Making Charcoal

I do some voluntary work for the Countryside Restoration Trust at their Pierrepont Farm site in Frensham Surrey. The farm is very much a  working farm run and managed by Mike Clear, his wife Bev and their herdsman Tony Timmis. Unusually in these days of intensive farming Mike has a herd of Jersey cows. I say unusually as the milk yield from Jerseys is about 20% less than that from Fresians but the trade off is that the milk and cream is far superior to that of other breeds.

The farm includes some 20 hectares of woodland.The dominant species are Sweet Chestnut, closely followed by Silver Birch, Sycamore and Oak and the volunteer group is actively trying to manage this by coppicing and removal of the ever present Rhododendron. The coppiced wood is made into post and rails and the wood that is of little use either becomes firewood or is made into charcoal. The CRT did have a charcoal kiln that Mike, his son Patrick and I made out of an old diesel tank but it failed spectacularly when the lid warped during a burn and became an incinerator rather than a kiln. This was an emotional time and I think I invented some new expletives. We now have a shiny new furnace which has only been used twice but both burns have been successful producing very good charcoal.

Charcoal is not a recent invention and has in fact been in use for 000s of years. It is even mentioned in the Bible (John 21:1-19) and the method of production has changed very little. The basic principle of charcoal production is to extract all the water and oils from the wood in a controlled manner; shutting the kiln down by closing  off the air inlets and outlets before the dehydration becomes an actual burn.

Choosing the correct time to shut down the kiln comes with experience but as a general rule of thumb when the white smoke, which is mainly steam, starts to turn blue the wood in the kiln is burning. If left to burn the kiln when opened will contain nothing but a pile of ash so it is important the kiln is monitored.