The Power and Transportation Future - Hydrogen and Fuel Cells: Advances in Transportation and Power - page 281

electricity generation. This is true for natural gas as well as renewable
power in the near future. A natural gas fuel cell vehicle running on hy-
drogen produced from natural gas may have little or no net CO 2 benefits
compared to hybrid vehicles. Natural gas does have major benefits when
used to replace coal plants. Coal plants have much lower efficiencies at
around 30% compared to natural gas plants at 55%. Compared with natu-
ral gas, coal has nearly twice the CO 2 emissions, while gasoline has about
one third more CO 2 emissions than natural gas.
In the United States, vehicle emissions other than CO 2 , have been de-
clining steadily. Noxious emissions are being reduced by federal and state
regulations and the turnover of the vehicle fleet. As the vehicles go out of
service, they are replaced with newer and cleaner vehicles.
The federal Clean Air Act Amendments of 1990 appear to be work-
ing. In the 1990s, Tier 1 standards greatly reduced tailpipe emissions of
new light-duty vehicles which includes cars and most sport utility ve-
hicles.
By 2010, Tier 2 standards should further reduce vehicle emissions
by extending regulations to larger SUVs and passenger vans. The use of
gasoline with a lower sulfur content will also reduce emissions and it also
makes it easier to build cars that can achieve further reductions. These
standards should allow new U.S. cars to be extremely free of air pollut-
ants. But, the Clean Air Act does not cover vehicle CO 2 emissions. Many
new cars are called near zero emissions by their manufacturers and may
have tailpipe emissions cleaner than some urban air. Hydrogen fuel cell
vehicles will have almost no emissions besides some water vapor and
would be much cleaner.
COAL AND NATURAL GAS
The U.S. has been building new natural gas power plants because
they are more efficient and cleaner. By 2003, the nation had more than 800
gigawatts (gW) of central station power generation. One gigawatt is 1,000
megawatts (MW) and is about the size of a very large existing power plant
or three of the newer, smaller plants. Almost 145 gigawatts were added
from 1999 to 2002 and almost 96% of this was natural gas. This included
72 gigawatts of combined-cycle power and 66 gigawatts of combustion
turbine power which are used generally when demand is high.
The Energy Information Administration predicts an increase in coal