Page 329 - Synthetic Fuels Handbook

FUELS FROM WOOD 315

When used as a solid fuel, some fuel wood (firewood) is harvested in woodlots man-
aged for that purpose, but in heavily wooded areas it is more usually harvested as a by-
product of natural forests. Deadfall that has not started to rot is preferred, since it is already
partly seasoned. Standing dead timber is considered better still, as it is both seasoned, and
has less rot. Harvesting this form of timber reduces the speed and intensity of bushfires.
Harvesting timber for firewood is normally carried out by hand with chainsaws. Thus, lon-
ger pieces—requiring less manual labor, and less chainsaw fuel—are less expensive (but
the user must ensure that the lengths will fit in the firebox!) Prices also vary considerably
with the distance from wood lots, and quality of the wood.
Firewood usually relates to timber or trees unsuitable for building or construction.
Firewood is a renewable resource provided the consumption rate is controlled to sustain-
able levels. The shortage of suitable firewood in some places has seen local populations
damaging huge tracts of bush thus leading to further desertification.
As with any fire, burning wood fuel creates numerous by-products, some of which may
be useful (heat and steam), and others that are undesirable, irritating, or dangerous. Thus,
before wood is used there are several processes that are necessary for application:
1. Wood selection: Firewood can be sold by weight. Freshly cut (green) wood can contain
from 40 to 60 percent moisture by weight, whereas properly seasoned wood contains
only 15 to 20 percent. Select the driest wood when buying by weight. Green wood will
shrink approximately 8 percent in volume (i.e., approximately a cubit feet per cord)
when properly seasoned.
2. Preparation and drying: Wood should be dried as much as possible before burning.
Properly seasoned wood has about 7700 Btu maximum usable energy per pound versus
only about 5000 Btu available from green wood. For best results, season or air-dry wood
for at least 6 to 8 months after cutting. This should bring the moisture content down to
15 to 20 percent by weight. The best time to cut wood is during the winter or early spring
before the sap runs. If the tree is felled when fully leafed out, let it lie until leaves have
become crisp to allow leaves to draw out as much moisture as possible from tree before
further cutting. Drying time is greatly reduced if wood is cut into firewood length and split,
especially pieces larger than 8 in in diameter. Splitting is easiest when wood is frozen or
green and should be done before wood is stacked. Wood must be properly stacked for
satisfactory drying. The greater the surface area exposed to air, the more rapid the drying.
Therefore, stack wood loosely and keep it off moist ground. The stack should be located
in an open area for good air circulation—avoid stacking in wood lots for seasoning.
3. Storage of wood: Store firewood outdoors, under partial or full protection from the ele-
ments, and no closer than 25 ft from the house. Keep area around wood clear of weeds,
leaves, debris, and the likes, to discourage rodents, snakes, insects, and other unwanted
pests from making their home in the stacked wood. Avoid storing large quantities in the
house, warm garage, or basement because the heat will activate insect and fungi or spore
activity and bring about hatching of any insect eggs in or on the wood.
4. Building a fire: Before lighting a fire, make sure the thermostat is turned down so air
heated by the central furnace will not go up the chimney. The easiest and best fire for
either a stove or fireplace is achieved with a mixture of softwoods for easy igniting with
hardwoods for longer burning and good coaling qualities. A cardinal rule of fireplace
management is to keep a thick bed for glowing coals that drop through. The coals yield
a steady heat and aid in igniting fresh fuel as it is added. Keep the fire burning by adding
small amounts of wood at regular intervals. A small, hot fire is much better than a large,
roaring blaze because it burns more completely and produces less creosote.
5. Precautions: Coal should never be burned in a stove or heater designed for wood.
Artificial or manufactured logs, which are composites of sawdust, chips, colorful