Environmental Engineering Reference
In-Depth Information
s coal and gas plants in the United States
were converted to even
If all of today
'
cient natural-gas plants,
emissions from electricity generation would drop by
nearly
%ef
million tonnes per year or nearly
%of
total emissions. Gas plants are not only more ef
cient
than the best of coal plants, but emit less greenhouse gas
for the same amount of energy used. In the United States
a move away from coal is happening because of the dra-
matic drop in the price of natural gas that goes with the
increase in supply from shale gas. At the end of
,
coal-generated electricity had dropped to about
%of
the total while gas-generated had risen to about
%.
With the change goes a reduction of emission from the
electricity sector of about
%, a lower average cost of
electricity, and a healthier public.
The reasons for continued reliance on coal for electri-
city generation are that there are a lot of plants already in
existence, and, more importantly, coal is cheaper than gas
as a fuel in most of the world. The United States is a
special case that I will come to below. Even though a coal
plant with all its pollution-control equipment costs more
than a natural-gas plant to build, the difference in fuel
costs make coal a source of
lower-cost electricity
(according to the EIA, in
, before the shale-gas revo-
lution, gas cost more than three times coal for the same
energy content).
A reminder; gas gets half of its energy output from turning its hydrogen
into water with no greenhouse gas emissions whereas coal gets all its
energy from turning carbon into CO . Add to this the better ef
ciency of
a gas plant compared with a coal plant, and conversion of an old coal
plant to a modern gas plant reduces emissions threefold for the same
electricity output.
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