Quality and standards
Boilers and stoves require high quality logs. Key
characteristics are:
- Moisture content
- Species type
- Size of log
- Contamination (e.g. soil)
- Bark content
Quality criteria are set out in European
standards (CEN 355). Within these standards are properties for
logs.
Drying
Logs should be dried for one to two years before they are ready
to be used as fuel. The exact drying period required depends upon
when then tree was cut. If a tree is felled in spring or
summer it will have a much higher moisture content than if it is
felled in autumn or winter and will require a longer drying period.
Drying periods will also be determined by local climatic
conditions.
Small roundwood should be dried in stacks, raised up from the
ground, in a sunny place, exposed to the prevailing wind.
The stacks should be covered from rain, using either a roof or
waterproof/semi-permeable sheeting. The ends of logs should be
uncovered since this is where most moisture loss takes place. Air
should be allowed to flow through the stack.
To aid drying, bark can be scored, or partially or fully
removed. If they are over 15 cm in diameter, logs should be split
to accelerate drying.
Splitting
The majority of log splitters are simple hydraulic
devices, powered either through the electric mains or a
small petrol engine. The hydraulic device pushes the log against a
sharp axe like blade which cuts the log in two.
Log splitters are often rated by the tons of pressure they can
generate, the higher the pressure rating, the greater the thickness
or length of the rounds that can be split. Most log splitter models
for home use have a rating around 10 tons; professional hydraulic
models may exert 25 tons of pressure or more.
Other types are:
- Manual log splitters which use levers to force
logs through a sharpened blade assembly
- Screw or 'corkscrew' log splitters, driven
directly from an agricultural tractor's power take-off shaft where
the splitter is mounted on the three point linkage.
Firewood processors
Firewood processors consist of a log cutter (typically a
long-blade chainsaw welded in place to the frame) and a log
splitter.
In a standard firewood processor, logs are fed into the
processor by a feed-in system or log deck. The log is then sawed to
a preset length, and a hydraulic ram pushes the sawn portion
against a steel plate with a sharpened edge, which splits the log
in half. An operator rotates the split half and resets it for
another pass against the splitter, which yields log quarters
suitable for firewood. A hydraulic lift is useful in lifting logs
onto the log deck for processing, although a large tractor can also
perform this function
Firewood processors are essential tools for cutting and
splitting large volumes of firewood efficiently for the commercial
market but can be costly, so it is worthwhile looking into
purchasing second hand machinery from a dealer.