Wonderful Wood Gas

For the most part, the Internet is full of... well, there's no other way to say it... Crap!

Yet, every now and then, you happen across a real gem of a concept. Something that really blows your mind. It's even better when you come across something that has real world application.

In this case, that something was the knowledge on how to make and use a wood gas stove. This simple device has the potential to revolutionize the way we think about making and using fire. The strange thing is that these things have apparently been in use for the better part of a century.

Now, I could spend the rest of this page explaining how to make one, how they work, what the scientific principles behind them are, and all that jazz. But that's already done. You could know everything I know about these devices with a little google search on the subject.

Seriously, there is nothing I can say here, about the construction of these things, that has not been said already.

So what's the point then?

Well, I made one out of an old Milo tin, and a 340ml Soft drink can. It took me just under an hour to construct. There was no welding or gluing of any kind. Everything you see here was done with a hammer, a screw driver, a carpet-knife and two screws.
And here it is:

So this post is all about experimenting with it.

The whole point behind these things, is that you end up cooking a meal with the volume of wood you would normally use to kindle a fire with. In the end, you should not use more than two hands full of wood chips, to make 3 to 4 cups of coffee.

My first attempt didn't go very well, I was using wood that has been outside for the past year, and the last month of rain has not helped my situation with the first test. Here you see the total amount of wood I was using for my first attempt.

I have to mention again, this wood was very, very wet.

In order to help get things going, I had some news paper and paraffin available.

My kettle was ready to do it's thing. I filled it with exactly 1 liter of tap water, the minimum needed to make 4 cups of coffee.

And here I prepared the area for the burning.

I decided to try and get things going with just news paper. This seemed to work at first.

This was at 17:31 this afternoon. I quickly added some wood, after seeing the fire was stable.

The fire did get going, but I had to help it along with some paraffin, in order to get the heat high enough, for the wood to gasify.

Ever hopeful, I put the kettle on.

Here you can see, that gasification is actually happening.

What you can't see, is the amount of water building up at the bottom of the kettle. The wood was so wet, that all the moisture condensed on the kettle. Effectively nullifying all the heat that was being generated.

And this is the point at which I called the first experiment a failure.

The thing about wood gas stoves, is that you instantly know something is wrong when you see smoke. The whole principle behind them is that they don't burn the fuel, they burn the gas being emitted by the fuel, due to the heat of the stove. Smoke means you are burning fuel, and the stove isn't working properly.
With these stoves, smoking should only happen when you are starting the fire. Once the fuel starts gasifying, the smoking stops.

Never mind that though, there is always the next attempt.

This time I decided to scrounge in the garage for some scrap wood. My main criteria being that the fuel must be dry. I found some strips of hard board and 4 little blocks of wood.

I broke the hard board into smaller peaces.

And split the 4 blocks of wood into 8 peaces each. Giving me 32 smaller peaces to work with.

Giving me this fuel for the second attempt:

At 18:36 I lit the stove again, and filled it with all the hard board I had.

18:37 Gasification! Woot!

This time, full of confidence, I put the kettle on again. Take note that I dumped the water from the previous attempt, so as not to contaminate this experiment's results with water that was already partially warm.
I filled the kettle again, with exactly 1 liter of tap water.
This was at 18:40.

At 18:41, bubbles were already forming on the bottom of the kettle.

I added 8 of my 32 peaces of wood, at 18:44. The water was getting close to boiling

I got so excited I ran inside to prep the makings for a cup of coffee. This was at 18:46.

At 18:47, I added another 8 peaces of wood. The bubbles in the kettle were getting bigger.

Between 18:50 and 18:55 I added the remainder of my 16 peaces of wood. Here you can see it at work.

At 18:57 I checked the water for boiling, things were looking good!

At 19:00 The water was boiling.

So I did what any normal human would do:

This wasn't the end though. The stove was still going, so I decided to see how long it would continue to boil the rest of the water.

The water stopped boiling at 19:13, so I took the water off and let the stove complete the burn. After scratching in the stove with a long twig, I was amazed to note that there was hardly any ash. Not even enough to get a decent tea spoon full of ash.

So there we have it. These little devices pack a rater big punch. I can proudly say I've never used scrap and rubbish in a more productive way. Everything used in this experiment, would normally have gone to the dumps somewhere. I've also never used less wood to do so much.

A couple of lessons I learned were:

1. In order to make this work with wet wood, your stove would have to be considerably bigger, you will use more fuel and although the fuel will gasify, it will be inefficient.

2. Making a bigger stove would allow for more time between adding fuel.

3. For this particular stove, I'll have to figure out a better fuel feeding mechanism.

My next objective though, would be to get this knowledge out into the rural areas of South Africa. I'm damn sure there are people there who could make better stoves than this, and use them far more productively than I ever could.