[Terrapreta] biochar and sugarcane growth (reply to AD Karve)

[Tom Miles]

Ron,

 

The inorganic salts in the cane tops and leave melt and vaporize at low
temperatures. Even in pyrolysis there is some loss as these elements
volatilize at low temperatures. But since pyrolysis occurs at lower
temperatures (300-500C) than combustion (750-800C) more of these elements,
particularly sodium and potassium, stay with the char.  In Japan the raku
glaze is made on pottery by simply subjecting rice straw to temperatures
above 750C which is the melting point of the naturally occurring mixture of
potassium and silica (2:3) in rice straw. Other glazes like the ones you
describe are simply combinations of these salts. In gasification sometimes
we can gasify the carbon in a crop residue by gasifying it inefficiently,
i.e. leave more carbon, which offsets the tendency for the melted components
of the ash to agglomerate.

 

Bagasse is generated at the mill as a result of crushing the cane. It has to
be delivered back out to the rural smallholder for him to use it. Trash, on
the other hand, is left in the field where it must be harvested separately
from the cane for use. Harvesters like you'll see in Australia make billets,
or short chunks, of cane and strip the leaves. There is increasing
environmental pressure to stop burning all over the world so if the trash
has a use that will justify collecting it then it will be used.   There
still is a "cane energy network" of sugar mills around the world who have
been either using or experimenting with combination s of bagasse and trash,
or bagasse and wood, that can be used to generate power when the mill is not
crushing. This is the basis of the growth of [power generations from bagasse
in India. In South and Central America the mills are also modernizing to use
less energy and to use their residues. You don't change an industry
overnight. We've been working on this with some mills for about 20 years. 

 

Sugar mills making alcohol are still using molasses. Cellulosic ethanol
(from bagasse) is still in development which is why it has gotten such a
large subsidy.  I don't think we will see pyrolysis of bagasse or trash
until a market value is apparent for the charcoal. It is my understanding
that oil yields from pyrolysis of grasses and agricultural residues are very
low which is why woods are preferred.  

 

I agree that an important objective of this group should be to demonstrate
the value and use of charcoal. Then let the open market or the policy makers
make it attractive for industrial interests to produce charcoal with
qualities that are useful. We have already seen Kingsford/Chlorox ready to
deliver charcoal by the truckload and that's not the barbecue quality
charcoal.    

 

Tom Miles

 

 

 

From: Ron Larson [mailto:rongretlarson at comcast.net] 
Sent: Saturday, May 19, 2007 5:46 PM
To: Tom Miles; 'adkarve'; terrapreta at bioenergylists.org
Subject: Re: [Terrapreta] biochar and sugarcane growth (reply to AD Karve)

 

Tom, AD,  terrapreta list members:

 

    I add a few questions to your message of last night:

 

As others have remarked the trash (leaves) contain high concentrations of
nutrients that make it difficult to burn in industrial boilers. These are
appropriately retained in the char in the ARTI process, which would make a
good agricultural char.       [Tom -  This is possibly the first time I have
heard this - or are we talking about the presence of some components of ash
that can generate a "glassy" residue?   Is the problem avoided in all
pyrolysis approaches?   

    This is way off topic - but I saw a "kiln" (right word?) once in
Uzbekistan solely dedicated to combusting (not pyrolyzing) a particular
difficult-to-harvest mountain-top plant, whose composition led to "pockets"
of a ceramics glaze (with very nice properties - with almost no further
processing).  What is a combustion problem for many was the whole point of
their operation.  (They are doing it now only to honor their village
traditions  better glazes are available at much lower cost.)]

 

We need to think on two levels in this discussion: (1) the rural
smallholder, and (2) industrial production.

 

Charcoal made from leaves and applied directly by the rural smallholder is
one economy. The example is the ARTI kiln.   [RWL:  I have been thinking
also of some rural small-holder pyrolysis of bagasse - perhaps in
charcoal-making stoves - but perhaps even without that logical by-product
use.  I don't believe we have to assume leaves only at the household level.]

 

Charcoal made by processing the bagasse residue after processing the cane at
the mill is another economy. Or, collecting the trash for conversion to
charcoal at the sugar mill is an industrial economy distinct from the
smallholder. The examples are the processes converting 100 tpd or more like
Dynamotive, Renewable Oil Corporation, Ensyn, EPRIDA, and Carbon Diversion
Technologies (Antal). [RWL:  Agree mostly.  But this large-scale conversion
may prove to be best with both bagasse and the leaves.  I think it probably
sub-optimum to leave the leaves (no pun intended) in the field for burning
(as seems to be practiced worldwide).  The mill I visited a few weeks ago in
Australia will for the first time ever be leaving no leaves in the field (I
think in large part because of objections to the uncontrolled combustion
there)!

 

In recent years large gains have been made in India in converting bagasse to
heat and power at the sugar mills. And there is pressure at all (900?) mills
around the world to process the trash. There are also pressures and
incentive to convert the bagasse and/or trash to liquid fuels. We have
worked on industrial projects involving both those processes.  [RWL:  Tom -
do you know of ANY of those (besides the two I learned of in Australia about
to start), who are operating the electrical side of the sugar mill operation
year-around?  I think the mill economics should much improve with that mode
of operaton - and experts I have talked to say this is not being done to
their knowledge - and of course have confirmed by experience that no-one in
the mill business is pyrolyzing anything.

    I like the alternative conversion of the bagasse to liquids (either
cellulosic ethanol or fast pyrolysis) and know of companies doing both with
bagasse.  But I know of none who are emphasizing charcoal - except as a
minor byproduct.  Have you worked with any along those lines?  (For anyone
wanting to try it, I recommend Tom as the best person to start with this
discussion.)

 

Initially there may be more incentive for a sugar mill to make heat and
power from bagasse than to make charcoal. There may not be enough value for
the mill to bring in the trash from the fields for converting it to
charcoal. That is where there should be an opportunity for small producers
like JFBiocarbon, BEST Technologies, or char from the modular oil producers
like Advanced Bio Refinery, Renewable Oil International or Agritherm.  [RWL:
Yep - the incentive is not there yet - but to prove there might be an
appropriae incentive is the reason you started this list.  

    I think/hope that the world will soon discover (with the help of people
in the field like AD and yourself) that the climate and soils benefits
(neither now being considered in the sugar business apparently) of charcoal
will exceed the value of any other form of their waste conversion, and
especially of combusting leaves in the field.  I agree there is a role for
pyrolyzers at all scales.  Fortunately, AD is an expert on this at the
family level as well.]

 

See: http://terrapreta.bioenergylists.org/company

 

   Tom - you are doing a great service by advertizing the existence of these
pioneering firms!      Ron]

 

Tom

  

 

 

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