Charcoal and wood vinegar

Here we are making charcoal and wood vinegar. These are both very useful materials and easy to obtain.


Charcoal has a multitude of uses, for example it is an excellent cooking fuel since it produces very little smoke for the amount of heat that it emits (and since many Asian people cook over a fire indoors, indoor air pollution can be a big problem). It can be ground up and added to soap to provide a gritty quality that’s good for scrubbing. Some Thai religious groups make and sell fruits and flowers baked into charcoal that are decorative and are used to absorb smells, like in your refrigerator. (Pi Jo says you can put a rose into the charcoal oven and it will come out completely intact – so you have a charcoal briquette that looks like a rose bloom.) And bamboo charcoal from the Kanchanaburi region of Thailand is sold all over the world for activated carbon used in water purifiers.

Wood vinegar is a by-product of charcoal making that also has several uses. It is a mild and non-toxic wood preservative – insects don’t like it so you can apply it to construction wood and it will keep the termites away. Also since insects don’t like it, it’s good for pest control in the garden. It can be diluted and added to compost as an activator, and has mild antiseptic properties that make it good for applying to cuts to encourage healing.

The way to make charcoal (and thus wood vinegar) is to burn a lot of wood with little oxygen. In this way it doesn’t really burn; rather, it bakes as the water and volatile organic compounds are driven off. The water and organics are condensed from the smoke and collected in liquid form – this is concentrated wood vinegar, which is diluted typically 1:1000 for application to plants, lumber, etc.

The apparatus we are using for a charcoal oven is an old discarded 55-gallon metal drum. The drum is laid on its side and insulated with adobe bricks and sand. We packed the drum full of cut wood and built a fire at the entrance of the drum. Smoke and heat are drawn by the long, slanting bamboo chimney into the drum. The fire at the opening of the drum is stoked for 1 – 2 hours, until the smoke coming out of the chimney changes from a thick darker smoke into a wispy, white smoke. The entrance of the drum is then sealed up with adobe bricks and mud.


The smoke travels up the chimney and water containing uncombusted organic molecules condenses near the top – this is the wood vinegar, which is collected through a small notch near the base of the chimney. (The spoon helps the liquid to collect and drip into a bucket). This design with a bamboo chimney is the simplest, although more efficient collection can be achieved using a cold-water condenser around the chimney.

Burning one drum-full of wood yields 1 – 2 liters of wood vinegar.

Gradually over a few hours the smoke will become even lighter and wispier. At this point, wood vinegar collection is discontinued and the chimney is sealed up to allow the wood in the drum to finish turning into charcoal (an overnight process).

Rural Thai people have used wood vinegar for a long time, but Pi Jo says now Monsanto has moved in and begun to market a commercial, patented formula. It’s just like Monsanto to take some technique that people have been doing forever and patent it and sell it back to the people for a profit. Then people gradually forget how to do it and end up becoming dependent on Monsanto to supply them with something they used to be able to make for themselves.