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

[Tom Miles]

Ron,

 

An efficient gasifier, like one used for gas turbines or synthesis to liquid
fuels,  shouldn't make any char, or the char fraction is low in the
resulting ash. Small scale gasifiers usually make  3-5% char. Run poorly
they can make about 10% char. Pyrolysis systems dedicated for oil make about
12% char. Char yields from advanced processes are something like 33-40%
char. The off-gases from pyrolysis are typically used for driving the
charcoal making process. In that case char is the principal product so all
the value of the product must pay for the process. 

 

I see char as both a potentially valuable byproduct of gasification and
pyrolysis for bio oil and a prime product for pyrolysis for biochar.
Gasification and combustion will remove different proportions of the
nutrients. In the processes being developed by EPRIDA and Iowa State
University the intent is to not only capture the ash nutrients but also to
capture the nitrogen which otherwise is lost in gasification. Energy as
hydrogen may be a lower value byproduct of these processes. (I haven't
studied the ERPIDA proformas.) 

 

The Cane Energy Network is now informal. It was lead by Winrock
International from about 1989 to 2000.
http://www.winrock.org/clean_energy/publications.asp?BU=9054#s10

Much of the activity transferred to India under USAID supported programs.
See Cane Cogen India
http://www.renewingindia.org/newsletters/canecogen/current/index.htm

I know of mills in Latin America that are using eucalyptus with cane trash
and bagasse for power generation. I had a visit earlier this year from
Central Americans interested in harvesting cane trash to use in a local coal
fired power plant.  

 

If there is a market sugar mills will find ways to make biochar. They have a
history of trying many different products and processes for bagasse and
trash disposal including feed, building products and energy. African, Latin
American, Asian and US sugar mills have made substantial investments in
residue use.  Australia has often been a leader in this experimental
process. 

 

Tom 

 

 

 

 

 

 

From: Ron Larson [mailto:rongretlarson at comcast.net] 
Sent: Sunday, May 20, 2007 10:02 AM
To: Tom Miles; 'adkarve'; terrapreta at bioenergylists.org
Subject: Re: [Terrapreta] biochar and sugarcane growth (reply to AD Karve)

 

Tom  (cc AD, terrapreta list members):

 

    Thanks.  Below, I add a few more comments to your message of last night
on sugar cane.  You said:

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.

 

   [Tom:  Thanks for the added information.  I take this to mean thatyou
believe pyrolysis is a simpler (therefore cheaper?) means of obtaining char
than is gasification.  Do we have any data on whether gasification removes
nutrients that we would rather not remove?  Or is our need for liquid fuels
so great also - that we should be emphasizing fast pyrolysis and
gasification?]

 

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. 

 

  [Tom -  I had not heard of the "network".  This is very encouraging.  Is
there a web location for that dialog?

   Are these mills thinking of CHP - so that "waste" heat is available to
other types of factories that can then be encouraged to locate near by - and
further improve the economics (and further reduce overall energy consumption
and CO2 production)?  

   What is the ratio of sugar mills "using" vs "experimenting"?

   Any other biomass residue-using industries that are moving from part-year
to full-year operation?

   Agreed this will take time - but do you see a new sense of urgency within
the network?

   Will or could the transition be speeded up or slowed down by
consideration of Terra Preta ideas?]

   

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.  

 

   [RWL:  Interesting.  At the IAI meeting, one person emphasized that the
word "agrichar" should be replaced by "biochar" - perhaps for the reason you
suggest - that wood will be big for TP purposes.  I think we also need more
data on whether the char from leaves and trash is as soil-effective as that
from wood (thinking of surface area issues).

   The market value question is indeed critical and badly needs the
much-increased involvement of soil scientists - and I have been amazed at
how many of them there are.  They need funding.]

 

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.    

 

  [RWL:  We on this list can and must do a lot - but we need a much
increased world-wide governmental involvement as well (providing $ and
interest in the topic).  We are seeing amazing growth in literature on TP -
but we are still mostly unknown.  

   Thanks very much for the added education - where I know you have been
involved for many years.

 

Ron]

   

 

Tom Miles

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