[Stoves] Calculating cooking costs and char costs ----Re: [biochar] Where to discuss STOVES AND CARBON offsets and drawdown

[Nikhil Desai]

Crispin:

Thank you for pointing out market signals due to fertilizer subsidies. Very
interesting.

China also must have a great deal of animal waste from the food industry -
couldn't that go to fertilizer and climate char?

CDM and GS computations are driven by theories that have not been validated
in practice.  Invent a theory that can win a nod by opaque methods signed
off by a technical advisory council stacked by pals, and gold taps will
open.

Nikhil


On Sep 18, 2017, at 3:21 PM, Crispin Pemberton-Pigott <
crispinpigott at outlook.com> wrote:

Dear Paul



>Beginning with the baseline fuelwood use of 187,800 kg of fuelwood per
year per village, if we assume a 10% moisture content, the baseline
fuelwood is equivalent to 170,700 kg of dry fuelwood.



Correct.



Convert that to char using a pyrolytic gasifier and you get 25% of 170,700
= 42,675 kg of charcoal (not carbon).



The carbon fraction is probably about 36,300 kg.



Of the original carbon some 170,700 x 50% = 85,350 kg of C, minus 36,300 =
49,050 kg of carbon which creates 179,850 kg of CO2.



As pointed out here years ago, the challenge for pyrolytic stoves to have a
heat transfer efficiency that more than makes up for the additional fuel
requirement. If you look back far enough I provided a formula for
calculating the requirement.



As whole-wood burning cooking stoves have reached the 33-35% efficiency
range, the efficiency of a gasifier has to be high enough to compensate for
the additional fuel, if the fuel savings matters to the project, which in
the case of CDM and GS it does. If the char retention is 25% of dry mass,
and that fraction contains 50% of the original energy in the fuel (at
least), then the stove will have to be twice as efficient as the wood
burner, i.e. 66-70% heat transfer efficiency. In theory it is possible, in
practice I haven’t seen it. All pyrolytic gasifiers consume more fuel than
the best wood burner available at the time.



Your stoves might compare favourably with an open fire or a declared 10 or
15% efficient baseline, but they will not be as fuel efficient as a stove
that burns wood completely.



A stove that burns wood completely paralleled with a small charcoal making
operation in the same community might use less total wood and produce more
total char because both technologies can be optimised to their function. If
the purpose is to create the most char and the most cooking from a given
source of biomass, so at least, a pyrolytic gasifier is not the best
option. It is *an option* but it is not yet out-competing other technology
combinations. The cleanest wood burning stoves are as clean-burning as an
LPG stove, or there is not enough between them to find a meaningful
difference.



If one can sift through a biomass source and take out everything ideal for
a wood burner, and pyrolyse the rest into char, that is a reasonable thing
to do if the char has a use or value.



I proposed two years ago that in Hebei, which has a serious problem with
air pollution caused by the in-field burning of crop residue, that they put
a small price on the material making it worth collecting it to a central
point. This could be charred while making wood gas that can be piped into
the local distribution network. The remaining char would go into the input
line of local fertiliser factories that are making organic fertiliser, of
which char is one component. There are multiple factories making these
products, almost of all of which is sold outside the province to others
which subsidise organic fertiliser products (Hebei doesn’t).



They are not so unsophisticated as to advocate randomly planting char in
the soil. They make compounded fertiliser products designed for typical or
particular applications. I think it is a good use of millions of tones of
agricultural wastes. So far they are not doing it.



Regards
Crispin
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