Charcoal - good or bad?

[mikepepler]

As you may have seen, Gervais Sawyer has contributed an interesting article on charcoal: http://www.swog.org.uk/articles/small-woodland-owners-and-charcoal-by-gervais-sawyer/

I actually agree with much of what he says, in particular that:

- energy-wise, charcoal makes no sense at all. it's much better to just use the wood, rather than waste all that heat converting it to charcoal.

- pollution wise, a traditional charcoal kiln emits a lot of smoke!

However, that's not the end of the story. Other points to consider are:

- if people are using charcoal anyway, is it not better that it comes from a local source?

- the wood being converted to charcoal may not have any other use, especially if the extraction route is difficult, as charcoal is a lot lighter to carry out by hand than wood.

- if making charcoal and selling it provides money to pay for management of the wood, that could be a positive thing for biodiversity.

I wonder if what's needed is a cheap and simple design for a retort kiln, that lets you burn scrappy wood to convert the better wood to charcoal, and the gases driven off in the process are used to provide part of the heat, thereby reducing the pollution?

Anyone aware of such a design? We improvised something with a couple of metal drums (a design suggested by Gervais) but it only works on a very small scale. http://peplers.blogspot.com/2008/06/charcoal-kiln-test-and-stuff-thats.html

Mike

[Darren]

here is a retort kiln. http://64.176.180.203/charcoalretort.htm

[Solar Wood]

We do a little charcoal burn in a large drum which we use scrappy bits of wood in. If we get it right, which is not often, we use it as a easy lighter for outside fires. It is easier to transport also

[RichardKing]

I can see that there is advantage to the retort method in that you could heat the retort using brash or other "waste" wood.

Gasses from retort heated wood have other potential, including running engines. Apparently they can be fed directly into the air intake of a diesel engine & greatly reduce fuel use. But only has half the energy output. This was done widely during the second world war.

[Chris]

We got a charcoal kiln last year and have been making charcoal on a reasonable scale since. Yes, you get volatile materials in the smoke which is not pleasant.

The main advantage we find with charcoal burning is that we can use wood in it that is unsuitable for firewood and would otherwise be unuseable.

Environmentally, if people want to use charcoal for barbecues, forges, or soil conditioning, it is better to use charcoal produced in this country. It minimises fuel miles, creates rural employment, uses 'waste' wood from woodland management, and does not require lighter fuel to get it going. We also know that all woodland in this country is managed sustainably, unlike some of the foreign sources of charcoal.

Personally, if I want to cook outside, I usually use wood, but if others want to use charcoal, it is worth providing it from British woodland.

[Gervais Sawyer]

I am familiar with the drum kiln and it is a great idea. In practice it needs a bit of further engineering because drum steel is rather thin and cracks, corrodes and distorts quickly leading to gas leakage. If the cover plate were made up in thicker (stainless) steel, things would start to get better. An internal fan to circulate the hot air and gases would improve efficiency too. It would be great to engineer something better that could be used by a group of woodland owners. I would add to my article that leaving the wood only part carbonised would make the charcoal much easier to light and would give lots of smoke for flavour.

[Darren]

Glad you said that, Gervais. I had a thicker steel lid made for my oil drum. I have found that the best way to make sure the heat spreads is to fill the the drum half way then fill up with newspaper and kindling. Set on fire once roaring throw in the other half of the wood. I tried this last weekend and had only a few browns.

[Franakapan]

I know this is an old thread but I thought I'd comment on retorts.

The retorts that I have seen at CAT consist of two (or more) oil drums contained within a steel oil storage tank. The drums were raised from the ground using railway tracks if I remember correctly, one widthways at the front of the tank to support four more welded to the first which provides stable support for the drums. Each drum has an exhaust pipe welded to an opening that has been cut into the side of the drum that is closest to the fire at the bottom of the tank.

Here are a few of pictures if you fancy having a look. They're not the best unfortunately, and ignore the wood stacked at the bottom of the tank.

http://i31.photobucket.com/albums/c396/Franakapan/Retort/DSCF2613.jpg

http://i31.photobucket.com/albums/c396/Franakapan/Retort/DSCF2615.jpg

http://i31.photobucket.com/albums/c396/Franakapan/Retort/DSCF2617.jpg

http://i31.photobucket.com/albums/c396/Franakapan/Retort/DSCF2618.jpg

http://i31.photobucket.com/albums/c396/Franakapan/Retort/DSCF2620.jpg

Using a retort is the method I'd use because of the relatively high efficiency rate (bigger yield) compared to burning in a drum, and the harmful or polluting elements of the smoke are burnt off in the process. Using a retort is also pretty quick, about 2 hours I think.

[Darren]

I'm not sure if a retort kiln is that much more efficient. Looking at those picture you burning nearly as much wood to get charcoal. Does look like a good way to get rid of brash.

[Franakapan]

Yeah there is that but, as you say, using scrap/waste wood would be better then using wood that could be used for something else.