Creating charcoal in an airtight stove

[calamari]

Winter's a time for reflection and even more so now with COVID. I've been wondering if when you've been burning a lot of hardwood with the stove damped down if those "clinkers" you see that eat up the capacity in the fire box, are actually charcoal that can be used to BBQ with? My oak and Madrone result in a lot of them and I have to take them out eventually to make room for more firewood. Eventually I think they go to loose ash but I can't wait. I need them out of the stove while glowing hot but not as hot as fresh burning wood. Charcoal is created by burning wood in a low Oxygen environment but I've never seen or heard of anyone saving those lumps out of the wood stove and using them for BBQ.
Ideas?

 

[Del_]

Winter's a time for reflection and even more so now with COVID. I've been wondering if when you've been burning a lot of hardwood with the stove damped down if those "clinkers" you see that eat up the capacity in the fire box, are actually charcoal that can be used to BBQ with? My oak and Madrone result in a lot of them and I have to take them out eventually to make room for more firewood. Eventually I think they go to loose ash but I can't wait. I need them out of the stove while glowing hot but not as hot as fresh burning wood. Charcoal is created by burning wood in a low Oxygen environment but I've never seen or heard of anyone saving those lumps out of the wood stove and using them for BBQ.
Ideas?

Approximately half of the btu's are in those coals.
Have you well researched on how to burn down those coals? Sometimes reducing or closing off secondary air input burns down coals quicker. I've done it in our Jotul but only as an experiment as we don't have a hot coal build up problem.

I'm made biochar in my Jotul F600CB but I did it by putting chunks in an over roasting pan. It's really neat when the gasses start pressuring their way out of the roasting pan raising the lid slightly. Once gasses stop it's time to remove and cool off.

 

[calamari]

Sometimes reducing or closing off secondary air input burns down coals quicker.

In our "Sweet Home" stove, the stove pipe is offset slightly in the top of the stove for some reason. There's also a sliding damper that when closed completely still leaves some passage directly up the stove pipe while forcing most of the exhaust gasses to be directed back to the front door and from there up into a chamber that runs the length of the stove just under its top before exiting into the stove pipe above the damper. This really heats the top of the stove. There is a small sliding air damper at the base of the stove that regulates the air entering the stove.
When the stove reaches a sufficient temperature to maintain combustion with the top damper closed, we close it and regulate the combustion with the air valve. We close it down some for less heat and longer burn but when we do those klinkers are created more aggressively. If we close the air valve completely, we put the stove's fire out. We run it close to the kill zone and end up with a stove full of red hot clinkers that limit the burn box capacity and that don't produce enough heat for our purposes.

 

[Del_]

Does your stove have primary and secondary air supplies? Reducing secondary should increase the speed of coal burn but it sounds like you may not have secondary air.

Can you push the coals closer to the air input?

In our Jotul the air head is at the front of the stove and coals pushed there burn pretty fast. Coal in the rear of the firebox burns quite slowly.

 

[calamari]

No, only the one small sliding valve in the front. Pulling coals forward to allow them to burn isn't really an option the way the stove is used and constructed. Too many coals like that to do it efficiently. Great for cooking dirty steaks in the stove in the winter however so maybe I'll just live with it and continue to buy charcoal for the BBQ.
It's just something that wasn't an issue in years past. It's been a stove that's used as the primary heat source for the house so I need it to be working right. Every year there seems to be a new issue that didn't exist in the past with the stove or exhaust pipe. I guess it helps to keep my little grey cells active but still...
Thanks for the replies.

 

[stumpy75]

Add some pine or other softwood, if you have it, when you get a lot of those coals. Burn the coal up as the softwoods keep the temperature in the stove up.

The woods you are burning are known for their coaling properties because they are so dense.

BTY, I think I would call what you are seeing coals and not clinkers. Clinkers that I occasionally get while burning elm are hard pieces of mineral that do not glow/burn.

 

[calamari]

Add some pine or other softwood, if you have it, when you get a lot of those coals. Burn the coal up as the softwoods keep the temperature in the stove up.

The woods you are burning are known for their coaling properties because they are so dense.

BTY, I think I would call what you are seeing coals and not clinkers. Clinkers that I occasionally get while burning elm are hard pieces of mineral that do not glow/burn.

I'll try some different wood in the mix but "SHE" has a real aversion to pine, both the smell and the fear of resulting creosote and a chimney fire.
I never knew the difference between a clinker and a coal so just assumed that what was left after it had burned down was a clinker. These are pieces of the wood left after they are cold to the touch. Never had anything but ash before but now have these.
The wood I'm burning has been drying for two years in a place that has single digit humidity in the 7 summer months when it is often just below and above 100 during the day. Maybe it's too dry!

 

[stumpy75]

I'll try some different wood in the mix but "SHE" has a real aversion to pine, both the smell and the fear of resulting creosote and a chimney fire.
I never knew the difference between a clinker and a coal so just assumed that what was left after it had burned down was a clinker. These are pieces of the wood left after they are cold to the touch. Never had anything but ash before but now have these.
The wood I'm burning has been drying for two years in a place that has single digit humidity in the 7 summer months when it is often just below and above 100 during the day. Maybe it's too dry!

Sounds like the wood you are burning is fine. Single digit humidity is an unknown in my area! And, as you can read about all over the place on here, there is no problem burning pine, as long as it's seasoned. Same as any other wood. Many people burn nothing but softwoods(pine, spruce, hemlock, fir, etc), because it's all they can get. I burned Douglas Fir and Hemlock exclusively for three years when I lived in the Pacific NW.

The unburned charred pieces of wood that are left in your stove are coals that have gone out. If you have been burning down to ash every time before this, good for you. You are using every bit of the energy stored in that wood. That never seems to happen in my stove, and most people use the glowing coals of the still burning charred pieces to start the next load of wood. Eventually though, these coals and pieces of charred wood build up to the point that you have to open the drafts a lot more to just get them to burn down to ash. That's where the softwoods come in. You can keep more heat in the stove, while the hardwood coals are burning down to ash, by burning chunks of softwood, that will burn fast and hot and produce mostly ash.

Hope this helps a little...

 

[TRTermite]

Sounds like the wood you are burning is fine. Single digit humidity is an unknown in my area! And, as you can read about all over the place on here, there is no problem burning pine, as long as it's seasoned. Same as any other wood. Many people burn nothing but softwoods(pine, spruce, hemlock, fir, etc), because it's all they can get. I burned Douglas Fir and Hemlock exclusively for three years when I lived in the Pacific NW.

The unburned charred pieces of wood that are left in your stove are coals that have gone out. If you have been burning down to ash every time before this, good for you. You are using every bit of the energy stored in that wood. That never seems to happen in my stove, and most people use the glowing coals of the still burning charred pieces to start the next load of wood. Eventually though, these coals and pieces of charred wood build up to the point that you have to open the drafts a lot more to just get them to burn down to ash. That's where the softwoods come in. You can keep more heat in the stove, while the hardwood coals are burning down to ash, by burning chunks of softwood, that will burn fast and hot and produce mostly ash.

Hope this helps a little...

My experience too.

 

[calamari]

Sounds like the wood you are burning is fine. Single digit humidity is an unknown in my area! And, as you can read about all over the place on here, there is no problem burning pine, as long as it's seasoned. Same as any other wood. Many people burn nothing but softwoods(pine, spruce, hemlock, fir, etc), because it's all they can get. I burned Douglas Fir and Hemlock exclusively for three years when I lived in the Pacific NW.

The unburned charred pieces of wood that are left in your stove are coals that have gone out. If you have been burning down to ash every time before this, good for you. You are using every bit of the energy stored in that wood. That never seems to happen in my stove, and most people use the glowing coals of the still burning charred pieces to start the next load of wood. Eventually though, these coals and pieces of charred wood build up to the point that you have to open the drafts a lot more to just get them to burn down to ash. That's where the softwoods come in. You can keep more heat in the stove, while the hardwood coals are burning down, by burning chunks of softwood, that will burn fast and hot and produce mostly ash.

Hope this helps a little...

I'll try to open the vent toward the end of things as a way to burn more of the wood. Thanks for the suggestion. I do use the coals to start the next days fire but over time those pieces build up where they didn't before.
I like that you only have two saws. A small one and a bigger one. I only have two as well. A 35cc Redmax with a 14" bar and a 61cc with a 28" bar. An old truck to haul it and that's all you need. You can only use one saw at a time in the end so having duplicates makes no sense, to me anyway.

 

[stumpy75]

I'll try to open the vent toward the end of things as a way to burn more of the wood. Thanks for the suggestion. I do use the coals to start the next days fire but over time those pieces build up where they didn't before.
I like that you only have two saws. A small one and a bigger one. I only have two as well. A 35cc Redmax with a 14" bar and a 61cc with a 28" bar. An old truck to haul it and that's all you need. You can only use one saw at a time in the end so having duplicates makes no sense, to me anyway.

Yes, burning as much of the wood to ash each time is definitely a way to keep the coals in check.

I used to have a few more saws(ok, maybe a LOT more ), but have whittled it down to these. For what I scrounge, these two saws, in these sizes, is what works for me. I keep other bars and chains available in case I really pinch a bar, but that really shouldn't happen if you are watching what you are doing. I also have a supply of plastic wedges...

I have a neighbor with a MS440 if I really need it, but it's been a while since I have asked to borrow it. I just don't want to get into big wood anymore. Many(many!) years ago, I used a MS090 on a daily basis(bucking old growth). That would probably kill me now just to try and pick it up!!

 

[SS396driver]

I use the coals in my smoker I load the stove with hickory or cherry and let it burn down to big chunks of coals I shovel the out into a bucket and fire up my smoker. As I smoke I add more to the stove and use the coals as needed in the smoker. Found it to work very well .

 

[ken morgan]

i purposely load my stove full right before I leave the cabin and totally close all air feed and shut the damper as much as possible. I come back the next friday to a load of charcoal that I put in a bucket and use for grilling over the weekend. do it every week during the winter.

 

[calamari]

i purposely load my stove full right before I leave the cabin and totally close all air feed and shut the damper as much as possible. I come back the next friday to a load of charcoal that I put in a bucket and use for grilling over the weekend. do it every week during the winter.

Interesting! I'm going to try it.

 

[northmanlogging]

Winter's a time for reflection and even more so now with COVID. I've been wondering if when you've been burning a lot of hardwood with the stove damped down if those "clinkers" you see that eat up the capacity in the fire box, are actually charcoal that can be used to BBQ with? My oak and Madrone result in a lot of them and I have to take them out eventually to make room for more firewood. Eventually I think they go to loose ash but I can't wait. I need them out of the stove while glowing hot but not as hot as fresh burning wood. Charcoal is created by burning wood in a low Oxygen environment but I've never seen or heard of anyone saving those lumps out of the wood stove and using them for BBQ.
Ideas?

"clinkers" are not charcoal, but silica and other minerals that have bonded through heat, if they are proper "clinkers" they are essentially just super heated ash.
Granted I've never seen actual clinkers form in a wood fire, its generally a coal fire that makes them (and they are ******* annoying) Wood ash does create a crusty surface sometimes that acts much like coal clinkers, if they become a problem just shovel them out.

now if its actual charcoal, then it will burn up and make the next fire easier to start, I just herd them all to the middle so they make a nice coal bed when I relight the fire.

to create good charcoal for use in a bar-B-que then you need to heat the wood with zero oxygen until all fumes stop, a tin can with a small hole punched in it, stuffed slam full of wood (hardwood is best) then set in a hot fire works pretty damned good. That said, saving the left overs from a fire will work just fine for a bar-B-que as well or maybe better then store bought "cowboy" charcoal and a helluva lot better then briquets, after all charcoal, is charcoal, its just unburnt carbon free of impurities, the density is really only up to species of raw wood, though I suspect the canned zero oxygen method makes better charcoal, I don't think it matters.

 

[calamari]

"clinkers" are not charcoal, but silica and other minerals that have bonded through heat, if they are proper "clinkers" they are essentially just super heated ash.
Granted I've never seen actual clinkers form in a wood fire, its generally a coal fire that makes them (and they are ******* annoying) Wood ash does create a crusty surface sometimes that acts much like coal clinkers, if they become a problem just shovel them out.

now if its actual charcoal, then it will burn up and make the next fire easier to start, I just herd them all to the middle so they make a nice coal bed when I relight the fire.

to create good charcoal for use in a bar-B-que then you need to heat the wood with zero oxygen until all fumes stop, a tin can with a small hole punched in it, stuffed slam full of wood (hardwood is best) then set in a hot fire works pretty damned good. That said, saving the left overs from a fire will work just fine for a bar-B-que as well or maybe better then store bought "cowboy" charcoal and a helluva lot better then briquets, after all charcoal, is charcoal, its just unburnt carbon free of impurities, the density is really only up to species of raw wood, though I suspect the canned zero oxygen method makes better charcoal, I don't think it matters.

I've burned coal one winter and never again. What I was trying to describe was wood pieces that looked like either clinkers of chunk mesquite charcoal we can get down here retaining the wood look of the oak and Madrone I burn. If I don't do anything with them they'll all turn to ash over time but sometimes they cool at a rate that leaves briquet size and a little larger pieces that I thought might stretch my regular charcoal. The simplest thing to do is just do it and see but I thought there might be a whole culture built around such frugality or being cheap if women are to be believd.

 

[muddstopper]

"clinkers" are not charcoal, but silica and other minerals that have bonded through heat, if they are proper "clinkers" they are essentially just super heated ash.
Granted I've never seen actual clinkers form in a wood fire, its generally a coal fire that makes them (and they are ******* annoying) Wood ash does create a crusty surface sometimes that acts much like coal clinkers, if they become a problem just shovel them out.

now if its actual charcoal, then it will burn up and make the next fire easier to start, I just herd them all to the middle so they make a nice coal bed when I relight the fire.

to create good charcoal for use in a bar-B-que then you need to heat the wood with zero oxygen until all fumes stop, a tin can with a small hole punched in it, stuffed slam full of wood (hardwood is best) then set in a hot fire works pretty damned good. That said, saving the left overs from a fire will work just fine for a bar-B-que as well or maybe better then store bought "cowboy" charcoal and a helluva lot better then briquets, after all charcoal, is charcoal, its just unburnt carbon free of impurities, the density is really only up to species of raw wood, though I suspect the canned zero oxygen method makes better charcoal, I don't think it matters.

I use a metal 5gal bucket with a hole in the lid for cold smoking meat. I use a propane burner under the can to heat the can. I fill the can with maple or apple or whatever kind of wood flavor I am looking for. The wood will smoke without burning or catching fire. The end result is a biochar that can be used for your garden or for bbq grills as charcoal. Stove wood charcoal is not the same as biochar because it is exposed to oxygen and burns. This doesnt matter if you are just wanting charcoal for your grill, but it does make a difference if you are looking for biochar for your garden. I would often empty the charcoal chunks out of my stove to save for the grill. I would keep a bucket of water handy and place the hot charcoal in the water to keep it from burning up and save it for summer cookouts.

 

[ken morgan]

Interesting! I'm going to try it.

I made my stove from scratch so it has some interesting properties first the fire bricks are all 2" thick, means it hold heat for a long time. when I close off all of the air inlets and shut the damper to about 80-90% it sometimes leaks a little smoke back past the seal on the door, so I open it just a bit more. then the wood smolders for an hour or two and by the time it cools enough to reach your hand in there, (6 or 8 hours later) voila charcoal! I only use oak though as other lighter woods, at least those available here locally do not make for good charcoal. Its handy because if SHTF you can make your own water purification unit using activated charcoal, and then a gravel/sand bed among many other uses.

 

[northmanlogging]

I've burned coal one winter and never again. What I was trying to describe was wood pieces that looked like either clinkers of chunk mesquite charcoal we can get down here retaining the wood look of the oak and Madrone I burn. If I don't do anything with them they'll all turn to ash over time but sometimes they cool at a rate that leaves briquet size and a little larger pieces that I thought might stretch my regular charcoal. The simplest thing to do is just do it and see but I thought there might be a whole culture built around such frugality or being cheap if women are to be believd.

coal is knarly... unless it burns hot it smokes and stinks... and is messy at best, Damned good in my forge though.

Charcoal shouldn't turn to ash all on its own, it should more or less stay together even when wet, either way, if you wanna go through the trouble of collecting it for the grill, I don't see any reason it won't work.

As for bio char, and regular charcoal, there is no difference, as I stated before, they are both simply unburnt carbon, stuff out of your fireplace may be a little softer then the canned charcoal method, simply because more of the carbon is burnt off as its not an efficient method of making charcoal, but its still the same stuff, and probably works better as it breaks up into smaller pieces quicker. Honestly the best way to create "bioChar" for your garden is to burn a brush pile on it ever winter, not a huge one so it doesn't get so hot to sterilize the dirt, but enough to put all that charcoal and ash into the soil.

 

[muddstopper]

coal is knarly... unless it burns hot it smokes and stinks... and is messy at best, Damned good in my forge though.

Charcoal shouldn't turn to ash all on its own, it should more or less stay together even when wet, either way, if you wanna go through the trouble of collecting it for the grill, I don't see any reason it won't work.

As for bio char, and regular charcoal, there is no difference, as I stated before, they are both simply unburnt carbon, stuff out of your fireplace may be a little softer then the canned charcoal method, simply because more of the carbon is burnt off as its not an efficient method of making charcoal, but its still the same stuff, and probably works better as it breaks up into smaller pieces quicker. Honestly the best way to create "bioChar" for your garden is to burn a brush pile on it ever winter, not a huge one so it doesn't get so hot to sterilize the dirt, but enough to put all that charcoal and ash into the soil.

I got to disagree with your statement that there is no difference in biochar and charcoal. The charcoal left behind in your wood stove or brush pile is made in the presence of air. Biochar is made using a process called pyrolysis at much higher temperatures than charcoal, which leaves intact all the capillaries of the wood structures and allows for the biochar to uptake and hold moisture as well as microbiology. In the soil charcoal will breakdown in just a few years but biochar can last for thousands of years. Burning a brush pile over your garden will produce ash, not charcoal. Not to say you wont find some chunks of charcoal left behind. Wood that has been burnt in open air will have lost most, or all, of its carbon content (C02), and any gaseous nutrients the wood contained. You are left with some calcium, potassium, and other metals that dont burn.

None of this matters to a person that wishes to save their stove charcoal to use in their BBQ. I have done it, and lots of others have as well. Both charcoal and biochar will work, one will smoke more than the other and I aint one to go to the trouble to make biochar to use in my grill when I can get all the charcoal I want from my wood stove. But if I want carbon for my garden, I will make biochar instead of charcoal.