Overview

Energy-related carbon dioxide (CO2) emissions vary significantly across states, whether considered on an absolute (Figure 1) or per capita basis. Total state CO2 emissions include those from direct fuel use across all sectors, including residential, commercial, industrial, and transportation, as well as primary fuels consumed for electric generation. The overall size of a state, as well as the available fuels, types of businesses, climate, and population density, play a role in determining the level of both total and per capita emissions. Additionally, each state’s energy system reflects circumstances specific to that state. For example, some states have 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 consumed. Therefore, 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. Analysis attributing emissions to the consumption of electricity, rather than the production of electricity, would yield different results. For feedstock application, carbon stored in products such as plastics are subtracted from reported emissions for the states where they are produced.

 

The calculations presented in this paper also assume that biomass used by electricity generators, industry, and by homes and commercial buildings is carbon neutral, with combustion emissions fully offset by land sinks in a sustainable biomass cycle. Emissions may be underestimated to the extent that actual use of biomass energy is not carbon neutral.

Total state emission levels

Over the time period from 2000 to 2014, CO2 emissions fell in 35 states and rose in 15 states (not including the District of Columbia) (Table 1). The greatest percentage decrease in CO2 emissions occurred in Maine at 26%, or 6 million metric tons (mt). The greatest absolute decline was 43 million mt in New York (20%). The state with both the greatest percentage and absolute increase was Nebraska, at 25% (10 million mt).

From 2013 to 2014, 19 states saw a decrease in emissions, while 29 experienced an increase and 2 were unchanged. This is reflected in the national data for 2014 as emissions were up about 0.9%. Because of differences in data aggregations it is difficult to compare the total for all states with the total for the United States. See Appendix A 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 2014, coal consumption accounted for 78% of CO2 emissions in West Virginia. In California, 1% of CO2 emissions came from coal, with 63% from petroleum. In Rhode Island, which had no emissions from coal, 46% of emissions were from natural gas. Hawaii's and Vermont’s share of CO2 emissions from petroleum in 2014 were 91% and 90%, respectively. Maine's petroleum share was 79%. No other state's petroleum share exceeded 70%.

Emissions by sector

There can also be significant variations in terms of CO2 emissions by sector (Tables 3 and 4). 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 2014 came from the transportation sector (56%), predominantly from petroleum, but the electric power sector share was 0.2% because Vermont had almost no generation using fossil fuels. 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, had 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 (54%). However, unlike Vermont, Hawaii's electric power sector share was relatively high (36%). The dominant fossil fuel for the generation of electricity in Hawaii is petroleum.

Per capita carbon dioxide emissions

Another useful 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 variation in 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. The 2014 CO2 emissions in Wyoming were 112 mt per capita, the highest in the United States. In 2014, Wyoming was the second- largest energy producer in the United States. Unlike the largest energy producer, Texas, with a population of 27 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 Fahrenheit²). 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 79 mt per capita. West Virginia (53 mt per capita), Alaska (48 mt per capita), and Louisiana (47 mt per capita) round out the top five states in terms of per capita CO2 emissions.

 

 

New York, with a population of 19.6 million people, had the lowest per capita CO2 emissions – fewer than 9 mt 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 multi-family units that provide efficiencies of scale in terms of energy for heating and cooling. The New York economy is oriented towards low-energy-consuming activities such as financial markets. For example, New York contained about 6% of the U.S. population in 2014, but consumed only 1% of the country's industrial energy.³New York's energy prices are relatively high (the average retail electricity price of 16.25 cents per kWh was fourth highest in the country in 2014), which in turn encourages energy savings.⁴ The other states with low per capita CO2 emissions—all fewer than 10 mt per capita—include California, Connecticut, Massachusetts, and Vermont.

Energy intensity

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 (GDP), plays an important role in its overall emissions profile (Table 6). The states with the highest rates of emissions per capita in 2014 also tended to have the higher energy intensity values: Wyoming (23,000 Btu per chained 2009 dollar of GDP), Louisiana, North Dakota, and West Virginia (all in the 17-19,000 Btu per dollar range), and Montana (14,000 Btu per dollar). California, Connecticut, Maryland, Massachusetts, and New York were the lowest – all around 3,000 Btu per dollar. Many of the states with the lowest energy intensity are clustered in the relatively densely populated New England and Middle Atlantic regions. The 2014 national average was 6,000 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 2014 in terms of the carbon intensity of the energy supply as measured in kilograms of CO2 per million Btu (kg CO2/MMBtu)—West Virginia (81 kg CO2/MMBtu), Wyoming and Kentucky (both 76 kg CO2/MMBtu), Utah (72 kg CO2/MMBtu), and North Dakota (70 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 2014 was 55 kg CO2/MMBtu. The states with lower carbon intensity of their energy supply tend to be those states with relatively substantial non-carbon electricity generation such as nuclear or hydropower. These states include, for example, Vermont (27 kg CO2/MMBtu), Washington and Oregon (both 35 kg CO2/MMBtu), New Hampshire (38 kg CO2/MMBtu), and Maine (39 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 (mt) of CO2 per million dollars of state GDP (mt CO2/million chained 2009 dollars of GDP) are also the states with the highest values of energy intensity and carbon intensity of that energy supply. In 2014, these states included: Wyoming (1,744 mt CO2/million dollars of GDP), West Virginia (1,463 mt CO2/million dollars of GDP) North Dakota (1,183 mt CO2/million dollars of GDP), Louisiana (1,019 mt CO2/million dollars of GDP), and Montana (821 mt CO2/million dollars of GDP). The 2014 U.S. average was 339 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 (135 mt CO2/million dollars of GDP), Massachusetts (152 mt CO2/million dollars of GDP), Connecticut (153 mt CO2/million dollars of GDP), California (170 mt CO2/million dollars of GDP) and Maryland (192 mt CO2/million dollars of GDP).

Electricity trade

This analysis assigns all emissions related to the primary energy consumed for the production of electricity to the state where that electricity is produced rather than where it is consumed. As a result, the states that produce electricity from fossil fuels (especially coal) and sell that electricity across state lines tend to have higher per capita CO2 emissions than states that consume more electricity than they produce (Table 9). 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 be different.

Renewable energy

Historically, the primary non-carbon-producing energy forms have been nuclear and hydroelectric generation. Neither energy form has experienced significant capacity increases in the United States in recent years. On the other hand, non-hydropower renewable energy forms such as wind have experienced significant growth over the past decade. While California dominated wind generation in 2000 (Figure 3), the northern and southern plains states have seen the fastest growth in recent years. In 2005, Texas and California generated about the same amount of electricity from wind, but in 2014 Texas generated over three times the amount of electricity from wind as California, which fell to third behind Iowa. Wind generation is spreading beyond the early adopting states. In 2000, the top four states (California, Minnesota, Iowa, and Texas) accounted for 93% of wind generation, but by 2014, the share of these four states had fallen to 43%. Oklahoma, which had no wind generation in 2002, was rapidly approaching California-levels of wind generation by 2014. If Texas had generated the same amount of energy from a roughly equal mix of coal and natural gas as it did from wind in 2014, it would have produced about 24 million mt more in CO2 emissions, more than Vermont’s and New Hampshire's total emissions in 2014 combined. Other states are adding more solar from both utility-scale power stations, as well as distributed generation, to their energy mix. In 2014, California produced about 43% of the U.S. total of 420 trillion Btu and was the only state to produce significant energy from both wind and solar. Other leading solar energy states included Florida (12% of U.S. total), Arizona (11%), and New Jersey (6%).

 

See Appendix B for other EIA state-related energy and environmental products.

 

---

Footnotes

¹U.S. Energy Information Administration, State Profiles and Energy Estimates: http://www.eia.gov/state/.

²http://www.wrcc.dri.edu/narratives/WYOMING.htm.

³U.S. Energy Information Administration, State Energy Data 2013, state population and energy consumption by sector.

⁴U.S. Energy Information Administration, State Electricity Profiles, Table 1, 2013 Summary Statistics http://www.eia.gov/electricity/state/newyork/pdf/New_York/.