I'm a little confused about wood gasifier vs. owb.

[trailmaker]

I've been reading up on wood gasifiers and they appear to be very efficient, clean burning units. Then I hear about people frustrated with their owb spewing smoke and consuming lots of wood. If they have the same function (maybe they don't) then why would anyone get on owb instead of a wood gasification unit. Are owb's cheaper? I'm sure I'm missing something. Can anyone explain to me the major differences between these two and the advantages and disadvantages. thanks.

 

[rob206]

One reason OWB's appeal to people is because the unit sits outside and away from the house. Another reason could be price, because the gassifiers are pricier. Also, from what I have read, the wood going into a gassifier needs to be quite dry. An OWB already has the water storage built in, no need to locate a used 500 gallon propane tank, or two and set them up for storage.

Smoke? Don't believe the hype about OWB's. I burn seasoned wood and my boiler produceses very little smoke when the damper is open, and when it is closed, there is just a wisp of smoke floating out of the stack.

Advantage of the gassifiers is less wood consumption and maybe longer useful life of the unit.

 

[taxidermist]

I own a eko 60 gasser the difference is a owb is a set it and forget it unit. The eko you build a fire in it and burn it wide open and store the btu in water storage. For me I have the eko in my barn and 2 500 gal tanks in my basement. When it is really cold out I have to burn for about 10 hrs to heat my 1000 gal of water to 175* then the rest of the 14hrs I run off storage. The wood needs to be seasoned to 30% or lower for the best burns. If you burn seasoned wood in a owb it will not smoke but most people throw in wet wood and they smoke like crazy. The eko will not burn wet wood.


Rob

 

[Jon E]

My OWB (CB 5648) will burn just about anything - wet, green, punky, wood if necessary; shovels of bark chips; paper and cardboard; big stuff, little stuff - it eats it all. However, I try very hard to feed it clean, dry, split, well seasoned wood. The same wood you'd feed a gasifier. My business partner installed an EKO 40 in his house and he has a 1000 gallon insulated tank in his basement. He can run 24-36 hours in the winter, might even be a week in the summer with solar backup. He can't burn any of the junk I can. The nice thing about the OWB is that I have a pile of stuff I wouldn't feed an indoor woodstove or gasifier, and about once a week I'll try to get a big bed of hot coals going and toss some of that punky, gnarly, knotty junk in there with some smaller sticks and it will burn right up.

Also, if the OWB is fed properly, it will not emit much smoke at all. Almost nothing visible toward the high end of a burn cycle, and just thin wisps of smoke, probably more steam than smoke, when it's shut down.

 

[IndyIan]

I'd estimate a good wood gasifier would be about twice as efficient than most OWBs (ones without firebrick) when burning good dry wood.
A gasifier has much higher burn temperatures so more "smoke" is burned making it more efficient.
The low tech OWB's do have advantages of course but efficiency isn't one of them. I drive by a guy that sells OWBs that always has his boiler stinking up the neighborhood... It's not a good sales pitch. The load it and forget it for 24 hours strategy with a low heat load makes alot of stink from any boiler.
Ian

 

[Dirttracker]

Overall OWBs are less expensive and easier to operate. Gasifiers are more efficient and the overall installed cost is higher. I had a Pacific Western OWB for 5 years and burned 10 to 12 full cords per year. At the end of last season, the OWB as it was leaking from numerous locations and was not worth fixing. I replaced it this winter with a gasifier. For me, using less wood and being able to have a closed water system were the deciding factors. Based on what I have used so far I believe I'm using less than half of the wood I used with the OWB. The wood needs to be split smaller, so even though you are handling less wood it takes more time to process. The gasifier takes more time to tend as you are re-lighting the fire almost every time you load it. There also seems to be a learning curve to figure out how much wood to load based on wether conditions and anticipated need for heat. It's definately not as simple to operate as the OWB.

I only burned dry wood in the OWB, so I did not notice the "giant deadly noxious smoke cloud" that seems to be generally associated with the word OWB these days. The OWB smelled on ocasion when it was idling and I don't get that odor with the gasifier. Other than at idle I think if you burn good dry wood in an OWB the sights/smells are not any worse than any other wood fire.

When I bought, the price of the gasifier was about $1000 more than a CB 5036, but when you add up all of the support equipment, I probably spent another $4000 on bits and pieces to install the gasifier. The additional price includes building a shed to house the unit, a 500 gal tank for heat storage, and miscellaneous plumbing to hook it all together. Of course I just had to buy everything last November & December when prices were at their peak. The current price for the additional materials may be a bit less.