Carbon Capture and Storage (CCS)
Keeping Industrial CO2 Out of the Atmosphere
Human (anthropogenic) activity, including the use of fossil fuel
, releases greenhouse gases
to the atmosphere.
Carbon capture and storage (CCS) is a method of capturing CO2
before it is released
to the atmosphere and then placing the CO2
into long-term storage. Geologic sequestration
is a major option for long-term CO2
storage. CCS is best suited for
use in large stationary facilities, like thermoelectric power plants
Most large facilities like power plants consume coal because it is a plentiful and economical
fuel. In a large facility like a power plant, thousands of tons of coal are burned each day. The
heat from burning the coal heats water in huge boilers until the water becomes steam. This steam
is used to power large machines called generators. As the generators turn, they make electricity.
The coal is usually burned in air because it is the simplest and most economical system to use.
Air consists of about one-fourth oxygen (O2
) and about three-fourths nitrogen
). The air also has very small amounts of some other gases (argon and CO2
The oxygen in the air combines with the carbon in the fossil fuel, but the nitrogen does not
take part in combustion. As each ton of coal gives up its energy, it also gives off bits of
material that can’t burn (bits of mineral matter called ash), carbon dioxide (the result of
combustion—the reaction that happens when oxygen combines with carbon), nitrogen, and small
amounts of sulfur combined with oxygen, which is known as sulfur dioxide.
Over the past 30 years, power plants have added equipment to reduce fly ash, nitrogen, and
sulfur emissions. But managing CO2
emissions is much more challenging because
is a very small part of the exhaust gas
As a result, scientists are developing new technologies to capture CO2
processes that will make CO2
Today, the CO2
can be captured at three points in the power production process: before
combustion, during combustion, or after combustion. The majority of capture technologies focus
on separating the CO2
from the exhaust gas stream after combustion
After the CO2
is captured, it must be compressed either for storage prior to truck
transport or to be put directly into a pipeline to the sequestration site. CO2
be compressed to about 1200 to 1500 psi
for transport in a pipeline. Compression is
energy-intensive, so improved methods of compression are also being developed.
The energy in fossil fuel is stored in the bonds between the atoms of hydrogen and carbon.
To break those bonds and release energy to do things like drive a turbine in a power plant,
we add enough heat to start a reaction in order to break some of the bonds in the fuel
(this is why we need a match to get a wood fire started). Then we introduce enough air to provide
enough oxygen to attract carbon and hydrogen atoms in the fuel—this keeps the reaction (fire!)
going. As the bonds in the fuel break, energy is released in the form of heat.
Much more heat is given off than we put in—that is the energy stored in the fuel. In the meantime,
the atoms that have been released as the energy is released combine with the free atoms
available in the air. These new combinations of atoms form new materials, mainly water
vapor and carbon dioxide.