[Gasification] Oil drum charcoal

[Ken Boak]

List,

Yesterday I spent a very enjoyable day in a 28 acre mixed woodland that belongs to a friend.  Six of us were helping out with some coppicing work.

We made charcoal in an old oil-barrel, and cooked "dough and sausage twists" over the campfire.   Charcoal making  and hot tasty food too  -  what more could a gasification enthusiast desire, as well as a day spent mucking about in the woods!

I know that many of the list members will be familiar with making charcoal, and have their own techniques, but the method described below appeared to be simple and low tech, and may be of interest to members.  

Oil Drum Charcoal.   Take a standard oil drum and remove the lid at one end. The lid is retained and it should be a loose fit in the drum, so that it can be placed on top of the wood charge and resulting charcoal.   Punch 6 or 8, inch diameter air-holes into the bottom.    Using a spade,  dig a shallow pit (4" deep, 18" diameter) below the drum  and open up some air channels that allow air to the underside of the drum. Sit the drum over the ash-pit.

Prepare about 150lbs of timber.  We used 5" diameter alder logs, cut into 5" rounds and then split into  5" x 1" x 1"  (very approx) chunks.

Light a fire of twigs in the bottom of the drum  and keep fuelling until the wood is blazing across the whole bottom of the drum. You will see swirls of burning woodgas emitted from the wood, when the fire is burning correctly.

Add the prepared timber on top of the burning fire and replace the lid onto the drum, weighted down with a couple of rocks or logs.

The barrel will steam and smoke profusely for about 2 hours.  If necessary reduce the air supply to the bottom of the drum by blocking one or more of  the air channels with mud or sand.   The smoke will have a yellow tinge to it, which is obviously due to the tars and other volatiles being burned off.

Very suddenly the smoke will reduce and have more of a blue colour to it.  This is the signal that almost all of the volatiles have been driven off.  Tap the barrel with a spade and the yellow smoke may return briefly as the charcoal settles.  The lid will have descended in the drum to about one third of the original level of the  wood.

Almost without warning,  orange/blue flames will emerge from around the lid.  This is the mixture of hydrogen and carbon-monoxide burning from the charcoal - now effectively a charcoal gasifier.  Block all the air-vents with dirt.  Seal the gap around the lid with more dirt, so no smoke gets out.   

The charcoal will now extinguish due to lack of oxygen, and can be removed from the barrel , the following day having allowed to cool for at least 12 to 24 hours.  Opening the lid too soon will cause the hot charcoal to re-ignite.

This method produces about a 25% to 30% yield.  Too much air during the early stages will result in more of the charcoal being consumed and will lower the yield.

Dough and sausage twists   - simple dough made from self-raising flour water and salt (like a pizza dough).   One variation is to add finely chopped, young nettle leaves into the dough - just like a herb-bread, comes with my personal recommendation!    Thread sausage onto end of green-shoot stick, having removed the bark.  Grill sausage until brown, over hot embers.   Take a small ball of dough and form into a long sausage, wrap the dough in a spiral around the cooked sausage and further cook the twist over embers until golden brown.   Sweet versions can be served with jam or marmalade.



regards



Ken