True, but the compressed product is probably very dry compared to the wood they selected for testing. One of the New England pellet makers buys scrap sawdust from my wood supplier, CT hardwood Group. They sell dried wood at about 8% mc and also use it for custom moldings and truck floors. Once compressed, the pellet is probably about the same 8% so if you compare that with typical 3 month old firewood at 30%, the numbers, pound for pound, are probably true.
And I thought a btu was a btu. hmpft!
Yep it probably is very dry, but compression has nothing to do with the moisture content, unless it is so wet that the water is shoved out. It's kind of like comparing a fresh apple with dried slices.
I don't know what 3 month old firewood is? you mean green stuff cut and left for 3 months? I never burned any green cut stuff that sat less than 1 year. Living in an arid climate my firewood was probably 8 % mc or less.
Much of the stuff I burned had been downed from 3-15 years and was very dry.
Well, no. Resins occupy the areas of the wood otherwise filled with air, and they have a higher BTU yield by weight.
No it isn't. The species makes a huge difference.
I've noticed the redirect doesn't happen if I type a phrase into the search pane in Safari (Mac browser) but does if I type the url directly.
Most odd.
"Sure it is!" he said loudly in front of the Congressional Inquiry Board secretly hoping they did not ask how the measuring devices were calibrated.
You got the money? We got the data!
Thre are a few transcripts of NRC Advisory Committe on Reactor Safeguards (ACRS) hearings from (much) earlier life wherein my youthful cheek comes out rather more strongly than intended...But one particular member back then and I just could never seem to avoid antagonizing one another---years later I learned he actually had enjoyed it while I was sweating bullets rueing my just uttered indiscretion...)
You've got an uphill climb to prove that here, Andy. Pick any place I've seen, and a pound of hemi/cellulose makes as much heat as any other. You wouldn't have some data to support your statement, would you?
Unless it's red gum. Cut it, whack on it 50,000 times with all manner of splitterly devices, then saw the damn stuff up with a chainsaw after failing utterly to split any of it. Then burn it.
Or better yet, turn on the gas logs when you're in the mood for a fire. Every time I start to get romantic about how much different it used to be having a real fire in the fireplace, I just look at my old mangled maul standing in the corner and smile. :)
(I was a lot more lithe and lean and stuff in those days though, boy. Especially swinging that damn 16# sledge that used to belong to my great grandfather.)
How about this white paper from Forest Product Lab ( a pretty reliable source I've found):
In there a range there of 9120 BTU/lb for Redwood to 8440 BTU/lb for Yellow-poplar. Thats an 8% difference. Not huge but significant.
There is another document at:
That has a much more comprehensive list. This shows a range of ~7300 to ~12200 BTU/lb. The highest is more than 60% above the lowest. Now there are different studies all in that table, but even comparing like studies gives almost as big of a range of values.
The softwoods are generally higher because of their resin content. (that pitch is just like oil)
Hope that helps.
Dan
Comparing cellulose to cellulose is pretty dull, but try resinous larch vs birch or willow. Even though the pound per pound difference is much less than the volumetric difference, it's still significant.
That we knew, Dan. I've mentioned it a few times already, as have others. Plus or minus extractives, is the phrase I've used. The greater the amount of extractives, the greater the energy density, which, as you note, can vary from a resinous high of 12K to a miserable low of 8K 33% (50 if you're trying to make your argument) is a big swing, but the majority clusters within 10%. Your low is for bark.
Then there's the footnote - "clusters at 8500" and the disclaimer of a post hoc study that the methods used to determine the data were not consistent.
Maybe that was part of the problem. My neighbors next farm south had been doing wood forever. One used a maul (go-devil for NE folks), the other an axe, to split elm. Sixty seven and seventy three were their ages, with the
73 swinging the axe....I retired my sledge this year. No more kids in residence to help the old man with 4' lengths. Susan and I went to 20", and a splitter.
I used a maul instead of a sledge. The hard part of using a sledge is getting your wife to hold the wedge while you swing.
I think you missed the point! And they don't have weight? You are telling me that a pound of sap has more BTU's than a pound of cellulose and lignin? Could be, but it isn't going to be significant in normal tree proportions.
Read a book. Read several. We're talking about per pound not volume. Dried wood of any type is composed mostly of cellulose and lignin. Slight differences in aromatics. You may be thinking about density, that's why we are comparing BTU's on the base of weight.
On Wed, 09 Feb 2005 20:48:21 -0500, Tom Watson vaguely proposed a theory ......and in reply I say!:
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If you had _posted_ to the thread that would have made it all a lot easier to follow on....
On Wed, 09 Feb 2005 20:02:03 -0500, Tom Watson vaguely proposed a theory ......and in reply I say!:
remove ns from my header address to reply via email
Simple. Because it's dry. - Water has a negative calorific value in burning. It turns to steam which takes energy, and that all goes up the chimney - water causes the wood to burn slower, and smoke more. That all goes up the chimney as unburnt material.
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