Environmental Engineering Reference
In-Depth Information
Residential
5%
Commercial
6%
Agriculture
8%
Electric Power
34%
Industry
19%
Transportation
28%
FIGURE 2.5 U.S. greenhouse gas emissions by sector in 2006. Source: U.S. EPA (2008).
alized countries such as the United States, the difficulty in reducing emis-
sions will depend in large part on the lifetimes of the
existing
capital stock
associated with the major emitting sectors. The electric sector is the largest
source of manmade emissions in the United States, primarily due to the
carbon dioxide emitted during the combustion of fossil fuels. The lifetime
of coal-fired power plants is measured in decades. The next largest source
of U. S. greenhouse gases is the transportation sector, again due to the
combustion of fossil fuels. Here the lifetime of the capital stock is typically
a decade or two.
Although developed countries historically have been the major emitter
of greenhouse gases, developing countries are on track to overtake them
in the next few years. In their case, the issue becomes one of the capital
stock put in place in the
future
to support their industrialization process.
With the huge economic growth projected for developing countries and in
the absence of incentives to act otherwise, these countries will likely turn
to the cheapest energy sources to fuel their growth. These fuels currently
are fossil based: coal, oil, and gas. A recent study by the Energy Modeling
Forum, based on eight Energy-Economy models, projected an annual growth
rate of CO
2
emissions globally from the burning of fossil fuels and industrial
uses to be of the order of 1 to 2 percent per year over the remainder of the
