Woodgasification Efficiency Math Made Easy

Hi All
For those of you spending a lot of thinking on “new” “modern” development gasifer reactor ideas that will “modernize” “update-improve” here is some easy math for you to consider just where you will get your best return for your developement expenses expended.

Take the woodfuel carbons and hydrogens molocules heat energy value as if ALL were completly oxidized (burnt) as an arbitary 100 units of total available energy to you. Now it has been well documented that the better gasifier designs are able to convert the fuelwood H’s and C’c at 70% effiency into gasifier fuel gases molocules potential energy delivered out to an engine, or a combustion burner.
So 70 energy potential units will be delivered out of the gasifier system out of the original 100 units of wood fuel energy put in. 30 energy units got used up as either needed gasifier system internal energy drivers; or, lost as bled off “wasted” gasifer system heats bled away. If you take a resonable 1/3 of these as system internally needed and NOT availble as unrecoverable used up in blowers, pumps, drive motors, ect then you could only ever be able to truely recover 20 energy units in the gasifier system as “improved” recoverable at the very best.
Remember this 20 unit energy potential at this part of the whole process.
Good to note here the 70% conversion efficicncy is for the BEST of current known in use gasifier systems. These will be the ones that you can hand touch while in operation and DO NOT tie up huge amounts of woodfuel HC combinations in tars needing multiple filering steps to collect as toxic hazardous waste disposal Goo’s. You will do well just to just be able to develope up to this 70% gasifier conversion rate others are at now.

Now consider that here on the DOW we are very today/practical into making woodfuel gasses for the purpose of making and using shaft mechanical power: “Drive On Wood” “Power With Wood” Gonna need some way to make that shaft power out of woodgas fuel. For us this is not a head trip hobby. It is a passion to make work and practical daily use in our Lives to power our lives.
Again well documented that to do wood energy into shaft power with the most devloped triple expansion external combustion piston steam systems will you only yeild a 16% overall fuel energy to shaft energy conversion efficiency. And this in larger heavier more complex marine and stationary based systems. And this IS UP from the old only ~11% traditional old single stage piston steam conversion rates - like carried forward in American/British/German and last 1980’s Chinese used rail engines. So you are only going to get ~11.2 to 16 units of our original 100 energy units out as usable shaft power with an external combustion piston steam engine. Small gas turbines worse. Small Stirling engines worse yet. And any of these will all be at least 5X to 20X the cost to set up and use versus just using a readily available internal combustion piston engines.
IF you can even find a manufacturer anymore willing to make and sell you one of these “It’s Different, SO It Must be a better idea” heat engine systems still in business.
Face reality: you ARE going to be using an existing available internal combustion engine of some type. Period.
Now it is even more well doculmented that spark ignition internal combustion piston engines only actually convert the delivered fuels combustion heat and pressure energy at a 22% to 28% conversion efficency into useable shaft power. Compression ignition internal combustion heavy oils (diesel) engines are a bit better at 28% to 33% converion efficicncy.
So lets say of our fuel gasses delivered to the engine of 70 energy units we are going to be able to in the engine convert an easy to calculate 1/3 or 33% into usable shaft energy.
Out of the 70 fuelgas energy units engine in we will get 23.3 of shaft energy units out. Now this fits in with the well documented 1990’s multi-published overall combined gasifier/IC engine systems ratings of 21% to 23% for woodfuel to IC engine shaft efficencies. Where did the rest of the delivered to the engine woodgas energy go?? ~Half as now needing to be rejected out unconverted heat to shaft out energy in the engine exhaust as “wasted”. If you do not let these out you will heat kill the valves and not be able to let in. and seal in, more new fuel energy to created into new heat and pressure rise against the piston face that is doing the actual work. And the other half as needed to now reject out unconverted to shaft energy as “wasted out heat” in the engine air or water cooling system. Do not let this heat out and your internal engine surface temperatures will rise up and you will heat kill the piston rings and cylinder bore so they are no long able to capture the heat produced pressure rise to be ONLY directed to the movable piston face.
Bottom line is that would be 23.3 units + 23.3 units = 46.66 units of our original 100 wood fuel energy units as now actually in the engine converted to high quality heats available to be put to some kind of usable work.
That is over twice as much available heat energy to farm out from the engine as would ever be availble to you at the gasifier even with PERFECT 100% conversion woodgasifier system “Improvements”.

My point is this:
Quit myopically scheming, brainstorming about those hard, hard to capture final 20 energy units in the gasifer system side of it and letting the easy 40+ heat energy units in the woodgas fuel to mechanical shaft converter ENGINE just be blown-away and wasted unused for anything useful at all!!!
It doesn’t take rocket science, Advanced Degrees or modern electronics to be using these easily used engine heats to woodfuel pre-dry and warm; put back into the gasifier system for gain; use to out of system space heat with; OR, even use to absorption refrigerate with. ANY easy to set up use of these now being wasted engine heat energies THAT WERE WOODGAS ENERGY DERIVED will UP your total overall SYSTEM efficiency utilization.

This is what Mr Wayne is doing now recycling engine exhaust and gasifer core bled out heats right back into the gasifier system.
Why he can now document and claim better full cycle efficiency on woodfuel now than when the engine is powering with pump spec gasoline.
Mobile or stationary take a page out of that book and quit chasing gasifier system side slippery, elusive remaining Devils and go NOW after some of those engine side ignored heat Angels crying out wanting to be put to some useful work.

Steve unruh

Good laying out of the rules of the road Steve.

I was thinking about this today. I have machines undergoing lab testing and have two more I’m building to be modified and have additional testing done.

However for my own testing, does anyone know of a simple hand held gas analyser that can determine the H2 production in the gas. If any one knows of one available for a couple hundred bucks let me know. The analyzer the lab has is something in the ballpark of $60,000.00 bucks. That is just slightly out of my budget!!

But anyways, for example;

If the conversion chart I found is right 1 kW is equal to 3412.142 BTU/hr. and 1 lb of most hardwoods are around 8500 BTU’s. So if I use up say 3 lbs of fuel to create the 1 kW for one hr, I would have consumed 25,500 btu’s to net the 3412.142 btu’s to create the 1 kW. So if multiply the the net output by 3 I get 10,236.426 btu output from the gasifier. The efficiency rate of the machine then is around 40% ??

Hi Steve
I see what you say as to efficiency of the system, there are few places to get any more out of the system, but that’s what we are here to do. If Mr Wayne had just taken the Imbert gasifier and put on the back of his truck where would we be today ? It all about evolution , trail by error, “there are many ways to skin a cat” .

I agree with you about using more waste heat from the engine in various ways and to try insulate the gasifier better to increase the efficiency , bearing in mind what Wayne says at what point will you get diminished returns! But the only way is put the ideas out there and get some constructive critisium.

Hi Steve,

I agree with you on gasifier development, Wayne has far more gasifier than we have engine.

Engine development will most likely be the next major break-thru.

coming from a stationary build perspective i’ve always looked at the exhaust of the engine running and thought look at all the heat being wasted. I do have some ideas on how i’ll try putting it to use… once i have tried them i’ll post :slight_smile:

Good Morning Fellows
I am going to go back and edit out my very regional useage “anal” wording to a wider understood “myopic”.

Experience perpectives: Mr Wayne has huge piles of scrap metal build up and burnt outs from ideas tried, found wanting and moved forward from. I hooked up with a fellow named Ben Pereson who was on his third year of going this same route of fabbing, welding up every possible system type he could find, think of, and then operate and wring them out for performance. Again truck loads of in real metal made up systems/ideas found wanting or having just one aspect worthy to to be carry forward as realistically usable. And then I was involved with this best idea/trail and error of everything possible for two years working with him. I never, ever want to spend another minute dinking around with passive grate systems ever again!! Yuk! PITA! When ME physically reaching out and shaking the whole unit system could always restore performance! Active grates for me now ONLY!! Any of the 30’s/40’s German/Swede developer s would have told us this. AND DID in their pictured/illustrated sysems! You can see this same “done that-tried that-moved on” eveolution in pictures and words in Mr Vesa book.
Sigh. It is painful to hand sit and watch so many ideas kicked around already been tried in real metals, hot fuels and found wanting. It IS true “There IS more than one way to skin the cat” - but really only ever 3-4 really good effective ways. There have been literally thousands of men for over a couple of centuries now tring every possible combination with millions of running hours in the reactor systems/filtering and cooling side of it now.
Be no big leaps made here. Tiny single componet improvements? Yeah, sure, for single point percentage changes.

Meanwhile I’ve only seen/read of exactly THREE efforts: Doug Willliams, then Jim Mason’s and now Wayne Keith reaching out into the engine heat areas for those easy avaialble low hanging ripe fruits that I saw and felt with the very first woodgas fueled loaded running engine.

I am very unapologetic with the four of you responed so far. All of you are declared wood to fuel engine guys for useable shaft power. All very down to earth practical fellows who I respect much. From the get go start putting that very high quality dry engine exhaust heat back into your gasifier process. From the get-go take the lower grade but also Dry heat from the engine cooling system to reduce the fuel drying/warming heat-load OFF of the gasifier hopper. And do this with intended to be woodgas fueled engine heats even if having to intially fuel the engine for these heats with gasoline/diesel while sorting out the gasifier system. Give the gasifier core system these “extra” heat imputs then will make it much easier and you will find not the need then to be effort expensive chasing single percentage points improvements there.

MattR if you use a more realistic real in this world obtainable 5000 BTU’s per pound of fuel wood (this accounts for the heat needed to vaporize normal 20% moisture fuelwood instead of unrealistic bone dryed LAB wood) then your system performance would be as you are calulating 68%. Not bad at all man.
Two other ways to rule of thumb this.
Are you paint burning off at your reactor core areas? Yes. You can improve here with heat recycling or insulating. Are you having to filter out and collect lots of unconverted primary and secondaty tars - these are the heat vaporizable, lighter brown ones - not the thick black unvaporiable asphalts? Then you can core hearth improve here to convert those into valuable engine grade fuel gases versus toxic filter clogging wastes.
David Bloom summed this up in a responce recently asking if he was still bubbler washing/filtering/cooling his gas. He said not anymore. That he was letting the hot char do it’s job of oxegon stripping the CO2 to make CO.

Steve Unruh

Steve I’m sorry if I have offended you it was not my intention. I have the utmost respect for the guys on the forum and what they have and are trying to accomplish. It is unfortunate that Wayne and other wood gas pioneers did not document all their systems that were found wanting , so that we may learn from them. That is why we newbies ask the “dumb” ( already been done ) questions and you old timers role your eyes and say here we again.

Sorry :frowning:

Do we have a standard means to calculate thermo efficiency of the machines? Im looking for lost heat that is shed from the gasifier or other processes.

I dont think this is the message here. Its more like keep it simple, if aint broke dont fix it and fix the obvious. We always want to try and improve the systems, but we need to keep it practical. The simplest ideas usually work better than any elaborate plan. There are lots of things we can do but taking these things to the extreme is not necessary. This can get very elaborate. instead look for the simpler things like adding exhaust heat and things like this. You all are doing just fine keep building and have doing it :wink:

Hey PatrickJ really no need to apologise.
Actually the differet reactor ideas I read are not dumb at all. It is very difficult as I said to have to sit silent and watch them tried again and again with the same poor results.
Any of us old enough, experienced enough, know well now that many times it is wiser to let people try and learn on thier own. Sticks better with them then. If you step in every time with a “been there - done that” then it is human nature the fellow soon just tunes you out. “The boy who cried Wolf!”. Then when something really safety related warned about gets shrugged aside, ignored and someone gets badly unrecoverable hurt.

Here’s one:
NEVER, EVER, OPERATE A CARBON MONOXIDE CAPABLE PRODUCING DEVISE INSIDE HUMAN AND ANIMAL OCCUPIED BUILDINGS AND SPACES!!! Or attached garages. In the WWII Swede vehicle gasification era expereince they were losing an average of two people a week dieing from vehicle in garage accidental gassings. I read annually of people here in the PNW doing just that with charcoal braziers and portable engine generators no matter how big the the manufactueres warning labels are. And I read weekly on woodgas forums of fellows recomending must downdraft by design “Ohh! Wow! Better way Rocket Stoves!” for people space heared areas. They are called Hippy Killers here in Washington State for a reason. Real people have overnight died in their sleep from thier “Oregon” rocket stoves. Always updrafting maintaining woodstoving may seem old fasion and passé but it is evoled to start up safe, cool down and end safe IF the eveoled learned stove and chimney codified principlals are followed. AND in the 1980’s-2000 these were internally improved and modified from 40-60% fuel/heat effiency recovery to 70-85% efficiency if you pay for models with these features. I now use 40% Less fuel wood annually. This is as good as it gets for No Electricity Needed Att All To Operate with good user safety. Want 90% plus performnace?? Then you need combustion air and draft inducer blowers. www.garn.com

Now here’s a wood fuel gasifier practical “Rule”:
Only trasport hot volatilized wood tars freely, openly less than one meter distances while keeping exposed to continuos heat to keep them hot, voletile and moving. ANY tubing, or piping directing them will heat reduce and velosity slow these enough they will liquify condense, adhere, then layer by layer build up with soots and ash and clog all flows.
You just peeked into 20% of those scraped out system, set-aside build-ups, in the piles of three well known developers.

Yes MattR that is correct. Pick any one of the now proven 3-4 system types to be your base - build it faithfully on the designers layed out bread crumb trails. Then scratch your creative itches going after the ignored ripe engine heats areas for overall system efficiency improvements.
Simple message. I am heartened some are actually listening.

Steve Unruh


so true!

Every year, there will be 5 to 10 fatalities due to carbon monoxide poisoning in Germany (suicides not included, that is). Half of it because of the reasons you mentioned (operating (car) engines in the closed garage, heating closed rooms with improvised open fire gas, coal, wood or oil stoves and the like…there was even a family that could not pay their electricity bill, so they were disconnected by their electricity supplier. They started running a generator inside the corridor to make their own juice - 4 out of 5 died, one was caught just in time…If I recall correctly).
The other half occurs, tragically, due to blocked chimneys. This happens when jackdaws decide to build their nest in this very chimney. They keep dropping sticks into it until one of them (sticks) gets stuck and jammed so they can put their nest on it. That way they block the chimney and the exhaust gases have to face high resistance which leads to them leaking into the house and higher CO contents…

Do you have those problems with jackdaws as well?

Best regards,


Sam: We don’t have “Jackdaw” specifically, because those only live in Europe. Jackdaw is a sub-species of the bird family “Crow” though, which we have SEVERAL types of here, on this side of the “pond” (AKA Atlantic Ocean).

I can’t say that I know of any cases of them building nests inside chimneys though. They are a general pest and I could see them trying to do something like that though.

Hi Steve,

Do you think all the low hanging fruits have been harvested in engine development? I am referring to the actual engine ---- not heat recovery.


Same question as Peter, and also when your talking about using the heat are you referring to preheating the gasifier air supply or externally drying the fuel before use or both.


Well you fellows really like to kick me to streach down into my old dieing brain cells don’t you. Really cuts into my napping time you know.

MarvinW the woodgasification we are doing is a thremal-chemical process. The chemicals are in the woodfuel and the air inputs. Process NEEDS thermal heat imputs to work. The more external BTU’s/Calories of heat we can supply the less of the internal needed woodchar we must sacrifice in addition to the volatiles to make the internal needed process heat. Takes heat to operate a condensing fuel monorator hopper. Much better to sacrifice a little heat here “wasted” and get the excessive moistures out at this point then to superheat and vaporized them ALL to pass down through the complete gasifer HOT reactor core zones to then have to “waste” away ~5-6 times that amout of BTU’s/Calories of heat condesne them out later so the engine can get the cooled/densified fuel gases it wants to be happy. Mr Wayne and APL/Jim Mason are both adding engine exhaust waste heats now in addition to output gasses heats to help with this. Energywise it would be just as effective to out of gasifier system pre-dehumidify and warm the incoming fuel wood just before hopper filling. Some are doing this now. See the latest Victory Gasworks 5kW intergrated system. The complete engine/generator assemblies are completly covered with a tilt up dumping woodfuel drying/heating bin using the engines/gen heads heats and moving airs to just-in-time before into hopper filling fuelwood condition. Heat ALWAYS wants to migrate from areas of more to areas of less. Mr Wayne and APL/JimMason by putting normally wasted engine exhaust heat into the center of the gasifier are also replacing with “Free” heat the normal higher temperature bleed out core heats there. ANYPLACE you can put already made “Free” engine BTUs/Calories of rejected out heat into the overall system for a benifit will up your overall effiency.
Sure. Sure. Vehicle trailer guys will all say the engine heat sources are too remote to access. Well stationary power that doesn’t have to be the case is it? And truck guys proven now to be close enough access engine heat. Anybody ever had to work on VW WasserBoxes or fullsize vans, suburbans and busses with rear AC’s and heaters knows you can get effective engines heats tranfered over 20 feet/7 meters away. Pusher engined motorhomes another example. No excuses.

My take on engine woodgas advances? In the 30’s/40’s you can read the vehicle and stationary guys dreamed about being able to get engines with compression ratios and gasses in/out flows that aircraft engines had with expensive aircraft only then aviation spec gasolines. In the 50’s/60’s you can read the gasifer guys speculating now that they had the CR’s if they could just get the into and out of cylinder flow heads that advanced racing already had.
Well with the early 90’s and later individual elecronically Port injected gasoline and ignition timed engines and control systems some here are now actively woodgas fueling are better set up then any of the early 80’s guys could have ever hope for.
You Premium members look up Vesa Makinen at his posts. Read his comments of turboing and supercharger engine pressurizing on woodgas. One of his post links to his DOHC Audi V engine system. This will be a free flowing electronically controlled system. He links to pictures of lots of Finn fellows doing different late model engine systems also.
Then look up Francois Pal’s threads. Look at his recent adaptation of an electronically controlled V series large GM/Opel sedan.
Then you know have the different electronic FI Dodge and Ford driving vehicles here now. Soon Dodge/Jeep SOHC V engines. Ford SOHC “modular” V engines.

PeterC I actually think the American “breakout” go-to engine will become the 2005 to current GM/Chevy LS V engines chassis retro fitted backward to step around the OBDII limits. Not going to be turn-key easy or cheap to do though.
I anally used to think compression ratio was the key. Wrong. CR yes. But an oversquare bore to stroke. Allows BIG valving. Along with a long rod to stoke for a slow piston speed. Flat faced coated pistons to hold in the heat. Even though woodgas can run on these later engines at over 4000 RPM - I’ve done it too - the gearing and expereinces of many Premium siders here now says for actual efficiency you want to load it at engine speeds of 1000 to 2000 RPM. This matches most electronically shifted vehicles just fine. Stationery genration not so much unless you DC or 1500/1800 RPM generate. “I think” an open no-shear edged combustion chamber like a shallow hemi, or quad/penta chamber will prove to be the best for woodgas fuel. Still Fuzziest the most on this point.

We are all really just engine playing catch up with the already proven and in service specialized gasious fuels developed engines from the GE Jenbacher series; Waukesha APG1000; Mitsubishi Industrial; some dedicated Caterpillar gasious engine models, and I am sure there are some Hyundai Industrial engines out there powering gasious fuel needs now also.
Now BIG, Expensive and suppoerted, what they are doing differently is they are taking the gasifier system suction load off the engines and electric or hydraulic variable speed blower driving to pressure blow or suck the gasifier systems. They are ALL single and even dual stage turbocharging these engines.The Jenbacher J920 series for sure is oil pressure driving/electronically controlling (like late model diesel injection) actuating thier intake and exhaust valves. AND they electronically sense and do this on on the fly with each cylinder individually! This combo will give them Miller Cycle like capable running variable CR control. Explains their straight on valve, open cylindrical combustion chambers.

I think the finely developed “i” for intellegent now variable camshaft timed factory engines are either going to be just OK versus the earlier fixed cam timed or a bust on woodgas as now TOO gasoline pressure curve specific developed. Woodgas ain’t gasoline.

Instead of viewing woodgas as any kind of “drop-in” substitute fuel for one of the highly developed spec grade fuels like diesel, gasoline, propane or natural gas I just view it like my in room space heating woodstove as a energy source I can personally make, control and use. Then ALL of its characteristics like condensates, soots and fuel prep is just the price for personal energy freedom independence. I am not in this to save the world as we know it now. Assists those who will work for it save themselves. Don’t need or want any Gov’mint addictive beholding ass-sis-tance. Not into Missonary off and save/improve the lives of others while actually personally useing supplied “natural gas” and nuke/coal/big hydro electricity like too many on both sides of my families.
As an example that you can too still be free and energy independent with some sweat, blood and a few tears?? Sure. You betcha! Teach to fish by example.
Where I had to stop being so damn anal myself was to take a page out of MR Waynes practical lifesyle. Instead of scheming/dreaming of how to never ever buy any more gasoline or diesel and replace it ALL with woodgas. Be practical and eliminate the big expensive buy-out use Dragons and feed the little ones less and less.
I buy out annually 1/5 of the farm diesel now and 1/2 of the farm gasoline that I did just four years ago by making everything a must use needs demand instead of a “connivance” and doing some engines upgrading.

Steve Unruh

OK here you go:

Uses the words woodgas twice. Describes gasification. Pictures woodchips fuelstock. Describes special Jenbacher engine mods and controls systems needed for high hydrogen and high carbon monoxide gasses fueling.
Pictorial shows the suction blowers.
Says 37% overall cycle efficacy base fuel stock in to electrical out.
Easier to read than me.

Enjoy and learn
Steve Unruh

This one table has got me…

Syngas Composition
The following table provides a typical range for the composition of syngases. This will be dependent upon the specific chemical composition of the feedstock to the gasifier

Substance Composition (%)


Only 2 to 5% nitrogen?? How are they making this gas, using pure oxygen or something?

Yes ChrisKy - pure oxegen. These are quoted for industrial sized “process” gas makers. Why the all lumped together “syngas”.
Search out and you will find a Swiss installed power producer using purpose grown and harvested trees; an IISc-DASAG woodgasifer plant fueling acouple of Jenbacher engine/gen sets. You will see more “normal” fuel gases listed with 40%+/- nitrogen. From my EGR emmisions expereince/training I think the nitrogen carry through modifies the different CO and H2 combustion speed to more like a gasoline rate and helps us. Does displace secondary oxegen and fuelgasses though. Natually aspirated hurts the untimate power.
There you will find a sad story of how the fuel prep/gasifier plant side made some nasty wet wood gas - the engine operator accepted and used it NOT willing to shut down and take the engines off line and trashed the engines. Jenbacher had to rebuild the engines earlier than the normal pre-paid annual service contract and charged and billed them.
Big or small hurts to learn.
I long ago lost the link. Too slow now to find it again

Thanks Steve,

Sorry about the nap time. I have been listening. Trying to learn. Automatic transmissions seem easy to pull a lot of heat from. Pulling some heat from the cooling system might allow the use an electric fan instead of engine driven to save even more power. Am I on the right track or any more low hanging fruits besides exhaust?


Since I may be stuck with a trailer-mounted system, I have been thinking about how to try to use engine heats to the gasifier. One of the primary questions that keeps coming up in my head is this: Could one safely insulate the whole exhaust system from headers to tail-pipe and get moderately hot exhaust to a heat exchanger on the trailer?

That brings up a second, more generally useful question: Could someone with a standard WK system insulate the frist 1/2 of their exhaust system to get more heat to the exhaust heat exchanger for salvaging?