[Stoves] [biochar-production] Re: Stoves Digest, Vol 14, Issue 17

Frank Shields frank at compostlab.com
Mon Oct 31 12:05:30 PDT 2011

Dear Tom,


For compost the purpose is to 'stabilize' the carbon to a point the
environment can replenish oxygen and nutrients at a rate plants and biota is
not effected.  When in an ag situation we have growers ready to supplement
nutrients (nitrogen) at the ready when plants or lab tests indicate needed.
Stabilized values I like to see is < 4 mg CO2-C / g organic matter / day.
This dry weight.  But many people use 8 mg CO2-C as a stabilized value. 


I think biochar is not even in the picture for nitrogen up-take or oxygen
depletion in an ag soil because they will be so low. Perhaps over time in a
non ag environment the carbon may deplete the nitrogen  - put more likely
just hold the nitrogen from being leached for later use. 








From: stoves-bounces at lists.bioenergylists.org
[mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Tom Miles
Sent: Friday, October 28, 2011 11:50 AM
To: 'Discussion of biomass cooking stoves'
Subject: Re: [Stoves] [biochar-production] Re: Stoves Digest, Vol 14, Issue


Crispin, Frank,


Apart from fraud, it is nice to have a general indication of how much of the
fuel will convert to a gas before burning and how much would, in theory,
remain as char. IN practice you oxidize part of he "fixed" carbon as well. 


In carbonization the volatile carbon is a useful indicator of the extent of
carbonization. We look for volatile carbon to be less than 20% for most
applications. That does not mean that all biochar needs to be less than 20%
volatile carbon. Other measures of labile carbon would be helpful. 


For biochar applications it would be useful to know how much of the carbon
is likely to be consumed by organisms and will thereby have a demand on
nitrogen or other nutrients. I have assumes that is the volatile fraction.
How much char C do you include in calculating a C:N ration for composting,
for example?  If you intend to deliver a char to a uses that will supply
it's own N how much to you have to add? How much char from stoves can you
estimate will have a demand on plant nutrients if used as biochar? 




From: stoves-bounces at lists.bioenergylists.org
[mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Crispin
Sent: Friday, October 28, 2011 1:09 PM
To: 'Discussion of biomass cooking stoves'
Subject: Re: [Stoves] [biochar-production] Re: Stoves Digest, Vol 14, Issue


Dear Frank


My main disagreement is the term Fixed Carbon and that it means the total
weigh DAF where it should be a measure of carbon in that fraction. I will
need to get over that. 


I assure you that Fixed Carbon does not have a clear and scientific meaning.
I have given up hope with analyses that use the term. That means, it is
'helpful' but not an exact measure of anything.


It really is taken to mean the carbon that happens not to disappear when the
sample is treated in a certain way. Treat it in another way and the 'fixed'
portion changes so it is an inherent property of the protocol times the
fuel, not a property of the fuel alone.


The coal industry is so large that they feel they can get away with internal
definitions and that makes huge problems for stovers because we never really
know what we are being handed to burn. With biomass that has historically
been the 'chemistry' of the fuel contents. But the principal users of 'fixed
carbon' are the coal consumers like power stations. To give the DAF value of
anything is misleading because we need to know what % it is of the fuel, not
of part of the fuel.


There are many tricks played by people promoting processed fuels that
involve switching the fuel energy content numbers during the conversation.
For example, people will report the 'as received' heat content as the fuel's
heating value (which is true) and then point out that their 'Processing'
increases this to a much higher 'DAF value' showing a '60% increase in
energy per kg' even though it takes energy to remove the water and calculate
out the ash.  Plain fraud. Whenever someone reports the energy content you
have to not only ask on what basis the figure was derived, but also
investigate the protocol to see if it really is what it claims to be. Many
people believe that there is free energy to be harvested in this manner.





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