"What to expect from a wood gas system"

Section 1.4 of the FOA 72 publication downloadable from the DOW library

Just a few paragraphs. Short. Direct. And so very true.
True as written and published in 1986. Re-proofed, again, and again, three decades later.
tree-farmer Steve unruh


Try this link.

or this one…


For those with slow internet:

1.4 What to expect from a wood gasifier system

Operation of modern spark ignition or compression ignition stationary engines with gasoline
or diesel fuel is generally characterized by high reliability and minor efforts from the operator.
Under normal circumstances the operator’s role is limited to refuelling and maintenance.
There is little need for action and virtually no risk of getting dirty. Start and operation can in
fact be made fully automatic.

Anybody expecting something similar for wood gas operation of engines will be disappointed.

Preparation of the system for starting can require half an hour or more.
The fuel is bulky and difficult to handle.
Frequent feeding of fuel is often required and this limits the time the engine can run unattended.
Taking care of residues such as ashes, soot and tarry condensates is time-consuming and dirty.

It is a common mistake to assume that any type of biomass which fits into the opening of the
refuelling lid can be used as fuel.
Many of the operational difficulties which face inexperienced users of gasifiers are caused by the use of unsuitable fuels.

In order to avoid bridging in the fuel bunker, reduced power output because of large pressure losses, or “weak” gas, slag cakes, tar in the engine and damage to the gasifier caused by overheating, it is necessary for most designs that the fuel properties are kept within fairly narrow ranges.

This is not necessarily a more serious limitation than the need to use gasoline of super grade for high compression spark ignition engines rather than regular gasoline or diesel fuel.
But in the case of gasifier operation, more of the responsibility for quality control of the fuel rests with the operator.
The need for strict fuel specifications is well documented in the experiences reported from the Second World War (43).

It is unfortunate that some commercial companies, with little practical experience, but trying to profit from the renewed
interest in gasification, have advertised the possibility of using almost any kind of biomass even in gasifiers which will work well only with fuels meeting fairly strict standards.

This has in some cases created unrealistic expectations and has led to disappointments with the technology.

Operation of wood gas engines can also be dangerous if the operator violates the safety rules or neglects the maintenance of the system.

Poisoning accidents, explosions and fires have been caused by unsafe designs or careless handling of the equipment.

It may be assumed that modern systems are designed according to the best safety standards, but it is still necessary to handle the equipment in a responsible manner.

Finally, it must be realised that the current technology is generally based on the designs of the mid-1940’s.
Only a few persons have retained detailed practical knowledge of design, material selection and operation and maintenance procedures.
Many of the currently active manufacturers have no access to the experience of such persons and base their designs on
information available in the literature, and on recent and comparatively limited experience.

There has been some improvement of the technology, for instance of filter designs based on new materials, but the practical operating experience with these improved systems is limited.

A consequence of this is that equipment failures caused by design mistakes, choice of the wrong materials, or incomplete instructions to the user on operation and maintenance, must be expected in the first period of reintroduction of wood gasifiers.

The reports on operational difficulties presented in this publication and elsewhere must be evaluated with this in mind.
It can safely be assumed that second generation systems will show improved performance.

Those interested in the technology must accept that it demands hard work and tolerance of soiled hands by a responsible operator, and that it is not yet perfect.

But as will be shown, it is both serviceable and economic in many applications in spite of its inconveniences.


Well, my 2 cents…

The mentioned book is 32 years old yes, but still very actual…
Dough, new technology combined with this old know how is ’ IMHO" a very suitable solution…

Can anybody point me out another source of fuel that does clean the air prior to be used as energy source ?

Wood gasification can be used to substitute any fossil fuel in use at this very moment, without the “side effects”
The first conversions with catalysators were performed already 116 years ago…


09 15 -18

Agreed about the improvements in design and materials, members of this group stand as arguably the world’s leading example of successful daily operation and improvement. And who knows how much better it will get.

But to the central point, I believe we can replace a small amount of fossil fuels with syngas. However, the evidence would indicate we are at least 10 or 20 times beyond sustainable biomass to be able to continue conducting our global culture as now.

Solar should be able to supply significant electrical power now, but the gap is huge.

If the goal is sustainability, or avoiding catastrophic ecosystem damage and mass extinctions, or avoiding cultural failure post FF peak, or the rising disaster of climate change, we first will need to get a grip on our gigantic over use of energy generally.

If we can pare down our needs, and aim for efficiency, we might have a future.

My 2 cents…


Thanks for the downloadable links MikeR. I was trying to be too clever and just have the one section direct download.

Thanks very much for the full 1.4 section print up KoenV.L.

GarryT, I do not disagree as long as the “energy-use” reduction efforts are began as individual and maybe expanded out to local, WITH broad local buy-in approval.
Once you step up to regional “solutions”. National solutions. Global solutions. Then . . . as Marxist Communism and the mid-era’s Roman Catholic Church discovered there will be intense push back resistance to the “we know best for you all” top-down forced implemented NOT solutions.

Woodgas. Woodgas is an ideal solution for any individual willing to work it.
Woodgas. Woodgas can be a very good solution for a co-operative village. A Religious school. And same scale of voluntary social endeavors.
As history shows again, and again, wood-for-power-for-all is actually a terrible Regional/National/Global solution. “Needs” will always out strip re-growth resource replenishment. This War. That grand Cathedral. A bigger University, Opera House, sports stadium.
The woodcutter and charcoal maker of old times were pushed-down as far lower class’es. Just one step above grave-diggers and common streets shit-picker-uppers.
Now the charcoal user like the metal working blacksmith; and the wood user carpenter, did get craftsman respect, acknowledgement and pay. it is in the languages: wheelwright, barrelmaker, tinsmith - all craft skills. But a black-gang stoker? Steam engine fireman? Sweat 'till you drop. Get another warm body to sweat-it-out.
Today is no different. A firewood maker/seller is a low regarded “comodilized” (he-so-dumb) pursuit. The Music-maker/Entertainer gets respect. The Artist gets respect. The Programmer get respect.
GaryT you try to mid-scale food farm. You know this. Supply&Demand, bid-down, rules-all.
Wood-for-power is no different WHEN FOR OTHERS.
Charcoal-for-power will be no different WHEN FOR OTHERS.

The last two sentences that KoenV.L. bold printed up shows why.
tree-farmer Steve unruh


Your link works if you change foa to fao. I wasn’t sure what you wanted it to do. Good information for sure.


Thanks MikeR,
Yep. I stand corrected. Correction made, and indeed it does work now.
(this is why triple checking seldom works - if you did not see it right the 2nd time you will most likely re-see-it-wrong the same way every time thereafter)
tree-farmer Steve unruh


One of the more “touching” sentences i did read in the publication is that all boils down towards man’s ability and to a person’s knowledge…

If we compare the old day’s, passed, behind us, those old folks who could do anything without a smartphone even fly to the moon and back… and now to the new age, where as people can not start their cars anymore without the consent of a sofisticated computer inside…

I am sure yes that new tech is good… but what is tech without know how ?

Here in Thailand, between the farmers, i notice the smiles if i try to explain something about computers… but i feel their respect if i start a waterpump (theirs) without expensive gasoline and use their charcoal instead…

a wood gas system is similar, the


Haha, very familiar… :smile:


Same here when we explain benefits of woodgas, charcoal and biochar to an “expert” and the diference when explained in simple words and understood from the local farmers. I understand this, because it´s almost everyday living.


That’s all true. But these days some of us take apart old washing machines and reuse the motors to make crazy contraptions in the garage. I say we like to tinker, or that it’s a hobby. Why? In my case I want to know how things work. I hate ‘black boxes’, ‘sealed units’, “no user servicable parts”. I think there will always be a few of us who will question the text book explanation for everything and insist on seeing things for ourseves. This is a much bigger issue than gasification. We insist that we HAVE the “Right to Repair”. "Right to Repair" Is About a Whole Lot More Than iPhones