Carbon Dioxide
The preliminary estimate of U.S. carbon dioxide emissions from both energy
consumption and industrial processes in 2004 is 5,973.0 million metric
tons (MMT), which is 1.7 percent higher than in 2003 (5,871.8 MMT) and
accounts for 83.9 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 1.3 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 2004, this measure was 21 percent lower than in 1990. Carbon dioxide
emissions per capita, however, were 1.2 percent above 1990 levels in 2004.
Population growth and other factors resulted in increased aggregate carbon
dioxide emissions per year from 1990 through 2004 (a total increase of
19 percent). Carbon dioxide emissions per unit of net electricity generation
in 2004 were 1.1 percent lower than in 2003.
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 2004 U.S. carbon dioxide emissions
(adjusting for U.S. Territories and bunker fuels), 98 percent, or 5,868.0
MMT, resulted from the combustion of fossil fuels. This figure represents
an increase of 1.7 percent from 2003 levels.
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 1990-2004 period were 2.0 percent for the commercial sector, 1.7 percent
for the residential sector, 1.5 percent for the transportation sector,
and 0.2 percent for the industrial sector.
Carbon dioxide emissions from the transportation sector are the largest
source of energy-related carbon dioxide emissions. At 1,933.7 MMT, the
transportation sector accounted for 33 percent of total U.S. energy-related
carbon dioxide emissions in 2004. Transportation sector emissions increased
by 3.1 percent in 2004 relative to the 2003 level of 1,875.7 MMT. Almost
all (98 percent) of transportation sector carbon dioxide emissions result
from the consumption of petroleum products: motor gasoline, 1,162.6 MMT
(60 percent of total transportation sector emissions in 2004); middle distillates
(diesel fuel), 428.2 MMT (22 percent); jet fuel, 237.4 MMT (12 percent);
and residual oil (heavy fuel oil, largely for maritime use), 54.6 MMT (2.8
percent). The growth in transportation-related carbon dioxide emissions
in 2004 included increases in emissions from the use of motor gasoline (21.2 MMT), diesel
fuel (17.9 MMT), residual fuel oil (10.0 MMT), and jet fuel (8.2 MMT).
Industrial sector carbon dioxide emissions, at 1,730.2 MMT, accounted for
29 percent of total U.S. energy-related carbon dioxide emissions in 2004.
The 2004 emissions level represents a 2.6-percent increase over 2003 emissions
of 1,685.6 MMT, the largest since a 3.0-percent increase from 1995 to 1996.
The 2004 increase in industrial emissions resulted from strong growth in
industrial production, up 4.1 percent from 2003. In terms of fuel shares,
electricity consumption was responsible for 38 percent of total industrial
sector carbon dioxide emissions (660.9 MMT), natural gas for 26 percent
(441.9 MMT), petroleum for 25 percent (440.6 MMT), and coal for 10 percent
(181.0 MMT). Carbon dioxide emissions attributable to industrial sector
energy consumption, while fluctuating from year to year, have increased
by an average of 0.2 percent per year since 1990. As a result, total energy-related
industrial emissions in 2004 were 2.2 percent (38.0 MMT) higher than in
1990.
At 1,212.0 MMT, residential carbon dioxide emissions represented 21 percent
of U.S. energy-related carbon dioxide emissions in 2004. The 2004 residential
emissions were 0.1 percent lower than the 2003 level of 1,213.2 MMT. A
warmer winter in 2004, relative to 2003, was a contributor to the 2004
decrease in residential sector emissions. Additionally, while the winter
was warmer than 2003, the summer was cooler, leading to a drop of about
4 percent in both heating and cooling degree-days.4 The residential sector’s
pro-rated share of electric power sector carbon dioxide emissions, 837.3
MMT, accounted for more than two-thirds of all emissions in the residential
sector.5 Natural gas accounted for 22 percent (265.5 MMT) and petroleum
(mainly distillate fuel oil) represented 8.9 percent (108.0 MMT). Since
1990, when residential sector carbon dioxide emission totaled 953.7 MMT,
the growth in residential carbon dioxide emissions has averaged 1.7 percent
per year.
Commercial sector carbon dioxide emissions accounted for about 17 percent
of total energy-related carbon dioxide emissions in 2004, at 1,024.2 MMT,
of which 78 percent (795.4 MMT) was the sector’s pro-rated share of electricity-related
emissions. Natural gas contributed 16 percent (162.7 MMT) and petroleum
5.7 percent (57.9 MMT). Commercial sector carbon dioxide emissions increased
by 0.3 percent from the 2003 level of 1,021.1 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 243.4 MMT since 1990, accounting for 27
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 0.9 percent (19.7 MMT), from 2,278.8 MMT in 2003 to 2,298.6 MMT in 2004.
Carbon dioxide emissions from the electric power sector have grown by 27
percent since 1990, while total carbon dioxide emissions from all energy-related
sources have grown by 18 percent. Carbon dioxide emissions from the electric
power sector represented 39 percent of total U.S. energy-related carbon
dioxide emissions in 2004; 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 6.6 percent, emissions from coal-fired generation increased
by 0.1 percent, and emissions from petroleum-fired generation increased
by 0.3 percent in 2004 from their 2003 levels (see box on page 9 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 2004, nonfuel uses of fossil
fuels resulted in emissions of 114.3 MMT carbon dioxide (Table ES3), an
8.6-percent increase from the 2003 level of 105.2 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 316.6 MMTCO2e in 2004, a 7.7-percent
increase from the 2003 level of 294.0 MMTCO2e.6 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 11.0 MMTCO2e was emitted as carbon dioxide from the burning
of the plastic components of municipal solid waste to produce electricity
in 2004. The 2003 estimate of 18.8 MMTCO2e is used in this report as an
estimate for total 2004 emissions of carbon dioxide from the burning of
wastes. The U.S. Environmental Protection Agency (EPA) estimates total
emissions from waste burning, and its 2004 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 31.9 MMT
from total U.S. carbon dioxide emissions related to energy consumption
(5,899.9 MMT), resulting in an adjusted total of 5,868.0 MMT for energy-related
carbon dioxide emissions in 2004 (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 2004 are estimated at 61.7 MMT (Table ES3).
For 2003, the carbon dioxide emissions estimate for military bunker fuels
was 9.2 MMT.7 In 2004, approximately 93.6 MMT carbon dioxide was emitted
in total from international bunker fuels, including 84.4 MMT attributed
to civilian consumption of bunker fuels. In Table ES3, that amount has
been subtracted from the U.S. total. Just over one-half 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 half,
with most of that coming from residual fuel.
Other Carbon Dioxide Emissions
In addition to carbon dioxide emission from fossil fuel combustion and
use, a total of 105.0 MMT was emitted from other sources in 2004 (Table
ES3). Cement manufacture (44.8 MMT) and industrial sources (28.7 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 (17.8 MMT) and natural
gas flaring (5.9 MMT). An additional 7.8 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 and Sources |
