Fuel Dryer Systems

I haven’t seen much for drying fuels. I may have missed this somewhere, I dont know. But anyways this is probably the most important part of the wood gasifier system DRY FUEL!!! Just like charcoal systems a wood gas system does require some fuel processing and drying is part of this process. If you do not have dry enough fuel that your system can process, it is simply not going to make tar free gas. Some systems are more tolerant than others but fuel still needs to be held to a level the machine can process. As for my machines we do not market them optimistically. Sure they can process up to 30% moisture and still perform ok. Id rather have our customers use 15% moisture content or less to help ensure satisfactory operation.and successful operation of the machine.

Well fuel processing is something we have been looking at producing for any wood gas system. Time however is never on my side so we have not been able to put a lot of time into this. Now the sun has gone away here in Mich we wont see it again till next April / May haha. So sun bathing is not an option right now. Ok the fuel we have been running comes from a landscaping company just up the road from us. The bad is the chips are rain soaked, Ive noticed after drying this fuel in the sun it would check out with our meter and then it would not run in the machine. After further investigation If I cracked those chips open the center core I found to still be soaked!! why the meter does not read this in the center is beyond me; maybe I have a bad meter who knows. So Im now working on crude methods for the time being that may turn into open source projects and kits available from us.

So what Im working on is pretty simple. I have a trash can with 1" holes drilled in the bottom and an exit blower at the top with a heat sourcing blowing into the bottom. A vacuum cleaner in this case. I have an automotive cooling fan on order and I plan to scale this up to a 55 gal drum. The fan will get mounted to the top lid and Ill drill holes in the bottom or install some expanded metal at the bottom. This will get an AC to DC power supply to run it and when we have time we can just run this with no heat source and over longer periods of time it should still dry the fuel. To add a heat source that uses wood I plan to build a simple barrel stove with heat exchange tubes going through it. Later I may possibly attempt a rocket stove or adapting a gasifier to supply heat.

All other designs are welcome here :fire:


At some point Id like to get my hands on a grain dryer.


Hey there Matt. Since used/broken skids are free and plentiful around here in Michigan, instead of having to put labor into right sizing them for BTU’s, how about building a squat rectangular metal box to hold whole skids with maybe the holding capacity of four metal drums on top. Put it on wheels, or at least attachable wheels, and roll it into your shop with a chimney then attached to the exterior and supplement your shop heat in the appropriate months and then outside in those warmer months. Wayne used to prechar using barrels and under fire that way. You would be surprised at how good your eyes get at spotting skids when driving down the road. I use my luggage rack and ratchet straps for picking them up anytime in my AMC station wagon.


Hi Mat ,if you like the idea of a grain dryer then , a much better idea , if you are running chips , would be a grain blender , we used these in our plastic recycling , for mixing pigments and also helping to dry damp materials , we used to pick them up pretty cheap and can hold many tons , you simply pour the chips into the dish at the bottom and the screw takes them up and distributes them around evenly .
For really wet wood we would put hot air dryers blowing into the main silo and let the moisture vent out the top .



i have noticed the wet center problem with chunks and now always save the biggest chunks to wack in half to check moisture inside if its good the smaller are plenty good.


I do the same thing.

On a clean split of a wet chunk, you’ll see the drying pattern, only dry about 1/4" to 1/2" from the surface, rounded on the corners. This is enough to fool a moisture meter. Something like this (random internet picture):

In cool weather, lacking a meter, just split the chunk and touch the fresh surface to your cheek. It should feel warm or neutral = dry. If it’s cold, it’s still wet.


I think wood chunkers like mine “fracture” the ends of the chunks which really speeds up any drying that may be necessary. For that reason I am not a fan of sawing chunks. TomC



Had to split some of my wood in half to see the inside moisture content…got me wandering.

Sacked wood put away in the barn 5% inside and out. Some chunks out in the weather that have been drying since this fall…5% on the inside and 8 to 10% on the outside.

I was very suprised about the wood that was still outside, I thought it would have taken on more moisture…small sampling but interesting results.

Does dry would not take on much moisture after it is initially dried?



As far as wood chips go:
I am slowly working toward a plan to use about 1000 pounds of wood chips a day, one day a week. My chip drying plan is to use old 165 bushel “gravity boxes” to store and dry the chips. Google “165 bushel gravity box” to see what I mean if that term is unfamiliar to you.
They get pretty rusty as they get old and then are pretty cheap. I got my first one for free. They are sometimes sold sitting on the ground, but they are usually installed upon a hay wagon chassis (running gear).
The idea is to cut sections of the angled bottom away, then cover the whole bottom with 1/8" hole hardware cloth (woven wire). I’d fill the box most of the way to the top with more or less freshly cut chips and then blow air or hot air (not engine exhaust gas) upward through the chips from the bottom up. Of course, I’d have to build a plenum of sorts to direct the air. It may take some experimentation to get the air flow right. But the cost to build the thing would be low.
And, as some of you know, I prefer to get my wood chips from roadside operations so volume is not a problem since I know the folks who do most of it around here.
BTW, I classify (sort) my chips before drying, so that takes almost all of the moisture-entrained fines out before I even dry them.

If I ever get the system totally in operation, I plan to use 3 of these setups, with the gravity boxes on wheels for portability, I am pretty sure I can get close to my 1000 pounds of chips into one gravity box. If so, I’d have over 2 weeks to dry a load.
And no, I haven’t quite figured out how to get chips in the dead of winter in Wisconsin. But, since electricity, propane and gasoline are currently pretty cheap here, I still have some time to ponder that issue.

Old Gravity boxes WITH running gear can sell for as little as $250 to $350 at the local on-line auction company.

Pete Stanaitis


Hello Neighbor; [quote=“spaco, post:9, topic:2826”]
And no, I haven’t quite figured out how to get chips in the dead of winter in Wisconsin.

How about spending some extra time during the “warm months” and collect the chips and store them on the ground under a big plastic cover with weight ( old tires ) like the farmers are doing with silage now. During the winter you could pull the chips out as needed For you, compacting the chips down might be a problem if you don’t have a tractor you could run over them. Silage will rot if you don’t get the air out. I don’t think wood would go bad that fast. TomC

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Not really, no. Even wood that’s been out in heavy rain will only get wet on the surface. When the sun comes out and the surface dries again, it will be virtually the same as before.

5% is very low for air dry wood, you must be in a dry climate. Most areas, wood will stabilize around 12-15%.


Well since this IS posted up in the Small Engines section . . .
ALL SMALL RUNNING PISTON ENGINES are kicking out enough heat and air flow to pull down the the engines-sized gasifiers wood chunks from an as cut-green 40% to an easy to gasify just-in time 10% moisture.

I had this mathed out for me by a known named eastern Canadian fellow back in 2008 on Yahoo woodgas.
The heat maths again done for me in 2009 by a smart eastern European engineer woodgassser on the Victory group site.
Then I did it repeatedly for real with loaded working engines 2010 and on.

Winter over out in rains sitting woods here PNW wetside will reach 60% moisture by weight.
Even that can be use-engine dried down to an acceptable 20% just-in-time to monorator hopper refuel.

“How I Learned To Stop Hating MY Rainy Wet Climate for WoodEnergy” Put the all of the engine’s energies to useful work in combined total cycles. IT IS ONLY WASTE HEAT IF YOU WASTE IT AWAY, UNWORKED.
Steve Unruh


Here’s the reply I made to Tom before I realized that it didn’t go to the DOW group:

Thanks for your thoughts, Tom.
Yes, that probably would work, but you MUST dry the chips before storage, and as I have said in the past, the wood must not have been chipped early in the spring. A friend up in Ridgeland had a load of April-cut “power line” chips delivered to his place a couple of years ago. They started to heat and to mold within a week or two. We could only use the outer 3 or 4 inches of chips for woodgas. Luckily for him, they have huge gardens and were able to use the rest of the chips for mulch.
Currently, once I get my smaller batches of chips dry, I put about 40 pounds in a heavy 55 gallon drum liner and toss them into the gravity box that I was talking about.
Lately though, the woodgas thing is on hold, but I hope to get back to it soon.
Because of the woodgas project, I got involved with the “Arduino” when I saw that the GEK folks were using one and that has blossomed into a whole new hobby, including a monthly Arduino group of about a dozen folks.
That, in turn, got some of us buying electronic stuff online, which lead to some interesting cheap induction heating devices and that led to---------

There must be several dozen woodgassers her in Wisconsin. Too bad we all can’t get together from time to time. I think my Ridgeland friend, George Adams, has been over to your part of the state a couple of times for an alternate energy exposition.

Pete Stanaitis


Yup I put it here for us little guys haha. Since our smaller scale machines are not as tolerant as the big guys running trucks. So I think its even more critical to have good dry fuel in our smaller compact machines. Not to mention the scale Im currently looking at. Lots of great ideas coming forth here though.

I set up the 55 gallon drum today, we simply punched a bunch of holes in the bottom and the automotive fan came in today we temporarily mounted it to a piece of OSB board for a lid. I have a brand new lid on the way we will mount this too. Anyways we gave it a go today with good results, it ran for around 4 hours with the torpedo aimed at it. I left it run overnight with out heat to help continue the drying process.

This barrel dryer is stupid simple and was free for the most part. The fan I got on amazon for 20 bucks delivered. This size system is about perfect for small systems if my fuel wasn’t so wet it would not take as long. This stuff I got drips on the floor if you grab a handful out of the pile haha. Yes exhaust heat is also the plan for this as well… Are you running straight through? or through a heat exchanger?


one might look at scrap clothes washer sand dryers for perforated drums some even tumble. as Steve has said many times it is not waist heat if you use it


O.K. Then. Here is the direct easy way to wood-chunk fuel dry Just-In-Time using the engine/gen heads heats and air flows.
Personal use electrical generation figure on using no larger than a 1/2 gallons of gasoline an hour sized systems.
So an easy to figure needed 10 pounds of dried down fuel wood an hour.
For a four hour running time you will need 40 pounds of fuel wood.
Make up six expanded metal baskets as X" x X" x 5" deep. Size to hold that dried down forty pounds of YOUR wood in each basket. Be ~50-70 pounds wet with the basket weight.
Length and width sizing of each basket also to be able to in a square hang directly onto medium open frame gen sets. Or free-standing corners hooked square stacked around the smaller gen-sets.
Four baskets need there. The 5th one set on over the top.
Allow enough off bottom spacing to let fresh air to be drawn into your now made up noise abatement, engine generator enclosing fuel drying “box”. 100% moisture laded warm air and exhaust gases will naturally rise on up through the over-top basket and the top edges of the sides baskets. The engine/genrator blowing around a stirring up inside this enclosure.
Experience will teach you which side of the gen-set kicks out the most heat energy. IMPORTANT. Put the newly filled, wettest crib-bin here first! Near hot engine exhaust dry wood will heat enough to smoke and even catch on fire. Wet wood will not.
Gasifier hopper refueling time - pull the finished, final position crib-bin off, and dump directly into the gasifer hopper.
To this now open spaced side rotate the baskets one position from hottest side to experience found coolest side postion.
That sixth basket was for being able to off-time, idle-time pre-fill directly from however you will chunk. The more steps individual chunks handling the better.

In four hour run times, each basket will have had 20 hours heated forced air dring down.

“Belt and Suspenders” would be wise to keep backed up with at least one hopper loads worth of plastic bagged pre-dried wood.
Just like you’all learned to have some bagged up hearth replenishing charcoal. Right?!

Steve Unruh


That is something I have envisioned before with 4 to 6 baskets. Ive had a hard time with envisioning transferring the heat via heat exchange as then it just wont be worth it with losses. Another contraption I want to build is sort of like this but like a giant tumbler dryer. I plan to run the exhaust straight this via the center tube and rotate it with a gear reduction motor.

Cheers Steve!!


Matt, Steve,

Having a moment of dementia and dejavu at the same time now :wink:
What was that name again from our guy in South Africa, using a WK design for his saw mill, drying his wood with a tumbler in front of his radiator/exhaust…?

I am a huge fan of this kind of thinking… zero waste of energy

Matt, maybe an idea to construct a gas cooler that pre-heats the basket/content before putting it in the hopper ?


Patrick Johnson, Thread Topic. "Woodgas in South Africa ".




My chunks are all from a tree that died on the stump. It was Hard Maple, 30 inches on the butt, and a 40 foot trunk. It was all 15 to 20% moisture when I chunked it all and the sun baked out the rest I guess. I was suprised myself!