Questions regarding wood gas production

[sortanormalish]

Does anyone have any information on woodgas? In particular, how much wood gas is formed from a set amount of wood?

I have access to a large, free(ish), and steady amount of wood, and want to put that wood to use sometime other than the winter. I pondered a steam engine, but effiecency issues prevented that idea from taking off, as well as my limited plumbing skill. Naturally, wood gas is the next choice.

Any answers will be most appreciated.

[The Riff-Raff Element]

Distillation of wood in closed retorts is pretty old technology, but also pretty straight forward. I don't know what you'll find on the www, but the book I have on the subject was printed in 1917...

Pine and similar yeild more gas than hard woods, such as oak or beech. As a rough guide a cubic metre of dry pinewood will yield about 100kg of gas (which is mostly carbon monoxide and is toxic) plus about 120kg of charcoal (retort charcoal is spontaneously combustable so need careful handling), 25 kg of wood tar (useful stuff, but again needs care) and maybe as much as 160kg of "wood vinegar." Wood vinegar is for the most part a mixture of acetic acid (ethanoic acid) and methanol...which is poisonous.

Are you sure you want to get involved in this gig?

One thing you could consider is burning the wood for charcoal. This is, of course, a fine cooking fuel and could be used in outdoor stoves during the spring - autumn period.

Wood gasification via pyrolysis is more complex technology, though you might find more about that on the web as it is being looked at as a serious use of biomass for powergen. In principle, wood gas from pyrolysis could be convereted via some well-established chemisty into motor fuels.

EDIT: You might find this site interesting - http://www.woodgas.com/

[dave45]

I have one of those little stoves from www.woodgas.com - they work really well once you get them lit.

(much better than one of these ! http://www.eydonkettle.com/stormkettle.html)

the battery on a wire is a bit naff though and will doubtless break pretty soon.

[sortanormalish]

Thanks for the feed back. The website seems very helpful. Wood gas from pyrolysis was more of the avenue I was considering, though now you mention it, wood alcohol does seem promising except for the containment issues.

[JayBee]

sortanormalish,

What do you want to do with your woodgas, heat, cook or drive a car with it?

There are many kinds of woodgas producers and generating woodgas is never an exact science.

You will, no doubt, have to build something to your exact requirements.

I set up a blog gathering together all the most useful information about woodgas at http://wood-gas.blogspot.com/

[sortanormalish]

Thanks JayBee

The family owned sawmill produces tons, literally, of wood waste. We thought we should figure out a way to harness the waste other than winter heating, which doesn't crap the top off all of it even with four different houses. We were thinking along the lines of water heating and cooking, as well as a fuel for some of the equipment.

So you see we need more than one system.

[JayBee]

We were thinking along the lines of water heating and cooking, as well as a fuel for some of the equipment.

So you see we need more than one system.

Well, if you are going to run a stationary engine to drive a generator then the cooling systems for cooling the wood gas and cooling the engine can be used to heat water. For an engine, you need clean gas from a downdraught gasifier. Have a look at the GEK http://www.gekgasifier.com/, which can be built from plans, kit or pre-assembled.

Cooking with wood gas is not easy. Most people just build MIDGE stoves for camping-style cooking. However, I have seen a Chinese gas cooker and hob that uses wood gas as fuel. I shall track that down from somewhere and put it on the site.

To date, I have cooked with a MIDGE wood gas stove and am halfway though a downdraught gasifier. I have emigrated to Spain and when settled I will attempt to finish my projects.

[sortanormalish]

To run a peice of equipment, say, a small tractor, would it be more practical to run the engine directly off of the generator or does there need to be some sort of holding phase, such as a couple of propane bottles?

[JayBee]

Wood gas is not storable so you use it straight away.

Part of the art of wood gas generation is sizing your producer to the engine.

The suction from the pistons will draw the gas from the hearth of the producer.

To get things started you will use a blower. When gas is being produced you will then start your engine. The starting motor will turn the engine over and the vacuum from the pistons will draw the gas through.

Your tractor would have to be gasoline powered rather than diesel or TVO. Wood gas is for a gasoline powered vehicles only. I have heard some talk of introducing a little wood gas whilst running a diesel engine on bio-diesel but that just sounds like too much hard work.

PS - I was going to suggest looking at a set of videos but they appear to have been removed from YouTube. I will see if they are elsewhere.

[The Riff-Raff Element]

Wood gas is not storable so you use it straight away.

Why can"t it be stored, Jaybee?

[JayBee]

Wood gas is not storable so you use it straight away.

Why can"t it be stored, Jaybee?

It's not the cleanest of gases, no matter how much you try and clean it.

It will come out of the hearth at a few hundred degrees, along with tar and soot.

It is not just the one gas, there are many alkanes & alkenes, there is hydrogen too, which will embrittle metal containers.

The beauty of a wood gas generator is that it produces at the rate you take it. Drive fast and the producer will run more quickly. Slow down and so does the producer. Stop and the producer will smoulder.

The bag on top of Corporal Jones's meat van (and other WW2 private vehicles in reality) was Town Gas, which was much more professionally produced by coke works and stored in the gasometers we used to see in every town, though some are still used for natural gas today.

It's better to just use wood gas than cool it right down and contain such a dangerous mixture.

[The Riff-Raff Element]

Thanks. All the experince I've had, hands-on as it were, with pyrolysis gas has been on industrial plant where cleaning-up the gas stream is part of the process. Soot and tar I suppose could be removed easily enough on the small scale (though what you'd do with them is another matter) but the unsaturates and hydrogen are another kettle of fish.

[sortanormalish]

Thanks both, off to do some research and hunt parts.