According to folklore firewood will heat you three times:
When you cut and extract it,
When you split and store it,
When you carry and burn it.
A wood fire can cook food, act as a focal point, or heat one room or an entire house.
In the wider picture, the careful and efficient use of firewood, a carbon neutral resource, can also contribute to reducing our dependence on fossil fuels and reduce global warming provided it is sourced, managed and transported sustainably.
Types of firewood
The type of firewood depends on use. A safely organised and atmospheric outdoor fire will require tinder, kindling and main fuel which can be derived from all parts and types of hard or soft wood trees. Naturally the dryer the better. Birch, cherry and cedar bark can be used as tinder, and for a slower, longer-lasting fire then harder denser sticks and logs are best once the fire is underway. Although less dense, softwood conifer sticks and twigs are good for kindling (including pine cones) as being more resinous they burn hotter and are easier to ignite. Pine and larch also give off a fresh outdoors fragrance but conifers are not recommmended for cooking with. To see some different types of outdoor log fires for either heating or cooking purposes click link here - http://www.inquiry.net/outdoor/skills/b-p/wb/fires.htm
If you do not have an indoor fire but are thinking of getting one, then it is best to seek advice as to the most suitable type, capacity and installation for your room or building.You should also first check to see if you live outside a smoke control area. Click on uksmokecontrolareas.co.uk to find out.
Looking at the different firewood options for indoor fire places or woodburning systems in order of highest efficiency first:
A wood or biomass boiler burns mainly woodchips or pellets and is the most efficient (65%-95%) in terms of heat generation and waste, using all the converted main and by-products from felling. They are however more suited to serving a larger farmhouse, group of houses or commercial application.
The more common woodburning stove, with closed doors to control air and heatflow, and which ranges in efficiency from about 40-70%, will burn both hard and softwoods efficiently so long as they are sufficiently dried for at least a year and preferably two summer seasons. Given like for like moisture content (ideally down to 20-25%), there is little difference in the calorific value between hardwood and softwood, but there is a difference in weight density. Hence an oak log may contain double the energy as a similarly sized spruce log. Logs should be split no more than 10cm in diameter as this maintains a high area of reaction surface which is vital in generating enough heat during the early three endothermic stages of a fire (where temperatures reach up to 250°C) and allowing progression through to the clean and complete combustion stages (which occur at about 700°C). Freestanding stoves are more efficient than built-in stoves and the better stoves have both primary and secondary air systems which are crucial to the fire going through the full six phases of the burning process ensuring maximum heat output and clean efficiency. The enclosed stove also provides the visual glow and cheery sensation of a flickering flame if it has a good sized clear-view glass window.
For an open fire, which has the lowest efficiency of converting fuel to useful heat (10-35%) due to poor air control, generally seasoned hardwoods are best because they are less likely to spit or create smoke or tarry (and creosote) deposits in the chimney. However once seasoned properly, conifer woods which are easier to split and softer hardwoods such as birch and sycamore can be mixed with harder firewoods and still create a good, red, hot and virtually smokeless fire.
Supply and quantity of firewood
In medieval times, country folk were allowed to collect as much deadwood as they wanted from the royal forests – just so long as they could reach it “by hook or by crook”.
Presently there is an increasing demand for logs and woodburners – triggered largely by recent soaring energy prices as well as lifestyle/environmental choices – which has made finding good firewood more challenging and has caught suppliers on the hop. In certain areas suppliers are being forced to buy logs from further away and in future there could be a shortage of locally sourced, good-quality, seasoned hardwood logs unless better and less profligate forestry and woodland management techniques are adopted. Effective woodland management must also ensure that a whole array of flora and fauna is continuously supported and conserved which includes leaving plenty of dead wood lying around.
If you are lucky enough to have your own woodland then it can provide some or all of your firewood requirements depending on the woodland size, tree species present and the way the woodland is managed. The easiest way to do this is on a coppice cycle. If you have firewood that is surplus to requirements then you can always give or sell to a friend/neighbour or supply a local reseller.
If you need to supplement your own supply of wood then the good news is that wood supplied as domestic fuel attracts only 5% VAT (as do the appliances that are dedicated to burning it, provided they are installed by professionals). As a rough guide, to entirely heat a well-insulated 4 bedroomed house all year with an efficient woodburner stove or system requires 7 tonnes of air-dry wood a year (14 tonnes green wood). One acre of well-managed woodland will produce 1 tonne of dry wood per year so it would need about 7 acres to produce enough firewood on a sustainable basis. A greater area of older, more mature woodland is required since this is slower growing.
Main references or other useful info sources:
Centre of Alternative Technology booklet – “Home heating with wood”