New guy with basic questions

Im an enthusiastic but unskilled tinkerer.
Im building an outdoor boiler powered by a TLUD.
Googling brought me here, and raised more questions than ever.

Just the one for now: can you run an engine on the exhaust from a TLUD?

I suspect not, if its burning cleanly.
I did see a builder on YouTube that said he had charcoal at the end of his burns.
That doesn’t seem right, but what do I know?

Making char for a vehical while fueling a stationary generator would be phenomenal, but its not something Ive found here on the site.

I know from studying up on japanesd barrel kilns that some kinds of char making can produce flammable gasses along with tars and vinegar, if condensed, but a TLUD is a flame cap char maker, and the Japanese barrel kilns are a kind of retort.


You can’t fuel an engine from TLUD fumes, but what you do to make charcoal from it is once the fuel has burned down to the coals just either extract the coals or shut down the TLUD by closing off all holes. A charcoal gasifier is pretty simple to make and while a little bit of a challenge, can be made without welding.


I make my charcoal using a plain barrel with a removable lid, start a fire in the bottom and slowly feed it until it’s full of coals and snuff it out by putting the lid back on weighed down with bricks. That’s still the flame cap method just without the TLUD pre filled aspect.

If you had the same barrel but with air holes at the bottom you would need to cover the holes with mud or sand as well as use the lid, and that would be a TLUD for producing char, very popular in South East Asia from what I understand.

Also please take pictures of your boiler! We like to see what people are building. You’re still using woodgas even if it isn’t powering an engine!


Welcome to Drive on Wood forum. You will find lots of interesting reading here. All the guys on the forum will help you with questions. Don’t be afraid to ask questions. There are no stupid questions here.


Thanks for the nice welcome!
Let me see if I have any photos worth sharing, since I’m far from finished:

Im working with a wrecked natral gas water heater.
I cut off the top 2 feet or so, but left the entire center stack attached to the bottom half.
That top two feet is inverted and becomes the burn chamber for the TLUD.
Burn chamber is not the best word for it, the real function is to deliver forced air to the TLUD.
My TLUD is a harbor freight stainless steel stock pot.
On its own It uses 6" diameter food can for a chimney, but I intend to build a stainless or refractory chimney into the boiler.

The bottom of the tank now becomes the top of the boiler,providing a water tight chimney with a water jacket , complete with threaded openings.
Such a heat exchanger is usually expensive to come by unless you weld one yourself, and maybe even then.

The whole thing is pretty small for heating a house, but its mostly about proof of concept.
My inspiration is mostly from the Permaculture Playground Youtube channel, though Garrys sawdust stove and at least one other space heating TLUD build also helped excite my imagination.

Right now I make char using the “trench” method, in a waterheater tank, the side cut out.
I douse it when it’s full and I get about 20 gallons a burn.
It mostly goes into the chicken composting yard.

Letting all that energy go unused was bugging the crap out of me.
TLUD’s do require more processing for their fuel than a trench burn, but if I can use the resulting energy to heat the house, it serms worth while.
Even better is the way you guys use wood gas to process wood, to make more woodgas!


What you can do with this TLUD is find some tools or safety equipment to handle the body of the TLUD when hot. Once you notice the heat levels petering off most of the pyrolysis gasses have burned off and you’re left with charcoal.

You could extract the TLUD and dump the charcoal into any sort of metal container that seals, metal trash can or cleaned out oil drum with a lid.

Lots of the charcoal guys actually save the coals from their fireplace as well. Lots of ways to passively make engine grade charcoal.

Dousing with water can add too much moisture to the char so I would leave that for composting.



A young family member of the late Tom Reed built a TLUD that powered a generator. It was going to be marketed for the RV world. That was my understanding at the time. To my knowledge, it never went anywhere.


Yes, I think you could.

I use the 50 gallon tank from a water heater as a TLUD. I light it from the top. The fire separates into two parts, as the burn works its way down through the stack of wood chunks. In the picture you can see that the heat has discolored the metal down about one third of the tank.

I’ve noticed that when the burn has worked its way all the way to the bottom of the tank the color of the flames coming out of the afterburner changes from red and purple to just yellow. This is when I stop the burn because all the tar is now gone. But that nice yellow flame is just chargas burning. And I know chargas will run an engine. I hope that answers your question.

I’m not set up to use the tarry gas for anything. It just gets flared off. But I’m sure it could be used to heat a boiler or something.

Best of luck to you, and welcome.


It seem like a TLUD might give off some burnable gasses, especially if we dont introduce secondary air.
They will also seem be the dirtiest gasses, the very stuff we avoid when using charcoal gasifiers.

I think i understand char gas filtration, but I need to understand woodgas filtering.
Whats a good thread for that?

1 Like

You would want a cyclone filter OR an expansion chamber/dropbox, then cooling rails to bring moisture out and bring gas temp down, and some sort of aggregate filter like hay is what most of the raw wood guys use in their vehicles.

With charcoal your biggest worry is soot, ash, and unburnt charcoal dust so you use a tighter filter like a canvas bag filter.


Ok, it is pretty simple then.

I know many gasifiers are mobile, so weight is a concern, but are there stationary gasifiers that cool the gas with water?

I ask because I’m fascinated with scavenging heat from the process of producing woodgas.


You could do jacketed cooling rails, sure. Run water through the jacket to scavenge heat. Maybe even make a water jacket for the drop box or cyclone whichever you decide to go for.


I uses two pair of socks as a filter for my gen set on chargas. They acted like a kill switch the first time I got a little tar in them. Making charcoal - #153 by r_wesseling

Back in the day the old coalgas guys liked to draw the gas up through a column of lime chips. This would remove sulfur from the gas. Sulfur is corrosive to copper alloys and zinc. There are several cases on this site where the openings in throttle bodies have gotten to big so idle speed has increased (1). And @JO_Olsson had a brass throttle plate corrode to the point where a piece of it broke off and was sucked through the engine. ‘Sour gas’ has always been a problem in coal gas, natural gas, bio gas, and other gaseous fuel systems.


Circulating water heat recovery?
The current in-build effort is Tones “Properties of a Good Woodgasifier”.
Start reading viewing at post #121. Look at the on-topic R.H. slide bar tool to quick scroll to where you want.

You know man, you are starting out on the wrong foot with this.
A wood fueled wood gasifier are consistently 72% efficient at turning the theoretical wood energy into motor fuel gas chemical energy. Multiple articles, multiple studies on this. So you will only have ~28% heat energy to work with.

A good wood for heat burning device; bulk wood stove/furnace; is an actual 75% to 85% efficient converting the wood theoretical energy to space heating. So only 15-25% energy to work with. And the best of the best with forced down drafting and heat recovery are 90% efficient. GARN’s; TARM’s; J.O.'s and a few others.
And that 75-85% achievable is ONLY if you do not steal the hot charcoal from it.

Doing these combined cycle dream systems is a bit like thinking a person can eat their sweet, layered sugar frosted party cake three times a day exclusively; Be healthy; Not blood sugars spike; Not rot their teeth out.

There are reasons many here heat with wood at 75% efficiency.
Separately woodgas drive with wood at 72% efficiently.
And needs must: then woodgas fuel an electrical generator off of their 72% efficient woodgasses vehicles.

Of course an open fireplace or air leaky woodstove at 40% efficacy gives lots lost-waste potential energy to improve on.
And a TLUD is what 50% conversion efficient? 60%? Still behind what I can do in-house with any of my off-the shelf QuadraFires. Or a Royal. Or 10-15 other truly modern 21st Century commercial built wood stoves.
I thought the 1980’s TLUDS main claim to fame was smokeless combustion.

Steve Unruh


Then to add, if you are recovering heat while engine running then this heat will not be a constant. So you will still need a primary heat source while engine system is off and then add the complexity of controlling multiple systems to work together. If your thinking your going to run a gasifier to run an engine for both power and heat around the clock that is very inefficient and simply impractical. Make only the power you need and store that power in a battery bank. Store your heat in the wood itself and create that heat using better technology such as a good ole woodstove. You can doing your cooking on this as well. KISS.

An engine grade gasifier is good for one thing and that’s running an engine. Its not a good solution for heating or cooking. You can not run a gasifier indoors as hopper back drafting will be an issue and you will lose that 28%. in process heat as it will need to be outside. Not to mention that percent is actually a bit less in heat output as a portion of it is lost in exothermic process.

Yes I have ran liquid cooled heat exchangers and its not worth your efforts to harness this heat unless it is used to maintain a hot water heater, Actually thats not a good solution either as the purpose of your cooler is to extract that heat and cool the gas. A hot water heater is going to retain and return hot water and defeat the purpose of the chiller.


All true, true MattR.

(in Tones case as he is a well versed refrigerant cycle man, I would expect him to be heat concentrating his gasifier hopper “cooling” heat)

Steve Unruh now the owner of two air-heat sourced Mitsubishi ductless heat pumps. Come true winter any heat input really helps the refrigerant heat concentrating cycling.
Delta-T rules.


It seem like I’ve touched a nerve?
I’m just trying to use waste from things I would be doing anyway.
I promise, if I ever do build a wood gasifier , it will start life without water cooling, because one should learn to walk before one tries running backwards uphill without spilling ones martini.

Matt has that incredible charcoal making stove that gives off a lot of heat.
The heat is cleverly contained to cook the feedstock, before it is released to heat the shop.
He has even mentioned a build that would capture the heat in water.
I’m sure this isn’t an efficient space heater , since at least half of the energy is left in the resulting char.
But its a very efficient way to make charcoal, with free space heating on the side.
I would probably not have even started my build if I had seen his first.
Seriously , it has the best qualities of both a retort and a TLUD, plus its tame enough to use inside a shop- totally amazing.
I will probably emulate it eventually, but with water heating, because it will have to live outside.
The home insurance, the city and my wife all agree, no home built wood burners in the house!

I will finish my own build, out of stubbornness if nothing else.
It was always going to be a hydronic heater.
I have big basement, and a cheap way to store water.
I envision a hundred gallons to start with, water that will also be an emergency storage for my family.
Storing excess heat from the various wood refining I’m doing anyway is a no brainer.
No real controls, just a thermal mass in the basement, maybe a convection loop in the return air vent.
I suspect my heater will not make dent in my bills, but it should be fun.

I still want to use the heat during the summer, but I have another idea for that.
Selling small batch, artisanal, local, wood fired distilled water is a dream of mine…
Seriously, with a pinch of Himalayan pink salt and some homemade liquid smoke, I think I can really clean up with the hipsters.


No not at all. Like you all of us here started somewhere and we all had crazy ideas. lol But we built we learned and here we are, you are the new comer and we are the vets. At the end of the day though we all are here learning together. There is an unwritten code in this community and that is we respect all.

We are merely giving explanations, keep in mind we see you as a new builder as your post implies.

““I’m sure this isn’t an efficient space heater , since at least half of the energy is left in the resulting char.””

actually I believe these pellet stoves are quite efficient. I wont really know until I can get proper test equipment and gas analyzers. This may sound contradictory, that char is not waste and I am using a multi stage gasification process so these stoves are converting more CO2 to CO converting more of that energy to heat energy. The produced charcoal is simply reserved energy for electric power generation instead being used for heat energy. In the bigger more developed picture this tech will be very efficient. I will have new tech coming out here soon and will continue on with this development so more to come.


Please dont ever let anyone on this forum deter you from your experimentation. If you tell me “you cant do that!!” I will litterally die trying to prove you wrong LOL. Take in what you feel is the good advice you are looking for and throw the rest away. Some of what we present are our onw opinions based on our own experimentation and experiences. Some things however are fact. Each one of us are an individual and each of our builds are unique, I doubt there are two identical gasifiers built by any two separate individuals here. If you dont innovate we go no where we just continue on doing the same old thing without improving anything. In this space there is plenty room for innovation and easier ways to do things. Some here live in the world of “if aint broke dont fix it” Others live a world of “What If??”"

Welcome to the community, you belong here :slight_smile:


Introduction/whys to J.O.'s whole house wood fired heating system:

Then his whole system explained out:

Best to read and view the whole topic.
His system diagram is on comment #33.