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Firewood and heat values to keep winter cozy

Ned Birkey

EAST LANSING, MI. — December is the first of three months of climatological winter.  People who use firewood enjoy the heat, light and crackling sound produced by this renewable resource.  

The denser and drier the firewood, the better it will burn and the more heat it can produce.  Because of its density and comparatively low levels of sap or pitch, hardwoods generally make for better firewood than softwoods.

Homeowners should not burn green wood (freshly cut) that hasn’t had a chance to dry out or “season” as this will create a lot of steam and smoke.  For an inside fireplace, don’t burn driftwood, which can be wet or construction wood, which may be treated with chemicals, contains nails, screws, glue or finishes.

One cord of wood with a high heat value, as measured in BTu (British Thermal units), will replace about 200 to 250 gallons of fuel oil.  These wood species include (listed alphabetically); American beech, apple, ironwood, mesquite, red oak, shagbark hickory, sugar maple, white ash, white oak and yellow birch.

One cord of wood with a medium heat value will replace about 150 to 200 gallons of fuel oil.  These wood species include; American elm, black cherry, Douglas fir, red maple, silver maple, tamarack and white birch.  

One cord of wood with a low heat value will replace about 100 to 150 gallons of fuel oil.  These wood species include: aspen, cottonwood, hemlock, lodgepole pine, red alder, redwood, sitka spruce, western red cedar and white pine.  

The cord is a standard measure of volume used for stacked wood.  The volume of one cord of wood is 128 cubic feet of stacked wood.  Generally, a cord is laid out in stacks that measure four feet tall, four feet wide and eight feet long.  Due to air space between the stacked wood, the volume of solid wood in a cord may be only 0 to 90 cubic feet.  A “face cord” in generally four feet tall, two feet wide and eight feet long.  A “rick” is generally four feet tall, eighteen inches wide and eight feet long.  Some wood is simply sold “as is” to the stack.  

Freshly cut wood contains up to fifty percent moisture and must be seasoned (dried) to 20 to 25 percent moisture before burning.  Wood of higher moisture is wet, or green, and should never be burned in a fireplace or wood stove.  If steam bubbles and hisses out of the end grain as the firewood heats up, the wood is wet.  

Splitting wet wood is easier than dry wood.  Wood must be split into pieces and stacked out of the rain for at least six months to season properly.  It can be covered or leave the top pieces with the bark side up to repel the rain.

Buying firewood from local sources is recommended due to invasive species such as gypsy moth or Emerald ash borer.   Wood should never be stacked inside the house or garage as termites or carpenter ants can hide in the wood and invade the house.  Pine should seldom be used as firewood as it is a resinous softwood.

Wood ash is a readily available source of potassium, calcium and magnesium, which are three of the 17 nutrients needed by plants.  It is also one way to quickly increase the soil pH as wood ash is water soluble and changes the soil pH rapidly.  Apply roughly twice as much ash by weight as a soil test lime recommendation.  A cord of wood will leave about 20 pounds of ashes, or about one five-gallon pail to apply per 1,000 square feet of garden, flower bed or other ornamental outdoor space annually without raising the pH unduly.  Do not add ashes to acid loving plants such as blueberries, rhododendrons, azaleas or holly.