It’s the time of year when I start making charcoal again on a small scale. As it’s only a sideline for me I use old 40gallon oil drums which means my investment is minimal and I don’t need a lot of wood to feed a kiln, instead I take advantage of the wood that comes my way. It’s an ideal way to make small amounts of charcoal or to start learning about charcoal making.
The big advantage for me of using oil drums (other than not costing me anything) is that it only takes a couple of hours from lighting the drum full of wood to being able to shut it down and let it cool so I can fit in a burn of 2 or 3 drums in the afternoon or evening and come back the next morning to collect the charcoal.
When the drum is first lit it produces a lot of white and brown smoke, mainly steam boiling off from the wood and mixed with the tars, resins and other volatile chemicals. The intent of the burn is to have enough air flowing through the bin to maintain a high temperature but not so much that too much of the wood is burnt too quickly which reduces the yield – though if you only want a bag of charcoal for your own bbq it doesn’t matter so much.
As the burn continues you will see the white smoke lessen and eventually cease as all of the water is driven off. Be careful if you lift the lid and peer inside at this point – you can lose your eyebrows. The reduced level of oxygen in the bin means that volatile chemicals released will not mix with enough oxygen to burn until they leave the bin – though if you are used to it you can arrange quite an impressive display with a ring of fire around the rim of the bin.
Once the volatile chemicals have finished being released the bin is ready to be shut down and the remaining wood will finish cooking in the heat of the bin. Shutting down involves sealing the bin with soil so that no air can enter or exit the bin – otherwise you will return to find no more than a pile or wood ash when you open the bin. It takes a few hours for the charcoal to cool sufficiently so that when you open the bin you don’t start an instant barbecue.
I should now show the finished charcoal, but somehow I seem to have taken a gratuitous photo of a Landrover the next morning. Strange that!
Making charcoal in an oil drum is not really economically viable in comparison with the big kilns, it’s a lot of work for a bag or two of charcoal but if you are generating a small amount of waste wood from a small amount of woodland then it might be a way to start making enough for your own needs and spend an enjoyable evening, whether it for the bbq or to use on your vegetable patch or to start making your own carbon sink.
Much of this wood would have been burned on site, chipped or left to rot away (not that leaving some wood to rot away is a bad thing and it is as always a balance) so making charcoal with it doesn’t affect the amount of carbon released into the atmosphere. If more trees are regrown in their place then it’s effectively zero carbon. As always with carbon issues it’s not quite that simple of course and the conversion of the wood does release other chemicals aside from carbon dioxide. The next stage is to convert my drums into ‘ovens’ or retorts as they are often known and burn the volatile chemicals to cook the wood, improving the yield and reducing the amount of woodfuel I have to prepare.