Toso Bozic, bioenergy and agroforestry specialist with Alberta Agriculture and Forestry explains what to keep in mind.
“First off, the wood must be dry. You don’t want to use green wood,” says Bozic. “If your wood is already dry, you still need to keep it free of moisture. Green wood requires at least one summer to dry, and the time needed to do so depends on species, weather, and whether the wood has been split. For optimal firewood, the moisture content needs to be around 15 to 20 per cent.”
“With some experience, it is relatively easy to tell if the wood is dry,” explains Bozic. “Green wood weighs more than dry. If cracks appear in the end of the wood, it is probably dry. If you hit two pieces of wood together, dry wood makes a different sound than green. Lastly, dry wood is darker than green wood.”
Bozic offers a few tips for drying. “Keep the wood at least 8 to 10 inches above the ground. The drying site must have good air flow and low humidity, and don’t stack the wood against the wall or anything that could block the airflow. If you don’t have a firewood shed, you need to protect your firewood with a plastic, metal, or wood cover. Another option is to use a small kiln or dry unit.”
As for choosing a tree species for firewood, Bozic says that all species have about the same energy content per pound. “The main variation between different species is the tree density, which means they have different calorific values, or amounts of heat, per volume of wood. A cubic foot of air-dried white birch weighs about 16 kg, while the same volume of white spruce weighs about 11 kg. Therefore, you will need a larger volume of spruce to get the same weight and, the same heating value as birch.”
Low density wood has a larger volume - creating transport, storage, and handling issues. “Coniferous species – larch, pine, and spruce - contain a higher amount of resins than hardwood species – birch, maple, poplar, willow, etc. These resins can create a problem with creosote buildup.”
To avoid creosote buildup, wood needs enough oxygen to get hot enough to vaporize and burn completely. Explains Bozic, “Instead, the vapor condenses and creates the creosote. Creosote is not a problem with wood or wood moisture, but it is an issue with the burning appliance, such as a stove, operating without enough oxygen to burn the wood completely. Creosote is highly flammable and can create fire hazards in your house, so regular maintenance is necessary.”
Bozic adds that it is vital to avoid bringing firewood from outside Alberta into the province to prevent the spread of insects and disease.
Contact:
Toso Bozic
780-415-2681 |
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