Wet wood btu chart

martyinmi

Member
Dec 26, 2011
78
Central Mi
I was wondering if someone knows of a study done that outlines the extra energy from wood required to burn seasoned wood(20% mc as an example)vs unseasoned wood(30%+ mc) through a gasification boiler.
The wood in question is 35-40% mc, and the operator believes that his boiler should be able to efficiently burn at that high mc.
I'm thinking his poor gasification flame and short burn times are a direct result of the wet fuel.
What we'd like to know is just how many btu's he is losing trying to boil out the extra moisture.
He doesn't think he's losing too many.
I believe he's losing a boatload.
Is there a link someone could provide?
Thanks!
 

peakbagger

Minister of Fire
Jul 11, 2008
4,638
Northern NH
The available BTU of wood goes negative when green meaning you need supplemental heat to burn it as it doesn't have enough fuel it in to offset the energy required to vaporize the water into steam and them vent it out the roof, so a chart would be difficult. A simple approach may work better. Weigh a load of good dry firewood of a certain volume (like a cardboard box full ) now weigh the same volume in wet wood. The difference in weight is mostly water. Now fill a container of water that weighs the same. Now light the fire with dry wood and then start slowly pouring the water in and see the reduced output. The rough number is it takes 1000 btus/lb to convert water to vapor (steam), so for every extra pound of water he is throwing 1000 btus up the stack. Its actually far worse as if the fire isn't burning hot enough he gets only get partial combustion of the carbon into Carbon Monoxide which also had btu content so that goes up the stack.

I think its a losing battle. My neighbor burns green and goes through 8 cords plus a year, I used 3 to 4 cords dry and with the minisplit I am closer to 2.5 cords. Good luck
 
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maple1

Minister of Fire
Sep 15, 2011
9,931
Nova Scotia
I was wondering if someone knows of a study done that outlines the extra energy from wood required to burn seasoned wood(20% mc as an example)vs unseasoned wood(30%+ mc) through a gasification boiler.
The wood in question is 35-40% mc, and the operator believes that his boiler should be able to efficiently burn at that high mc.
I'm thinking his poor gasification flame and short burn times are a direct result of the wet fuel.
What we'd like to know is just how many btu's he is losing trying to boil out the extra moisture.
He doesn't think he's losing too many.
I believe he's losing a boatload.
Is there a link someone could provide?
Thanks!
I don't have a link or the exact info you're asking, but thinking that 35-40% wood could be efficiently burned in a gasifier is just, well, very wrong. I notice a difference in anything much above 20%. I would be surprised if you could get any gasification going.
 

salecker

Minister of Fire
Aug 22, 2010
944
Northern Canada
Just tell him...
Green wood contains water.
Firemen use water to put out fires.

But
Sometimes you can lead a horse to water.
And sometimes you have to hold it's head underwater and kick him in the nuts to make him drink.
 

Bad LP

Minister of Fire
Nov 28, 2014
878
Northern Maine
If he likes the extra work of cutting/splitting/stacking/burning wood with out getting full efficiency for his efforts then so be it because he is wasting a lot of time and wood. Instead of a gasification boiler he should have saved a few $$$ and just bought a smoke dragon.

I drive by a place in Maine on Rt150 where the wood boiler looks like its on a trailer next to the house and they have lines from the boiler thru a cellar window for the supply and return. The smoke coming out of that from the unsplit green rounds is disgusting. What a god awful mess.
 

brenndatomu

Minister of Fire
Aug 21, 2013
4,143
NE Ohio

Fred61

Minister of Fire
Nov 26, 2008
2,430
Southeastern Vt.
And sometimes you have to hold it's head underwater and kick him in the nuts to make him drink
That's called "Bricking". One brick in each hand.
 
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goosegunner

Minister of Fire
Oct 15, 2009
1,468
WI
I once weighed a piece of green red oak. It was 13" diameter and 17" long. I then left it in my warm boiler room for over 6 months.

Weights:

Green 69lbs
dry 44lbs


So one piece lost 3 gallons of water. If one does not believe that does not cause waste of btus then I am afraid their is no help.

I have a coworker who is convinced it is better to burn green wood in his heatmor because when he fills it the burn time is longer.....fills its 50+ sq ft fire box twice a day that is.
 
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martyinmi

Member
Dec 26, 2011
78
Central Mi
This is perfect! Thank you !
 

Marshy

Minister of Fire
Dec 29, 2016
815
NY
Wood has nearly identical BTU/lb regardless of species so this chart applies to all species.
 

JRHAWK9

Minister of Fire
Jan 8, 2014
1,144
Wisconsin Dells, WI
I have a coworker who is convinced it is better to burn green wood in his heatmor because when he fills it the burn time is longer.....fills its 50+ sq ft fire box twice a day that is.
This co-worker doesn't happen to have a second job at Home Depot in Lake Delton, does he? ;lol

Had a similar conversation with a HD employee a couple years ago. He insists he has to burn green wood for the same reason. The guy still works there as I saw him a few days ago when I was in there.
 

goosegunner

Minister of Fire
Oct 15, 2009
1,468
WI
This co-worker doesn't happen to have a second job at Home Depot in Lake Delton, does he? ;lol

Had a similar conversation with a HD employee a couple years ago. He insists he has to burn green wood for the same reason. The guy still works there as I saw him a few days ago when I was in there.

No but our are is loaded with Burn green wood disciples.
 
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goosegunner

Minister of Fire
Oct 15, 2009
1,468
WI
I hear ya.

BTW, did I read that correctly...50 (as in fifty) SF firebox!?!? !!! _g

I stand corrected.

The fire box is only

28"wide X 54" long X 42" High

36.74 cu ft

But hey you only have to fill it twice a day.

Another guy has one he fills it 3 times a day when cold.....
 

JRHAWK9

Minister of Fire
Jan 8, 2014
1,144
Wisconsin Dells, WI
I stand corrected.

The fire box is only

28"wide X 54" long X 42" High

36.74 cu ft

But hey you only have to fill it twice a day.

Another guy has one he fills it 3 times a day when cold.....

;lol

insane. I sure hope they aren't buying their wood!
 

Bad LP

Minister of Fire
Nov 28, 2014
878
Northern Maine
I stand corrected.

The fire box is only

28"wide X 54" long X 42" High

36.74 cu ft

But hey you only have to fill it twice a day.

Another guy has one he fills it 3 times a day when cold.....
I'm tired just thinking about it
 

JMihevic

New Member
Feb 3, 2018
17
Medina, Ohio
Should the vertical axis on Btu/Lb chart be multiplied by 100? The number I have seen many times is 8600 But/Lb for wood. The chart says 86 Btu/Lb. for 0% moisture content.

John M.