[Stoves] [biochar] Pine char gasification

Crispin Pemberton-Pigott crispinpigott at gmail.com
Thu Jan 2 15:46:46 CST 2014


Dear Kevin

I was not sure where this message went so I am reporting it.

Regards
Crispin

+++

> # KC: This seems to be "The Unspoken Elephant in the Room." Just how
> did the Terrapretians actually make Terra Preta??? Did they actually
> make it on purpose, OR did it just happen, when they disposed of
> wastes, either ``jungle wastes`` or ``domestic wastes``? What is the
> difference between making "Terra Preta" and the Milpa Agriculture, as
> practised in Belize?

 A member of this list is Cecil Cook, the stove anthropologist. He doesn't say much on this list but he reads it.

When he was at Harvard doing his PhD research (meaning, in Motto 
 Grosso, Brazil for 4 years) he encountered Terra Preta and he has the 
 following observation which is important for all the duffers 
 like me discussing it.

The original peoples of Brazil definitely farmed on terra preta soils. These soils appear in patches. There is nothing like 'big farm lands stretching to the horizon' when it comes to terra preta. What he observed is that the terra preta occurs on those places where they practised slash and burn agriculture on land chosen because it was already the most productive. Doh!

In short, the reason the land is so productive is that it was already 
the most productive before the slashing and burning started tens of 
thousands of years ago. To attribute, in its entirely, the 
productivity of the soils to char alone is quite incorrect.
There is a combination at work of slash and burn (which provides 
minerals and soil conditioner – char) on land that is already the best 
in the area for what might be a multitude of reasons, but drainage and 
good watering would be two.

Cecil points out that in a rain forest the fertilising resource is above the ground.

I have read that ‘on the edge of the farmed TP area the soil is much 
worse’ blah-blah-blah but all they are documenting is the fact that 
the First Nations people picked the good agriculture spots and worked 
those. That can’t be too surprising.

The accumulation over millennia of additional char is accidental, not 
crafted, and it is not the source of the ‘fertility’. Char is not a 
fertiliser. Minerals from the ash are.  After a few short years the fertility drops and they let it go back to forest for a few years to accumulate 'inputs' for the next go-round. I have heard of cycle times of from 3 to 7 years.

Yes all sorts of amazing things can happen within char, or not,  
depending on whether the char created is toxic or benign or   
beneficial. As you know it is easy to generate dioxins by burning  
chlorine containing biomass, and all sorts of other things. Nature  
is not as simple as our understanding of it.

Neither is Terra Preta. Where the land was good, they farmed it.  
Where it was not, they left it alone as not worth the effort. It is  
still true. We should be both cautious and not surprised.

Regards
Crispin





More information about the Stoves mailing list