Ever since people have needed to heat their homes, wood has been used as a source of fuel and until it was replaced by coal, oil and gas, wood was the main fuel used in the UK. In fact, most of the woodlands in the UK have been managed for hundreds of years with woodfuel being a key product that is derived from woodland operations. Today, the term Woodfuel can apply to wood that is used to generate either heat or electricity but in these webpages, we are referring to the use for woodfuel to generate heat.
Woodfuel can come in three forms: logs, chips or pellets. Logs are used by most people with domestic open fires or wood stoves, whereas woodchips and pellets are destined for specialised woodfuel boilers which usually heat larger buildings. Wood stoves and wood burning boilers have become increasing popular in the UK in recent years partly as a response to rising energy prices as well as a lifestyle choice.
Woodfuel – a Renewable Resource
The use of fossil fuels – oil, coal and natural gas – is ultimately unsustainable because these cannot be replaced in human life-spans. They also can cause environmental damage because they release carbon dioxide (CO2) as they are used up, which can add to global warming.
Wood is a renewable resource because trees can grow back from cut stumps through coppicing or the trees can be replanted. Trees also take in CO2 as they grow and use the carbon in new tree growth, whilst releasing oxygen to the atmosphere. When wood is burned, the stored carbon is released back to the atmosphere, some of which will be absorbed by trees and other vegetation. By using wood, the net CO2 production is reduced as well as reducing the reliance on fossil fuels at the same time.
Woodfuel – Good for the Woodland
As well as providing useful woodfuel, managing a woodland for woodfuel can be very beneficial to the health of the woodland. By removing some trees for woodfuel, more light is allowed into the woodland and this increase in light levels helps younger trees to grow faster and provide the next generation of mature trees. Woodland biodiversity will also thrive in lighter conditions - ground flora, shrubs, insects like butterflies and birds like nightingales will all do well in sunnier glades but will struggle to flourish in darker, unmanaged woodlands.
Woodfuel – Good for the Woodland Economy
Utilising woodfuel from woodlands can help to stimulate woodland management and in turn help to provide an income for woodland owners, forestry contractors and fuelwood suppliers, as well as the suppliers and installers of wood boilers. It can help to provide another source of domestic heating to reduce reliance on oil, gas and electricity.
Six Key Questions to ask when buying woodfuel
If you need to source woodfuel, here are six key questions that you could ask a supplier:
1. Where has the fuelwood come from? Has the fuelwood come from a sustainably – managed woodland? Has it come from a local woodland rather than having come from another region of the UK or from abroad? Has it been harvested legally, i.e. through a felling licence application?
2. If buying logs, what size are they? Buying logs which are too large for your heating system will require extra work to cut or split them down to size.
3. What type of wood is being sold? Are you buying hardwood or softwood? What wood do you need to use for your appliance?
4. Are they fresh green logs or have they been seasoned? Green logs should be cheaper but will need to be stored until they are dry enough to use. Seasoned logs will be more expensive but you can use them straight away.
5. How is the fuelwood delivered? Is the material delivered bagged up, left on a pallet or dumped on your drive? Will you need to stack the fuelwood yourself? Does the fuelwood price include delivery?
6. Is the fuelwood sold by weight or by volume? Many firewood merchants sell their product by the load – but this can be a pickup truck load, a trailer load or some other measurement. If sold by weight, green wood will be heavier than seasoned wood due to the higher moisture content. Fresh conifer wood will also be lighter than hardwood, so there will be more of it by weight.
Storing and Drying Woodfuel
Green logs will be much cheaper than buying seasoned logs but because they contain more moisture, they will be heavier to move around and they will also need to be dried out sufficiently before being used. Different species of wood will take different amounts of time to dry out but in most cases, logs will need to be dried out to below 20% moisture content before they can be used which can take around two years. They will need to be stored off the ground and be stacked under a rainproof cover preferably in a sunny spot where the sun and wind can help to dry them out. If the logs have been split, this will help to speed up the drying out process even more by increasing the surface area of the logs. You can soon estimate when the logs are dry enough by looking for radial cracks across the cut surface of the log but moisture meters can also be purchased fairly cheaply to indicate the moisture content of the logs. Bringing the logs inside the home for a few days prior to burning can also lower the moisture content even further.
Getting the most from woodfuel
The heat output from woodfuel is dependent on two main factors: Moisture Content and Wood Density.
Dry wood will produce more heat than wet wood because most of the energy will be used in combustion rather than having to push any remaining moisture out of the log. The amount of heat per unit is expressed in the Calorific Value or CV and is related to the moisture content, so the lower the moisture content (and hence the drier the log), the higher the CV is.
The other factor in determining the amount of heat is the wood density. Very dense wood will burn for longer which entails fewer loads of logs needed for the log burner. Hardwood is denser than softwood so hardwood logs burn for longer than softwood. But if you buy logs by weight, a tonne of hardwood logs will take up a smaller space than a tonne of softwoods logs because they are denser.
There is a third factor which can affect the amount of heart output which is the type of tree species. However, this has very little effect on heat output once the logs are all at the same moisture level.
Using and Burning Woodfuel
Burning damp logs is not an efficient way to use woodfuel because some of the heat used in burning them will be forcing out the moisture which will appear in the form of steam. Unseasoned logs can sometimes cause deposits of tar to be left in a chimney or log stove which can increase the risk of a chimney fire. Logs which are dried sufficiently will produce more heat because less of the energy is being used to force out the moisture in the logs.
The cleaner that the woodfuel is, the better it will burn and the better it will be for a wood-burning appliance. Wood should never be burned if it has been contaminated with substances such as preservatives, paint or varnish because these can accumulate in the chimney as well as releasing poisonous chemicals when burned. This includes wood that was preserved with CCA (copper, chrome & arsenic) for use out of doors because it will release these noxious substances during burning.
Using a log stove rather than an open fire to burn logs is much more efficient way to utilise woodfuel. An open fire takes much of the hot air up the chimney whilst drawing warm air in from the house but can produce a lot of smoke, ash and soot and will require a fire guard to prevent any sparks from jumping out of the fire and into the room. A log stove provides an attractive focal point to a room and is fairly cheap to install. They are more efficient than open fires because it is possible to regulate their burning requirements by using vents, plus they radiate the heat back into the room effectively.
Always check for any local restrictions on burning woodfuel by contacting your local planning authority who can advise further. There is also information on smoke control areas on the DEFRA website as well as your local planning authority's website.
Is there enough woodland in Britain to produce sufficient woodfuel?
Britain has around 12% woodland cover which is fairly low by European comparisons so some people are concerned that an increase in the demand for woodfuel will diminish our woodland cover even further. This scenario is very unlikely however because broadleaf trees will usually grow back if they are still young when felled or coppiced, so that a tree could in theory carry on producing firewood for hundreds of years if continually managed sensitively. The Forestry Commission also have strict felling regulations which means that all felled areas of woodlands have to remain as woodland so either the landowner has to restock them through natural regeneration or through replanting.
There are also many under-utilised woodlands in Britain where woodland management is minimal or non-existent and where more use could be made of potential woodfuel products. The Forestry Commission have estimated that up to two million tonnes of woodfuel a year could be generated from under-utilised woodlands in the UK which would save 400,000 tonnes of carbon emissions per year.
There are also other types of wood which can feed into the woodfuel resource as well as using trees from woodlands. For example, utilising arisings from forestry or arboricultural operations such as "lop and top", residues from sawmills and "recovered wood" from old pallets, buildings and furniture that would otherwise go to landfill and be a lost source of energy.
Creating new woodland will increase the area of woodland cover nationally and help to increase the future woodfuel resource. This is particularly beneficial in areas of low woodland cover because the woodfuel can be produced locally rather than having to be brought in from further away which will keep haulage costs down. The Forestry Commission administer a Woodland Creation Grant which can help with the costs of establishing new woodland.
Therefore there is no risk at present of demand for woodfuel oustripping supply in the UK at this time for the reasons above. Demand for woodfuel is down to factors like the cost of other (fossil) fuels and lifestyle fashions and is just one of a collection of fuels used by consumers for heating energy in the UK.
Ensuring woodfuel has been felled responsibly
Felling trees must be done legally through first gaining a felling licence from the Forestry Commission if more than five cubic metres are felled in a calendar quarter. Many woodland owners follow the information contained within the Government's UK Forestry Standard (UKFS) which has strict requirements on woodland management and must be complied with in order to be able to apply for forestry grants. Some owners have certified their woodland management against the requirements of the UK Woodland Assurance Standard (UKWAS) and they are allowed to use the Forest Stewardship Council (FSC) or Programme for the Endorsement of Forest Certification (PEFC) logo on their woodland products. In Exmoor, the local group certification scheme, Exmoor Woodcert, is made up of several woodland owners who want to demonstrate their commitment to managing their woodlands responsibly.
Woodfuel suppliers near to Exmoor
There are several woodfuel suppliers who are based within or near to Exmoor. For a list of local woodfuel suppliers, please click here.
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