Using Firewood

 
  From the November 6, 2017 Issue of Agri-News
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 If you are planning on using wood as a heat source this winter, there are a few things to keep in mind.

“First off, the wood must be dry as you don’t want to use green wood,” says Toso Bozic, bioenergy/agroforestry specialist, Alberta Agriculture and Forestry. “If your wood is already dry, you still need to keep it moisture free. Green wood requires at least one summer to get dry, and the exact time needed depends on species, weather, or whether the wood is split or not. The moisture content has to be around 15-20 per cent for optimal firewood.”

Bozic says to make sure the wood is dry before use. “With some experience, it’s relatively easy to tell if the wood is dry. For example, dry wood weighs less than green. If cracks appear in the end of the wood, it’s probably dry. If you just bang two pieces together of wood together, you hear a different sound from dry wood than from moist wood. Lastly, dry wood is darker than green wood.”

Bozic has a few tips for drying. “Keep the wood at least 8-10 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 will block the airflow. If you don’t have a firewood shed, you must cover your firewood with a plastic, metal or wood cover. Another option is a small kiln-dry unit for firewood. Basically, any contact between the wood a moisture will create problems down the road.”

When it comes to choosing a tree species for firewood, Bozic says the key to remember is that all wood 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 (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, subsequently, the same heating value as birch.”

Low density wood has a larger volume, creating transport, storage and handling issues. “The difference between coniferous species (larch, pine and spruce) and hardwood species (birch, maple, poplar, willow, etc.) is that coniferous species contain high amount of resins that can create a problem with creosote buildup.”

To avoid creosote buildup it’s important to provide enough oxygen for the wood to get hot enough to vaporizes and burn completely. “If the fire is not hot enough, the wood will not burn completely and, instead, the vapours will condense and create the creosote. Creosote is not a problem with wood or wood moisture, but rather is an issue with the burning appliance (stove) operating without enough oxygen to burn the wood completely. Creosote is highly flammable and can create great fire hazard in your house, so regular maintenance is necessary.”

Bozic adds that it is vital to not bring any firewood into Alberta from other provinces due to insect and disease problems.

Contact:
Toso Bozic
780-415-2681

 
 
 
 
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For more information about the content of this document, contact Toso Bozic.
This document is maintained by Ken Blackley.
This information published to the web on October 18, 2017.