Peter,
I remembered a really excellent video on this very subject. It is a real-world implementation of this earth energy harvesting method. Kirsten Dirksen is the videographer, the greenhouse is in Nebraska, USA. Worth watching. 
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Hi David, and welcome to forum.
I thought i could post some opinions here too, altought im not running any stationary woodgas (but i have lot of ideas for it, if i find my dream place to live in the future (lots of place for wood handling, no neighbours))
First im with SteveU, i think you could start directly with wood gasification, nothing wrong with charcoal, but start the hard way, and be aware you may have some struggles and fails in the future.
Heres how i would do, probably nothing right, but anyhow: use a sturdy engine, to big for the use, maybe twice as big as your generator needs, inline 4 or 6 cylinder, a push-rod, no interference engine is to prefer. Dimensioning your gasifier smaller than the engines needs, it’s not going to work full power.
Make sure it’s pretty common where you live, maybe get two for spares? Check out head gaskets are available.
Make sure it is easy to run it on liquid fuel, for tests, are the trouble in the gasifier or the engine?
For safety: do you suspect you made some tar?-run it on gasoline 5 mins before shut-down.
You need “emergency” electricity? Run on gasoline a short time, without need to start gasifier.
Starting on woodgas is hard for the beginner, run on gasoline, give it more and more woodgas until it “chokes”, turn down liquid fuel and “wooh-hoo!” it runs on woodgas!
This are stuff very helpful for the “beginner/experimenter”
Build your woodgas system easy to dismantle, i use to weld mine, and in experimenting, all you save by using wood is lost on grinding discs 
I would build it with the opportunity to save all the heat, gas cooling, engine cooling, exhaust heat regeneration, even if it’s not much win, it’s nice to have the opportunity.
Safety: preferable build it under roof, no walls, absolutely not in the same building as living space!
Use some Co detectors, they are cheap.
As Sean points out in another thread, exhausts “robbed” on their heat, will stay closer to the ground, use a high enough “chimney”.
Older engines with atmospheric crankcase ventilation, should have the breather tube connected to the air-intake.
Imagine your generator stops by some reason, a hot gasifier will produce some “after-gassing”, if you walk in that room, to check whats wrong, you may never walk out again…
Better have air openings, don’t trust fan ventilation.
As for the gasifier, you have best luck with proven designs, if you want to implement own ideas/improvents, do it after you have a working system, you’re learned to operate.
A WK gasifier is a good, proven design, but i can’t remember at the moment if there are many stationary operating systems? You need to check with them operators.
The Ben P system is also a good, proven design, mostly designed for stationary use.
Use the feedstock suggested here, as dry as possible. Round cuts flow the best.
Woodchips is terrible, chips tends to flow as a “plug”, a chip fed gasifier probably needs forced feeding, automation, don’t start with chips.
Don’t use pellets or briquettes, it will sooner or later decompose into sawdust.
If you have made electricity out of wood, for, say a year successfully, then start trying all this, don’t rebuild your working gasifier, use it, and build the “new” experimental one beside, this is more fun. And is somewhat addictive, which others will agree with.
Well, i think i’ve forgot most i wanted to say, but heres some ideas (most of this is exactly the opposite of how im doing it, it’s the guarantee i know it works better…)
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I like your responses and reasonings GoranK.
DavidP. begin thinking hard about his beginning advices:
" . . . if I find my dream place to live in the future (lotsof place for wood handling, no neighbors))"
Well taking over the old family place you seem to have the room, and access to a self-regenerating woodlot. Positive check. And check again.
But how about the neighbors?
How will they object to you making maybe more smoke in wood gasifier early warming up by-pass venting than you currently are?
How will they object to you open air bathtub visibly burning to make charcoal?
How will they object to you, “selfish person” appearing to try and detach ourself from being energy dependent while they remain energy taxing contributors?
We mostly all have had real, significant, local horror experiences with all of these at times.
My wood stove selfishly using up trees, and chimney exhausting into “their atmosphere” I have countered by learning to wood stove virtually smokeless under all conditions. Those were hard learned lessons. Even at my best I figure I lose 10% recovery efficiency just to be stealthy. Remain innocuous.
At the same time our liability home owner insurance company decided to go politically-correct Eco and lied about a house demanded mandatory fire safety inspection just to give the reason to cancel us and all other wood stove users.
Solution? Pay off; clear off; all loans and montages and drop out of home owners insurance racket. It is not an absolute all-must mandatory here.
Previously were we had lived for 27 years on the Wife old family farm; new neighbors moved in, were removing wood stoves and fireplaces to meet the new insurance requirements. They then jealous began objecting to our use-wood for energy practices.
I did not dare ever make the smokes, making charcoal would have made. Especially in the dry wood times of the year.
A wood gasifier oversized suction blower fanned was the solution to on our property to wood gasifing. Make a tiny bit of early smoke blended in with other bypasses air for only 3-5 minutes.
As GoranK has said . . . we moved from that area with never less than 11-13 adjacent neighbors to the very end of a dead end road with only 4 adjacent neighbors. Only one still heats with wood. The others converted to only mini-split heat pumps. These others would only object if any one of us brings in family riff-raff, or riff-raff friends to the end of the road resulting in a lot of EMS and police response activities. No fun at all having our common use 400 meters single lane access clogged; and lite up by flashing white, red and blue lights. What the pervious owners had evolved into creating.
So be honest with yourself on the reaction by others to what you do.
“They” will insist. Sometimes directly. Sometimes by burying you in complaint driven investigations from authority agencies.
Woodgas. woodgas, woodgas if you think it out, and take precautions.
Charcoal making??? I can well remember three guys in different locations, personally known, who got shut down by complainers.
Steve Unruh
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Good morning David and a warm welcome to the DOW ( drive on wood )
Below is a thread I think might interest you .
https://forum.driveonwood.com/t/woodgas-in-south-africa/839
Thanks Wayne
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Hello Goran,
Thank you for the great advice, and I think I’ll follow it in my own way (I’m stubborn).
I’d like to get the engine from a 2003 Opel Corsa C, my partner’s old car from last year, and the biggest problem is the head gasket.
It needs replacing, which will already be a challenge for me (this type of engine is very common here).
I received BenP’s book yesterday and I’ve started reading and translating it.
I’m looking forward to getting the WK as well.
It’s clear that I’ll stick with a ready-made system, at least initially. Regarding safety, I don’t see it the same way…
I’ll send my neighbor to check it out (the one I don’t like), just kidding, of course.
I think tripling the safety systems would be my approach; life is precious.
The building is detached from the house, 40 meters away, and has a large sectional door that runs almost its entire length (useful for venting air as a fourth safety measure).
Regarding the neighbors, I already burn wood, but I was planning to filter the fumes completely, or almost completely.
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Hello Steve,
You’ve certainly had quite a few adventures in your life.
You’ve always managed to come out on top brilliantly.
Respect others and they will respect you, excuse me, I’m daydreaming.
In Belgium, it’s exactly the same as your examples, but luckily I live in a small village.
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Hello Wayne,
Thank you so much!
Thank you for the link, I’ve made a note of it.
Without meaning to flatter you, I also wanted to express my admiration for building your own gasifier, and especially for remaining as humble as you are.
I think that’s partly what has brought so many enthusiasts together here.
By the way, you’re not the only one to have accomplished this feat; in short, everyone here impresses me greatly.
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Welcome aboard David.
I had too long of a Sunday afternoon nap and now I cant sleep so I thought I would throw in my two cents here.
the guys talking on this thread know what they are talking about even though some have differing opinions. I have built and operated gasifiers of many different styles and in many different applications.
I learned basically the way @KristijanL described. with a simple fire charcoal gasifier. after several iterations of those I built my first WK my first real drive with that truck was to northern indiana from my home in central alabama about 700 miles. I was so green and ignorant of the entire subject that i didnt know anything about overheating a gasifier or anything about hot leaks along with many other things. i survived the trip only due to the fact i was traveling with three of the worlds foremost experts on the subject of practical gasification @JO_Olsson @KristijanL @Wayne . i remember on that trip when i hada lot leak (which i had never heard of before) that Kristijan made a patch with a beer can and some silicone. i would have been clueless at the time. @Woodrunner has extensive knowledge on gasification and his plan would probably also work. The resounding message here that everyone is saying is that this is going to be work. There is an incredible amount of knowledge that has to be learned on how to build and operate any gasifier. some are defiantly more complicated than others. and some are safer and more user friendly that others. I couldn’t agree more with the idea that if you are going to build a wood gasifier as your first (which i don’t think is a terrible idea) pick a proven plan and build it EXACTLY. as much as i thought i knew when i built my first wood gasifier looking back i knew almost nothing. if you build an exact design, if its built right you don’t have to worry if its a design flaw. possibly builder error or operator error when you have problems. it is one big element of variables to take out of the picture.
Remember that their is a lot of learning in this also have fun. it was a great way to spend my later teens. i don’t do as much with it now because of season of life but i still enjoy it.
also one of the best pieces of advise i was given was don’t be a purest. don’t build something that is hard to use because you want to go pure woodgas. it will be hard to use you will get frustrated and you wont use it.
study lots, post lots of pictures, and ask lots of questions were all happy to help answer questions.
burn some wood, and have fun!
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Hello Jakob,
Thank you for your advice, it helps me a lot in making a choice, especially at the beginning, as I don’t know much about gasifiers yet.
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