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1.4.2 Preparing firewood
The firewood manufacturing processes vary greatly depending upon the final type of fuel to produce: wood pieces, briquettes or
pellets.
Wood pellets or briquettes are produced only in big sawmills that have large quantities of shavings and sawdust at disposal, which
become valuable products for an appealing market.
Individuals who are landowners can easily obtain the amount of wood that will be needed for their home heating.
Those who are not landowners can address dealers experienced in firewood combustion, who can advise about quality and wood
species locally available.
The most important steps in producing firewood are the following:
Cutting of trees or suckers (usually on waning moon or in winter).
Trimming of the smaller branches from the trunk (usually when they are less than 4 cm in diameter).
Cutting of trunks and branches into 1 m long logs.
Cutting of the bigger logs in half along their length (quartering).
Piling of the sawn logs in a dry, ventilated location favouring preliminary wood drying.
Covering the upper part of wood piles with clothes as shelf from the rain.
Cutting of the wood logs into small pieces whose length will vary to suit the user's needs. Final wood stacking in a dry,
ventilated location away from rain and humidity.
Air-drying for at least:
2 years (outdoor).
1 year (indoor, in an adequate place).
1.4.3 Purchasing firewood
The units of measurement commonly used in selling firewood are mainly three:
Cubic metre (cu.m): unit of measurement referring to any type of wood and corresponding to 1cu m of solid wood (the weight
of 1cu m of wood varies greatly depending upon species and humidity).
Stere (metre) (sm): unit of measurement referring to the stacked wood pieces and corresponding to 1 cu.m including the air
space between the pieces of stacked wood. The amount of wood contained in a space of 1 stere depends upon species,
relative moisture content, diametre and shape of the wood pieces, and the way in which they have been stacked (one stere of
wood logs 1 m long corresponds to approximately 0,7 cu.m of wood).
Quintal (q): officially suppressed, this unit of measurement (100 kg; 0,1 t) is still the most widely used in selling firewood.
"Deadwood" does not necessarily mean "dry wood": the dryness of wood is greatly determined by the time it takes
to dry but also by the place where wood is stored for seasoning. Should the wood be stacked for a long amount of
time without providing any protection or be kept in a humid, unsufficiently aerated place, it will rot and decay
easily under the action of mildew with consequential lost of its heating value.
Knowing the type of firewood and its moisture content, if it is sold on a space basis, allows you to get an idea of its heating
value, whereas it is not necessary to know the species of wood if it is sold on a weight basis as with an equal moisture
content the heat value differs slightly.
The heating value of wood varies greatly depending upon its moisture content, thus when you buy wood as a source of
energy it would be better knowing its moisture content.
If we compare as a way of example a piece of beech having a moisture content of 30% with a well seasoned piece of the
same wood type having a moisture content of 15%, the latter will release 25% more heat. When the moisture content is
50% the heat value is reduced by the half.
Purchase of green, damp or wet wood, could mean that you are also buying the water inside. To be sure the firewood you
have purchased has been seasoned for about one year, you should always buy your firewood in the summertime (June-
July) since trees are mostly cut in autumn.
Be careful with any painted or treated wood whose combustion can give off harmful fumes, and whose use is only allowed
in authorized combustion plants.
ENGLISH
TECH 3
12
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