Engine grade gas from FEMA?


Is it possible to get engine grade gas with high tar fuel from a stratified, downdraft gasifier?

Can i filter out the tar or crack it in some kind of afterburner?


Yes it’s possible. One would have to add preheated air to added jets and seal off the top of the hopper.
From my understanding there is no way to filter out tar. It’s better to burn the tar and convert it into fuel. otherwise it’s wasted energy.
That question brought many of us to this site.


But then we have a imbert gasifier and all the benefits of the stratified gasifier is lost.

I quess the FEMA gasifier is worthless to use with fuel with tar then.

Disappointing as it’s a good design (IMO) otherwise.

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Not true JimH. Stratisfied is a failure by all measures.
The CPC; the H.S. Mukunda IISc gasifiers and Wayne Kieths all did start out as stratified, and/orFEMA’s.

Only after adding zone controlling air jets. Then hopper air-in and emissions-out tops did they ever become usable.
VERY much NOT Imberts.
An Imbert “type” is an internal velocity dependent design. Understand the velocities. Adhere to the needed internal velocities.
Sttratisfied was/is a lower velocity; LONG internal gasses in residence duration design. Needs long time duration flows pathways.
Then the Drizzler stratified differences.
Then there is the rarer super internal Temperatures designs. None yet making it out of Labs/deigns trials yet to the DIY level. They need super materials to endure their super internal temperatures. Very, very low internal velocities.

Now fess up. Methanol? To be a feedstock? For seed-oil to bio-diesel making?
Why bother. Study the Isbett engine system to use seed-oils directly. They convert many standard diesel engines.
Make good engine grade woodgas and use it directly in proper IC engines applications.

Either approach: make an IC piston engine run with power for real working purposes.
Never lose sight of the real-use purposes.
Steve unruh


Ok, thanks for the info and sorry if I confused the systems, I’m quite new on this.

I do not fully get the difference between the Imbert type and the stratified low velocity design, could you post some drawings/visuals to help me?

The goal of my project is to independently manufacture IC grade fuel.
I can’t make or easily get inexpensive seed-oil.
And as it seems now wood-gas is probably my best bet.


Fema uses big volume of reaction zone with low gas speeds, the reaction zone is a cylinder but it is not in a fixed place; the flame can wonder anywhere it likes, usualy towards air so up. Imberts use small wery turbolent high speed reaction zone usualy diabolo shaped. Good for cracking tar but foces drag on the system.
A WK gasifier is a kind of a cross between the two.


Ok, what advantage does the WK gasifier have over the Imbert?

Do you know of any simple/fast build gasifier for wood just so I can get started experimenting?


i ad this to my favorite listing…


Hi Jim_H, welcome to DOW…

It is always good to read in and compare before you start building and i will ad my 2 cents to that…

If you are “dissapointed” with the quality from the Ben Peterson book/build and not quite well knowledgable in different gasifier type’s but you still want to start building your own gasifier; then i suggest you start with the Simple fire from Gary Gilmore and work your way up from that.

Where as i consider a FEMA as a smoking charcoaler unit ( the gas is smelly and tarry ) and where as a Simple fire is a charcoal gasifier that works amazingly well…

Then picture yourself a Mix from a good charcoal burner at the bottom and an excellent fema on top and you get yourself a WK.
(sorry for the poor comparing Wayne, the real WK is much better then my words can describe it )

Jim, the question is: what do you want to achieve ?
A short learning process ? nope, not gonna happen…
Its going to be a learning by doing process where as to learn and understand that your fuel and your gasifier are going to depend on YOUR skills… and then some…
The satisfaction when your engine run’s on woodgas… the lemon craving smile…
priceless… and rewarding…

Think about what YOU want, people on DOW are going to help you with their knowhow…

I have the WK book, its worth it…
I have all documents from Ben Peterson, worth it…
I have all books you can imagine about gasifiers… its worth it…

And still, i learn every day and still i build my own designs and learn from my mistakes…
The most i learn however , is from the encouragements from the members here on DOW
again: Priceless and worth it any given moment…


@Jim_H, to help you get started quickly, I would recommend taking a look at the Simple Fire charcoal gasifier, by Gary Gilmore – who also is a member on this site. It is appropriate for many small engines, like generators, that will help you experiment and learn. A build document is here http://www.driveonwood.com/static/media/uploads/pdf/simple_fire.pdf. After finding success with that design, moving to more complex systems will be easier.

By starting with charcoal, you’ll sidestep some of the major hurdles merely by creating and processing the charcoal separately. There is good information regarding charcoal gasifiers throughout this site.


Ben Peterson book is good, but I expeted more of a general woodgas and technical book.
His book is just a construction/plans of his design, nothing wrong with it but not what I expected.

And what i want to achieve is to be able to make fuel for IC engines on a reasonable budget.

Thanks for the help it is appreciated!

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I second what has been said, but why can’t you get Wayne’s book, you were able to get Ben’s? I have both, if you follow either you will have a working gasifier. And we will help you no matter what you build. If you go to the library on this site, should have all the info you need.


I would buy it but it’s not sold to any EU countries.
“orders from these countries will be refunded”

I can maybe buy it secondhand if anyone have a extra copy?

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If Chris sees this maybe he can let me know how I can help get you a copy, and premium side of site.

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Unfortnately Jim is right, we can’t sell to the EU anymore, it’s due to some VAT tax laws passed in 2015.

The way around it, is to have someone state-side buy it for you as a gift. I’ll mail a book anywhere you like, as long as it was purchased outside the EU.


Ok thanks for the clarification.

If anyone have one or want to buy one for me then I will pay you for it and shipping by paypal, send me a PM of intressted.

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Hi JimH.,
To immediatly read about gasifaction technical details open up the Library button at top of page.
Read/study these in this suggested order:
Driving On Wood: The Lost Art of Driving Without Gasoline (good overview comparing the differences between “constricted hearth styles” when using raw wood; wood charcoal; fossil coal; peat sod)

Auburn University Efficiency Tests (show WayneK with his system load tested on different fuel mixes)

World Bank Tech Paper #296 (maths and systems types comparisons for community sized systems with much much costs of operations details)

FOA72 ( similar to WBTP#296 but with a different outlook approach more emphasizing fuels stock indigenous)

Read, study one. Real all. Read more DOW Library listings until you are grounded to your willingness to make up a real system to actually start learning the real-in-usefactors. Theses are what Ben’s and WayneK’s and VesaM’s books do superior to these free/and no-cost information sources.

From your Ben’s Book commnet I’ll assume you have the first verson copy with the welderman pictured on the cover?
The second version release with the charcoal gasifier converted Mustang car cover pictures has an added in gasification history section and chemical/enrgy maths.
No need to re-purchase if you have the Just-Build-It first addition.
Read the above DOW supported papers above and you will get plenty of background history and more relevancy maths than you can handle.
Steve Unruh


Has someone run a FEMA gasifier on charcoal?
What would the difference be between a running a updraft/simplefire gasifier vs a FEMA type on coal?


Hi Jim, I made a FEMA gasifier and could not get it to produce good gas. That was my first build. I then went to charcoal gasification and had success. That was over ten years ago. With the knowledge gained over that time, let me tell you why a FEMA gasifier will not work on charcoal. This unit is open topped. Oxygen comes in from the top and burns the charcoal. This creates CO2 which cannot burn. In order to convert CO2 to Carbon monoxide, you have to reduce the CO2 by passing it through charcoal (carbon) OK, so fill the FEMA with charcoal. light it at the top and start pulling a vacumn on the gasifier. The charcoal will burn really hot and unevenly. In some areas, rat holes will occur and when the heat from that burning charcoal hits the grate, you will start pulling CO2 into your gas stream. Lose power and shut down. You cannot simply fill the gasifier back with charcoal because now you have hot coals sitting on the grate. As the vacumn pulls oxygen down, this hot charcoal will consume it and created CO2. There will be no chance to reduce this CO2 because there is no carbon below the grate. You really seem fixed on a FEMA. They are known as tar makers and will gum up your engine. Tar is hard to filter out of a gas stream. If you are looking at running small engines, may I suggest a charcoal gasifier. You can build one of these in a day or two and have something that is known to work. Then the learning really starts!
Good luck, Gary in PA


That is where I started, it did me a lot of good.