June 4, 2007 – Vol.12 No.11
TERRA PRETA: SEQUESTERING CARBON IN SOIL.
For the Amazonian Indians of 500-2500 years ago sequestering carbon may have been part of daily routine. Not for controlling greenhouse gas emissions, of course, but to improve soils for more productive farming.
Once thought to use slash-and-burn farming practices, the Amazonian’s land-clearing farming technique has now been redefined as slash-and-char. They used a cooler, controlled burn of undergrowth and crop waste that left behind a charcoal-like, almost pure black-carbon substance known as biochar. Char was mixed with pottery shards, plant residues, animal feces, fish bones to make terra preta - or black soil. Terra preta in the Amazon region is now considered some of the richest soil on earth.
Fast forward to today. Can terra preta be recreated to enhance soils while sequestering carbon that might otherwise find itself into the atmosphere as carbon dioxide?
The process would be carbon negative: More carbon (in the form of char) would be stored in the earth (and thus sequestered) than would be if the same bio matter was allowed to go through its normal carbon-neutral, grow-die-decompose-regrow cycle. Instead, carbon from the original plant is stored in biochar, does not decay and is not released into the atmosphere. New plant growth - perhaps growing in biochar improved soil - absorbs carbon dioxide from other sources.
In a project led Heartland BioEnergy of Webster City, Iowa, 14 tons of biochar, a co-product of Dynamotive Energy Systems process to make its proprietary BioOil (tm), will be mixed in various proportions as a soil enhancer to test crop yields, in this case corn. Yields, in this replicated terra preta, could be as much as 20 percent. The biochar in the soil changes its bulk density, modifies the soil structure, regulates water storage, and loosely binds soil nutrients ready to help plants grow.
And the ability to sequester carbon? That’s a given. Carbon in biochar, originally extracted from the atmosphere by growing plants, produced by Dynamotive’s fast pyrolysis process to make its proprietary fuel, is stashed away safely in the ground, perhaps for centuries. That’s sequestering.
Heartland is planning to build a biorefinery in central Iowa that would include a BioOil and biochar facility developed in partnership with Dynamotive and others. BioOil is an industrial fuel made from cellulose waste material. It’s compatible with industrial heating oils.
Visit Dynamotive at http://www.dynamotive.com/
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