| Overview | Energy Consumption | Electric Utilities | Industrial Sources | Adjustments to Energy Consumption | Carbon Dioxide Data Tables |
Three factors contributed to the 1995-1996 growth in U.S. carbon emissions: (1) the economy grew at a fairly robust
rate of 2.4 percent; (2) total energy consumption
grew by 3.2 percent; and (3) the largest growth in the energy sector was in coal consumption, which was up by almost
5 percent. Thus, not only did energy use increase, so also did its average carbon content, reversing a trend prevalent
in most of the 1990s, when the growth in energy consumption and emissions lagged behind trends in the economy
(Figure 4).
In 1996, weather-related factors contributed significantly to increased energy use and relatively greater reliance on coal. Increased heating requirements, especially in the Midwest, spurred higher demand for both natural gas and electricity. The rise in natural gas demand for heating drove gas prices up by more than 30 percent during the winter months of the last quarter of 1996 and caused power generators to switch from natural gas to coal for their fuel requirements.(31) From an emissions standpoint, these developments more than offset the benefits of increased hydropower production associated with above-normal precipitation in the West.
EIA energy statistics partition total energy consumption into four end-use sectors: industrial, transportation,
residential, and commercial. For all the sectors excepttransportation, a substantial portion of the energy used is
consumed as electricity. In the future most of the growth in energy consumption is expected to be in the transportation
sector and in the use of electricity. In this report, emissions for each sector are defined as the sum of emissions resulting
from the direct burning of fuels plus emissions associated with the production of electric power used in the sector. This
approach makes sectoral analysis more meaningful and helps to reveal the full value of electricity conservation. Not
only is delivered energy saved but also the substantial amount of energy (and associated emissions) taken as "losses"
in electric power generation. About two-thirds of the carbon dioxide emissions in the residential and commercial
sectors are derived from electricity (Figure 5).
Industrial primary energy consumption exceeded 32 quadrillion Btu in 1996, up 0.7 quadrillion Btu from 1995.(32) Over the past decade, the industrial sector has accounted for one-half of all U.S. energy consumption growth. About one-third of end-use carbon dioxide emissions are accounted for by the industrial sector (Table 6), which comprises
manufacturing industries, the largest part of the sector, along with mining, construction, agriculture, fisheries, and
forestry. Energy consumption is dominated by the need for heat and power; however, a large share of industrial energy
use involves consumption of raw materials for petrochemical feedstocks. Natural gas and electricity consumption each
account for about one-third of the
energy consumed in this sector (with losses in electricity generation included).
Although some carbon in the "nonfuel" use of energy is sequestered (Table 7), emissions amounted to about 477 million
metric tons of carbon in 1996, up by more than 2 percent from the previous year (Table 8). Energy efficiency
improvements, combined with low growth in energy-intensive industries, have moderated trends in carbon dioxide
emissions while total industrial output has expanded. Between 1990 and 1996, emissions for this sector increased by
23 million metric tons of carbon, or more than 5 percent.
Fuel use for transportation exceeded 24 quadrillion Btu in 1996, and gasoline consumption exceeded 7.8 million barrels
per day.(33) More than two-thirds of U.S. oil consumption is for transportation, which accounts for about one-third of
U.S. carbon dioxide emissions. Growth in this sector is more rapid than in the other end-use sectors. Low fuel prices,
low stock turnover of existing older vehicles, and stable average fuel efficiency in vehicles all contribute to expanding
energy consumption. In addition, of the newer vehicles being purchased, a higher proportion of them are sports utility
vehicles or light trucks. Thus, even though fuel economy may be stable by category, the shift to less fuel-efficient
vehicles means a higher growth rate in consumption.
Motor gasoline accounts for nearly two-thirds of transportation sector energy consumption. Together with emissions
from distillate, residual, and jet fuels, total emissions were about 469 million metric tons of carbon for the
transportation sector in 1996 (Table 9). Transportation sector emissions have accounted for more than 35 million metric
tons, or more than 29 percent, of the national increase in emissions from the end-use sectors since 1990 (Table 6), and
transportation could shortly overtake the industrial sector as the largest source of emissions.(34)
In 1996 energy consumption in the residential and commercial sectors combined totaled 33 quadrillion Btu, up 1.5
quadrillion Btu from 1995. Increased use of natural gas and electricity accounted for most of the change in energy use.
Electricity supplies two-thirds of the energy used in these sectors.Of the 19 quadrillion Btu of energy consumed in the
residential sector in 1996, nearly half was used for heating and cooling. Carbon dioxide emissions from this sector
accounted for less than one-fifth of U.S. emissions (Table 6). Most of the emissions from the residential sector are
associated with the use of natural gas and electricity for space heating and air conditioning and thus are subject to the
vagaries of the weather. In 1996 residential emissions jumped by more than 6 percent, as severe weather (Figure 6)
increased the consumption of distillate fuels and natural gas. In the 6 years since 1990, residential emissions have
accounted for 34 million metric tons, or about 28 percent, of the increase in carbon dioxide emissions from all end-use
sectors (Table 10).
Energy consumption in the commercial sector was about 14 quadrillion Btu in 1996. Electricity use accounted for more
than one-half of that amount, with lighting the largest single use. The commercial sector contributes the smallest share
of carbon dioxide emissions among the end-use sectors, making up about 15 percent of the total. Since this sector
includes all business establishments that are not engaged in transportation or in manufacturing or other industrial
activity (agriculture, mining, or construction), most of the energy consumed is electricity and natural gas. Commercial sector
carbon dioxide emissions increased by almost 17 million metric tons, or 5.5 percent, to 230 million metric tons in 1996
from 218 million metric tons in 1995 (Table 11). Between 1990 and 1996, the commercial sector accounted for 24 million
tons, or about 19 percent of the total increase in U.S. carbon dioxide emissions.
Although end users create the demand for electricity, electricity producers (primarily electric utilities) make decisions
about how to meet that demand, based on fuel prices and capacity availability. In 1996 consumption of electric power
increased by 2.4 percent, but utility carbon emissions increased by about 4.7 percent (Table 12) because coal-fired
generation met a disproportionately large share of the increased demand for electricity.
Although utility efforts to improve efficiency in production and to implement demand-side management programs
have kept emissions lower than they otherwise would have been,(35) emissions from the burning of fossil fuels to meet
end-use demand between 1990 and 1996 accounted for an increase of 40 million metric tons of carbon. Coal, which in
recent years has fueled about one-half of all U.S. electric power generation, produces more carbon emissions per
kilowatthour of electricity generated than do the other fossil fuels. The existence of underutilized coal-fired capacity
in the United Statesmay be contributing to the current increase in coal use. In the future, however, expansion of
natural-gas-fired generation could slow further growth in emissions.
Emissions from industrial sources (other than energy consumption) account for only about 1.5 percent of total U.S.
carbon dioxide emissions. These emissions depend largely on the level of activity in the construction industries and
production at oil and gas wells. The remaining, relatively minor sources are limestone and dolomite consumption, soda
ash manufacture and consumption, carbon dioxide manufacture, and aluminum production. Emissions from these
sources have remained in the range of 16 to 19 million metric tons per year since 1990.
When an oil field is developed for petroleum extraction, any natural gas associated with that field may be flared if its
use is not economically justifiable. This is typically the case with a remote site or when the gas is of poor quality or
minimal volume. In the United States, the total amount of natural gas vented or flared has increased in recent years,
from about 150 billion cubic feet in 1990 to 284 billion cubic feet in 1995; however, it is estimated that the amount may
have dropped to 263 billion cubic feet in 1996. The portion flared caused 3.4 million metric tons of carbon emissions
in 1996 (Table 13).
Industrial processes account for about 17 to 19 million metric tons of carbon emissions per year (Table 14). Since 1990,
emissions from industrial processes have increased, with increases in emissions from cement manufacture and
limestone consumption partially offset by a decrease in emissions from aluminum manufacture. More than one-half
of the emissions from industrial process are from cement manufacture. When calcium carbonate is heated (calcined)
in a kiln, it is converted to lime and carbon dioxide. The lime is combined with other materials to produce clinker (an
intermediate product from which cement is made), and the carbon dioxide is released to the atmosphere. In 1996, the
United States manufactured an estimated 79 million metric tons of cement, resulting in emissions of about 10 million
metric tons of carbon.
There are numerous other industrial processes in which carbonate minerals are used in ways that release carbon
dioxide into the atmosphere, including the use of limestone in flue gas desulfurization and the manufacture and some
uses of soda ash. Approximately 5 million metric tons of carbon per year are emitted from these sources. Carbon
dioxide is also released during aluminum smelting, when carbon anodes (with the carbon ultimately derived from
nonfuel use of fossil fuels) are vaporized in the presence of aluminum oxide.
Under the Framework Convention, parties to the agreement committed to providing information on emissions trends,
using methods that would facilitate international comparison of emissions estimates. To support such comparisons,
a generalized reporting format was adopted. The format differs slightly from that used in the preparation of U.S.
national energy statistics, primarily with respect to the definition of "consumption" and the treatment of energy
consumption in U.S. territories and consumption of bunker fuels for international transport.
EIA's energy data for the United States cover the 50 States and the District of Columbia but not the U.S.territories.
Bunker fuels (fuel consumed by ships and aircraft fueled in the United States and engaged in international trade) are
subsumed in EIA's transportation sector energy consumption data. By contrast, energy data used by the International
Energy Agency for the United States include U.S. territories and exclude bunker fuels. Finally, the generalized format
uses a "top-down" approach to estimate "apparent energy consumption" from data on energy production and trade.
For most countries around the world, this is the best approach, because energy consumption is not always accurately
reported. For the United States, however, the EIA provides information (used for estimates in this report) on
consumption by end-use sector and fuel type for a wide array of petroleum products, coal, and natural gas.
Collectively, these differences in treatment can produce variations of several percentage points in reported energy
consumption and, hence, in the estimates of carbon emissions. The methodology for calculating U.S. territories'
emissions and other adjustments is described in Appendix A.
In this report, carbon dioxide emissions for the U.S. territories (Puerto Rico, Virgin Islands, Guam, American Samoa,
Micronesia, and Wake Island) are included as an adjustment. Their combined energy consumption is only about 0.5
quadrillion Btu and is concentrated on petroleum products; only Puerto Rico uses coal. Together, they are estimated
to have emitted almost 11 million metric tons of carbon in 1996 (Table 15). Emissions from Puerto Rico's cement
production are also included in this total.
In this report, emissions from bunker fuels are subsumed in the estimates of carbon emissions from energy
consumption.(36) These emissions are also shown separately in Table 15. The estimate is based on purchases of fuel by
ocean-going ships in U.S. ports and by international air carriers in U.S. airports. In 1996 bunker fuel emissions
amounted to about 22 million metric tons of carbon.
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