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Wood Fuel ~ by Mike Pepler

Wood Fuel

Mike Pepler works for the Ashden Awards for Sustainable Energy and also owns some woodland near Rye, East Sussex, which he manages with his wife Tracy.

Using wood for heating

According to government figures (from BERR), heating buildings and water uses about one third of all energy (including transport) in the UK. Much of this energy is supplied by fossil fuels, and so is resulting in large amounts of carbon dioxide being emitted, contributing to climate change.

Wood has been used to provide heating for thousands of years, but with the convenience of gas, electricity and heating oil in the UK there is now a significant quantity of wood that could be used for sustainable heating but is not. Some of this comes from waste, such as tree surgery arisings and the building industry, but there is significant scope for managing woodland to produce wood for heating. Burning wood is carbon-neutral, as the carbon dioxide emitted when it burns was absorbed from the air while the tree was growing. If this replaces the use of a fossil fuel then it has helped tackle climate change.

Woodland management for wood fuel

As a woodland owner the use of wood for heating is worth thinking about. Management of woodland, done properly, can be helpful to wildlife and biodiversity, and also make the wood a more pleasant and interesting place to be. Coppicing in particular is very sustainable, as after harvesting the wood the tree is still alive and will grow back extremely rapidly, as we found in our own wood, where the sweet chestnut re-grew to a height of six feet during the summer after cutting. Coppicing also makes a unique habitat that some species of birds and insects depend on, and it encourages a wide diversity of ground-level flora. Having said this though, whatever management technique is used, it is important to leave plenty of dead wood lying around, as many fungi and insects need it to feed on, and other creatures in turn feed on them.

Many woodland owners will produce wood fuel on a small scale, processing it by hand. In order to get the best out of the wood, you should:

- Fell trees in the winter, when there is less sap in the wood.

- Split the wood as soon as possible to allow it to start drying.

- Store the split wood with plenty of space for air to flow round it, and with some shelter overhead to keep the rain off (but not at the sides, so air can get in).

 - Store the split wood for as long as possible before burning it. Aim for a minimum of two months of warm weather, but longer if possible.

Seasoning the wood (allowing it to dry out) is important, as you will get about 20% more heat out of a piece of wood when it has been seasoned compared to when it was green. If you can season it in your woodland, then it will be easier to carry out afterwards as it will be lighter. One tip we learned recently was to split the wood in long lengths (a couple of metres) using wedges, and stack it to dry in such a way that when you're ready to use it you can slice through the whole stack repeatedly with a chainsaw, cutting the ready-split wood to the length you need.

Using the wood fuel

You will obviously get the most out of the wood fuel you produce if you can use it yourself. While an open fire is pleasant to look at, the efficiency can be as low as 10%, because so much air is drawn into the house, heated, and then sent up the chimney. In addition to this there can be incomplete combustion of the wood, causing the emission of some gases that contribute to climate change, and others that are local air pollutants.

A stove can do much better, being perhaps 40-70% efficient and achieving near-complete combustion, depending on the design and how it is used. It is important to choose the right capacity of stove for the space you want to heat. If it is too small then it will need to be run very hot, and will send excess heat up the chimney and reduce the efficiency, while if it is too large it will be run at a low power, causing pollution and reduced efficiency due to incomplete combustion. You should take advice from a stove installer on what would suit your house best.

Aside from open fires and stoves, there are also boilers that will burn wood pellets or wood chip. Pellet boilers (or stoves) are available in small capacities, but you're unlikely to be making wood pellets yourself so you will be dependent on a supplier, and the pellets could be travelling a long distance to reach you. Boilers burning wood chip are only available in larger sizes, suited to public or commercial buildings. Although you're unlikely to install your own wood chip boiler, you could help supply one, as explained below.

Supplying wood fuel

If you find you have more wood fuel than you can use yourself, you might decide to start supplying it to other people. The simplest way to do this is in the form of split logs for an open fire or stove, but producing wood chip is another option. Chipping machines come in various sizes, but even the smallest will process tens of tonnes of wood in a day, so you would expect to hire one (with an operator) rather than buy one. Also, you may well need to team up with your woodland neighbours to provide a big enough pile of logs to keep the chipper busy for a day. Finally, you will need a customer for the wood chip, but fortunately there are several groups across the country setting up schemes to pool the wood resources in a region and sell them to large customers. The details of some of these groups are given below.

Ashden Awards wood fuel winners

In my work for the Ashden Awards for Sustainable Energy I've come into contact with a range of people working with wood fuel. Over the past few years we've given a range of awards in the UK to organisations using wood fuel for heating. The links below take you to information on them, including detailed case studies and short documentary films:

Thames Valley Bioenergy won an award for their work collecting wood fuel from woodland management, tree surgery and short rotation coppice and supplying it to customers such as a power station and local schools.

BioRegional Development Group won an award for creating a "TreeStation" in Croydon, which allowed local tree surgeons to drop off their waste wood instead of sending it to landfill. The wood is chipped, dried and then delivered to customers in the region.

 Wood Energy won an award for their work installing wood chip boilers across the UK, and helping set up local wood fuel supply chains.

Barnsley Metropolitan Borough Council won an award for their work in collecting tree surgery waste from their own parks and gardens and using it to run boilers in council flats and offices.

 Nottinghamshire County Council won an award for their project to convert schools with coal-fired boilers to run on wood pellets instead.

The Rural Energy Trust promotes the use of wood fuel in schools and public buildings, giving training, demonstrations and presentations to encourage the sustainable production and use of wood fuel.

Posted in: Flora & Fauna, Practical Guides, Woodland Activities ~ On: 14 November, 2008

25 comments so far

Dom
14 December, 2010

We have our woodland now, and currently have a 32 ft by 12ft static caravan.
We do have central heating, but that gets through gas very quickly – thankfully we now also have a small Nordpies Orion stove from Fluesystems (found a local installer) http://www.fluesystems.com/stoves/info/nordpeis_orion.htm

It is a lovely little stove and into the bargain it has a hot plate on it to boil the kettle or slow cook your dinner! Now we just need to sort out storing some wood – there is plenty around, but it is all very wet, so guess we need to get it under cover and save it for next year and buy in wood for this year.

Simon
10 December, 2010

Some great advice here, an interesting article. Just for information, if anyone is looking for Logs Nottingham, Nottinghamshire Logs supplied mine last winter and I have more ordered this year. Great for log fires at Christmastime!

Jason Webb
4 August, 2010

Pellet stoves generally cost very low and the Installation costs are relatively low,

Regards
Jason Webb

Tony
11 June, 2009

Nice article, its the kind of thing I’d like in mu library on my site.Ay chance?nt

Tony
10 June, 2009

Great article, wood is the future for us for heat and for the planet. More importantly trees are the most fasinating thing on the planet

James Harman
17 March, 2009

If anyone is looking for a wood stove, i purchased mine via the websit http://www.stovesandchimneys.co.uk

Tracy Pepler
29 January, 2009

WoodNet in East Sussex are having a couple of open days at the woodland enterprise centre- all about woodfuel. Take a look at their website for more

http://www.woodnet.co.uk

Dave
12 January, 2009

Hi Sam…….. Re POLLARDING.

Pollarding was usual practice where animals would graze beneath, allowing full regrowth.

Coppicing works with most British broad leaved trees (Oak, Ash,Hazel, Sweet Chestnut….), but is prone to grazing damage. In our woodland in Kent, the deer are probably quite fat, and so are the rabbits !. If coppicing.protect the newly cut stools.

Dave.

Tracy Pepler
26 December, 2008

Hi Sam

I am sure people will answer your question here, but you may also wish to try posting this question on the Small woodland owners site –
http://www.woodlands.co.uk/swog

Tracy

Sam
26 December, 2008

Hi, i was just wondering wether anyone knows wether coppicing is more productive than pollarding, and which types of tree are good for pollarding. Coppicing seems to be done more where it can therefore i’m guesing maybe coppicing is more productive, although perhaps this is because coppicing produces wood suited for poles and such.
Thanks.
Sam.

Mike Pepler
18 December, 2008

Hi Jim,

The carbon locked up in your trees was absorbed from the air while they were growing. If you cut them down and used them as fuel, but didn’t allow them to grow back (e.g. converted the land to grass) then yes, that would add carbon to the atmosphere.

However, if if felling them you allow them to grow back (if they’re coppiced), or plant new ones, then the new growth will absorb the CO2 produced from burning the trees that were felled.

Of course, you need to make sure you’re only felling the trees and using them for fuel at the same rate that they will grow back. If you use them faster then it’s not sustainable in the long run.

Do ask if you need any more info.

Cheers, Mike

Jim
16 December, 2008

I have a small 0.5 acre wood in surrey. I am interested in seeing if I could set up a charity in combination with other owners who are also concerned about CO2. However, I am concerned that taking existing woods are burning will release a lot of locked up CO2 are there any studies that have been done into this.

mart
21 November, 2008

Spotted in passing and appropriate to wood fuel

For those with 3 days days to spare , 2nd -4th December and can get to near Brecon, Wales

http://www.ecolots.co.uk/index.php/classifieds/advert/3-Events/20-Training-&-Education/14615-Ignite-Woodfuel-Training-Course,-Brecon-Beacons-National-Park

Mike Pepler
21 November, 2008

Hi Tim,

Yes, as you say, 2 months is a minimum for drying, and will only be enough in ideal conditions (i.e. warm and windy). More is always better.

I didn’t get into it in this article, but different types of wood have different qualities (as you probably know). For example, Ash will burn green (though seasoned is still better), Sweet Chestnut is often avoided for an open fire as it spits, but it’s great in a stove. There’s a table with the properties of various types in wood on page 97 of “Caring for small woods” by Ken Broad.

Mike

Mike Pepler
21 November, 2008

Hi Andy,

The only thing I can think is that you’re not getting complete combustion – the chemicals that form the resin should be burning. As they are not, they’re condensing on the heat exchanger, which will be cooler than anything else inside the stove.

Have you tried running the stove a bit hotter, with slightly more air, to see if that helps? If it’s turned down below the optimum level there’ll be incomplete combustion. Try experimenting a bit and make a careful note of how you run the stove, then see what the resin buildup’s like.

Hope that’s helpful?

Mike

Mike Pepler
21 November, 2008

Oh, and another thing, you might want to check out the forums on SWOG, as you can discus these issues there: http://woodlands.co.uk/swog/

Mike Pepler
21 November, 2008

Hi Sean & Claire,

You can coppice anywhere the trees are the right species, but keeping animals may require some permission, and fencing of course. As for building a home… not easy to get planning *in* the wood, though some have done it (Ben Law). Your best bet may be what we did – buy a wood and then move house to be near it.

Mike

Tim Tierney
18 November, 2008

An interesting article. I have never seen any publication suggesting drying for as little as two months, but given ideal conditions and short logs, I tend to agree. Test for dryness by weighing a sample. Write the date and weight on it then store for a few days in a very warm dry place, then weigh again. Burning wet wood is a waste and sometimes troublesome, keep it until dry.

Many boilers are more efficient than stated. Those with wraparound back boilers are less efficient, but our Hunter is still quoted at 73.6% and it heats the house.

We made a log store with old pallets on the ground and lightweight pallets, boarding and felt forming the roof. It is supported by tanalised fence posts and is a lean-to against a wall of the house. Our firewood now travels just 10m to 300m, from the tree to the log-burner, via the store!

Andy
18 November, 2008

THis a very useful article because it draws attention to the fact that wood chip boilers are only available for commercial purposes. We are fighting a battle against an unsuitable development which is proposing to heat an eco house with wood chip/pellets on 1/2 acre! So most fuel would be brought in by road!! Very eco!!

But on another tack I have a question. We have a wood burning stove with a back boiler which suffers from resin build-up particularly on the heat exchanger (because the water jacket acts as a condenser). Any suggestions?

N. W. Pierce-Jenkins
18 November, 2008

Good straight forward information that is very useful when in discussion with others.

NPJ.

sean & claire
18 November, 2008

we are trying to start a woodland smallholding with lodges bought in dumfries .but trying to find places that will alow coppicing, animals and living off, on or near the woods seems almost impossible?
have you come across anyone combining any of these activities successfully?

Steve Guy
18 November, 2008

Hi MIke,
Cracking article. I work for Jon Roberts in the coppice at the Weald and Downland Museum near Chichester. Here we cut and process the woods to supply the museums houses with “historically accurate” firewood using traditional methods, mainly the axe and billhook. We make faggots for the bread ovens on site, provide poles for beans and hops, supply fence material and a host of other products from the Coppice.
I think a lot more could be done with the woodlands that are languishing within the reach of many homes.

Regards,

Steve

Dom Earl
18 November, 2008

Lovely article and very informative, we are considering buying some land to start Willow Coppicing and we are attending a FREE Seminar by Business Link – check out http://www.ruralbookings.co.uk

Thanks

George
18 November, 2008

We have had a wood burning stove ( villager) for the last 6 years and I only wish I could connect up a back boiler to it for heating. Unfortunatley all the pipes are buried under the
floor. My supply of logs apart from those gathered locally comes from a firm doing tree work for the local authority, they give them free! I also get all the wood chips which we spread on the paths of the local commons during the winter. Better than landfill
You cannot beat the joy of an open fire, to say nothing of what good it does to the house, air flow, keeping down damp etc

Tony
18 November, 2008

Great item just thought it is worth mentioning cassette fires such as Riva which are inset into the chimney breast which if you are short on space is easier than a stove and provides convected heat as well as radiant and claim up to 70+ conversion. We have just had ours fitted and are looking forward to a highly reduced dependancy on Gas for financial and ecological reasons.

I would also like to echo the point raised that altrough wind throw should be harvested some should be left to just rot away enriching the wood’s ecology.

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