Things to consider when using wood as a fuel
One of the most common mistakes people make is to burn green, non-seasoned wood. Green wood can contain up to 75% moisture, a figure that has a considerable effect on the calorific value (heat output) of the wood, since part of the heat released is used to evaporate the water content and is then dispersed into the flue along with the water vapour produced. Wood for burning in a wood stove must first be seasoned for about 18-24 months, to reduce its moisture content to 15-20%.
All wood can be divided into two categories: “hard” or “soft”, according to its weight in kg per cubic meter of wood.
Softwood, weighing approx. 300–350 kg/m³, includes spruce, pine, poplar, alder, chestnut and willow. It burns more rapidly, producing greater heat: this makes it ideal for starting the fire, although if used as the main fuel, the stove will require more frequent refilling.
Hardwood, weighing approx. 350–400 kg/m³, includes elm, oak, beech and ash. It is generally denser and less resinous than softwoods; for this reason it burns more slowly, producing longer-lasting heat.
The best way to achieve a hot, lasting fire is to mix 20% softwood with 80%hardwood. And use properly seasoned wood. A simple guide is A1 A2 B. A class is suitable for fireplaces and stoves while B class is suitable for boilers and needs seasoning for another year to be used in fireplaces and stoves.The Wood Fuel Quality Assurance (WFQA) scheme for Ireland provides a simple but reliable way for consumers to purchase quality wood fuels that are accurately described and meet the supplier’s stated product specifications. Using a Wood Fuel Quality Assurance (WFQA) wood fuel will ensure that you are matching the correct grade of wood fuel to your wood burning appliance, ensuring optimal efficiency & heating. Using a Wood Fuel Quality Assurance( WFQA) certified supplier will ensure that you are sourcing a fuel of consistent quality from a sustainable origin. Look for the Wood Fuel Quality Assurance (WFQA) label 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.
By Lady Celia Congreve, © 1929, All rights reserved.
The firewood poem was written by Celia Congreve, is believed to be first published in THE TIMES newspaper on March 2nd 1930.
For a more indepth look at wood classification check out this article by Pieter D. Kofman on European standards for solid biofuels