Your advices for building a gasifier

Hello all,

I am new to the forum and I am planning to build a gasifier mainly to power a 3kw gasoline generator, but I don’t have access to a wood chunker and uniform wood chunks, so my question is would it be possible to generate any usable wood gas from non-uniform and fairly big pieces of wood?


Welcome to the forum Mr. So what size engine is needed for a 3000 watt generator, about 6 to 8 horsepower? That sounds like the size wood chip gasifiers like to run and charcoal gasifiers. Usually the smaller gasifiers need smaller fuel sizes. If you have the time you can make any size wood you need with hand tools so you don’t really need a chunker.

Welcome on board Wali!
5. of January 2017

What would be the biggest and smallest bits of wood?
Uniformity is the general aim. General size goes hand in hand with the gasifier size.
In Australia, there was probably a Danish settler who managed to drive his “ute” (half pic-up) with firestove wood.
But that is for a ~30 – 40 times bigger motor!

If you can “baby-sit” the “plant” you may have a chance with stick-wood.

But describe more before Steve Unruh serves the solution?

Thanks guys, I will be using wood from tress I have on my property like mulberry(a very common tree over here), willow, pomogranate, and I could get oak tree woods, the size of wood will mostly depend on me what size I make them, the wood from small trees will be combination of sizes up to 1" diameter and 1" long.

I am thinking of using 200 liter barrel for the gasifier, if it produces more then I have bigger engines to run on.

I only came to know wood gas after my 5KW water turbine failed to produce any usable power. I don’t want to repeat same with wood gas.

Hi, Wali!
5. of Januari 2017

D = 1" X L = 1" sounds to be in the ball park.

You still did not mention if you can “baby-sit” it, or if you intend to leave it for longer times!

Look at Mr. PEPE’s systems, they work past 2 hours… on one silo batch.

A 200 liter silo can perform condensation pre-drying, and it can feed the hearth if it has a suitable funnel in between the silo-bottom and the hearth, with its preheating mantel, etc.

If the wood is heated in the center-region of the silo, and the sides are kept cool, the drying process gets good circucation.

A silo barrel of iron will rust fast by the accids in the wood, but a stainless gives a reasonable lifetime!

Another general thing: A gasifier is dimensioned for a certain production = the max demand of a certain motor under certain conditiones!
Not the other random way around!

Your turn…

Hi Wali
Start off with a charcoal setup for ease of build over a single weekend , the fuel size you mentioned sounds just about perfect to turn into charcoal , and will run a 3KW generator for at least 5 hours on a 200 litre barrel .

Check out Gary Gilmore’s video’s and also Koen Vanlooken video’s on Youtube

good luck Dave


Hi Max, Dave

Yes I will be able to frequently check it, but not continously stad by the gasifier.
My guess is that since the barrel will not serve as a pressure vessel so it would be ok to use a thing-walled stainless barrel.

Also another question I have is how much wood can produce equivalent to 1 liter of gasoline, I read online that 1.5 kg can make that amount but I would be happy if I can make equivalent of 1 liter with 2 - 2.5 kg of wood. But as Dave said if a barrel lasts for 5 hours then the yield is less than 1 liter / 2 kg.

I dont know for generators, but my car (109 hp) burns about 9l/100km of petrol or about 15-20kg/100km of wood so yes, about 2kg per 1l gasoline.

Makeing your fuel by hand isnt hard. All you need is a saw (chainsaw, bandsaw, buzzsaw…) and a hachet. I prepare all my woow this way. I saw logs to about 3 cm long pucks, and hit them with a hatchet. I can make enough wood to drive for 100km in about 15 min.

I am working on a research table, to compare fuels.

Not to be exact but as a general guideline.

To generate 1 Kwh Electric power with wood, best case scenario, you need 1,2 Kg wood
With gasoline: 0,36l
So comparing gasoline with wood: 1 liter gasoline is substituted by 3,3 Kg wood

Most cases you’l need more gasoline and subsequently equal more wood…

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Hi, Wali!
Dave talks of charcoal, not wood! / lighter and (energy)tighter!

Especially, if the lid is full-diameter (barrel-diameter), puffing does not risk the barrel! That gives other advantages too! Put the sealing in the lid-edge so it will be protected from fillings and other handlings!

Than you all for your input and clarification.

Today I saw an old electric water heater and thought it may be better to use one of those instead of the iron barrel since it is got insulation, any thoughts?

Hello Wali.
You said that you wanted to run a 3Kw gasoline generator. Do you understand that a 3KW gasoline generator won’t generate that much electrical output running on woodgas? I’d be conservative and derate the generator’s output (on gasoline) by 50% for woodgas. So, you would only expect about 1.5 KW from a 3Kw genset.

Pete Stanaitis

Hi, Wali!

In a stationary installation the weight is of less consequence; more so in a mobile application.
But stainless is better in both cases. It lasts longer.

For a short experiment rusting away iron goes well…

Insulation prevents drying by condensation on the inside wall!
Not usefull in any climat. No condesation – no way of taking out water of the wood. And that is necessary in most cases.

Eaven if you use outer condesation tubes, you have to remove the insulation to be able to install outer condensation tubes. Outer tubes have to be cleaned of tar to remain functional.

Generally: Do you have access to a machine workshop, or do you have to do everything “by hand”?

Pete, thanks for the info.
I knew wood gas has lower energy value but I never thought it will produce less power than gasoline, I just assumed it will consume more wood gas to produce same amount of Kw.

Max, I will have to do everything by hand, unless welding is envolved then I go to a near by welding shop.

Hi Wali ,
On my charcoal gasifier the best output I can get my inverter 3KW generator is around 1200 watts constant load , I can get it to output more but It then it tends to surge from 1500 watts upwards .
I have a 8 kva inverter generator that will do the heavier loads , but that will use a 100lbs size propane tank full of charcoal in around 4 or 5 hours dependant on load being drawn .
The only reason I mention a charcoal Gasifier to you rather than a wood Gasifier , is its speed of build and simple construction and simple cooling / filtering , and is a great proof of concept to show yourself and other local’s how easily it can all come together .


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I usually have 3-4 laying around. Good for lots of things. Probably used 8-10 just for experimental projects. Failure is a chance to learn

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Hi Dave,

Those 3kw inverter generators have the tendency to be a sheep in the clothing of a wolf…

How does it perform on gasoline, load wise, and then compare it with gasifier fuel… you’l be amazed ( how strong your gas actually is )

i second on your advice for starting with a charcoal set, less complicated to build/maintain…

Building a gasifier Is a lot of welding , Farming this out could get very expensive, I would suggest buying a welder and learning to weld before attempting to build a wood gasifier. Much less welding in a charcoal unit, a much simpler way to get started and work great for small engines. much to learn running one and so easy to get started fast.

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Hi Wali, Im hosting a DIY wood gasifier project on Youtube. This is series and work in progress, Ill be doing another installment here soon building the hearth. Plans are available on my site, you can just follow the links in the videos to the plans and you can follow along. I must note however, there is also a supplied BOM, but these parts are mostly supplied by a US supplier and they do not ship outside the US. You will need to source parts our make your own equivalents. The flanges used in this project are a standard duct flange; however, we can create DXF files to have them lazer / plasma cut for an alternative. We will address this on my site when we run into it.

This small gasifier is about the size you need for your 3 kW gen. It can also be tuned for wood pellets if that is desired. No prep work with pellets and run times will be longer with better flow characteristics. I will work on automation systems for this project as well that will render it as reliable as if the gen is running gasoline.

Here is my Youtube channel scroll down to the TOG Playlist.


Hi, Wali!

What did you get out of Mr. PEPE’s systems?
Is that style and properties matching some of your motors’ need?
Matching a motor’s needs is normal planning.
You stated that you have motors of different size and power…
Are you equipped with the workshop tools for
fabricating a “gasplant” for some of your motors?
Foreseeing the full picture…