[Stoves] Biochar Projects for Science Students

[Crispin Pemberton-Pigott]

Dear Andrew

I have forwarded your comment to Cecil Cook the anthropologist to ask how the Amazonians further West treated the soil. His Amazonian notebooks are four feet high. Perhaps, just maybe, he can recall what the soil structure was like. They dig down 5 feet to get azure blue honey from a ground dwelling honey bee.

My view is that people were farming the region long before the generally accepted dates. I mention that because it seems the time taken to generate such thick layers of carbon is pretty substantial. Every time I try to calculate how long it takes to accumulate the measured amounts, the answer is millennia. Slash and burn is not an efficient way to create charcoal.

Trees precipitate dust out of the air: poplars can bring down 5 tons per ha/yr.  Soil build-up during fallow times mixed with a thin char layer from the previous burn would build terra preta soils so the theory is sound. The idea that they were created deliberately seems less sound. The fertility comes from the non-char portions of the ash and is quickly depleted. Perhaps over time the burning cycle can be shortened.

It concerns me the scale of enthusiasm of the stove community for suddenly promoting char-creating stoves with the under-pinning arguments being carbon offset cash to subsidise otherwise unaffordable stoves and the putative benefits of terra preta soil. The math and economics seem a bit thin on (in) the ground.

I love the stoves of course because I love innovation. It would be a shame if the whole initiative is squashed by someone with standing and skill and no emotional investment who does their homework and discovers this is just another confluence of enthusiasm of opportunism.

Regards
Crispin in sunny Ulaanbaatar

-----Original Message-----
Crispin and All,

In regards to "accidental" terra preta, I am including a post I made to  
wattsupwithat.com last January:

"Many years ago, I read a book on swithen agriculture in the upper amazon  
basin and the eastern woodlands of the US. The main point of the book was  
that these ecosystems supported many more times the current populations  
before european agricultural and land tenure patterns were established.  
The vast majority of land cleared in the late 1700′s and early 1800′s in  
the eastern woodlands has now reverted back to forest. The thin forest  
soils were quickly depleted after clearing and burning, forcing families  
to move West for better opportunities.

Swithen agriculture used a strictly managed rotation system that maximized  
the resources of the forest ecosystem, giving the native populations a  
sustained abundance of agricultural goods, forest products and wild game.  
(It is theorised that the devastating epidemics that followed the first  
european explorers left remaining populations unable to maintain forest  
management, which may explain why Hernando De Soto’s descriptions of the  
american south differed substantially from what later explorers and  
settlers found.)

I have not read much of the terra preta literature but the description of  
the charcoal being found in thin layers would seem to support the idea  
that the native inhabitants used a rotating swithen agriculture that could  
still be found in some areas of the amazon basin thirty years ago. Nothing  
magic or mysterious.

Now, I wonder if terra preta soils can be found in the eastern US?"

I still wonder about terra preta in the US.  Any soil scientists out there  
that can answer the question?


Andrew Parker



On Fri, 26 Nov 2010 08:54:16 -0700, Crispin Pemberton-Pigott  
<crispinpigott at gmail.com> wrote:


> It would be interesting to know if the terra preta soils were  
> artificially
> created or were the consequence of cyclical burning in a rotation (slash  
> and
> burn).