[Terrapreta] Flaring the more potent GHG in the off gas from a charcoal kiln?

[AJH]

On Sat, 2 Jun 2007 21:52:21 -0500, Sean K. Barry wrote:

>You say, 99% fixed carbon char with ~15% yield (= ~15% of the original biomass carbon)

No, 15% of the original dry matter in the biomass (ideally I guess you
need to refer it on an oven dry, ash free basis)


> or 78% fixed carbon char at ~45% yield (= ~35% of the original biomass carbon) ...
>
>Does the production (without flaring) of either material exhaust more high potency GHG than the other?

I'd say the low yield high temperature carbonising would put far more
CO2 equivalent GHG gases into the atmosphere than the low temperature
high volatiles would, if not flared. I don't think CO is considered a
GHG but IIRC it is linked to tropospheric effects and possibly ozone
layer depletion. Also consider particulates in smoke have opposing
effects, they can trap radiation and block it depending on where they
are in the atmosphere. There are big health aspects too.
>
>Un-flared "producer gas" from pyrolysis of wood into charcoal has a constituency like (~50%-N2(inert), ~29%-CO(not GHG), ~14%-H2(not GHG), ~4.5%-CO2, ~2%-CH4, <1%-others)).  Methane (CH4) is the most potent of those GHG in the producer gas.  It and CO2 are the only GHG of any significance.

I would have expected acetone and acetic acid to have some effect but
don't know.

>  Assuming your numbers are good, then 15% to 35% of the original biomass carbon is left in the char. 

You may like to rework that on the basis of original dry biomass
weight!

>
>I backed up your argument with my analysis, Andrew.  My analysis assumes your numbers and my numbers are relatively accurate and that my analysis isn't flawed 

Well done with the number crunching (and snipping!) but there is the
flaw that you interpreted my % of dry wood as being % of original
carbon. There can be other differences too, even given the same sort
of temperatures in that "flash" carbonisation of very small particles
leads to more gaseous products and far lest solid char.

AJH