# Firewood BTU charts don't agree



## ewlsey (Jan 2, 2015)

Are these firewood BTU charts based on any kind of actual science or are the numbers just pulled from the ether?

I guess I don't see how every chart can have a different number for most species. Most I have looked at differ by up to 5 BTUs. That's 25% for most woods. Elm seems to be all of the map, as well as Hickory and soft Maple.

Is there a definitive chart I should be looking at?


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## pen (Jan 2, 2015)

Which charts are you looking at?

Which woods do you have access to that you are interested in burning and perhaps separating for use at different times?

With more information on what you are looking to accomplish and what you have to work with, you might get some good answers even without a chart.

pen


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## byQ (Jan 2, 2015)

I've wondered about this, too. I would suggest you use the hand test. That is, physically pick up the dry firewood and feel its weight - compare it to other dry species. Growing conditions like sunlight, water, competition from other trees, etc.. affect a trees growth.

For example, 2 red oak. One growing on the low rain side of the hill and the other growing next to a canal. They are the same size but the low-rain tree is twice as old, and the density is much higher. So when you hold a piece of firewood from each tree one is heftier. So same species but different BTU ratings.

I  live in a low rain area, desert-like, so trees grow slower and are probably denser and higher BTU rated than the charts suggest.


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## ewlsey (Jan 2, 2015)

I burn Ash, Maple, Hackberry, and Honey Locust. But, I get it from tree trimmers, so I never know if it's green/white/black ash or silver/sugar Maple. Ash is my favorite, but Hackberry is good too. Locust makes heat, but it takes forever to dry and the thorns are a pain (literally). 

It doesn't really matter, I was just curious why the charts are different.


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## Woody Stover (Jan 3, 2015)

ewlsey said:


> Ash is my favorite


I love dat White Oak, but White Ash is probably about the quickest-drying of the upper tier woods due to its lower starting moisture content...
I pick and choose on a few of these values but most seem to be in line with what I've seen in my stoves.

https://www.hearth.com/econtent/index.php/articles/heating_value_wood http://www.engineeringtoolbox.com/wood-combustion-heat-d_372.html http://www.daviddarling.info/encyclopedia/W/AE_wood_heat_value_BTU.html http://firewoodresource.com/firewood-btu-ratings/ (White Oak low, I'd say. 25.7 seems right.)  http://mb-soft.com/juca/print/firewood.html http://worldforestindustries.com/forest-biofuel/firewood/firewood-btu-ratings/


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## ewlsey (Jan 3, 2015)

I never get Oak. I think they have people that will pay for Oak. I'm not going to do that. 

Honey locust is great except the thorns. It's one of the easiest woods to split by hand. Plus, it's basically a weed that grows in ditches and fence rows, so farmers are always trying to get rid of it. Hackberry is the same.


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## Seanm (Jan 3, 2015)

Ive thought this to. Crazy. Ive always referenced chimneysweeps btu chart because using different ones all the time would drive me nuts! https://chimneysweeponline.com/howood.htm



byQ said:


> For example, 2 red oak. One growing on the low rain side of the hill and the other growing next to a canal. They are the same size but the low-rain tree is twice as old, and the density is much higher. So when you hold a piece of firewood from each tree one is heftier. So same species but different BTU ratings


this seems to make sense to me!


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## Bigg_Redd (Jan 3, 2015)

ewlsey said:


> Are these firewood BTU charts based on any kind of actual science or are the numbers just pulled from the ether?
> 
> I guess I don't see how every chart can have a different number for most species. Most I have looked at differ by up to 5 BTUs. That's 25% for most woods. Elm seems to be all of the map, as well as Hickory and soft Maple.
> 
> *Is there a definitive chart I should be looking at?*



No.  Here's why. . .

There's just too many variables - soil, wind, temp, sunlight, rain, bugs, humidity - that affect how a tree grows.  Tree growth will vary from region to region, and even within the same stand.


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## Woody Stover (Jan 3, 2015)

Bigg_Redd said:


> There's just too many variables - soil, wind, temp, sunlight, rain, bugs, humidity - that affect how a tree grows.  Tree growth will vary from region to region, and even within the same stand.


That's true. I wonder what the biggest variable is though? Speed at which the tree grows? I've heard several people say that tighter growth rings mean denser wood. If so, trees of the same species, one that grows with unlimited access to sunlight and another in the woods competing for limited available light at a slower rate, would differ in density and BTU, with the woods tree having more BTU. Then there's the sapwood vs. heartwood factor...


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## Paulywalnut (Jan 3, 2015)

I agree with the tighter growth ring theory also. Locust , Osage and the oaks have the predominate rings or ray when looking at the cut ends. If you have nothing to do sometime, sand the end of one of these kinds. Very pretty!


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## nrford (Jan 3, 2015)

ewlsey said:


> Are these firewood BTU charts based on any kind of actual science or are the numbers just pulled from the ether?
> 
> I guess I don't see how every chart can have a different number for most species. Most I have looked at differ by up to 5 BTUs. That's 25% for most woods. Elm seems to be all of the map, as well as Hickory and soft Maple.
> 
> Is there a definitive chart I should be looking at?



 Of course they don't agree. Most created by hung-over college students!   To many variables, as has already been said. As with almost anything, take with a grain of salt after all 100# of Oak has as many Btu's as 100# of poplar, one is just a lot bigger pile!


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## HarvestMan (Jan 3, 2015)

I remember burning black locust in my younger years and wished I had some.  I just started working on this huge mulberry and find that it supposedly has higher BTU rating than BL (https://chimneysweeponline.com/howood.htm).  Never burned any mulberry, but hoping the two are close.


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## Wood Duck (Jan 3, 2015)

I wouldn't be surprised if the wood from different trees or different parts of a tree vary in BTU content by 25%. Not every tree grows at the same rate, has the same thickness of annual growth rings, etc. Plus there is error/inaccuracy in the test procedure and equipment, so a 25% variation in the published results doesn't seem strange to me.


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## Woody Stover (Jan 3, 2015)

HarvestMan said:


> I just started working on this huge mulberry and find that it supposedly has higher BTU rating than BL (https://chimneysweeponline.com/howood.htm).  Never burned any mulberry, but hoping the two are close.


No, they are not. BL is more dense. That list doesn't align with what I see. Black Locust equals Sugar Maple? Uh, no, I'm burning both right now in the Buck. Silver Maple the same as Douglas Fir? Anyone who's burned both care to comment? Apple about equal to Green Ash? Comments? Red Maple better than Red Elm? Red Elm, hands down; Both have been in my stove this week. Could be they are talking about some other "Red Elm" though...I'm talking Slippery Elm (Ulmus Rubra)


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## porkchopexpress (Jan 3, 2015)

All these posts sound good in theory. But,  a lb of oak is a lb of oak. Regardless of how tight the growth rings are.  I'm pretty sure these btu charts go off weight, not guessing that two different splits feel the same. "Which is heavier?  Lb of feathers or lb of lead"

ETA: but I still can't explain the differences between charts


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## ewlsey (Jan 3, 2015)

The charts go off of volume. It's the BTUs for one cord.


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## porkchopexpress (Jan 3, 2015)

ewlsey said:


> The charts go off of volume. It's the BTUs for one cord.


Really?  I was always told otherwise.  
But I guess you could say either way since most have how much a cord weighs also


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## ewlsey (Jan 3, 2015)

My understanding is that all wood has the same BTUs/lb. So, pine and hedge have the same BTUs per pound of wood, but hedge weighs twice as much. Or, you need twice as much pine to make the same heat as hedge.


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## porkchopexpress (Jan 3, 2015)

ewlsey said:


> My understanding is that all wood has the same BTUs/lb. So, pine and hedge have the same BTUs per pound of wood, but hedge weighs twice as much. Or, you need twice as much pine to make the same heat as hedge.


Agreed. I think we're saying the same thing.  You're just better at putting it into words


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