Burning unseasoned wood

[jrider]

Sounds like the op already had his mind made up before he asked the question . 6% loss due to moisture is laughable . Even a hobo burning trash in a 55 gallon drum knows that's nonsense .. Try that in a epa unit and you would have a cold smoke filled firebox in no time flat ..All math aside The reality is the higher the moisture content the less heat your going to get. .. Period . As far as your sticking a hand in the firebox test .. You must realize your trying to heat a whole lot of water up .. Not a mans hand of coarse it would be hot to a bare hand even if its smoldering and hissing . If you want the btu of a bic lighter have at it ...Might as well add some water in your gas tank to stretch the miles before you gotta stop at a gas station ..add some water to your beer to stretch between opening cans where does the madness end. ?

Add water to your beer to stretch between opening cans... You mean drink light beer? And what are these cans you speak of?? As my dad used to say, if I wanted to drink light beer, I would just add the water myself.

 

[branchbuzzer]

But when I stick a few sticks of uncured wood in and 12 hours later there is a noticeable amount of unburned wood left over vs dry wood which normally is completely burned 12 hours later-always enough hot coals to easily refire fresh wood then I can't help but post these results in question.

If the wood didn't burn it didn't put any energy into your home, no fancy math required there I would hope.

Common sense would indicate that dryer wood is better, I easily understand that. It's just that what I'm seeing doesn't match that logic.
After the holidays I'll adjust down the air inlet and see what difference that makes.

You'll see a nice slow efficient hot burn if you're using dry wood. The drier it is, the more the air can be cut back and the sooner you are on your way to complete combustion salvation and BTU heaven instead of the gates of smoldering hell brother! Can I get a witness?

 

[poloman]

Amen branchbuzzer


Live a positive life!

 

[Whitespider]

The drier it is, the more the air can be cut back and the sooner you are on your way to complete combustion...

Exactly right... the loss of heat does not end with the energy used to heat the water in wet wood. The fire also requires more air to burn wet/green wood... actually it needs the extra oxygen to keep combustion temperature high enough, but air is only about 20% oxygen... and all that air needs to be heated, which uses more energy. Even with the extra oxygen, wet/green wood makes more smoke... it smokes because the water and excess air robs heat from the fire, the combustion temperature is cooled. Smoke is lost energy; dry wood smokes less because it combusts at a higher temperature... higher temperatures cause it to burn more completely... a more complete burn means more energy is extracted from the wood.

It's the snowball effect... with each revolution of the snowball it becomes larger and heavier, gaining more mass than the previous revolution.
Burning wet/green wood the fire loses energy to the water causing combustion temperature to drop, the fire requires more oxygen to maintain combustion temperature, to get that extra oxygen the fire pulls in a lot more air, now the fire starts losing energy to the excess (80% non-oxygen) air causing combustion temperature to drop... during all this (relatively) cool burning the stuff in wood that requires more heat to combust (and releases higher amounts of energy when it does combust) just goes "up-in-smoke". It's not just the loss of energy to the water and excess air... but the best part of the fuel, the part that releases the highest amounts of energy, doesn't combust because there ain't enough heat available.

It's bad enough in an old smoke dragon/furnace/OWB/etc. (one hell-of-a-lot more than 6%, I promise you)... but toss wet/green wood in one of these newer "induced secondary burn" contraptions... heck, ya' might just as well dump a bucket of water in the firebox. I don't care what sort of appliance you use, anything that exits the stack is lost energy, the more smoke and steam you see, the more you lose... if ya' see twice as much smoke, just like the snowball, you're losing many times more than twice the energy.
*

 

[AIM]

I always thought that all the green vs dry weights/ calculations/ and tests were done at 20% for what is considered "dry".
I'm not sure it would be possible to get wood to 0% moisture. Even in a lab.

On the OP's question. ya it makes it burn longer if the wood is wet but it just doesn't do the job like dry wood.
My OWB is set at 170° right now. If I burn nice dry good wood my temp will float around 170 -180 without the inducer fan hardly kicking on.
If I burn green wood my water temp will hover around 150-170 with my inducer fan running almost constantly. I can show anybody this any day of the week.
Yes both ways will heat my house and shop just fine but it's obvious from this simple observation that green wood just doesn't do as well.

 

[philoshop]

I eventually get all my wood to 0% mc. It comes out of the bottom of the stove in buckets!
Merry Christmas everybody!

 

[Whitespider]

I always thought that all the green vs dry weights/ calculations/ and tests were done at 20% for what is considered "dry".
I'm not sure it would be possible to get wood to 0% moisture. Even in a lab.

"Dry" weight is at 0%...
"Air dry" weight is at 20%...
Nearly all energy "calculations" use "dry" (0%) weight as the base, and any moisture content is then allowed for...
EPA tests require the wood to be oven-dried to a certain moisture content (I don't feel like looking it up this morning... but it's something under 20%).

The only way to know what the true moisture content of wood is to weigh it, then dry it to 0%, and weigh it again...
There will always be some humidity in the oven... meaning there will always be some moisture remaining in the oven-dried wood. At any given temperature/relative humidity level the wood reaches what is known a Equilibrium Moisture Content (EMC), this value is known and is figured into/subtracted from the weight of the oven-dried wood. Wood oven-dried in a hot, humid climate will have more moisture remaining than wood oven-dried in a cold, dry climate. Still, it's possible outside of a lab to oven-dry wood to a moisture content of something less than .01% (I think, without looking it up, .008% is possible)... that's pretty damn dry. In a lab it is possible to oven-dry to something well under that... pretty much 0%... if you feed "dry" air to the oven, the wood will dry to 0%.

 

[Preston]

What I've found is seasoned wood but hot but pretty fast. If the last wood put on a fire is one of the denser woods it will leave a good bed of coals in the morning for a restart. Wood burned that is on the green side I've found it to give off a high number of the soot side. I think the "wetter" wood smokes the same way and sticks to the flue easier and builds up more creosote then want to just brush out. Seasoned wood is burns just so much cleaner.

 

[Chris-PA]

A good way to control burn time is to burn larger splits of wood and this is true of all woods regardless of density. Of course denser woods last longer. I can roll a 10 or 11 inch round in through the front doors of our Jotul F600cb and if put on a good bed of coals and if it's really good and seasoned this is how I get my longest burn times. Heat output is lower but for a longer period of time. If the same round were to be split up and placed in the firebox it would last for a shorter time but have a higher output. Likely about the same energy would be captured as heat into the house. This is wood burning 101 I know but just wanted to toss it into the discussion. The way I see wood in my woodshed is like money in the bank earning interest. The longer it is in.....the more btu's I'll get. Of course there is a point of not getting any drier and even a point of bugs getting into the wood decreasing it's value........more like money in the bank than I wish! Different bugs though.

Thanks - now I'm imagining bankers in my woodpile. I'd rather have skunks.

 

[brenndatomu]

Thanks - now I'm imagining bankers in my woodpile. I'd rather have skunks.

There's a difference?!

 

[stihly dan]

Spidey, how dang many words a minute can you type? Your replies in this post would take me 3 days to type. 1 finger only goes so fast, but say's a lot.

 

[Whitespider]

Spidey, how dang many words a minute can you type?

Don't know... ain't never counted 'em.
I use all the fingers, but not like "they" teach ya'... I'm self taught.

Just like makin' these symbols using only keystrokes...
¢ £ ¥ § © ® ⌂ ± √ ∞ ≤ ≥ ¶ ¼ ½ ¾ ... and fun stuff ... ☺ ☻ ♂ ♀ ♥ ♦ ♣ ♠ ♪ ♫ ... and a whole bunch more, all self taught.
*

 

[branchbuzzer]

A good way to control burn time is to burn larger splits of wood and this is true of all woods regardless of density. Of course denser woods last longer. I can roll a 10 or 11 inch round in through the front doors of our Jotul F600cb and if put on a good bed of coals and if it's really good and seasoned this is how I get my longest burn times. Heat output is lower but for a longer period of time. If the same round were to be split up and placed in the firebox it would last for a shorter time but have a higher output. Likely about the same energy would be captured as heat into the house. This is wood burning 101 I know but just wanted to toss it into the discussion. The way I see wood in my woodshed is like money in the bank earning interest. The longer it is in.....the more btu's I'll get. Of course there is a point of not getting any drier and even a point of bugs getting into the wood decreasing it's value........more like money in the bank than I wish! Different bugs though.

It is woodburning 101, but there is a never ending supply of Freshman attending our little university so it bears repeating. Stress on the faculty is high however, so a constant rotation of staff is necessary to avoid....wait for it....burnout. I hired myself though, so I can look in the mirror for blame can't I....

Und zo, vee are discussing surface area of course, we all know this right? Most people would be surprised at how long most "gofer woods" will last if they are well dried, large chunks packed in tight. Are high density woods better? Of course they are, but those misfit woods can do the job just fine in a lot of situations.

The opposite end of that is why one shouldn't pack the firebox full of all 1/4 inch twigs, a massive amount of surface area and an equally massive amount of energy released all at once resulting in over-firing of the appliance. A good lesson for one's children on how not to get a fire going to "surprise" dad as he returns from work for the day.....

ok I'm hitting the faculty lounge for a while

 

[angelo c]

Funny story... I have a great friend who is a engineer and pretty much only hangs out with engineers at work and home...other then me who is "the odd ball" with the "devils advocate" opinion...anyway he always insisted on getting "wet" wood...so thats what i dropped off to him...when ever i got a load of limbwood or smaller stuff not needing splitting i just dumped it off to him. He said all his "engineer" buddies swear the wet wood delivers higher heat output...one year we had a particularly cold winter and he ran out of "wet" prime wood...so i pulled a cord of my private stock...um seasoned oaks and ash... Now he doesn't get anymore wet wood dropped off...shame now we use the chipper more....
I used to argue with him about seasoned wood all the time....but who can argue with an engineer for long before you wanna poke your eyes out with a spoon.

 

[Chris-PA]

As an engineer, I can't imagine an engineer who thinks wet wood delivers higher heat output. He must have slept through a bunch of classes. I was going to type that I'd like to hear his explanation on how that would work, but on second thought I'd rather not.

 

[Fred Wright]

Some great wood burning info and charts here: http://www.naturalresources.umd.edu/Publications/PDFs/FS926WoodFuel.pdf

Somewhere in there, as memory serves, red oak is listed at 80% moisture content off the stump. I popped open a block of freshly cut red last week - it even looks wet inside. And this isn't even growing season.

Correct me if I'm wrong... it's my understanding that modern wood burners are designed for best scenario efficiency with fuelwood at 20% MC +-. Poorly or partially cured wood might burn. But it isn't gonna burn very well, no matter what type of appliance it's stuffed in, even a potbelly stove. Serious Btu is sacrificed to cook the moisture out of it. Think of boiling a pot of water on your kitchen stove. Takes heat and time to get that pot of water boiling. In a wood burner, that's Btu that ain't heating your home.

For good measure, burning green wood - if you can get it to burn at all, that is - will fill your flue with creosote deposit quickly.

 

[showrguy]

to the op,
if you throw a couple of old tires in there first, then toss the green wood on top, as the tires are making heat, they are also drying the green wood in sequence....

 

[avason]

Some great wood burning info and charts here: http://www.naturalresources.umd.edu/Publications/PDFs/FS926WoodFuel.pdf

Somewhere in there, as memory serves, red oak is listed at 80% moisture content off the stump. I popped open a block of freshly cut red last week - it even looks wet inside. And this isn't even growing season.

Correct me if I'm wrong... it's my understanding that modern wood burners are designed for best scenario efficiency with fuelwood at 20% MC +-. Poorly or partially cured wood might burn. But it isn't gonna burn very well, no matter what type of appliance it's stuffed in, even a potbelly stove. Serious Btu is sacrificed to cook the moisture out of it. Think of boiling a pot of water on your kitchen stove. Takes heat and time to get that pot of water boiling. In a wood burner, that's Btu that ain't heating your home.

For good measure, burning green wood - if you can get it to burn at all, that is - will fill your flue with creosote deposit quickly.

Great Resource! Many Thanks!

 

[angelo c]

As an engineer, I can't imagine an engineer who thinks wet wood delivers higher heat output. He must have slept through a bunch of classes. I was going to type that I'd like to hear his explanation on how that would work, but on second thought I'd rather not.

Umm...I said they were "engineers" never said they were "Smart"..

He would tell me it was something about gasification gobbelee gook blahh blahh type nonsense. I often feel like i pay them to shut up more then to speak up.. Thankfully they all think "sales" is so demeaning they never talk to the sales force. If they just think the problem enough it will "sell" itself.. Hehe.
Sorry, Chris, to hear you're one of "them" ...at least you're not an attorney

 

[Bushmans]

I think I'll start burning green wood too. The stuff I'm using makes my house too hot. Sounds like if I use green wood it will last longer and burn cooler. (Some juicy American Elm right off the stump still dripping!) Right? Or did I miss a page somewhere?
LMMFAO!!!!!!!!!!!!