My firewood can be TOO dry!!

[Rich L]

Ya I had picked up about 3/4 of a cord of wood last year from my tree guy and that wood was so dry it burned really quickly.I'm thinking I should of mixed it with some semi seasoned wood to make the burn last longer.As I look at my wood from last fall it looks gray from all the heat we've been getting.It's uncovered and I hoped it's not too dry.Even the two month old wood when split gives off that dry wood sound like a crack rather than a thud.This summer has been so hot and dry the dirt is like dust and the wood is baking.Give me some rain.

What kind of wood was it and rain is not going to put any moisture back into the wood, I have some 2 year old oak that was dead on the ground when I cut it and the 5 inch rounds are 17% on the inside, as the article stated (I believe) he has never seen wood below 14%. Having rotton punky wood is a whole other issue.

That wood was oak.It was solid but light in weight and burnt fast.This years wood that is graying is maple.I just went out and lifted some splits and they have good weight to them.So the graying is just a cosmetic thing.This wood will give a good long burn.Rotten punky wood I stay away from.I tell folks to smash it up with a sledge and use it as a peat moss or put it in the compost pile.Not a good burner at all.

Been burning oak for 30 years and the only "light" oak I have run in to was punky, so not sure what you had.

Now you got me thinking.Maybe it wasn't oak.The wood guy said it was oak.It was all split and had a nice golden color to it.I couldn't tell what it was.It cost me $50.00 and I just moved on it quick.One thing for sure it wasn't pine.

 

[Backwoods Savage]

Maybe it was popple.

 

[Pagey]

Maybe it was popple.

Or cardboard. :lol:

 

[Rich L]

Maybe it was popple.

Or cardboard. :lol:

Now that's funny.Thanks for the chuckle.It might of been Popple however fifty bucks for almost a cord still worked out for me.It lasted about ten days.

 

[Hiram Maxim]

i often burn the outs from our kiln dried maple production....at 6-8 % moisture ,all i can say is watch -out.just a couple of 1x6 x 12 inch peices and witha bit too much air,you get that weird smell comming off your stove that tells you maybe your getting a might warm....

Not trying to high-jack the thread :roll:
Roddy,

At what temperature do you use when kiln drying?

I spoke to a guy that has a cedar lumber mill and he told me 100 °F for three days in the kiln.

Thought seemed pretty low temp?

THx, Hiram

 

[North of 60]

water boils @ 212*f, woodgas @~600*, fire@~1200*

Those #s are only good at sea level. People that are at 4000+ are gonna have a different story along with results. Time to de-rate those #s. Oil and gas #s will show significant change at 2000 and up.
Just saying.

 

[vvvv]

water boils @ 212*f, woodgas @~600*, fire@~1200*

Those #s are only good at sea level. People that are at 4000+ are gonna have a different story along with results. Time to de-rate those #s. Oil and gas #s will show significant change at 2000 and up.
Just saying.

http://www.newton.dep.anl.gov/askasci/chem00/chem00182.htm

 

[roddy]

i often burn the outs from our kiln dried maple production....at 6-8 % moisture ,all i can say is watch -out.just a couple of 1x6 x 12 inch peices and witha bit too much air,you get that weird smell comming off your stove that tells you maybe your getting a might warm....

Not trying to high-jack the thread :roll:
Roddy,

At what temperature do you use when kiln drying?

I spoke to a guy that has a cedar lumber mill and he told me 100 °F for three days in the kiln.

Thought seemed pretty low temp?

THx, Hiram

for hard maple we start at about 39 degrees celcius and over about a 10 day span,we bring the temp up to 62 degees celcius for the last day,which is the conditioning period(thats the time we put moisture to he wood to get rid of the stress in the lumber that has occured during the drying period....ive never done cedar,but for pine the times and temp are close to the same as maple.you are right in assuming that those temps you heard seem a bit low.(again i,m not absolutely sure about cedar)also we are taking the lumber to 6-8 % moisture,which maybe different than what your cedar guy is doing.....rod

 

[Battenkiller]

Those #s are only good at sea level. People that are at 4000+ are gonna have a different story along with results. Time to de-rate those #s. Oil and gas #s will show significant change at 2000 and up.

Everything changes up high.

Most easy to measure would be draft. A chimney at 1 mile high will have 20% less capacity and a lower static draft than the same chimney at sea level. What would that mean regarding super-dry wood? I'm not at all certain, but I can think of one scenario. With reduced draft, residence time for flue gases would be longer. Adding a bunch of small splits of extremely dry wood onto a raging bed of coals could lead to a system packed with smoke.

Even if you opened up the air all the way (which can lead to some nasty backpuffing), there would still be denser smoke in this system than in the same one operating at sea level. It's totally possible that not enough air could be introduced to completely burn off this smoke. As well, there is less oxygen at those levels, so you would need even more air volume introduced for combustion to be complete. This could exacerbate the problem. Lower draft will also mean lower intake velocity, reducing the mixing effect of turbulence on air and wood gases, leading to incomplete combustion. If you can get the fire hot enough, the higher flue temps will increase the draft (and therefore, the intake velocity), resulting it improved combustion, but then more heat goes up the chimney. All things considered, not an efficient and controlled burn.

All hypothetical, I've never burned above 2000'. Maybe Beetle-kill can give us his observations at 8000'? ;-)

My feeling on the subject it that if you put a big load of kiln-dried pine cutoffs or split 2x4s into a hot stove, you are going to have problems, like creosote formation, lower temperature burns, severe backpuffing, and wasted fuel. If you put large splits or rounds of dense super-dry hardwood into the same stove, pyrolysis will occur much slower and the stove should be able to handle it no problem if you give it enough air. The answer lies in experience and observation, and not in a set of absolutes. But I personally think it's good to let new burners know that dry wood alone won't solve all their burning problems, and that in some instances, drier wood wastes more wood through smoke than less-dry wood.

Stoves are designed for wood around 20% MC, stoves are tested with wood around 20% MC, so it stands to reason that 20% MC should not be considered to be merely adequate, but rather, the ideal.

 

[Battenkiller]

for hard maple we start at about 39 degrees celcius and over about a 10 day span,we bring the temp up to 62 degees celcius for the last day,which is the conditioning period(thats the time we put moisture to he wood to get rid of the stress in the lumber that has occured during the drying period..

What's the RH of that air at 39ºC? I can go from fresh cut cherry to <20% MC in my stove room in less than 2 weeks. Temps are up around 86ºF (30ºC) and RH about 20-25%, fans blowing directly on the wood.

I'm curious about the kiln schedule you use. I've read that most commercial kilns start at high temps and high RH until the FSP (about 30% MC for most woods) is reached, and then humidity is gradually dropped. This is supposed to prevent case hardening and other internal stresses from occurring. If I understand what you are saying, you allow them to occur and then condition them out later? Correct me if I misunderstood.

 

[dannynelson77]

I got some wood last winter (mostly Red Oak) from an old farmer that had it stored in his barn for years. It was definitely oak, but I do have to say it was so dry it was very light for Oak. And it did burn much faster than any Oak I have burned. Too fast IMO. My moisture meter read it was 9% when i split a piece. IMO, it was too dry. Put out greaat heat but I had to keep feeding the stove way more than I normally do.

 

[oldspark]

I got some wood last winter (mostly Red Oak) from an old farmer that had it stored in his barn for years. It was definitely oak, but I do have to say it was so dry it was very light for Oak. And it did burn much faster than any Oak I have burned. Too fast IMO. My moisture meter read it was 9% when i split a piece. IMO, it was too dry. Put out greaat heat but I had to keep feeding the stove way more than I normally do.

Maybe RichL did have some old oak that was light, I remember reading other posts about very old wood that was inside and they thought the wood was fine but maybe it burnt too quick and they did not realize it was too dry. I burnt some wood while we were camping that was very old ash and it seemed like it still had a "normal" amount of moisture in t when I split it, had to be a good 10 years old, plus the wood was a normal weight for white ash.

 

[dannynelson77]

Yea I think being in the barn, kept it get so low on the moisture scale. In the hot summer it probably was like a kiln in there.....

 

[Rich L]

I got some wood last winter (mostly Red Oak) from an old farmer that had it stored in his barn for years. It was definitely oak, but I do have to say it was so dry it was very light for Oak. And it did burn much faster than any Oak I have burned. Too fast IMO. My moisture meter read it was 9% when i split a piece. IMO, it was too dry. Put out greaat heat but I had to keep feeding the stove way more than I normally do.

Gee it's good to see another has had a similar experience as I.

 

[North of 60]

Those #s are only good at sea level. People that are at 4000+ are gonna have a different story along with results. Time to de-rate those #s. Oil and gas #s will show significant change at 2000 and up.

Everything changes up high.

Most easy to measure would be draft. A chimney at 1 mile high will have 20% less capacity and a lower static draft than the same chimney at sea level. What would that mean regarding super-dry wood? I'm not at all certain, but I can think of one scenario. With reduced draft, residence time for flue gases would be longer. Adding a bunch of small splits of extremely dry wood onto a raging bed of coals could lead to a system packed with smoke.

Even if you opened up the air all the way (which can lead to some nasty backpuffing), there would still be denser smoke in this system than in the same one operating at sea level. It's totally possible that not enough air could be introduced to completely burn off this smoke. As well, there is less oxygen at those levels, so you would need even more air volume introduced for combustion to be complete. This could exacerbate the problem. Lower draft will also mean lower intake velocity, reducing the mixing effect of turbulence on air and wood gases, leading to incomplete combustion. If you can get the fire hot enough, the higher flue temps will increase the draft (and therefore, the intake velocity), resulting it improved combustion, but then more heat goes up the chimney. All things considered, not an efficient and controlled burn.

All hypothetical, I've never burned above 2000'. Maybe Beetle-kill can give us his observations at 8000'? ;-)

My feeling on the subject it that if you put a big load of kiln-dried pine cutoffs or split 2x4s into a hot stove, you are going to have problems, like creosote formation, lower temperature burns, severe backpuffing, and wasted fuel. If you put large splits or rounds of dense super-dry hardwood into the same stove, pyrolysis will occur much slower and the stove should be able to handle it no problem if you give it enough air. The answer lies in experience and observation, and not in a set of absolutes. But I personally think it's good to let new burners know that dry wood alone won't solve all their burning problems, and that in some instances, drier wood wastes more wood through smoke than less-dry wood.

Stoves are designed for wood around 20% MC, stoves are tested with wood around 20% MC, so it stands to reason that 20% MC should not be considered to be merely adequate, but rather, the ideal.

So I take it that you agree with me on elevation.
By the way, Blaze King prefers the MC of the wood for there Cat stoves to be between 12 to 18%.

 

[Battenkiller]

So I take it that you agree with me on elevation.

Not sure. All you said is that things change above 4000'. My position is that they may very well change for the worse regarding clean burns when using overly dry wood. Do you agree with that?


Here's the key points of the article as I view it:

Properly seasoned firewood still has a fair amount of water in it, say 15 to 20 of its weight. That water acts like a regulator of the combustion process along with a few other factors like piece size, load configuration and combustion air supply.

The dryer the wood, the more dense is the smoke at a given heat input rate.

The problem is that a firebox load of very dry wood produces far more smoke than the air supplies of stoves are designed to provide.

Wood that is very dry produces a fire that is hard to control without making a lot of smoke.

I suppose that firewood could get very dry by natural seasoning in desert conditions. Or firewood stored in old barns, which are like kilns in hot summer weather.

The right band of firewood moisture is between 15 and 20%.

[EPA stoves] are designed for wood that has a moisture content of twenty percent plus or minus one or two percent. Once you go far outside this band, their emission rate goes up.
If you have some very dry firewood, like kiln-dried cut offs or old wood stored in a hot place, mix it with regular firewood to raise the moisture content of a full load.

JG

Note the initials at the bottom. This article was written by none other than John Gulland. I don't know about his personal experiences using old wood stored in a barn or in the desert, but here is his CV:


http://www.gulland.ca/abtjohn.htm


The least of your worries with overly dry wood is that it burns too fast. It's the excessive smoking that can cause problems - in your burn, and in your flue. :zip:

 

[vvvv]

So I take it that you agree with me on elevation.

Not sure. All you said is that things change above 4000'. My position is that they may very well change for the worse regarding clean burns when using overly dry wood. Do you agree with that?


Here's the key points of the article as I view it:

Properly seasoned firewood still has a fair amount of water in it, say 15 to 20 of its weight. That water acts like a regulator of the combustion process along with a few other factors like piece size, load configuration and combustion air supply.

The dryer the wood, the more dense is the smoke at a given heat input rate.

The problem is that a firebox load of very dry wood produces far more smoke than the air supplies of stoves are designed to provide.

Wood that is very dry produces a fire that is hard to control without making a lot of smoke.

I suppose that firewood could get very dry by natural seasoning in desert conditions. Or firewood stored in old barns, which are like kilns in hot summer weather.

The right band of firewood moisture is between 15 and 20%.

[EPA stoves] are designed for wood that has a moisture content of twenty percent plus or minus one or two percent. Once you go far outside this band, their emission rate goes up.
If you have some very dry firewood, like kiln-dried cut offs or old wood stored in a hot place, mix it with regular firewood to raise the moisture content of a full load.

JG

Note the initials at the bottom. This article was written by none other than John Gulland. I don't know about his personal experiences using old wood stored in a barn or in the desert, but here is his CV:


http://www.gulland.ca/abtjohn.htm


The least of your worries with overly dry wood is that it burns too fast. It's the excessive smoking that can cause problems - in your burn, and in your flue. :zip:

it aint necessarily smoke, it can be uncombusted CO which is a significant energy source of heat & is invisible!

 

[dannynelson77]

Yea with the dry Oak I had I did not have a smoke problem. Only problem I had was it burning too quickly!

 

[vvvv]

Those #s are only good at sea level. People that are at 4000+ are gonna have a different story along with results. Time to de-rate those #s. Oil and gas #s will show significant change at 2000 and up.

Everything changes up high.

Most easy to measure would be draft. A chimney at 1 mile high will have 20% less capacity and a lower static draft than the same chimney at sea level. What would that mean regarding super-dry wood? I'm not at all certain, but I can think of one scenario. With reduced draft, residence time for flue gases would be longer. Adding a bunch of small splits of extremely dry wood onto a raging bed of coals could lead to a system packed with smoke.

Even if you opened up the air all the way (which can lead to some nasty backpuffing), there would still be denser smoke in this system than in the same one operating at sea level. It's totally possible that not enough air could be introduced to completely burn off this smoke. As well, there is less oxygen at those levels, so you would need even more air volume introduced for combustion to be complete. This could exacerbate the problem. Lower draft will also mean lower intake velocity, reducing the mixing effect of turbulence on air and wood gases, leading to incomplete combustion. If you can get the fire hot enough, the higher flue temps will increase the draft (and therefore, the intake velocity), resulting it improved combustion, but then more heat goes up the chimney. All things considered, not an efficient and controlled burn.

All hypothetical, I've never burned above 2000'. Maybe Beetle-kill can give us his observations at 8000'? ;-)

My feeling on the subject it that if you put a big load of kiln-dried pine cutoffs or split 2x4s into a hot stove, you are going to have problems, like creosote formation, lower temperature burns, severe backpuffing, and wasted fuel. If you put large splits or rounds of dense super-dry hardwood into the same stove, pyrolysis will occur much slower and the stove should be able to handle it no problem if you give it enough air. The answer lies in experience and observation, and not in a set of absolutes. But I personally think it's good to let new burners know that dry wood alone won't solve all their burning problems, and that in some instances, drier wood wastes more wood through smoke than less-dry wood.

Stoves are designed for wood around 20% MC, stoves are tested with wood around 20% MC, so it stands to reason that 20% MC should not be considered to be merely adequate, but rather, the ideal.

So I take it that you agree with me on elevation.
By the way, Blaze King prefers the MC of the wood for there Cat stoves to be between 12 to 18%.

you're right about altitude changing the boiling temps. question is= does it also change the flash point? got it posted on scientific forums but no answers yet.

 

[Battenkiller]

it aint necessarily smoke, it can be uncombusted CO which is a significant energy source of heat & is invisible!

Right.... all that carbon monoxide again. :ahhh:

Pook, the gist of the article is about increased particulate emissions (smoke) as you deviate either way from the ideal moisture content band of 15-20% MC, not about heat loss through unburned CO gas. CO never clogged anybody's flue with creosote and set their house on fire.

Not that there isn't significant heat loss going on as well. CO has one of the highest ignition temperatures of all wood gases, and it is one of the more abundant products of pyrolysis. It also has a lot of potential heat energy locked up in it, so making too much CO too soon is a waste of good wood.

I think it's a lot more important to properly size the pieces of wood that you add to the fire. Highly seasoned wood should be used in larger pieces than less seasoned wood. However you do it, pay attention to the top of the stack. If you don't see smoke, pyrolysis is proceeding at the rate it should for the wood you are using, and for your particular stove. If the rate of pyrolysis isn't excessive, you're not making excessive CO either.

 

[vvvv]

it aint necessarily smoke, it can be uncombusted CO which is a significant energy source of heat & is invisible!

Right.... all that carbon monoxide again. :ahhh:

Pook, the gist of the article is about increased particulate emissions (smoke) as you deviate either way from the ideal moisture content band of 15-20% MC, not about heat loss through unburned CO gas. CO never clogged anybody's flue with creosote and set their house on fire.

Not that there isn't significant heat loss going on as well. CO has one of the highest ignition temperatures of all wood gases, and it is one of the more abundant products of pyrolysis. It also has a lot of potential heat energy locked up in it, so making too much CO too soon is a waste of good wood.

I think it's a lot more important to properly size the pieces of wood that you add to the fire. Highly seasoned wood should be used in larger pieces than less seasoned wood. However you do it, pay attention to the top of the stack. If you don't see smoke, pyrolysis is proceeding at the rate it should for the wood you are using, and for your particular stove. If the rate of pyrolysis isn't excessive, you're not making excessive CO either.

lol the point of the article is to challenge folksy wisdom thru education so u respond with folksy wisdom about the burn which i'd believe if u had some actual data to back it up. If a fire develops from the coals up, its an accelerating phenomenom as the woodload heats up & produces more outgassing.
the excess CO wont plug a chimni but in a concentrated area of "clean burning" woodstoves with weather inversion factors ....

 

[Rich L]

Yea with the dry Oak I had I did not have a smoke problem. Only problem I had was it burning too quickly!

Me Too !