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Firewood ~ by Jonathan

Firewood

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” 

www.guardian.co.uk/environment/2009/jan/14/domestic-wood-burning 

http://www.wildeye.co.uk/trees/firewood.html 

http://www.aie.org.uk/aie_data/aie_firewood.html 

http://www.woodheat.org/firewood/firewood.htm 

http://www.usewoodfuel.co.uk

Posted in: Practical Guides, Woodland Activities ~ On: 13 March, 2009

12 comments so far

Solid fuels and wood burning stoves, | Woodlands.co.uk
30 April, 2018

[…] on fuel costs’.   Indeed, not only has the woodlands blog written about the pros and cons of different woods in stoves, but Angus has written enthusiastically about the installation of his wood burning stove (it keeps […]

Steven
8 August, 2016

Just a comment on kiln drying logs and eco stuff

Anything that produces heat eats up energy. Anything that is just moving stuff doesn’t as much.

For my wood I air dry it as long as I can in the sun (up till the westher starts turning bad, end of September), and then move it to the garage. I then use a small desk fan to ‘air dry’ it indoors until it is needsd (about 250w fan, 6 units a day electricity). Then when I want to use the wood it is very dry, though I haven’t measured it. In the next year or 2 I am going to hook up a solar powered fan. No heating and no big fuels costs to kiln dry wood.

On a business level kiln drying can work because you can get so much more wood processed in a smaller area (less rent, more sales) meaning a kiln can be as profitable as air drying where you need a large area and a long time between buying stock and selling it.

Pete
21 February, 2014

Fire Wood Poems
Wisdom of the ages

Author: Cilia Congrave 1930

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.

Ian B
1 January, 2014

Very informative. Definite bookmarked page. Rightly said – moisture content is key.

Seasoned logs
14 May, 2012

Good Advice.

Paul Garnett
21 November, 2011

Before using firewood always check it for the moisture content. Firewood that is not dry enough will not burn properly and give off fumes that can prove to be harmful to you. You can always test your firewood with a wood moisture meter. These moisture meters are easy and quick to use giving instant results.

Simon Wilson
16 November, 2011

“seasoned logs“ VS “kiln dried” Being in the trade (Logs firewood info) I hear this all the time “we must have kiln dried logs” but its not about HOW the logs are dried but how dry they are.

Think of the impact that kiln drying has, not very eco friendly when you consider the drying process usually involves large diesel kilns.

The better hardwoods can be air dried in 3-6 months and give around 20-25% moisture, plenty dry enough to use, and buying normal air dried logs will be cheaper as the kiln process is expensive.

daniel pearl
30 October, 2011

Experience the difference between burning “seasoned logs“ and “kiln dried” and you will appreciate the difference in heat output and that the fire burns steadily and consistently – unlike a lot of logs that are described as “seasoned“, but have only been air dried for a few months and often still have a 35% moisture content.

Wood Mizer
20 September, 2011

[…] to be used for a massive workbench.. What I did with some future fire wood…I &#… /> What I did with some future fire wood…I […]

hardwood doors
5 November, 2010

HI, found this really interesting, we have 2 wood burners, an aga and a jotarl (no idea how you spell that!). They are the best heaters! A great yearly ritual is cutting the wood with my Mum, she first taught me how to use an axe. Remember we had some little poem about the different woods to burn, can’t remember it now, but think it said something like ash wood burns longest and hottest.

Tony
11 June, 2009

Good advice, wish I owned a wood, one day1

Mike Pepler
13 March, 2009

Of course, you could heat your home with a much smaller area of woodland if you insulated it to a better extent. It’s possible to build homes that need almost no heating, and then the woodburner can be lit just at the very coldest periods of the year.

It’s hard to get an older house up to this level of insulation, but at the very least you should make sure that if you have cavity walls they have been filled, that your loft has 12 inches of insulation, that you have double-glazed windows and that all draughts have been sealed (windows, doors, floorboards). Then, and only then, should you look at adding renewable energy to your home, whether it’s a woodburner or a solar panel.

Of course, you may choose to have a woodburner for aesthetic reasons, but don’t kid yourself that it makes your house “green” if you haven’t insulated as well.

There’s a load of info about wood-fuel stuff on the Ashden Awards site:
http://www.ashdenawards.org/winners?filter0=19&filter1=31
and also on insulatio nand energy efficiency:
http://www.ashdenawards.org/winners?filter0=42&filter1=31

Mike

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