[Terrapreta] Net Present Value and Net Future Value ofTPBenefits

[Mark Ludlow]

Hi Sean,

 

We need to put this in perspective. If wood is left to termite digestion,
the amount of CH4 released skyrockets. Complete combustion, in theory,
essentially converts all of the cellulosic carbon (as well as the
saccharides in the sap) to CO2. Smothered combustion (pyrolysis) has at
least the potential to preserve 25-to-30% of the original carbon as
immobilized carbon.

 

If, as it is claimed, this carbon makes the soil more productive, then
subsequent cycles of pyrolytic combustion should even be progressively more
useful, as higher soil productivity would equate to higher photosynthetic
conversion of atmospheric CO2.

 

I doubt that the pre-Columbian farmers in Amazonia did much that was
deliberate; a late burn, into the rainy season (of a rain forest), probably
produced a fair amount of incomplete combustion or charring. Perhaps they
saw enough of a difference in agricultural productivity to intentionally
shift their methods toward the more labor-intensive char burning. We may
never know. An immediate goal of NGOs in places like Amazonia and Indonesia,
might be to encourage incomplete combustion in land-clearing efforts.
There's at least the potential of some upside compared to the alternative
method which leaves only ash. 

 

Ideally, retort-based charring (fueled by pyrolysis gases) would address
your concerns about CH4, but it's hard to imagine that retorts will replace
slash burning anytime soon, on a large scale. Even here in the Northwest,
slash burning is the norm although the number of Cat D-10s in the woods
should provide other combustion opportunities.

 

Mark

 

From: terrapreta-bounces at bioenergylists.org
[mailto:terrapreta-bounces at bioenergylists.org] On Behalf Of Sean K. Barry
Sent: Sunday, March 23, 2008 10:19 PM
To: Edward Someus; Richard Haard
Cc: terrapreta at bioenergylists.org; tjones at nas.com;
friendsofthetrees at yahoo.com; anaturalresource at gmail.com; hans at riseup.net
Subject: Re: [Terrapreta] Net Present Value and Net Future Value
ofTPBenefits

 

Hi Richard, et. al.

 

Attempting pyrolysis in the "semi-open" to make some charcoal of biomass and
complete combustion of biomass differ in an important way.  The limited
oxygen in a pyrolysis reaction can promote the production and emission of
Methane-CH4 (a significant and potent GHG), whereas in complete combustion
without the limit on oxygen, the biomass fuel is reduced to ash and complete
combustion products (CO2 and H2O), with very little or no Methane-CH4.

 

With Methane-CH4 even at a mere 2-3% component (volume/volume) of the
"producer gas", because of its potency as a GHG, releasing it will do more
damage to the atmospheric concentration of GHGs and the GHG warming
potential than the improvement that could be had by sequestering most of the
remaining carbon from the biomass.  The damage from CH4 emissions can wipe
out the advantage from sequestering the highest yield of charcoal (~30-40%)
by weight.

 

The implement that is used to make charcoal in situ CANNOT release
Methane-CH4.  The process must use it or flare it at the very least.

 

Regards,

 

SKB

 

 

----- Original Message ----- 

From: Richard <mailto:richrd at nas.com>  Haard 

To: Edward Someus <mailto:edward at terrenum.net>  

Cc: sean.barry at juno.com ; kchisholm at ca.inter.net ; folke at holon.se ;
tjones at nas.com ; anaturalresource at gmail.com ; friendsofthetrees at yahoo.com ;
terrapreta at bioenergylists.org ; hans at riseup.net 

Sent: Sunday, March 23, 2008 2:16 PM

Subject: Re: [Terrapreta] Net Present Value and Net Future Value
ofTPBenefits

 

Edward - Are you comparing 'semi open, "simple" home made to industrial
appliances or to burning of forest debris/ agricultural waste? It seems for
the subsistence farmers of the humid tropics slash and char offers a
reduction in net emissions even with simple methods so long as the biomass
is carbonized, even partially. In addition, use of biomass as compost or
letting decompose on ground will result in conversion of 100% to atmospheric
form. The challenge is to design an implement  and distribute the appliance
that can be economically used on a scale that is significant where biomass
either cannot be transported or is not economic to do so. In urbanized air
quality controlled  areas an air quality controlled implement is
appropriate, but in rural areas where debris is burned anyway then low tech
pyrolysis would result in a net permanent reduction of emissions.  

 

Further, the use of an appliance that requires an investment and maintenance
would be incentive to recover cash value of charcoal as fuel and at small
scale as yet economic return from carbon buyback is not significant. This is
what has me thinking that a low tech solution in or near the farmers field
that results in a partial charred/compost-able product would yield a higher
level of sequestration. 

 

Please critique this viewpoint. For example, can you conclude charcoal
produced in this manor has lesser value in agriculture than converting
forest and agricultural debris to ash?

 

Thank you 

 

Rich H

 

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