Print Posted By Lost in France on 23 May 2006 in Living in France - Living in France

Trees For Firewood

log pileMany of my clients in Brittany are keen to obtain cheap firewood, and hope that the trees I cut down for them will provide fuel for their fires and stoves.
There are many myths and legends about which woods are best for fires. For example, oak is widely considered to be excellent firewood. It is good, but there are several trees much better than oak. The list of timbers below shows the priority of woods as fuels. This was shamelessly lifted from 'Caring for Small Woods', and refers to open fires. I don't entirely agree with it, but it's close enough. Note that conifers are at the bottom. I have added robinia, which is fairly common in France but rare in the UK.
The reason sweet chestnut is commonly burnt in France is that it coppices well and grows quickly, and can be used for a range of things other than firewood.
What very few people seem to consider is how efficient their fire is. Starting from the most basic, the bonfire
Bonfires, once they are going, can burn just about everything. Clouds of smoke, (which is largely unburnt material) rapidly become someone else's problem. Nor does it matter if not everything is burnt, because it can be burnt later. Airflow is not a problem, though a stiff breeze will make the fire burn faster. However, most of the heat from a bonfire goes up.
A campfire is much more efficient. Small sections of dry branches are used to provide enough heat for cooking and warming people. As any boy-scout knows, dry firewood does not produce smoke because it all burns. Using a reflector, such as a wall of logs, behind the fire, will reflect the heat towards the people in front of the fire.

Bringing the fire inside will help to warm the house. A fireplace (with a chimney) uses fuel more efficiently than a bonfire, because more of the heat is retained by the stone in the fireplace or reflected into the house. However, a lot of heat still goes up the chimney.

{loadposition contentad}A back-boiler will trap more of this heat. Enclosing the fire further by use of a stove will further increase the efficiency of burning, in part because you can control the airflow and hence the speed of burning. This means that you will get more warmth from both good and bad firewoods. The use of air injection, automated fuel delivery and ceramic bricks will increase the efficiency of burning, though these innovations are not common in Brittany.
You can tell how well a fire has been burning by the amount of ash generated. A good wood fire will produce a tiny amount of ash (which is rich in nutrients, so put it on the garden.)
Woods. Any wood will burn, from quipo, a tropical timber with a density around 85kg per cubic metre, to ironwoods with a density of over 1000kg per cubic metre. As a rule, the denser and drier the wood, the better it will burn. Some timbers will spit, so are not good for open fires. Some smell very nice, notably apple.
Storage. For speed of drying, wood should be cut to size and stored under shelter, so it doesn't get rained on, and somewhere airy. Ideally the wood should be raised from the ground. Ash and holly can be burnt green, i.e. as soon as felled. Most others need to 'season' for at least one full Breton summer. Cherry, apple and pear all take slightly longer to dry, as does sweet chestnut. Leaving the wood longer is good for most timbers, which will dry further.
Most conifers are lousy firewoods. Cypresses and false cypresses (common hedge plants) tend to have a density of less than 400kg per cubic metre. If burnt wet they smoke, and deposit tarry material in the chimney. When allowed to dry for some time they burn very hot, very rapidly, like paper. Mixed in with other woods they are better, but should (in my opinion) only be used as firewood to get rid of them. They will burn tolerably in stoves.
Willow and poplar are grown for biomass, or Short Rotation Coppice, for fuel, simply because they grow extremely quickly. Any deficiency they may have as a fuel is more than compensated by the sheer mass of wood they generate. Sitka spruce, the mainstay of UK forestry, can produce around 20 cubic metres of timber every hectare every year. Poplars can produce 26, and can be coppiced. This is becoming a popular use of land in Brittany and many new areas of coppice are now springing up.

List of trees in order of priority as firewood.
  • Ash
  • Field Maple
  • Beech
  • Birch
  • Elm
  • Hawthorn
  • Hornbeam
  • Robinia
  • Hazel
  • Oak
  • Sycamore
  • Apple
  • Alder
  • Wild Cherry
  • Holly
  • Horse Chestnut
  • Sweet Chestnut
  • Lime
  • Willow
  • Poplar
  • Elder
  • Conifers

© Dave Robins
RFS Cert. Arboriculture, BSc. Forest Science

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