[Terrapreta] Alfred Harris on Volatille Matter, Pyrolysis Temperature and Adsorbed Water

[Michael Bailes]

>From Stephen Joseph. Images and a link to the article can be found at:

http://terrapreta.bioenergylists.org/?q=harrisimagesmay807

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All

 

Alf has given me permission to share this with you.  The article is very
interesting as it identifies a pyrolysis temperature where there appears to
be a structural change in the adsorbed water. 

 

Please pass it on.

 

Regards

Stephen

 

  _____  

From: Ann & Alf [mailto:aaassharris at xtra.co.nz] 
Sent: Sunday, 6 May 2007 6:42 PM
To: stephen at bestenergies.com.au
Subject: Thanks, classification 

 

Kia ora Stephen

Congratulations on the wonderful effort with the conference. I think your
contexting of the conference in the work (and by default knowledge) of
indigenous people is crucial. I hope that you can persuade the organizing
committee to increase the efforts of the IAI in assisting indigenous people
thoroughly document their practices and engage in establishing how those
practices can provide the key tools to maintain and increase soil fertility
in a reducing petrochemical era. I think also that agri or biochar has a
hill billy conotation when what we should be promoting is  that fact the
pyrolysed biocarbons (PBCs) are THE energy and agricultural biotechnologies
of the 21st Century, that they are of fundamental importance in reducing
fossil carbon use in agriculture and reducing the use of irrigation water,
and will contribute to saving the planet by reducing global warming and sea
level rise. 

 

 

Over 30 odd years of structural biology and materials science, I have had
the good fortune to work on, amongst other things, animal and plant
diseases, soils, fuel cells, purification of titanium from steel slag.  More
recently I have been working on charcoal/microbe/plant interactions. I have
attached one of my most recent SEM images (21.1b.1). The material on the
right is charcoal. The hyphae of one of the beneficial microbes we were
using are also clearly visible. Sadly the root hairs got slightly damaged in
transit to the SEM. The sample was simply fixed and dehydrated in analar
methanol and CPD'd. I am working in eliminating the CPD step.

 

I think your idea of the development of a classification standard for PBCs
is a key requirement for moving the biocarbon work forward. Michael Antal
has done the groundwork for an analogous system required for characterizing
PBCs for use in biocarbon fuel cells in his magnificent review  "Antal, M.
J., & Gronli, M. 2003 The art science, and technology of charcoal
production. Ind. Eng. Res.  42:1619-1640" of which, sadly, I don't have an
electronic copy. 

 

I am essentially a systems person. >From that perspective, I think we need
to consider a hierarchical classification system beginning with a clear
structural characterization of the feedstock. The reason for this starting
point is simply that pyrolysis, as Michael has pointed out to me on more
than one occasion, is a dry distillation, essentially leaving the
macrostructures unchanged. Indeed a good botanist is perfectly capable of
telling, often down the species level, what tree an archaeological sample of
charcoal has come from. With regard to the woody biomasses most commonly
used, good old botany is a very useful ally. The structure of NZ woods (wrt
to tracheid and vessel shape and size) have been extremely well
characterized and I would be most suspect that the same has been done for
Australian woods. 

 

However, I suspect that what literature exists for leaves, nuts, and fibers
(e.g. coir) is much more scattered. I believe that these materials may be
crucial for a number of reasons:

§        In many cases (e.g. mallee)  they are the wastes of other
industries

§         Unlike wood, they require very little pre or post-processing to
make them suitable for soil applications. 

§        Further, and perhaps most crucially, they provide a range of
macropores that are more likely to approach the size of the microbes that
are fundamental to determining the beneficial effects of PBCs on plant
growth. 

 

 

A month or two ago, I began to wonder whether animal derived PBCs may be an
altogether different category. Protein and chitin derived PBCs are the two
main types that come to mind immediately. My initial investigations suggest
that protein-based PBCs such as feathers and wool may have a tendancy to
melt at relatively low temperatures. Of course their functional groups will
also be different and I think there could be a reasonable expectation that
there effects on plants might differ from plant derived PBCs.  

 

Like you Stephen, I also believe that the information from the next level
down on charge, functional groups etc, will only really be useful in a
functional sense if it is related to the level above and the pyrolysis
conditions used (temperature, pressure, water content etc) used. Let me give
a couple of examples by way of illustration:

The structure of macadamia nut shells is very different from woody biomasses
. PBC from macadamia shells (h4a1&2) contain some nodules which EDX show to
have elevated levels of Si. Now it may be that a macro analysis of ground
macadamia PBC would also show Si concentrations above background, but my
contention is that the spatial location of the Si may be crucial in
determining the functional properties of the PBC and should be recorded as
part of the classification system.

 

This is already clear evidence that the presence of absence of volatile
material has a dramatic influence on PBC properties wrt to reactivity and
cation exchange capacity. While feedstock will have a fundamental influence
on relative amounts and nature of volatiles, temperature and pressure are
other key linked factors that determine the concentration, and I suspect
location. The appearance of microcrystalline graphite in biocarbons
pyrolysed above at 475C appears to be associated with the development of
numerous nm sized pores (see attached pdf). The effects of these on the
functional properties of PBCs is even more poorly understood than the
influence of volatiles on cation exchange capacity.

 

Anyway, I hope those random musings are of some valuein developing a
classification system. I would be very keen to be kept up with progress in
that area.

 

Humusly 

Alfred Harris 

 

 

 

 

 




-- 
Michael Bailes.
"Human beings,
who are almost unique in having the ability to learn from the experience of
others,
are also remarkable for their apparent disinclination to do so." 
Douglas Adams, "Last Chance to See" 

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