Re: GAS-L: The Mystery of heat variance in biomass

[Carefreeland@aol.com]

 Dear dglickd, 
    This is exactly what we need every now and then, a good organic chemist. 
 This formula is a great way to determine by analysis, what a plant is 
producing for the purpose of converting chemistry to physics. 
    What I am deriving from this formula is the way in which some plants 
produce higher caloric value per mass.  If one is to take a chart of local 
firewood's we can see a very direct correlation between strength/weight of 
fiber and heat value.  This could easily be explained by the presents of more 
high energy lignin, which is a bonding agent in the fibers. Lignin has less 
percentage oxygen than cellulose. 
    Osage orange (hedge) comes out near the top by my chart, at 7073 Btu per 
pound. It is indeed one of the strongest woods known to man hence it's name 
Boise, DE Ark or "wood of the bow."  This is from figures from Firewood for 
your Fireplace by Warren Donnelly, 1974.  Probably air dry wood. 
    How do we explain the high figure for Black cherry at 7142 Btu/pound, or 
Cottonwood at 7142?  I would say that the raw sugars present in cherry sap 
must be very high energy.  Any clue as to what their formula is?  Cottonwood 
may be low strength because of the light density of fibers lacking a good 
"weave."  Cottonwood also has so many large pores that it tends to rot fast. 
The high heat here may also come somewhat from low ash content. 
    Pine is much lower at 6190 Btu/pound, but again are we talking split 
heartwood or small stock with a high bark to weight ratio?  I would venture 
to say that the resin here, which is more hydrocarbon in nature, would be 
very high in heat, but present less in the core than in the bark.  Again, 
what variety of pine, and growing where? 
    Silver maple comes out lower at 5937 Btu/pound, probably due to simpler 
cellulose and ash.  Box elder is very low at 4783 Btu/pound but it is very 
high in ash. 
    I will say that all of this indicates that the usual ways that trees 
repair damage and add strength for wind resistance all seem to add heat 
density to the wood.  I cannot make this a rule though. 
     Cork bark elm is no higher heat than Siberian elm, yet it makes stronger 
wood.  Why? The woven grain of the cork bark gives it it's strength.  The 
open grain of Siberian elm makes an excellent charcoal though because of it's 
porosity and lower apparent ash. 
    I suppose we could do this complex analysis of compounds which change 
with the weather.  This is of great use to botanists who are unlocking the 
secrets of Btu. production. 
     The simpler way for most folks, is just to test raw heat value of what 
material you have, with an understanding of the processes by which those 
values vary.  Start with dry wood and subtract the ash.  Just don't be upset 
by a 2% variation from your neighbors experiments, it's not worth the trouble 
to track it down. 
    If 2% is the difference for you, than pay for good feedstock analysis, 
with a very consistent material.  F 1 Hybrid or cutting produced trees grown 
on plantations, wheat or other grain crops, sugarcane and grasses, all tend 
to be much more similar in final make up due to the trouble farmers have gone 
through to make a consistent product.  Just use test samples from the same 
crop to compare apples to apples.  
    Any good chemical analysis avalible of saps and resins?  What is cherry 
sap Vs maple sap?  How about pine sap Vs spruce?  What is in the high energy 
sap in locust wood? 
    This will expand the range of chemistry for analysis. 
                                      Daniel Carefreeland(scape) Dimiduk 

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