Best wood size for gasifiers?

There have been a number of posts on this subject. Based mostly on my experience and some on what others have posted, mine will be: 1) splits/rounds 3-5" or so diameter, 2) some may be larger diameter but those will be put on top of the pile in the firebox, 3) 2" shorter in length than the firebox, and 4) well dried.

No experienced input here but after my first winter with the Eko, I think (hope) I've learned something. I have historically cut or purchased my wood 18 months to 1 year ahead. The wood for next burning season was moved to the wood shed over the last 3 days. Before loading it in the trailer to bring it up to the shed, nearly every piece was given an additional whack or two with the mall. My wood supply is now at a diameter of about 2 inches to 5 inches. Although it split easily, there is the occasional piece that resisted up to 4 whacks that will have to be fed at 8 to 10 inches. I wish I had a moisture meter. After being stacked and covered for one year, the larger pieces appeared to be wet in the center. It was either wet or cold, couldn't tell. The new smaller wood size and my new storage should be an exciting experience next season.

As somebody getting ready to split 12 cord, by weight,(hopefully 9 cord stacked up) of rock maple and beech, this is a timely post. I'm going to push to keep my splits in the 4 to 6 inch size, maybe. But I agree that well dried hardwood, you can deal with stuff bigger. As jebatty pointed out, I will put my big splits on top of the firebox. Didn't notice a huge difference when I used bigger splits this season. My wood was well seasoned also. But a lot of times I haven't had the time, or patience to really pay attention. I was hoping I would, but didn't happen. My goal was to start a fire and get on to other business. The majority of time, I had 160 degree water coming into system in about 45 minutes, and 1 hour and 15 minutes, cruising well past 180. That worked well. Now that I have the next 2 1/2 months off for rehab, this would be a good time to experiment, maybe.


But the more I use this new system, I really like it. My kids might not, because of my shoulder, dad gets to be the foreman. I'll buy the gas and they will enjoy a few days over school vacation , bonding with each other. Over the wood splitter. So, we may have all the right size splits.

My experience is that the best performance comes with a mix of sizes, with the largest being about 4-5" diameter and the average being 'playing card' size, as someone suggested in another thread.

I'll run a bit larger if it's pine and/or really dry wood, and a bit smaller if it's dense hardwood or if the moisture content is a bit higher.

Is that playing card on the long dimension, or the short dimension?

I've gone on the Horse Standard here -- 1 hand, flat across the knuckles -- 4 inches. That, plus picking up a stick from the cut end with my finger tips, which might be about 5 inches plus.

As I work this wood up though, I wonder..... If you had to pay somebody to do this work, the financial advantatges of wood gasification boilers wouild probably 'go up in smoke...' I was going to remark on this and add the following flip comment: "but hey -- long as you have a wood splitter that works, -- and a good woman to run it -- who cares how fine you have to split the wood!" But it turns out that the "Good Woman" is busy and so the joke is on me...

Ah well.

It's no big deal for me at all. Most of my wood comes from smaller tress anyway. If I were using larger trees, I'd probably get a 4-way or 6-way wedge for my splitter.

My best figure of merit is that gasifiers use 40% less wood than well-run conventional indoor boilers, and perhaps 60-70% less than a traditional OWB. So - I could burn two big unsplit pieces, or burn only one but have to split it. Let me think about that......

You can burn bigger pieces if they're really dry. Of course, big pieces take longer to dry.

I also meant answer the question of length, I've been cutting very close to 20 inches.The firebox is 21, and trying to put as much wood in it. The wood I'm burning now is 16 to 18 long. I'm sure I've goofed on a few pieces, but I'm hoping this works better. The few odd ball pieces we'll use for campfires.


I'm with nofossil, with all the figuring i done, a lot of help from this forum, the gasifier is the way to go. At least for me. Best case with a typical indoor boiler would have been at least 8, more likely 10+ cord a year. I've roughly figured 6 should do me, but now that the heating season winds down, I actually should be able to do it on 5 . We'll see, I've got to wait until next jan 17th to find out.

I have found over the years with different wood burning appliances that trying to cut wood to the maximum length ends up in too many frustrating jam-ups while loading and just gets me cranky. If your wood were cut with a processor, nice equal length, square cuts, you can nudge up closer to max but I try to gage my cuts 2" shorter than max so those I cut slightly longer will still make it in.

I worry as well that wood that might just fit in when placed carefully by hand might hang up and bridge as it settles. I don't have the patience for that kind of thing.

I put a stroke limiter on my splitter so that if it can fit between the wedge and push block it has almost an inch of slack in my stove.

I've been using 20" splits 4"s, 5"s, & 6"s with 2"s & 3"s on the bottom. Only several burns with pieces hung-up and causing bridging. 3 cord of hardwood to heat 2352 square feet all winter. Thermostat was 64 degrees 24/7. I'll shut down Monday. Like the Tarm booklet says, It doesn't get any better than this. Next winter maybe less. sweetheat :cheese: