Environmental Engineering Reference
In-Depth Information
About one-third of all the CO
2
emissions from fossil-fuel-based energy sources
are from thermopower plants. The idea of capturing CO
2
from the gases exhausted
from power plant stacks did not originate from concerns over the greenhouse ef-
fect, but as a possible source of commercial carbon gas (for example, as used
by beverage and dry ice industries). Several such CO
2
recovery plants were built
and operated in the United States, but most of them failed economically and were
closed when the price of crude oil fell in the 1980s.
Once CO
2
is captured, the problem is removing it. Its commercial use is
extremely limited, and thus there is no economic incentive for capturing large
amounts of CO
2
. Apart from this, there is the risk of CO
2
leaking back into the
atmosphere. In high concentrations, CO
2
is toxic and may cause deaths, as oc-
curred in the Republic of Cameroon in 1986, when CO
2
leakage from volcanic ori-
gin in Lake Nyos killed over 1,700 people as well as livestock and wild animals.
CO
2
capture processes usually require a large amount of energy, reducing the con-
version efficiency of the plant and the available power—and thus increasing the
amount of CO
2
produced per power unit generated.
Although CCS technology is usually linked to coal and natural gas thermopower
plants, nothing prevents it from being applied to biomass power generation (as in
the case of sugarcane bagasse). In this case, the CO
2
liquid emissions would be
negative, as the carbon in the atmosphere is synthesized in the plants, transformed
into energy, and injected underground.
Finding adequate reservoirs for CO
2
storage is not a trivial problem and in prac-
tice might present great difficulties. One possibility would be to transport the CO
2
from the source to its final deposition, be it through a gas duct network (which
would cause problems with land owners and ecologically sensitive areas) or by
road or railway transportation (which would overload the transportation infrastruc-
ture and require more energy).
The cost of capturing and storing CO
2
from thermal electricity-generating
power plants using coal is appreciable. Although few pilot plant projects are in
operation today, estimates exist that the cost of electricity for the operation of
industrial-scale CCS projects would rise by at least 50-100%. Considering full life-
cycle emissions, CCS technology can reduce CO
2
emissions from fossil fuel com-
bustion from stationary sources by about 65-85%. The costs of capturing and stor-
ing CO
2
are estimated to be in the range of US$30 to over US$200 per ton of CO
2
,
depending on the availability of adequate places for storage and the characterist-
