[Terrapreta] What Hansen said about biochar

[lou gold]

Here's more of what Hansen is saying about biochar.
Hopefully this will put terra preta related technologies in the spotlight of
the policy makers.

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Improved agricultural and forestry practices offer a more natural way to
draw down CO2.
Deforestation contributed a net emission of 60±30 ppm over the past few
hundred years, of
which ~20 ppm CO2 remains in the air today (2, 81, figs S12, S14).
Reforestation could absorb a
significant fraction of the 60±30 ppm net deforestation emission.

Carbon sequestration in soil also has significant potential. Biochar,
produced in pyrolysis of
residues from crops, forestry, and animal wastes, can be used to restore
soil fertility while storing
carbon for centuries to millennia (82). Biochar helps soil retain nutrients
and fertilizers, reducing
emissions of GHGs such as N2O (83). Replacing slash-and-burn agriculture
with slash-and-char
and use of agricultural and forestry wastes for biochar production could
provide a CO2
drawdown of ~8 ppm in half a century (83).

In Supplementary Material we define a forest/soil drawdown scenario that
reaches 50 ppm by
2150 (Fig. 6B). This scenario returns CO2 below 350 ppm late this century,
after about 100 years
above that level.

More rapid drawdown could be provided by CO2 capture at power plants fueled
by gas and
biofuels (84). Low-input high-diversity biofuels grown on degraded or
marginal lands, with
associated biochar production, could accelerate CO2 drawdown, but the nature
of a biofuel
approach must be carefully designed (83, 85-87).

A rising price on carbon emissions and payment for carbon sequestration is
surely needed to
make drawdown of airborne CO2 a reality. A 50 ppm drawdown via agricultural
and forestry
practices seems plausible. But if most of the CO2 in coal is put into the
air, no such "natural"
drawdown of CO2 to 350 ppm is feasible. Indeed, if the world continues on a
business-as-usual
path for even another decade without initiating phase-out of unconstrained
coal use, prospects for
avoiding a dangerously large, extended overshoot of the 350 ppm level will
be dim.

Here are the links

Main paper, "Target Atmospheric CO2: Where Humanity Should Aim"

http://arxiv.org/pdf/0804.1126

For supporting materials:
http://arxiv.org/pdf/0804.1135
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