[Gasification] Biochar - Carbon Negative?

[Doug Williams]

Hi Mark,

You ask:
> After gasification, approximately 5% of the woody biomass remains a biochar
> which sequesters carbon, hence a 'carbon negative' claim can be made.

Qualify which type of gasification, because 5% would only apply to a
high performance gas making system. If however it was a pyrolysing char
making system, about 1/3rd of the fuel weight would be char, but two
thirds would be consumed by combustion to become a CO2 emission. So not
honestly carbon negative in my opinion (other than replacing fossil
carbon). Restoration of the environmental CO2 balance would be a tricky
calculation.

> Alternatively, if the woody waste is left to rot in situ, the carbon
> sequestration is 0% (all carbon is released/transformed into CO2 and other
> gasses).

That fits the normal explanations, we all go back to CO2 and CH4 if
left to rot(:-)
 
> True?

Truth can be very elastic sided when claims are made about
gasification, so take care to confirm all calculations regarding the
process in question.There is a lot of attention paid to carbon credits
as an intensive to cheat in the Souther Hemisphere, and one should be
careful if included in any proposals.

Doug Williams,
Fluidyne.