The
Discovery
�Somewhere,
Something Incredible Is Waiting To Be Known� Carl Sagan
The
lush growth of the Amazonian Rainforest belies a secret:
the natural soils, once cleared of forest, weathered by rain,
sun and tropical humidity, are unsustainable for the growing of
crops. Farmers continually �slash and burn� new territory in a
destructive cycle of �short crop /long-fallow shifting
cultivation� because the natural soils are exhausted in as little
as two years (Lehman et al, 2003:
xv, 17).
The Amazon has been labeled a �Counterfeit Paradise� by
Dr. Betty J. Meggers, who contends the region incapable of
sustaining the grand cities and extensive agriculture reported by
the explorer Francisco de Orellana after his 1540-42 Amazon
expedition.
It is only in the past few years that an international team
of scientists has uncovered new evidence of those civilizations, and
is making startling discoveries about how the Pre-Columbian
Amerindians created Terra Preta soils, producing the world�s best
soil from some of the worst (BBC Horizon) (Lehmann et al, 2003: 15,
21-22). |
The
Indian Soil
Terra
Preta de Indio is old, dating from 500 to 2500 BP, yet these soils
are still fertile today. Farmers on one Terra Preta site have conducted intensive
agriculture for forty years without the addition of fertilizer
(Peterson, Neves, Heckenberger, 2001: 92 pars 3).
Terra Preta is deep, with horizons that measure up to two
meters, lying in stark contrast to the yellow/white natural soils
from which they are made. Known
Terra Preta deposits are vast, covering an area twice the size of
Britain, an estimated 10% of the Amazon Basin, more sites may be
discovered (BBC Horizon).
The three primary components of Amazonian Dark Earths are
large quantities of Charcoal, Nutrient Material (primarily from food
and plant residues), and Ceramic potshards. Fire was the essential
tool for the formation of Terra Preta.
Rather than �slash and burn�, the Indians practiced
a
form of �slash and char�, incomplete combustion, a process
called pyrolysis, to form the charcoal or Black Carbon. Pivotal to
the formation of the Terra Preta, Black Carbon is found in levels 70
times higher than those of the adjacent native soils (Lehmann et al,
2003: 45, 47, 357) (Glaser et al 2001:37- 41). Black Carbon, stable
in the soil for centuries, has shown to have significant impact on
fertility, nutrient retention and high cation exchange levels. The
increased surface area in the soils due to bio-char, may provide
clues to increased nutrient cycling (Liang,
et al, 2006, pars 1,4, Conclusion). Charcoal is all �edges�.
�The
charcoal acts like a coral reef for soil organisms and fungi,
creating a rich micro ecosystem where organic carbon is bound to
minerals to form rich soil� (Eprida,
Explanation link). Studies
have documented the stability of Soil Organic Matter and
significantly elevated microbial growth potential with the addition
of charcoal amendments to the soil (Steiner, Zech and Teixeira,
2006) as well as increased crop production and prevention of
nutrient leaching (Marris, 2006) (Eprida, Home).
The
nutrient component, what we would call �compost�, included a
rich stew of food residues, fish bones, palm thatch, broken basket
materials, plant matter, even silt from nearby rivers. Traces of
human urine, turtle carapaces, animal bones, the remains of the
hunt, all went into the �midden� and were finally worked into
the soil. . (Lehmann et
al, 2003: 40, 45).
The
third pervasive ingredient of Terra Preta soil, the ceramic
potshards, which are present in amounts of 10 to 25% by volume, are
believed to add to the stability of the soil, provide drainage, as
well as act as a nutrient and moisture sink (Lehmann et al, 2003:
46)
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The
Potential
The
star of the Terra Preta firmament is the black carbon char, also
called biochar or agrichar.
Derived from herbaceous biomass as well as trees, the char
holds the key to lasting soil fertility, nutrient cycling and
retention, reduced runoff, and as a carbon sink to reduce Global
CO2. (Steiner, C., UNCCC Bali 2007)
Sequestering carbon is a simple effective method to reduce
atmospheric CO2.
To
follow the carbon cycle lets look at a tree.
The tree pulls carbon dioxide out of the atmosphere, and
locks it up in its biomass. (Lang, 2007) If the tree dies or falls
over in a storm and decomposes, the carbon is released back into the
atmosphere.
If the tree is burned, complete combustion releases 98% of
the carbon back into the atmosphere, and you are left with ash.
If instead of burning, this same tree is pyrolysed, or turned
to charcoal, the resulting black carbon can then be buried in the
soil creating a stable long term carbon sink, having removed 50% of
the tree carbon from the atmosphere for centuries.
The
real beauty of this system is when our tree, or biomass, is
�charred� the bio-energy it releases can be harnessed. Using
biomass to create �non-food source� sustainable energy and
biochar can reduce CO2 levels by as much as 10% (Lang 2007) (Eprida,
Flash, Explanation). Deforestation due to shifting slash and burn
cultivation could be halted. Biomass obtained from agricultural
waste, storm damage, and routine husbandry of public spaces could
all be transformed into clean energy, a soil amendment that is
fertile beyond our dreams, and a carbon sink that reduces the Global
CO2 (Cornell, Science Brief: 2)(Eprida, Home, Flash).
The work of dedicated scientists has inspired a worldwide
dialogue on Terra Preta at the World Conference on Climate Change in
Bali 2007, spurring a drive to create Dr. Wim Sombroeks� �Terra
Preta Nova� or New Age Terra Preta (Lehmann et al, 2003: xix).
Of keen interest is the finding that Amazonian Dark Earth may
not have taken centuries to form.
Research indicates the Terra Preta formation can be rapid, if
sufficient quantities of the essential components are present
(Lehmann et al, 2003: 46) While the Terra Preta soils are ancient,
the research is recent,
�40% of the papers on this subject were written in the past
six years� (Marris, 2006).
The first book on the subject, Amazonian Dark Earths
(Lehmann et al) was published in 2003. |
Conclusion
Rarely
do we find such an elegant solution to so many of the pressing needs
of our world. The promise of biochar embodies the principle of
sustainability as defined by the Brundtland Commission, �Meeting
the needs of today�s generation without compromising the abilities
of future generations to meet their own needs.�
(Hooker, W. Syllabus 2008) We can all participate, on scales large
and small, by incorporating char into our landscapes. (Note here
that biochar tends to raise ph levels, a benefit in the acid tropic
soils, but adjustments should be made accordingly)
Everyone can sequester carbon, no matter who you are or where
you live. From potted plants to vegetable gardens to large-scale
agribusiness.
Imagine the impact on your personal carbon footprint. What
greater gift to the future can we leave than rich fertile soil and a
clean environment? Click
Here To See References for the paper above. |
The
Challenge
My
project challenge is to create Terra Preta Nova, organically, with
readily available components.
I believe so strongly in the promise of biochar, the
experiment has begun.
To date approximately 450 pounds of char have been sequestered, mixed with
400 pounds of fired ceramic clay in user-friendly granular form, and
rich homemade compost. (Click
here to view annotated reference document) |
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