U.S. Energy Information Administration - EIA - Independent Statistics and Analysis
State-Level Energy-Related Carbon Dioxide Emissions, 2000-2011
This report reviews data on state-level energy-related carbon dioxide (CO2) emissions through 2011 that were first posted by EIA in February, 2014. The delay in the posting of the emissions estimates reflects significant efforts required to prepare state-level data on energy use by fuel type and sector that are published in the State Energy Data System (SEDS) and form the basis of the emissions estimates.
Beyond continuing its efforts to accelerate the SEDS data and the preparation of estimates of overall energy-related CO2 emissions, EIA also plans to accelerate the release of state-level emissions data for specific sectors, notably electricity generation, that can be issued much earlier that state-level data covering all sectors. For example, state-level electricity sector emissions data for 2012 is already available on the EIA website, and preliminary data for 2013 will be published shortly.
Energy-related CO2 emissions vary significantly across states (Figure 1), whether considered on an absolute or per capita basis. The overall size of a state, as well as the available fuels, types of businesses, climate, and population density, play a role in both total and per capita emissions. Additionally, each state’s energy system reflects circumstances specific to that state. For example, some states are located near abundant hydroelectric supplies, while others contain abundant coal resources. This paper presents a basic analysis of the factors that contribute to a state’s CO2 profile. This analysis neither attempts to assess the effect of state policies on absolute emissions levels or on changes over time, nor does it intend to imply that certain policies would be appropriate for a particular state.
The term energy-related CO2 emissions, as used in this paper, includes emissions released at the location where fossil fuels are used. For feedstock application, carbon stored in products such as plastics is subtracted from reported emissions for the states where they are produced.It is also important to recognize that the state-level CO2 emissions data presented in this paper count emissions based on the location where the primary energy is consumed as a fuel. To the extent that fuels are used in one state to generate electricity that is consumed in another state, emissions are attributed to the former rather than the latter. An analysis that attributed emissions with consumption rather than production of electricity, which is beyond the scope of the present paper, would yield different results.
Total state emission levels
Over the period from 2000 to 2011, CO2 emissions fell in 37 states and rose in 13 states (Table 1). The greatest percentage decrease in CO2 emissions occurred in Nevada at 26% (12 million metric tons). The greatest absolute decline was 65 million metric tons in Texas (9%). New York experienced a decline of 50 million metric tons (24%) – making it the largest percentage decline of the big states. The greatest percentage and absolute increase was in Nebraska at 26% (11 million metric tons).
From 2010 to 2011, CO2 emissions decreased in 42 states and rose in 8 states. Because of differences in data aggregations, it is difficult to compare the total for all states with the total for the United States. See the Appendix for a comparison of levels of data detail between the state and national data systems.
Emissions by fuel
States exhibit very different emissions profiles by fuel type (Table 2). For example, in 2011, coal consumption accounted for 81% of CO2 emissions in West Virginia. In California, less than 2% of CO2 emissions came from coal, with 65% from petroleum. Rhode Island had no emissions from coal consumption, but 51% of its emissions were from natural gas. Both Vermont's and Hawaii's share of CO2 emissions from petroleum were 92% in 2011. No other states exceeded 80% in terms of the share of emissions from petroleum; Maine's petroleum share was 76%.
Emissions by sector
There can also be significant variations in terms of CO2 emissions by sector (Tables 3 and 4) – even for states that have similar fuel emissions profiles. These variations are due to factors such as the use of different fuels for electricity generation, climate, and sources of economic outputs (e.g., commercial versus industrial activity). For example, in Vermont the largest share of emissions in 2011 came from the transportation sector (57%), predominantly from petroleum, but the electric power sector share was close to zero because of Vermont's reliance on nuclear power. Vermont's residential sector share was 23% – indicative of a relatively cold climate where petroleum is the main heating fuel. Hawaii, where a dominant share of emissions is also from petroleum, has a residential share of 0.3% – the lowest in the United States because of minimal heating fuel requirements. The largest sector emissions share in Hawaii, like Vermont, was from the transportation sector (51%). However, unlike Vermont, Hawaii’s electric power sector accounted for 39% of the total emissions, close to the national average emissions share for electricity. The dominant fossil fuel for the generation of electricity in Hawaii is petroleum.
Per capita carbon dioxide emissions
Another way to compare total CO2 emissions across states is to divide them by state population and examine them on a per capita basis (Table 5 and Figure 2). Many factors contribute to the amount of emissions per capita, including climate, the structure of the state economy, population density, energy sources, building standards and explicit state policies to reduce emissions. In 2011, CO2 emissions in Wyoming were 113 metric tons per capita, the highest in the United States. In 2011, Wyoming was the second-largest energy-producing state. Unlike the largest energy producer, Texas, which has a population of 26 million, Wyoming has fewer than 600,000 people, giving Wyoming the lowest population density in the Lower 48 states.1 Its winters are cold (the average low temperatures in January range between 5 to 10 degrees Fahrenheit).2 These factors act to raise Wyoming's per capita emissions compared to other states. The second-highest state per capita CO2 emissions level was North Dakota at 78 metric tons per capita. Alaska (53 metric tons per capita), West Virginia (52 metric tons per capita), and Louisiana (49 metric tons per capita) round out the top five states in terms of per capita CO2 emissions. All of these are fossil-energy-producing states.The activity of producing energy itself involves the consumption of large amounts of energy.
New York, with a population of 19.5 million people, had the lowest per capita CO2 emissions – 8 metric tons per capita. A large portion of the population is located in the New York City metropolitan area where mass transit is readily available and most residences are multifamily units that provide efficiencies of scale in terms of energy for heating and cooling. The New York economy is oriented toward high-value, low-energy-consuming activities such as financial markets. For example, New York contained about 6% of the U.S. population in 2011, but consumed only 1% of the country's industrial energy.3 New York's energy prices are relatively high (the average retail electricity price of 15.89 cents per kWh was fourth-highest in the country in 2011), which in turn encourages energy savings.4 Other states with relatively low per capita CO2 – all around 9 metric tons per capita – include Vermont, California, Connecticut, and Oregon.
The energy intensity of a state, as measured by the amount of energy consumed per unit of economic output or, specifically, British thermal units (Btu) per dollar of a state's gross domestic product (Btu/GDP), plays an important role in its overall emissions profile (Table 6). The states with the highest rates of emissions per capita in 2011 also had the higher energy intensity values: Wyoming (27,000 Btu per dollar), North Dakota (22,000 Btu per dollar), West Virginia (21,000 Btu per dollar), Louisiana (19,000 Btu per dollar), and Montana (17,000 Btu per dollar). Massachusetts, New York, Delaware, Connecticut, and California were the lowest – all around 4,000 Btu per dollar or less.
Many of the states with the lowest energy intensity are clustered in the relatively densely populated New England and Central Atlantic. The 2011 national average was 7,000 Btu per dollar of GDP.
Carbon intensity of the energy supply
The carbon intensity of energy supply (CO2/Btu) is reflective of the energy fuel mix within a state (Table 7). As with energy intensity, the states with high carbon intensity of energy supply tend to be the states with high per capita emissions. The top five states in 2011 for the energy carbon intensity as measured in kilograms of CO2 per million Btu (kg CO2/MMBtu) — West Virginia (81 kg CO2/MMBtu), Kentucky (76 kg CO2/MMBtu), Wyoming (75 kg CO2/MMBtu), and Indiana and Utah (both 72 kg CO2/MMBtu) — are all states with coal as the dominant emissions source (Table 2). The national average carbon intensity of the energy supply in 2011 was 55 kg CO2/MMBtu. The states with lower carbon intensity tend to be those states with relatively substantial noncarbon electricity generation such as hydropower or nuclear. These states include, for example, Vermont and Washington (32 kg CO2/MMBtu), Oregon (33 kg CO2/MMBtu), Idaho (36 kg CO2/MMBtu), and South Dakota (38 kg CO2/MMBtu).
Carbon intensity of the economy
Another measure, the overall carbon intensity of the economy (CO2/dollar of state GDP), combines energy intensity with the carbon intensity of that state's energy supply. As one would expect, the states with the highest carbon intensity of their economies (Table 8) as measured in metric tons of CO2 per million dollars of state GDP (mt CO2/million chained 2005 dollars of GDP) are also the states with the highest values of energy intensity and carbon intensity of that energy supply. In 2011, these states include: Wyoming (2,023 mt CO2/million dollars of GDP), West Virginia (1,721 mt CO2/million dollars of GDP) North Dakota (1,565 mt CO2/million dollars of GDP), Louisiana (1,082 mt CO2/million dollars of GDP), and Kentucky (1,045 mt CO2/million dollars of GDP). The 2011 U.S. average was 411 mt CO2/ million dollars of GDP. The states with the lowest carbon intensity of economic activity are also states that appear on the lower end of both energy intensity and the carbon intensity of that energy supply. These states include New York (156 mt CO2/million dollars of GDP), Connecticut (164 mt CO2/million dollars of GDP), Massachusetts (189 mt CO2/million dollars of GDP), Oregon (195 mt CO2/million dollars of GDP), and California (199 mt CO2/million dollars of GDP).
Because this analysis does not account for electricity trade, it is important to understand how much this can influence a state's CO2 emissions profile. The Net Electricity Trade Index (Table 9) indicates whether a state is self-sufficient in the generation of electricity in a given year (a value of 1.0); is a net importer of electricity in a given year (a value of less than 1.0); or is a net exporter of electricity in a given year (a value greater than 1.0). As indicated in Table 9, all but two of the 10 states with the highest per capita emissions are net exporters of electricity in at least some years. In particular, Wyoming, North Dakota, West Virginia, and Montana are large electricity exporters of power produced predominantly with coal. Oklahoma is a net exporter, but its dominant fuel is natural gas. Indiana is a small exporter in some years, but was export-neutral from 2009 to 2011. Kentucky, like Indiana, is a coal-fueled generation state, but has been export-neutral in recent years. Louisiana, the only state of high per capita emitters that is consistently a net importer of electricity, and Alaska, a state that is an importer in some years, but export-neutral in most, are both fossil-fuel producing states with a large, energy-intensive component of their economies.
Four of the 10 states with the lowest per capita CO2 emissions are consistent importers of electricity: California, Idaho, Massachusetts, and Maryland. Rhode Island was an electricity exporter in 2001 and was self-sufficient in 2000, 2008, 2009, and 2010. In 2011, it returned to being a slight exporter. In the other years Rhode Island was an importer of electricity (about 40% in 2004). Idaho generates its electricity principally with hydroelectric power and has historically imported 50% or more of its electricity from other states, although in 2011 that import percentage dropped to 30%. California consistently imports about 30% of its electricity, and natural gas is the dominant fuel for the electricity that it generates internally. New York, Massachusetts, and Rhode Island also use natural gas as the dominant fuel for electricity generation within the state.
In Vermont, which has been a consistent exporter of electricity, nuclear power is the dominant source of generation. The shutdown of Vermont Yankee, currently scheduled for the end of 2014, is likely to significantly change Vermont's electricity trade flows. Connecticut, also a nuclear power producer, is a slight exporter in some years, an importer in others, and roughly trade-neutral in yet others. Both Oregon and Washington are usually either self-sufficient or net exporters. However, in 2001, which was a particularly bad year for hydroelectric generation in the Pacific Northwest, both states were net importers of electricity. In 2011, a particularly good year for hydropower generation, both states were net exporters of electricity.
If the emissions associated with the generation of electricity were allocated to the states where that electricity is consumed, in many cases, the emissions profiles of both the producing and consuming states would change.
1U.S. Energy Information Administration, State Profiles and Energy Estimates: http://www.eia.gov/state/
4U.S. Energy Information Administration, State Electricity Profiles, Table 1, 2011 Summary Statistics http://www.eia.gov/electricity/state/archive/sep2011.pdf.