[permaculture] biofuels and soil carbon

Mathew Waehner waehner at gmail.com
Thu Oct 22 14:57:17 EDT 2009

> There seems to be a misconception that the soil doesn't lose anything when
> crops are turned into biofuels.

This is an important point.  We've all read about turning "agricultural
wastes" into fuel, and we all know there is no such thing as agricultural

But some biofuel processes produce humus- methane fermentation produces
humus.  In a compost pile, most of the carbohydrates are "burned" by
bacteria and fungus.  Anerobic fermentation makes it possible for us to
capture some incompletely metabolised material in the form of methane and
burn it.

There is some good research in the field of biochar, which fills many of the
roles of humus.  Biochar has a high cation exchange capacity, so it acts as
a nutrient bank.  It also has an incredibly high internal surface area, so
it can provide habitat for microorganisms.  Biochar has a longer lifespan
than humus, especially in warm climates.  But biochar doesn't provide the
water regulating properties of humus, and it probably needs some humus to
function in soil.  Biochar fixes carbon in the round, so the process can
pull a bit of carbon out of the atmosphere.

Permaculture needs to develop sophisticated and regenerative ways of working
with the fire element.

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