Carbon Dioxide
The preliminary estimate of U.S. carbon dioxide emissions from both energy
consumption and industrial processes in 2005 is 6,008.6 million metric
tons (MMT), which is 0.3 percent higher than in 2004 (5,988.7 MMT) and
accounts for 84 percent of total U.S. greenhouse gas emissions (see Table
ES3 for a breakdown of U.S. carbon dioxide emissions by source). U.S. carbon
dioxide emissions have grown by an average of 1.2 percent annually since
1990. Although short-term changes in carbon dioxide emissions can result
from temporary variations in weather, power generation fuel mixes, and
the economy, growth in carbon dioxide emissions in the longer term results
largely from population- and income-driven increases in energy use, as
well as consumer choices of energy-using equipment. The “carbon intensity”
of energy use (carbon dioxide emissions per unit of energy consumed) can
also influence the trend of growth in energy-related carbon dioxide emissions.
Figure ES2 shows recent trends in some common indexes used to measure the
carbon intensity of the U.S. economy. Carbon dioxide emissions per unit
of gross domestic product (GDP) have continued to fall relative to 1990;
by 2005, this measure was 23 percent lower than in 1990. Carbon dioxide
emissions per capita, however, were 1.0 percent above 1990 levels in 2005.
Population growth and other factors resulted in increased aggregate carbon
dioxide emissions per year from 1990 through 2005 (a total increase of
20 percent). Carbon dioxide emissions per unit of net electricity generation
in 2005 were 0.4 percent higher than in 2004.
Energy Consumption
The consumption of energy in the form of fossil fuel combustion is the
largest single contributor to anthropogenic greenhouse gas emissions in
the United States and the world. Of total 2005 U.S. carbon dioxide emissions
(adjusting for U.S. Territories and bunker fuels), 98 percent, or 5,903.2
MMT, resulted from the combustion of fossil fuels—0.3 percent more than
in 2004.
The Energy Information Administration (EIA) divides energy consumption
into four general end-use categories: residential, commercial, industrial,
and transportation. Emissions from electricity generators, which provide
electricity to the end-use sectors, are allocated in proportion to the
electricity consumed in, and losses allocated to, each sector. Figure ES3
illustrates trends in carbon dioxide emissions by energy consumption sector.
Average annual growth rates in carbon dioxide emissions by sector during
the 1990-2005 period were 2.0 percent for the commercial sector, 1.8 percent
for the residential sector, and 1.5 percent for the transportation sector.
For the industrial sector, carbon dioxide emissions have grown in some
years and fallen in others; industrial emissions in 2005 were slightly
below their 1990 level.
Carbon dioxide emissions from the transportation sector are the largest
source of energy-related carbon dioxide emissions. At 1,958.6 MMT, the
transportation sector accounted for 33 percent of total U.S. energy-related
carbon dioxide emissions in 2005. Transportation sector emissions increased
by 1.0 percent in 2005 relative to the 2004 level of 1,939.2 MMT. Almost
all (98 percent) of transportation sector carbon dioxide emissions result
from the consumption of petroleum products: motor gasoline, 1,170.5 MMT
(60 percent of total transportation sector emissions in 2005); middle distillates
(diesel fuel), 434.1 MMT (22 percent); jet fuel, 243.8 MMT (12 percent);
and residual oil (heavy fuel oil, largely for maritime use), 64.1 MMT (3.1
percent). The growth in transportation-related carbon dioxide emissions
in 2005 included increases in emissions from the use of jet fuel (6.5 MMT),
residual fuel oil (6.4 MMT), and diesel fuel (4.5 MMT).
Industrial sector carbon dioxide emissions, at 1,682.3 MMT, accounted for
28 percent of total U.S. energy-related carbon dioxide emissions in 2005.
The 2005 emissions level represents a 3.1-percent decrease from 2004 emissions
of 1,736.0 MMT. Although industrial production rose by 3.2 percent in 2005,
total industrial emissions fell, because three of the most energy-intensive
industries experienced downturns in 2005: primary metals (down 2.7 percent),
chemicals (down 6.9 percent), and petroleum (down 7.5 percent). In terms
of fuel shares, electricity consumption was responsible for 39 percent
of total industrial sector carbon dioxide emissions (662.8 MMT), natural
gas for 24 percent (399.7 MMT), petroleum for 26 percent (431.2 MMT), and
coal for 11 percent (184.5 MMT). Carbon dioxide emissions attributable
to industrial sector energy consumption in 2005 were 0.1 percent (1.3 MMT)
lower than in 1990.
At 1,253.8 MMT, residential carbon dioxide emissions represented 21 percent
of U.S. energy-related carbon dioxide emissions in 2005. The 2005 residential
emissions were 3.3 percent higher than the 2004 level of 1,213.9 MMT. The
residential sector’s pro-rated share of electric power sector carbon dioxide
emissions, 885.7 MMT, accounted for more than two-thirds of all emissions
in the residential sector.3 Natural gas accounted for 21 percent (261.7
MMT) and petroleum (mainly distillate fuel oil) represented 8.4 percent
(105.3 MMT). Since 1990, when residential sector carbon dioxide emission
totaled 953.7 MMT, the growth in residential carbon dioxide emissions has
averaged 1.8 percent per year.
Commercial sector carbon dioxide emissions accounted for about 18 percent
of total energy-related carbon dioxide emissions in 2005, at 1,050.6 MMT,
of which 78 percent (821.1 MMT) was the sector’s pro-rated share of electricity-related
emissions. Natural gas contributed 16 percent (166.3 MMT) and petroleum
5.3 percent (55.4 MMT). Commercial sector carbon dioxide emissions increased
by 1.6 percent from the 2004 level of 1,034.1 MMT. Since 1990, carbon dioxide
emissions in the commercial sector have increased on average by 2.0 percent
per year, the largest growth of any end-use sector. Commercial sector carbon
dioxide emissions have risen by 269.9 MMT since 1990, accounting for 28
percent of the total increase in U.S. energy-related carbon dioxide emissions.
Carbon dioxide emissions from the U.S. electric power sector increased
by 2.8 percent (65.6 MMT), from 2,309.4 MMT in 2004 to 2,375.0 MMT in 2005.
Carbon dioxide emissions from the electric power sector have grown by 32
percent since 1990, while total carbon dioxide emissions from all energy-related
sources have grown by 19 percent. Carbon dioxide emissions from the electric
power sector represented 40 percent of total U.S. energy-related carbon
dioxide emissions in 2005; however, as noted above, in calculating emissions
from the end-use sectors EIA distributes electric power sector emissions
to the four sectors in proportion to their respective shares of total electricity
purchases. Therefore, electric power emissions are already included in
the sectoral totals. By fuel, emissions from natural-gas-fired generation
increased by 7.7 percent, emissions from coal-fired generation increased
by 2.1 percent, and emissions from petroleum-fired generation increased
by 2.3 percent in 2005 from their 2004 levels (see box on page 6 for allocation
of all greenhouse gases to EIA’s end-use sectors).
Nonfuel Uses of Energy Inputs
Nonfuel uses of fossil fuels, principally petroleum, both emit carbon dioxide
and sequester carbon over their life cycles. In 2005, nonfuel uses of fossil
fuels resulted in emissions of 106.4 MMT carbon dioxide, a 4.7-percent decrease
from the 2004 level of 111.7 MMT. Emissions from nonfuel uses of energy
fuels are included in the unadjusted energy consumption subtotals in Table
ES3.
On the sequestration side of the ledger, nonfuel uses of fossil fuels also
resulted in carbon sequestration equal to 300.9 MMTCO2e in 2005, a 3.3-percent
decrease from the 2004 level of 311.1 MMTCO2e. The major fossil fuel products
that emit and sequester carbon include liquefied petroleum gas (LPG) and
feedstocks for plastics and other petrochemicals. Asphalt and road oils
are a major source of sequestration, but they do not emit carbon dioxide.
It is estimated that, of the amount of carbon sequestered in the form of
plastic, about 11.1 MMTCO2e was emitted as carbon dioxide from the burning
of the plastic components of municipal solid waste to produce electricity
in 2005. The 2004 estimate of 19.4 MMTCO2e is used in this report as an
estimate for total 2005 emissions of carbon dioxide from the burning of
wastes. The U.S. Environmental Protection Agency (EPA) estimates total
emissions from waste burning, and its 2005 value was not available at the
time this report was published.
Adjustments to Energy Consumption
Total U.S. carbon dioxide emissions and the estimates of energy consumption
on which they are based correspond to EIA’s coverage of energy consumption,
including the 50 States and the District of Columbia. Under the United
Nations Framework Convention on Climate Change (UNFCCC), however, the United
States is also responsible for counting emissions emanating from its Territories,
and their emissions are added to the U.S. total. Conversely, because the
IPCC definition of energy consumption excludes international bunker fuels
from the statistics of all countries, emissions from international bunker
fuels are subtracted from the U.S. total. Military bunker fuels are also
subtracted, because they are also excluded by the IPCC from national emissions
totals. On net, these adjustments resulted in the subtraction of 42.1 MMT
from total U.S. carbon dioxide emissions related to energy consumption
(5,945.3 MMT), resulting in an adjusted total of 5,903.2 MMT for energy-related carbon dioxide emissions in 2005 (Table ES3).
Energy-related carbon dioxide emissions for the U.S. Territories are added
as an adjustment, in keeping with IPCC guidelines for national emissions
inventories. The Territories included are Puerto Rico, the U.S. Virgin
Islands, American Samoa, Guam, the U.S. Pacific Islands, and Wake Island.
Most of these emissions are from petroleum products; however, Puerto Rico
and the Virgin Islands consume coal in addition to petroleum products.
Total energy-related carbon dioxide emissions from the U.S. Territories
in 2005 are estimated at 58.6 MMT (Table ES3).
In 2005, approximately 100.7 MMT carbon dioxide was emitted in total from
international bunker fuels, including 90.6 MMT attributable to civilian
consumption of bunker fuels and 10.1 MMT from military use.4 In Table ES3,
total emissions from international bunker fuels are included as a negative
adjustment to U.S. energy-related carbon dioxide emissions. Just over two-thirds
of the carbon dioxide emissions associated with international bunker fuels
comes from the combustion of jet fuels; residual and distillate fuels account
for the other one-third, with most of that coming from residual fuel.
Other Carbon Dioxide Emissions
In addition to carbon dioxide emissions from fossil fuel combustion and
use, a total of 105.4 MMT was emitted from other sources in 2005 (Table
ES3). Cement manufacture (45.9 MMT) and industrial sources (28.1 MMT) accounted
for nearly three-fourths of the total carbon dioxide emissions from other
sources. Energy sector components in the other emissions category included
the stripping of carbon dioxide from natural gas (17.3 MMT) and natural
gas flaring (5.9 MMT). An additional 8.3 MMT carbon dioxide is estimated
to have been released from the burning of wastes other than municipal solid
waste in the electric power sector.
Notes |
