Power in the Apocalypse (How to Build a Wood-Gasifier)




Posted in OutsideSurvival

Introduction: Power in the Apocalypse (How to Build a Wood-Gasifier)

In this Instructable I will be showing you the steps I used to build my Wood/Biomass Gasifier. It was really a fun project and I would encourage anyone serious about preparedness to build one. Now in case you don't know what a Gasifier is (and don't feel bad if you don't as very few people do lol), they are quite simple, let me explain. Essentially all gasification is, is a form of incomplete combustion, heat from the burning solid fuel creates gases which are unable to burn completely because of the insufficient amounts of oxygen from the available supply of air, it then filters those gasses(which is by weight: 20% hydrogen, 20% carbon monoxide, 50 to 60% nitrogen, and a little bit of methane) And you can really use any kind of Biomass(organic material) that will burn. You can even use things like paper, coal, peat, and lignite. You can then use that filtered gas to run any thing from a generator to a car. So now that you have a basic understanding of what gasification is, lets get down to the build!!!

Step 1: Basic Information.

Don't worry, for this project you wont need any fancy tools or equipment. Just a welder, an angle grinder, an oxy-acetylene torch, and a drill, along with the knowledge of how to use them. Most of the materials used were found in friends' scrap piles so for me cost wasn't a big issue. And you can (in theory) make this to whatever size you need, so keep that in mind when gathering materials. But don't forget, whatever fuel you use has to be able to feed through the fire tube easily. The fire tube acts as a sort of dryer and hopper. The fire tube feeds the fuel into the shaker grate, which is where the fuel combusts. The gasses are then sucked out of the gasifier unit and pulled through the filter units. And after doing some research I chose to go with a cyclone filter and a media filter. Ideally I should have added a condenser after the cyclone filter to to get as much moisture out of the gas as possible. But oh well lol. But I would recommend adding one if you plan on building one of these.

The size of the fire tube governs the size of the engine you can run. Here is a chart showing the fire tube sizes and the respective horsepower. The larger the fire tube, the more fuel it will burn, the more gas it will produce.

Inside diameter (inches) Minimum length (inches) Engine power (hp)

2 16 5

4 16 15

6 16 30

7 18 40

8 20 50

9 22 65

10 24 80

11 26 100

12 28 120

13 30 140

14 32 160

Step 2: Building the Gasifier Unit.

The first thing you need (as with anything) is a solid foundation. Because I was dealing with scrap metal, the frame is made from 1"x2" tubing and angle iron. I used a piece of 4.75" exhaust pipe for the fire tube, and the shaker grate is made from a brake rotor with the bottom cut out, and .25" rebar welded in place. The grate is suspended from chains welded to the fire tube supports. I left about 1" from the bottom of the fire tube to the bottom of the grate. I used 1.25" pipe for the ignition tube, which is that pipe leading into the side of the fire tube.

Everything on a gasifier needs to be air tight, which presented me with one of the main problems. How to get the shaker grate assembly through the side of the barrel and make it rotate while keeping it air tight, and it had to be heat resistant. My solution, was to run the handle rod through a piece of .75" pipe capped off on both ends, and then pack that with fine steel wool. And that seems to have done the job quite well. The purpose of the shaking action is to sift the ash and dead charcoal through the grate to make space for more fuel.

The ash clean out port is made from a piece of 6" pipe with a cover made from a .25" steel plate. I welded some lengths of 3/8" all thread to the sides of the 6" pipe and drilled corresponding holes in ears I left on the cover plate. And I sealed it with wood stove gasket maker and cemented it in place with stove cement. Then you just bolt and unbolt the cover plate as needed.

The pipe you see going into the side of the fire tube is the ignition tube. Its capped off with 1.25" coupler with a washer welded on to seal it off, and I decided to add a handle to make it easier to use.

Step 3: The Cyclone Filter.

Okay good, the hard part is over with lol. The filter units are the easiest part of the whole build. The first of the two filters is a cyclone filter which acts partly as a filter (obviously) and partly as a condenser. The water vapor, creosote, tar, and some particulates are collected on the inner sides of the filter as the cyclone of gas spins. These then run down into the collection jar. I chose to use a 5 gallon propane tank as the filter housing. All I had to do was run a pipe from the gasifier unit in through the side of the tank at an angle, to initiate a cyclone. Then run another pipe through the top of the tank which sits about 2" from the bottom. I flipped the tank over and used the original top of the tank as the bottom of the filter. The threads from the valve hole accept a .75" pipe nipple, which is attached to a flange and bolted to a jar lid. I added a rubber gasket between the flange and the lid to make a nice air tight seal. Now just screw on the jar and tadaa, a catchment basin lol. And that's really all there is to the cyclone filter.

Now. . . onto the next step.

Step 4: The Media Filter.

The media filter is made from a metal strong box tipped onto its side. The pipe leading through the top of the box comes straight from the top of the cyclone filter. And then you would just fill the box with an appropriate filter media such as wood shavings, cloth, or even as a more expensive but safer alternative, steel wool.

Next comes the plumbing. You can see the logic behind the pipe assortment there, but i'll explain anyway. So first there is a tee which splits between the air pump and the outlet to the engine. The valves are for switching between the two as well as acting as a choke for the air pump. And the pump leads up to the flare. The purpose of the flare is to check gas quality before routing it to the engine.

I figured that in the apocalypse the chance of having a working wall outlet is pretty slim lol. So I chose to use an air pump that could run off of a 12v car battery. Nothing special, just an air mattress pump that connects to a vehicles power point.

Step 5: Tips on Using Your New Gasifier.

If you decided to reproduce this project, here are some tips and tricks to get you started. Firstly, the fuel you use must be bone dry, and I mean REALLY dry. Store bought wood pellets seam to do the trick nicely.

So you built a gasifier and want to try it out... Now what? First fill the fire tube with your fuel of choice, then simply turn the pump on(with lots of choke at first), then uncap the ignition tube, insert a source of ignition, let the fire catch, recap the ignition tube, and as the fire progresses let off the choke a little bit at a time. After it has been running for awhile hold a flame to the end of the flare and, with any luck, the gas will ignite. Between the gasifier and the engine, the gas will need to be pre-carbureted, which is as simple as adding a tee in the hose to bleed off excess gas. Then you just run the line into the engine carburetor and that's it! Unfortunately, I haven't tested this on a full size vehicle yet, as I am only 15, and my mom wont let me get anywhere near her car lol.

Step 6: In Closing.

Lastly I added a handle and some caster wheels, as well as sealing everything with wood stove sealer and giving it a coat or two of high heat paint. This was a fun and very educational project, I would really encourage anyone who is interested in being prepared, or just looking for a fun project, to build a gasifier. If you enjoyed this instructable, let me know in the comment section below. If you have any questions please let me know and I will do my best to answer them.

This is not something you should use indoors. As it does produce flammable and toxic gasses.


As the reader, you assume all risks of reproduction of this project. I am in no way responsible for any damages or injuries to anyone or anything during the making or using of this project.

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    Please be positive and constructive.




    Well, thanks! But wait until you see my NEXT project...

    Grate job young man . Vary clear and understandable.

    You say your're 15 ? I can't remember that far back with out blacking out.

    My first attempt at gassification was a flop. Too many leaks.

    The second one works I use it to heat a hot tub.

    The shaker grate you came up with , Works Awesome Thanks .

    I'm a retired Millwright and I had issues with this part.

    1 reply

    Thank you! I appreciate the kind words, and I'm glad you could take something useful away from this Instructable.

    You did a great job on this project.

    I am planning on making A gasifier and was taking some notes.

    Was wondering, I know that the one handle on the gasifier is the shacker but what is the other one for.

    Also could you post a drawing or something of all the components that go into the actual gasifier unit because I am having troubles understanding the configuration of it.


    1 reply

    Hey there! Thanks for the comment. The other handle just makes it easier to take off the ignition port cap. As to your second question, I believe I showed everything on the inside. If you're still having trouble, let me know!

    very nice build, I've read there is a way to convert Syngas I to diesel, but I'm not sure how that exactly works.

    4 replies

    Yeah, I am currently working on a machine to turn coal into diesel. It's essentially the same process, only using indirect heating via a burner. The gasses produced are then condensed and ran thru a fuel scrubber.

    Thank you so much for the comment!

    do you know the process for converting syngas to diesel? could you point me at something to learn? I've been looking at a way to use plasma to turn material into syngas too.

    Are you on FB or IG? I'd love to follow you!

    1 reply

    Unfortunately, I don't have any social media accounts. However I do have a Youtube channel. I only have one video right now, but I have plans for many more! I'll post a link soon.

    15??? Dude, that's awesome! This article is the best I've seen on Gasification! Keep it up buddy!

    1 reply

    Haha, thank you so much!! I'm really glad you enjoyed it. I will :D.

    I've heard of gassifiers. They were popular in World War Two in Germany.

    4 replies

    Yes when you look at Google images of gassifiers the first couple rows are all WW2 German in origin.

    Some are still/again in use esp. in rural areas in Russia and Scandinavia for cars. But here in Germany you can actually buy those for heating your house. The following link is in German and I'm not affiliated with them, but bottom right you find a schematic of what the OP has build on its own. These gasifiers come at a price of ca. 5k € (or $). http://www.energieheld.de/heizung/holzheizung/holzvergaser

    That is correct. They were popular all over Europe at the time, due to the fuel shortages. I was debating whether or not to add a little history, but the instrutable was already quite long.