Wood energy contents

["Kirk R. Smith" <krksmith@uclink4.berkeley.edu>]

According to an authoritative report by the Tropical Products Institute
in London (Report G-162, 1982), there is actually little difference in
gross energy content among wood types by mass.  This can be seen
below (and attached) where the coefficients of variation (standard
deviation divided by the mean) of all woods tested is only 5%. 
Although it would be great to know everything about all aspects of the
system, it seems to me that, given the range of uncertainties we must
accomodate in wood stove work, intrinsic differences in energy content
among wood species is in most circumstances a relatively small
contributor to system uncertainties.  Usually of much greater
practical importance, for example, is the moisture content, which changes
lower heating value (and perhaps pollutant emissions) dramatically. 

What do you think?  Cheers for the new year/k

Gross Energy Contents of Hardwoods and Softwoods

                        Numbers of Samples      Range(MJ/kg)    Mean(MJ/kg)     Coefficient of variation (percent)

Hardwood                268                     15.58-23.72     19.7            5
Softwood                70                      18.61-28.45     20.8            7
All Woods               338                     15.58-28.45     20.0            5
Hardwood Bark   72                      15.75-24.03     19.3            9
Softwood Bark   56                      17.77-25.10     21.4            6
All Barks               128                     15.75-25.10     20.2            9
Hardwood sapwood        111                     18.11-21.98     20.4            4
Hardwood heartwood      111                     18.51-23.66     20.7            5
Softwood sapwood        3                       17.19-22.93     20.2            -
Softwood heartwood      3                       17.19-21.16     19.6            -

From: TPI, G 162, 1982, Calorific Values for Wood and Bark.

At 03:43 PM 1/2/2002 +1000, Peter Verhaart wrote:
> At 10:24 1/01/02 -0400, you wrote:
> > Dear Stovers:
> > I inadvertently sent Crispins original message to the list, rather than
> > the
> > following reply. Following is the reply I intendd to send. Sorry about
> > he
> > confusion.
> >
> > Kevin Chisholm
> > *********************************
> > Dear Crispin
> >
> >
> > I hate it when I have to say "The book is wrong." :It makes me
> > look
> > arrogant. :-) However, in this case, it is wrong. Firstly, the statement
> > was
> > made 90 years ago, when wood was generally bought and sold by the CORD,
> > a
> > volume measure, and not by the POUND (or kG). It is unquestionably true
> > that
> > "heavier woods give more heat per CORD" but it is
> > unquestionably wrong that
> > wood of higher specific gravity has more heat per CORD than woods of
> > lower s
> > pecific gravity.
>
>
> The book is wrong, I love saying that, the book is wrong. Resinous woods
> have a rather low density but a high combustion value, probably much
> higher than much denser woods not containing resin.
> What kind of accuracy do you think you need?
>
> Peter Verhaart
>
> Snip
>
> Kindest regards,
>
> > Kevin Chisholm
>
> And my compliments to Kevin for his exhausive analysis, which I enjoyed
> reading.
> Happy New Year
>
> Peter Verhaart
>
>
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gross_energy_hard_softwoods_table.doc

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