[Gasification] Biochar - Carbon Negative?

[Luke Gardner]

Karve,
I agree, fundamentally.   The way I see it is that there are a few carbon cycles that are happening on this third rock. And its important to keep the distinction between them.  for simplicity's sake lets just look at two of the cycles and call them the long cycle and the short cycle.  The long cycle locks up carbon and traps it within the earth n the form of hydrocarbons, and through the billions of years carbon cycles from earth to air, and and back again.  Then there is the short cycle, in which the carbon is not trapped underground in grand quantities for grand periods of time.  This short cycle it locks up carbon within the biomass on the surface of the earth for short periods of time.  I pose this question... what is the average length of time carbon is trapped in biomass.  On the west coast in the US carbon can be trapped for thousands of years in the wood of a once great temperate rain forest.  In the Midwest- not so much more like an annual event. I think it is important to understand the lag time involved, the effect of burning something that will grow again in one year, is far different from burning something that will take a thousand years to regrow.  A year from now one act would be nearly carbon neutral, whereas the other would be 999 years not so carbon neutral.  Consider this to be a “carbon lag time”.  While this “lag” is in effect there is more carbon in the air than there should be... and that is what the real concern is all about.  
   Burning biomass may induce a portion of the carbon into the long cycle, and burning fossil fuels injects nearly all carbon from the long cycle into the short cycle.  By burning fossil fuels we are short circuiting the long cycle and end up with more carbon in the air than should be – today.  Also by burning biomass we short circuit the short cycle and end up with more carbon in the air than should be - today.
  I think its safe to say that we collectively agree that interfering with the long cycle like we have is bad.   The question I pose is this.  By how many years is it acceptable to short circuit the short cycle?
Luke Gardner


From: Anand Karve 
Sent: Wednesday, April 20, 2016 1:43 AM
To: Discussion of biomass pyrolysis and gasification 
Subject: Re: [Gasification] Biochar - Carbon Negative?

Dear Doug, 
biomass is formed by the process of photosynthesis. Burning biomass is considered to be carbon neutral, because the carbon dioxide produced in this process was originally already in the atmosphere before it got sequestered in plants by photosynthesis. After being released into the atmosphere by burning, it would be sequestered again in plants by photosynthesis. Therefore, the carbon dioxide added to the atmosphere is zero. if any of the biomass is converted into char and buried into the soil, it creates a negative carbon dioxide balance, irrespective of the proportion of char going into the soil.
Yours
A.D.Karve

***
Dr. A.D. Karve

Chairman, Samuchit Enviro Tech Pvt Ltd (www.samuchit.com)

Trustee & Founder President, Appropriate Rural Technology Institute (ARTI)


On Wed, Apr 20, 2016 at 11:24 AM, Doug Williams <doug.williams.nz at gmail.com> wrote:

  Hi Mark,

  You ask:
  > After gasification, approximately 5% of the woody biomass remains a biochar
  > which sequesters carbon, hence a 'carbon negative' claim can be made.

  Qualify which type of gasification, because 5% would only apply to a
  high performance gas making system. If however it was a pyrolysing char
  making system, about 1/3rd of the fuel weight would be char, but two
  thirds would be consumed by combustion to become a CO2 emission. So not
  honestly carbon negative in my opinion (other than replacing fossil
  carbon). Restoration of the environmental CO2 balance would be a tricky
  calculation.

  > Alternatively, if the woody waste is left to rot in situ, the carbon
  > sequestration is 0% (all carbon is released/transformed into CO2 and other
  > gasses).

  That fits the normal explanations, we all go back to CO2 and CH4 if
  left to rot(:-)

  > True?

  Truth can be very elastic sided when claims are made about
  gasification, so take care to confirm all calculations regarding the
  process in question.There is a lot of attention paid to carbon credits
  as an intensive to cheat in the Souther Hemisphere, and one should be
  careful if included in any proposals.

  Doug Williams,
  Fluidyne.


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