Pros-Cons traditional wood boiler vs. Gassification?

[Expat_Latvia]

I recently moved into a house with a wood furnace-boiler system (powering floor heating and radiators), specifically a Viadrus (Czech brand) U22 with 7 sections (~40 kW rating with firewood). It's a pretty old and "dumb" style of furnace, no electronics, no fans, nothing fancy....just a furnace/boiler. To cut to the chase, does the following sum up the advantages of gassification vs. old style furnaces/boilers?

-somewhat more efficient at getting heat out of wood
-much cleaner, much less ash and cleaning necessary
-less gas/smoke leaking out into the house (usually have fans etc.)
-burn longer per load of fuel
-less pollution, particulate pollution into the air

Now that's all well and good but if that's all there is it isn't enough for me to justify replacing my existing furnace/boiler that is pretty much working fine with a $10,000+ gassification furnace/boiler like a Fröling, even thought it's clearly a superior piece of equipment.

My perception is that gassification furnaces/boilers are mostly forced on people by local regulations controlling air pollution and that, all things being equal, they aren't really justifiable vs. traditional furnances/boilers on a cost for performance basis. Am I on the money here or is there something I'm missing that's going to convince me to open the purse strings and shell out $10,000+ plus installation costs to swap out my dirty old furnace with a fancy new gassification one?

 

[peakbagger]

IMHO, if your wood is cheap and plentiful and you are willing to clean a chimney, conventional wood boilers have worked for decades. The problem is usually in "shoulder season" where you want overnight heating but do not need heating when the sun comes out during the day. In most cases folks wake up cold, fire off the boiler and warm up the place but then the demand effectively stops with boiler half full of wood. In this case the boiler will shut off its air supply to throttle the fire and that is when it become quite inefficient as boiler and very efficient as creosote generator and a producer of localized low air quality. IMHO, the far bigger impact on improved efficiency and reduced emissions is the addition of a thermal storage tank. That decouples the boilers heat generation from heating demand. The US distributor of Tarm no longer imports Tarm's (their final model was reportedly a rebadged boiler made by another manufacturer). The distributor now supplies Froling boilers. In both cases the distributor reportedly would not warrantee an installation without thermal storage.

Once adequate thermal storage is added, then adding in gasification means a cleaner more consistent burn. A gasification boiler gets its combustion temp up faster so less pollution up the stack and less condensable liquids to condense into creosote into the stack. The overall efficiency is higher due to lower stack temps.

My current wood/coal boiler (100,000 BTU/hr/ 29 KWs )is decidedly not a gasifier with all combustion air coming in through a bottom grate but I do have thermal storage (550 gallons/2500 liters) . It does burn hot quickly and creosote is not an issue but its always operated to heat up a storage tank quickly with no part throttle combustion. The flue gas leaves the heat exchanger at a high temp. I am in the process of purchasing a lightly used Tarm Gasifier which was being used without storage and there is pretty good evidence that it was a creosote producer as operated. The prior owner appears to have kept up with cleaning. My guess is if I replace my current boiler with the gasifier , my wood use will drop as it has more heat exchanger surface area leading to a lower stack temperature but the trade off will be loss of flexibility in operation with wood that has been poorly dried. I am thinking of building a new home and the gasifier may just get installed in the new home and I will keep my current setup in the short term at my current home. I also supplement my shoulder season wood burning with a cold climate air source heat pump fed from surplus solar power. The regulatory climate in my state supports net metering and electric space heating so it makes sense for me but would not make sense in any area that discourages solar or electric space heating.

 

[Bad LP]

I'll add on to the above in that if my boiler sprung a leak tomorrow I'd replace it in a heartbeat with another gasser. I'll be living full time where the boiler is installed soon it looks. I too have 600 gallons of storage so there is no shutdown of the boiler in mid burn. My two complaints are domestic hot water of the gasser and the fact if I replace it I will go up in size. I knew I was tight on my BTU needs but the boiler was at an attractive price.

I was questioning my sanity on starting this project so long ago when heat was cheap(er) but with the current jumps in price I may get a chance to realize some real world cash savings.

One thing that I look at now is IF my boiler was to fail is would I stay with wood? I've got a lot of money tied up in not only the boiler but also all the equipment to process it from standing trees down to tossing the ash on the snow banks and it was all done thinking 10 years ago at the age of 50. Now at 60 I do ask myself how long can I really do it? Should I look at a pellet boiler? What is going to happen with the price of pellets down the road? They need a lot of energy to process and get on site ready for me to burn. I'd be open to any and all market prices and exposure but with wood cut off my land or even if I continued to buy it my wood guy has investments in getting the wood to me like land leases, saws, skidder, trucking, processing then more trucking.

I don't think its a black or white response to everybody and their life styles. My health today tells me I made the right choice but who knows what next year brings to any of us?

 

[peakbagger]

BTW, the Tarm I am am buying is a Tarm 40 140K btu unit which is definitely larger than my current Burnham. I think I will miss not having more storage. They recomend 1000 gallons for the Tarm 40 so I will be short. The new house will have low temperature emitters so I will have end up with more effective storage capacity.

I have the same temptation, I will be 63 or 64 before the new house gets built (optimistically.) An air source or a small geothermal unit tied to storage on a super efficient home is tempting with a bank of solar panels out front and probably a home battery. Add in a backup woodstove or two and its quite tempting. I do have an effectively infinite wood source on my lot but its still a lot of work to cut split and move it.

Then again in the US biomass is on the fence as to if its considered carbon neutral, currently it is but the southern pellet mills shipping to Europe are a pretty big target and biomass in general could be swept away.

 

[Expat_Latvia]

IMHO, if your wood is cheap and plentiful and you are willing to clean a chimney, conventional wood boilers have worked for decades. The problem is usually in "shoulder season" where you want overnight heating but do not need heating when the sun comes out during the day. In most cases folks wake up cold, fire off the boiler and warm up the place but then the demand effectively stops with boiler half full of wood. In this case the boiler will shut off its air supply to throttle the fire and that is when it become quite inefficient as boiler and very efficient as creosote generator and a producer of localized low air quality. IMHO, the far bigger impact on improved efficiency and reduced emissions is the addition of a thermal storage tank. That decouples the boilers heat generation from heating demand. The US distributor of Tarm no longer imports Tarm's (their final model was reportedly a rebadged boiler made by another manufacturer). The distributor now supplies Froling boilers. In both cases the distributor reportedly would not warrantee an installation without thermal storage.

Once adequate thermal storage is added, then adding in gasification means a cleaner more consistent burn. A gasification boiler gets its combustion temp up faster so less pollution up the stack and less condensable liquids to condense into creosote into the stack. The overall efficiency is higher due to lower stack temps.

My current wood/coal boiler (100,000 BTU/hr/ 29 KWs )is decidedly not a gasifier with all combustion air coming in through a bottom grate but I do have thermal storage (550 gallons/2500 liters) . It does burn hot quickly and creosote is not an issue but its always operated to heat up a storage tank quickly with no part throttle combustion. The flue gas leaves the heat exchanger at a high temp. I am in the process of purchasing a lightly used Tarm Gasifier which was being used without storage and there is pretty good evidence that it was a creosote producer as operated. The prior owner appears to have kept up with cleaning. My guess is if I replace my current boiler with the gasifier , my wood use will drop as it has more heat exchanger surface area leading to a lower stack temperature but the trade off will be loss of flexibility in operation with wood that has been poorly dried. I am thinking of building a new home and the gasifier may just get installed in the new home and I will keep my current setup in the short term at my current home. I also supplement my shoulder season wood burning with a cold climate air source heat pump fed from surplus solar power. The regulatory climate in my state supports net metering and electric space heating so it makes sense for me but would not make sense in any area that discourages solar or electric space heating.

Thanks, I didn't know what creosote was. I thought it was rain getting in my chimney.

My understanding of the storage tanks is that they are sort of added into homes that weren't really designed for modern boiler heating (no floor heating tubes under all the stone tile floors...or there are no stone tile floors but rather carpets and such). I have floor heating tubes running under the floors in much of my house so those are my "storage" capacity for heated water. It's a big design difference.

"In this case the boiler will shut off its air supply to throttle the fire..." Yea mine doesn't do that. It is all manual, very old school. It burns until there's nothing left to burn or I cut off the air supply. The only temperature gauges in the house are glass thermometers I glued to the wall in various places. It burns fast and requires a lot of feeding to keep going. As you say it will go out and get cold over night during sleeping hours.

 

[Expat_Latvia]

I'll add on to the above in that if my boiler sprung a leak tomorrow I'd replace it in a heartbeat with another gasser. I'll be living full time where the boiler is installed soon it looks. I too have 600 gallons of storage so there is no shutdown of the boiler in mid burn. My two complaints are domestic hot water of the gasser and the fact if I replace it I will go up in size. I knew I was tight on my BTU needs but the boiler was at an attractive price.

I was questioning my sanity on starting this project so long ago when heat was cheap(er) but with the current jumps in price I may get a chance to realize some real world cash savings.

One thing that I look at now is IF my boiler was to fail is would I stay with wood? I've got a lot of money tied up in not only the boiler but also all the equipment to process it from standing trees down to tossing the ash on the snow banks and it was all done thinking 10 years ago at the age of 50. Now at 60 I do ask myself how long can I really do it? Should I look at a pellet boiler? What is going to happen with the price of pellets down the road? They need a lot of energy to process and get on site ready for me to burn. I'd be open to any and all market prices and exposure but with wood cut off my land or even if I continued to buy it my wood guy has investments in getting the wood to me like land leases, saws, skidder, trucking, processing then more trucking.

I don't think its a black or white response to everybody and their life styles. My health today tells me I made the right choice but who knows what next year brings to any of us?

Yea I am in the process of building out the fire wood pipeline from family owned land to my furnace. From felling trees, to hauling them out of the woods, to processing to dry in the wood shed on the farm, hauling them to the house (2 hours away) etc. It's quite an undertaking.

Hopefully by the time I am hitting 60 my sons will pick up the slack, that's the plan anyway. My wife's father used to burn wood and he switched to wood pulp/biomass brickettes and swears by them now. Pellet boilers are also popular here for many reasons (the feeding system is a big one).

 

[Expat_Latvia]

BTW, the Tarm I am am buying is a Tarm 40 140K btu unit which is definitely larger than my current Burnham. I think I will miss not having more storage. They recomend 1000 gallons for the Tarm 40 so I will be short. The new house will have low temperature emitters so I will have end up with more effective storage capacity.

I have the same temptation, I will be 63 or 64 before the new house gets built (optimistically.) An air source or a small geothermal unit tied to storage on a super efficient home is tempting with a bank of solar panels out front and probably a home battery. Add in a backup woodstove or two and its quite tempting. I do have an effectively infinite wood source on my lot but its still a lot of work to cut split and move it.

Then again in the US biomass is on the fence as to if its considered carbon neutral, currently it is but the southern pellet mills shipping to Europe are a pretty big target and biomass in general could be swept away.

Yea the powers that be surely do not like you being independent in any way. Obviously by definition burning firewood is "carbon neutral" but they'd rather you use electricity generated by burning gas from another country to heat your home. With the hysteria right now about sky rocketing oil and gas prices in Europe I am very glad I can heat my home by simply burning wood. There's no shortage of trees here.

 

[Bad LP]

BTW, the Tarm I am am buying is a Tarm 40 140K btu unit which is definitely larger than my current Burnham. I think I will miss not having more storage. They recomend 1000 gallons for the Tarm 40 so I will be short. The new house will have low temperature emitters so I will have end up with more effective storage capacity.

I have the same temptation, I will be 63 or 64 before the new house gets built (optimistically.) An air source or a small geothermal unit tied to storage on a super efficient home is tempting with a bank of solar panels out front and probably a home battery. Add in a backup woodstove or two and its quite tempting. I do have an effectively infinite wood source on my lot but its still a lot of work to cut split and move it.

Then again in the US biomass is on the fence as to if its considered carbon neutral, currently it is but the southern pellet mills shipping to Europe are a pretty big target and biomass in general could be swept away.

Linkletter (land and logging co) has a huge pellet making mill about 45 mins from the house in Athens named Maine Wood Pellets and they deliver both bulk and pallets.
Lot of moving parts in a pellet boiler and more parts if I set up for bulk but the house is easily served by either method, wood or pellets.
My wood room currently has 6.5 cords in it right now and there's still room for an easy 4 more full cords if I take out my splitter and logging winch.
I don't have to tell you that the 1000 gals would be the proper way to do it. A 40 is what I should have

 

[salecker]

Pro's and Cons
Old traditional water heaters
Pro's cheap to get into,basic design limited controls to go bad
Con's Used a lot of wood,yea used a lot of wood,bad smoke for your neighbors,short lifespan because of the design
Gasification Boilers
Pro's use less wood for the same heat,less smoke for your neighbors,less wood to process
Con's Cost to do it right,

 

[hobbyheater]

My perception is that gassification furnaces/boilers are mostly forced on people by local regulations controlling air pollution and that, all things being equal, they aren't really justifiable vs. traditional furnances/boilers on a cost for performance basis. Am I on the money here or is there something I'm missing that's going to convince me to open the purse strings and shell out $10,000+ plus installation costs to swap out my dirty old furnace with a fancy new gassification one?

We called it the pig. It burned 22 cords in a year!


This one burned 16 cords a year without storage and 10 cords a year with storage!



The Jetstream was our first successful Gasification boiler with storage. It averaged 4 cords a year over 35 years.
Over 35 years, gasification with storage burned 630 less cords of wood. You would have to force me to use something like the pig !

 

[JMihevic]

. . . . Old traditional water heaters -- Con's Used a lot of wood,yea used a lot of wood,bad smoke for your neighbors,short lifespan because of the design. . . .

I disagree with short life span. My Tarm MB 55 that I installed in 1980 is heating my house today, after 42 years of service. I use it every winter. The only part I replaced was the Samson draft regulator thermal sensor that is use to control the draft damper. Wood usage is not that bad. It is not a problem for me.

John M.

 

[Expat_Latvia]

Ended up going with a Domusa DualTherm 35KW which burns pellets or logs and has fans and all that. I think it's a gassification furnace but maybe not as much as the Austrian and German brands like SolarFocus and Froeling. One of the things I like most about this system is I can load logs and the system will ignite them automatically using pellets, then I can set it to either switch to pellets when the logs are gone or just stop and wait for more logs to be loaded. My house (3800 square feet) has never been this warm. The old system was a nightmare. The new one burns cleaner, burns hotter, burns more consistently, generations more heat, doesn't produce much ash at all.

Total cost of furnace, new domestic hot water tank, accumulation tank, various pumps and pipes etc. + delivery and installation: $13,000. Worth every penny to me to keep my house and family warm in this very cold climate (-30C is not unheard of. Tonight -12C).

Edit: also I had no idea what I was talking about with thermal buffer tanks/accumulation tanks when I started researching and discussing this matter. The addition of the thermal buffer/accumulation tank is a BIG deal for the overall efficiency and comfort of the system.

 

[TimfromPittsburgh]

I would concur with other responders that the lifespan of a wood fired boiler can be quite long. In my case, a Tarm 502 (with oil backup) which was installed in 1996 is still functioning very well. over the years I added 820 gallons of unpressurized storage which hugely reduced creosote accumulation in the boiler and chimney. I can't gauge the effect of storage on woodburning efficiency but with heat storage we have been able to greatly reduce the amount of heating oil used. When the day comes that our boiler can no longer be used I would go for state of the art gasification boiler but not before.