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Wood Fuel

Types of Fuel

There are few sources of energy as versatile as wood. It can be burned in a number of different forms and in different types of appliances. It can be used to heat an entire house, just one room, for cooking, or even to provide domestic hot water.
 For domestic small-scale applications, three different types of wood fuel are generally used: logs, pellets and woodchip. All three types are generally sold by volume rather than weight, as high moisture content would increase the weight but decrease thermal performance considerably. Most wood fuels are now labelled providing information on the calorific value of the wood, the moisture content and the sustainable sourcing.


Wood Logs are one of the simplest, cheapest and quickest methods of producing fuel ready for use by the consumer. Important factors affecting the amount of heat produced when burning are the time of year when the wood is felled and the length of time given to seasoning of logs. Wood felled in the winter months contain significantly less moisture than during the growing seasons of spring and summer, reducing the time needed for seasoning.
 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.


Well Seasoned Logs


Wood pellets are a type of wood fuel, generally made from compacted sawdust. They are usually produced as a by-product of saw milling and other wood transformation activities. The pellets are extremely dense and can be produced with a low humidity content (below 10%) that allows them to be burned with very high combustion efficiency. Further, their regular geometry and small size allow automatic feeding with very fine calibration. They can be fed to a burner by auger feeding or by pneumatic conveying.
 Wood Pellets high density permits compact storage and rational transport over long distance. They come in bags or can be conveniently blown from a tanker to a storage bunker or silo on a customer's premises.


Wood Pellets


Short rotation coppice, recycled wood waste, park waste, and tree thinnings are all potentially good sources of woodchip fuel. Unlike the smooth, uniform shape of manufactured wood pellets, woodchip sizes vary. The use of woodchips in automated heating systems is based on a robust technology and tends not to be used in household boilers due to the high costs associated with the feed mechanism and the superior burn chamber quality of the boiler.
 The advantage of woodchips is the low cost, however due to their bulk they must be delivered within a small radius to retain good economics. Woodchip also has a limited storage life as it tends to degrade due to mould growth if not used within a certain period.


Sample of Woodchip

The Firewood Poem  

  Beechwood fires are bright and clear
If the logs are kept a year,
Chestnut's only good they say,
if for logs 'tis laid away.
Make a fire of Elder tree,
Death within your house will be;
But ash new or ash old,
Is fit for a queen with crown of gold

Birch and fir logs burn too fast
Blaze up bright and do not last,
it is by the Irish said
Hawthorn bakes the sweetest bread.
Elm wood burns like churchyard mould,
E'en the very flames are cold
But ash green or ash brown
Is fit for a queen with golden crown

Poplar gives a bitter smoke,
Fills your eyes and makes you choke,
Apple wood will scent your room
Pear wood smells like flowers in bloom
Oaken logs, if dry and old
keep away the winter's cold
But ash wet or ash dry
a king shall warm his slippers by.

The firewood poem was written by Celia Congreve,
 is believed to be first published in
THE  TIMES  newspaper on March 2nd 1930.


The diagram illustrates how the pellets are transformed during combustion Once the complete decomposition cycle has taken place, wood releases a certain quantity of carbon dioxide into the atmosphere which is absorbed by plants during photosynthesis to be then turned back into oxygen.
Thanks to the combined action of the sun's energy, carbon dioxide,water and the dissolved mineral salts, the pellets are constantly renewed.

Great news for Irish Firewood Consumers – Buy Quality Firewood with Confidence:

The Irish Wood Fuel Quality Assurance (WFQA) scheme was officially launched at the Irish Bioenergy Association (IrBEA) / Teagasc National Bioenergy Conference on 18th February 2010 and applications for participation in the scheme are now being accepted.

Wood Fuel Quality Assurance   Read Wood Fuel Quality Assurance Press Release