It is frankly somewhat amazing that this review contains no mention at
all of what appears to be the single lowest cost and lowest impact way
of removing excess CO2 from the atmosphere, namely the accelerated
weathering of magnesium silicate bearing rock by spreading the
pulverised rock at land and littoral zones.
Given that this system is now quite widely published, such ignorance is
surely deliberate. How is it to be explained? Oliver.
On 18/02/2013 23:31, Rau, Greg wrote:
http://planetsave.com/2013/02/18/stanford-scientists-aim-to-remove-co2-from-atmosphere/
Stanford Scientists Aim To Remove CO2 From Atmosphere
Joshua S Hill
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Turn the clock back a decade and we had all sorts of grand plans for
reducing our greenhouse gas emissions levels, hoping that by 2020 we
would be on the path to saving our planet.
Reducing Carbon Means Destroying Carbon
<http://c1planetsavecom.wpengine.netdna-cdn.com/files/2013/02/750px-Cwall99_lg.jpg>
Image Credit: Wikimedia <http://en.wikipedia.org/wiki/File:Cwall99_lg.jpg>
Welcome to 2013 and … not so much.
Unsurprisingly, scientists at Stanford University have recently come
out and said that curbing our CO2 emissions may simply not be enough
any more. Instead of simply hoping the long-tail of emissions
reductions do /something/, they believe we need to start looking at
carbon-negative technologies that actively remove carbon dioxide from
the atmosphere.
“To achieve the targeted cuts, we would need a scenario where, by the
middle of the century, the global economy is transitioning from net
positive to net negative CO2 emissions,” said report co-author Chris
Field, a professor of biology and of environmental Earth system
science at Stanford. “We need to start thinking about how to implement
a negative-emissions energy strategy on a global scale.”
The Stanford scientists findings are summarised in a report
by Stanford’s Global Climate and Energy Project (GCEP), which describe
a suite of emerging carbon-negative solutions to global warming.
BECCS
“Net negative emissions can be achieved when more greenhouse gases are
sequestered than are released into the atmosphere,” explained Milne,
an energy assessment analyst at GCEP. “One of the most promising
net-negative technologies is BECCS, or bioenergy with carbon capture
and storage.”
For example, a BECCS system could convert woody biomass, grass, and
other vegetation into electricity, chemical products, or fuels such as
ethanol, leaving the CO2 emissions released during the process to be
captured and stored.
Estimates show that by 2050 BECCS technologies could sequester 10
billion metric tonnes of industrial CO2 emissions from installations
like power plants, paper mills, ethanol processors, and other
manufacturing facilities. But we have a ways to go before we are
technologically able to manage this.
Biochar
Biochar is a plant byproduct similar to charcoal that is made from
lumber waste, dried corn stalks, and other plant residues. A process
called pyrolysis — which heats the vegetation slowly without oxygen —
produces carbon rich chunks of biochar that can be placed in the soil
as a fertiliser, which locks the CO2 underground instead of letting
the CO2 re-enter the atmosphere as the plant decomposes as it
naturally would.
EHowever, long-term sequestration “would require high biochar
stability,” they wrote. “Estimates of biochar half‐life vary greatly
from 10 years to more than 100 years. The type of feedstock also
contributes to stability, with wood being more stable than grasses and
manure.”
Net-negative Farming
Another option included in the GCEP report is the idea of net-negative
farming. The authors cited research done by Jose Moreira of the
University of Sao Paulo who found that from 1975 to 2007, ethanol
production from sugar cane in Brazil resulted in a net-negative
capture of 1.5 metric tons of CO2 per cubic meter of ethanol produced.
“In this model, the system took 18 years to recoup carbon emissions,
with most reductions coming from soil replenishment from root growth
and replacement of gasoline with ethanol,” the GCEP authors wrote.
However, questions remain about the long-term effects of ethanol
combustion on climate.
Other Options
The report also explored other options, such as sequestering carbon in
the ocean, specifically the problem of ocean acidification. Currently,
the more CO2 the oceans absorb the more acidic they become, resulting
in algae blooms often seen in locations throughout Asia as well as the
Gulf of Mexico in the US.
However, research by David Keith of Harvard University suggests that
adding magnesium carbonate and other minerals to the ocean to reduce
acidity would also sequester atmospheric CO2 in absorbed in seawater.
For more information on these options, check out the full report here
<http://gcep.stanford.edu/events/workshops_negemissions2012.html>.
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