PAUL MAROTTA/GETTY IMAGES
THE CARBON QUANDARY
For the most part, American coalfired facilities, like those in most
of the rest of the world, rely on
comparatively simple, decades-old
pulverized coal technology that is
highly polluting and inefficient.
Further, only the very newest natural gas-fired plant designs could
conceivably meet any meaningful
greenhouse gas emissions standard for newly built power plants.
Most older coal and gas plants
— and even those using the most
advanced super- and ultra-supercritical coal technologies — would
fall well short. For these, the only
options in a carbon-constrained
world would be to shut down or
endeavor to capture and then either use or store — or “sequester”
as some definitions of CCS have it
— CO₂ emissions.
Capturing the stuff isn’t much of
technological feat. Three primary
methods are used: Pre-combustion,
post-combustion, and “oxyfuel.”
Post-combustion, the most mature of the carbon-capture methods, simply scrubs the CO₂ out
of the exhaust stream after the
fuel is burned — typically by injecting a chemical into the waste
that absorbs carbon dioxide. This
technique is well-developed and
can be retrofitted onto most of the
HUFFINGTON
09.15.13
standard coal-fired power plants
operating around the world today.
Pre-combustion — meaning the
CO₂ is stripped out before the
coal is burned — is a newer technique. But because it requires
the fuel to be converted to a gas
first, it’s really only an option for
that tiny percentage of newer,
high-efficiency, synthetic-gas
coal plants, and perhaps natural
gas plants as well. Like the postcombustion method, a so-called
“oxyfuel” system strips out the
CO₂ after the fuel is burned, but
it attempts to simplify the extraction by burning the coal in a
pure oxygen environment, leaving
behind only carbon dioxide and
water vapor. Condensing out the
In his 2009
book, Our
Choice, Al
Gore argues
that CCS
technology
remains a
pipe dream.