Quote:
Originally Posted by malcolmf
Has it simply been taken from a living carbon sink?
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True that. From a recalcitrance perspective, converting a living carbon sink to a charcoal sink is a good thing only if that charcoal ends up in the soil (versus under the BBQ). A net increase in soil charcoal levels world wide is more effective at global cooling than the same net increase in lignin because charcoal is more recalcitrant.
From a carbon sink dynamics perspective, converting a living carbon sink to a soil charcoal sink is a good thing. The living carbon sink functions to convert atmospheric CO2 to carbohydrates. Stimulating this rate capacity is fundamental to the attraction of biochar/agrichar utilization.
I find these two perspectives compelling but am concerned that it doesn't account for the relative impact on climate change of the differences in N20, CH4 and CO2 generated from the lignin breakdown versus pyrolysis: charcoal production can produce high levels of N2O under some, but not all, scenarios. N2O is potent greenhouse gas. Any scheme to produce agrichar should address the N2O production involved. High nitrogen content biomass increases N2O, as does lowering the temperature of pyrolysis. I expect (need to know more) that utilizing the wood gas for fuel can eliminate the N2O load to the atmosphere. How we make the biochar and what we do with the biogas are both as important as what we do with the biochar.
Note: the solar charcoal production mentioned earlier in this thread seems to produce CH4, but did not mention N2O. I would like more information in that regard.
