Charcoal Making

Woodland Charcoal Production

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Background

If there is anything you want to know about the history, uses, production methods and marketing of charcoal then Alex Arthur of Chew Valley Charcoal is the man to ask!

Fondly known as Charcoal Alex he lives and breaths his subject with huge enthusiasm and energy bounding through the woods like Tigger. Working at a relentless pace to achieve his goals and meet the strict timing he has for lighting and shutting down the burning kilns at odd hours of the day and night

After 10 years in woodland management Alex set up Chew Valley Charcoal to supply a gap in the Bristol market for British charcoal. He explains;-

“apart from the historical reasons for making charcoal (circa 2000 BC in Britain) much of the barbecue charcoal on sale in Britain is imported from the far east, often being produced from non-sustainable resources. That is, it is produced by using wood from trees which have been grubbed out or have been cut down and will not re-grow. It also uses our precious energy resources to transport it long distances.

The charcoal I sell has been produced from British native hardwood trees which have been coppiced as part of countryside management for the benefit of wildlife and has very low fuel miles attached. The trees which have been cut to produce it will grow again from their roots to produce another crop of wood for harvesting in 7-15 years time. There is a never-ending supply of this wood and so the source is sustainable indefinitely (unlike tropical rain forests).”

Apart from the production side of his business Alex is also a consummate educator with a training service which has delivered to a broad range of clients including The National Trust, Wildlife Trusts, land based therapy groups and various environmental projects.

In early September we gathered at The Cherry wood Project, who were hosting the weekend for Alex with plans for several burns using a Six foot diameter Commercial production Kiln (20-22 hour burn) a 3ft demonstration kiln (5 hour burn) and a barrel burn which takes just 2-3 hours or so and is viable for you to try at home or in your own piece of woodland.

We started with some history which is a long and interesting story but here it is suffice to say that until coke was produced from pit coal in 1735 charcoal was the dominant fuel for all domestic and industrial activities due to its efficiency as a heat source and the landscapes from South Yorkshire to The Forest of Dean to Epping Forest has all been sculptured by its exploitation.

Some ask why you cannot just wood on a fire to cook? You can, but it will take longer, more wood, more smoke and produce much less heat than charcoal will. A wood fire uses the bulk of its calorific value in burning off moisture, acids and tars rather than heating what you want to heat be that an egg in a pan or a horse shoe in the forge.

The Activities.

The group of students were of mixed interests:- A couple from London who live in a top floor flat wanting to feel the woods, a city worker who wanted to return to the family 30 acres in Ireland with a plan, a permaculture lecturer and a couple of woodland apprentices keen to see how a professional does it.

The first job is to open and empty the 6 foot kiln which Alex had burnt a few days earlier (it takes 2-3 days to cool down enough to touch) there was much discussion about the success of the burn based upon the amount of charcoal, about 6-1 by volume and weight, the colour of the tar and deposits on the kiln, the prevailing weather conditions cooling one side of the kiln and how many brown ends were left. These are the logs that haven’t carbonated completely which are put aside to go back in the next burn.

Good charcoal is as light as a feather, breaks to the hand, is jet black but you can still recognise its origin. It is in fact as much cooked as burnt with the immense heat at the bottom driving off the water, volatile gases and tar to leave the charcoal. When in this state and reignited it burns with a much more heat and purity with less smoke and without wasting energy.

While we were grading by size across a griddle and bagging up, Alex explained the main benefits of charcoal to the woods.

Mostly we are using the thinnings and or coppice material which would not be used for any other use but still weighs a considerable amount. If we brought in heavy transport to get the wood out it would damage the ground and increase the fuel costs in getting the wood to market. We are a low impact enterprise which treats the environment well and you can add value to poor wood and transport a light weight material to market in a very fuel efficient way. This is sustainable, efficient and ethical.

The 3 ft kiln is not big enough for much production but would be big enough to do the occasional burn for your own use. By preference the kiln should be sited on dry ground with as much shelter as possible from winds, some people use Hazel hurdles to protect the kiln from draught and affecting the evenness of the burn.

The layout at the bottom of the kiln is a star pattern to allow channels of air to efficiently drawn into the heart of the burn, after which it is a case of whichever log fills the gap  – put it in!. For this kiln the wood should be branch wood of 3-4 inch diameter or split appropriately. By midday we are able to light this kiln and watch its progress for the rest of the day turning the chimney ports alternatively to ensure an equal burn to all areas of the kiln.

The afternoon is spent grading, splitting and re filling the big 6ft kiln. By 5.30 no one is left with any doubt about how much hard work goes into charcoal burning with aches and blisters to share stories about.  It is however time to shut down the 3ft kiln as the smoke had changed from wet and grey to dry and a hazy blue indicating that all the volatiles and water had been driven off.

The two things that fire requires are fuel and oxygen so we must block off all oxygen sources to the fire and it will go out. In the old days this would have been using turf and soil whilst we can suffice with removing the chimneys and blocking the pots with bricks and sand.

It is also time to light the big kiln which will burn until the next afternoon. It takes Alex’s expertise to check the smoke, especially in the dark, so he spends the night dozing and checking the burn to see if the chimneys need turning.

That evening Alex imparted his expertise with the B-B-Q with the best cooked, most succulent meats I can remember having from a Bar-B, with only a few handfuls of charcoal (mostly the smaller bits) and a good handful of wet shavings of Cherry. He pulled the lid down tight and let the meat smoke and cook in the heat, rather than being grilled, a delicious end to the day.

The following morning the small kiln is cold enough to handle and so its back to grading and bagging. We use a 1inch mesh to start with the lumps going into the bags for sale. We then use a smaller mesh to re grade the balance into medium, and fine. The medium is sold to blacksmiths with the fine being used for paths and horticulture. There is no waste product in this business –it’s all gone up in smoke!

Barrell Burn

The cheapest and easiest way to create your own kiln is to acquire a steel barrel (but be careful what has been in it before!). There are 2 methods to try, either create a kiln by removing the top and bottom and creating a tight fitting lid similar to the manufactured kilns. Alex has one for us to use this afternoon which has a chimney but this is not necessary as long as you can put a lid on at the appropriate time and seal it with sand.

The other method is to cut a section out of the side of the barrel, lead and get a good fire burning and when you think its appropriate roll it over into a shallow trench and earth up the sides to seal. I cannot vouch for the efficacy of this method as we did not try it on this course. Those that have used it assure me that it does work, with some practice a good result can be obtained.

With the barrel burn underway the students walked the woods with Tim Gatfield who explained how his coppice rotation system would fit in with charcoal production and which timber was suitable for extraction.

An hour or two later the barrel burn is ready to inspect while the big production kiln is ready to be shut down for a few days cooling before the cycle of charcoal production begins again.

At the end of two hard days in the woods all agreed that it was a fascinating subject but really hard work. I doubt if any of the participants will become full time charcoal burners but their awareness levels were so much higher I am sure the experience will rub off on others as well.

If you want to know more about charcoal burning I can highly recommend Charcoal Alex as the man to visit. The only down side is you do get very dirty but it good clean dirty – don’t forget that charcoal is used in medicine and cosmetics as well.

Artists Charcoal – try it in the garden.

Although not part of this course I spent sometime experimenting with making small batches of charcoal from twig size round wood and very basic tools.

You really can use any size tin that you can find but please make sure it hasn’t had any volatiles in it or you could create a rocket. Alex uses a small metal electrical fuse box, I have used a biscuit tin before but they seem to be rarer these days. On this occasion I had a clean can with a spring closure to the lid which was ideal.

Firstly we need to let the gasses and steam out so create a hole about the size of a 5p and fashion a plug to fill the hole at the appropriate time.

I was lucky in having a bundle of seasoned willow to use as this appears to be an artists favorite but you can use any wood that is available, stick size pieces of dry twig which clearly snap by hand pressure. Load up your tin and put it on a good outside fire (not to be tried indoors on the kitchen cooker!)

Within minutes the wood will be cooking and steaming and giving off the volatiles etc and you need to assess when to stop the process, This is when the escaping gasses clearly change from white to a hazy blue grey with a heat tremor. I cannot teach this in a magazine article as it needs to be experienced and I do not have enough practice, so it will be trial and error.

A small tin will be approximately 30 minutes, a standard size biscuit tin maybe 45 mins. It all depends on the fire temperature, the ambient temperature, the state of the wood etc etc,  so don’t expect perfection.

After an hour or so, on a reasonable fire the results in this much larger tin, were disappointing with half the twigs still brown but with some progress on the other side. I stoked up the fire with some brown ends and charcoal to a good blaze and put the can back on the fire on the brown side. After a further 30 or so minutes the smoke had cleared again. The can was removed to safety, turned upside down, earthed up and left to cook for an hour or so.

After cooling and opening the results were really good with prime charcoal sticks any artist would be proud to use.

With some 400 sticks produced in this one burn and the cost in art supply shops of £3 for a dozen sticks we had really added some value to the wood which can now be used as a resource for school visits to Cherry Wood this Autumn.

So whey not have a go, buy a roll of lining paper and release the inner artist!