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

[Duane Pendergast]

Sean, Andrew,

 

With that list of off gas components which includes "criteria" pollutants,
Sean can expect a visit from the EPA before too long and Andrew from the
corresponding UK authority, whether the gases are flared or not.

 

http://www.epa.gov/air/caa/peg/cleanup.html

 

I've retained the interwoven quote for context.

 

Duane

 

-----Original Message-----
From: terrapreta-bounces at bioenergylists.org
[mailto:terrapreta-bounces at bioenergylists.org] On Behalf Of AJH
Sent: June 3, 2007 5:07 AM
To: Sean K. Barry
Cc: terrapreta at bioenergylists.org
Subject: Re: [Terrapreta] Flaring the more potent GHG in the off gas from
acharcoal kiln?

 

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

 

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