permaculture

[Dieter Brand <diebrand@yahoo.com>]

Toby,

I don’t see it as an either-or situation, but rather as two trends pulling in 
opposite direction and I have a hunch that biochar is pulling in the wrong 
direction.  The trend away from organics has started 160 years ago and has 
kept on accelerating at an every increasing speed during the last 60 years.  

To fully describe the destruction of biomass and humus that keeps on 
accelerating even as we are talking would require entire volumes.  It has 
started with the disappearance of draft animals and the introduction of the 
WC and has reached a preliminary high water mark with the production of 
biofuels, for the purpose of which forests are cut down to cultivate crops 
with GMOs, Roundup and the most abusive methods that the human mind can 
conceive of – all in the name of environmental protection.

> usable form. Just putting biomass into the soil does not
> sequester carbon; about 90% of the carbon is sent back into
> the atmosphere within a year, as opposed to biochar
> sequestering 30-40% of it for centuries. So in one sense,
> making humus out of biomass is far more damaging to the
> climate than making biochar, if I can play Devil's advocate
> for a minute. 

If you believe that, you probably also believe the Vegan argument that a cow 
is more damaging to the climate than an SUV ;-)

No, I think this argument amounts to not much more than rhetoric, because:

1.  Charcoal does not fulfill the same functions as humus, thus comparing the 
carbon sequestration of the two is meaningless.  Even if we do use biochar, 
we’ll still need humus.  If we don’t have humus, we’ll have to use synthetic 
and mineral fertilizers.

2.  How much biomass ends up in the soil depends on the type of land 
management (till, no-till, bare/covered soil, etc.), the type of crop, the 
temperature (humus in tropical climates depletes 6 times faster than in 
temperate climates, which is offset by higher biomass production in the humid 
tropics) and numerous other factors.  Thus the 90% is an arbitrary assumption.

3.  Even if 90% were gassed off, that would mean 100% of the biomass is 
turned to humus in 10 years (10% x 10 years).  To achieve the same with 
biochar, we would have to turn biomass into charcoal every 3 years (30-40% x 
3 years).  Even if we consider that the gas exchange between soil and 
atmosphere will continue after one year, there will be a gradual buildup of 
humus and carbon which will increase as humus levels and fertility increases. 
 Much of this added humus will remain underground in the form of dead roots, 
root exudates and Glomalin and not gas off at the surface, if soil 
disturbance is avoided.

But you are certainly correct in that anything that uses wood for heating 
more efficiently is very welcome.

Dieter