A Complex Emissions Picture

When it comes to emissions of carbon dioxide from energy use, states are all over the map. That’s because several factors determine whether a state ranks as a top releaser of CO₂or comes in as a low emitter of this major greenhouse gas, says a new analysis from the Energy Information Administration (EIA), a part of the Department of Energy.

The two main factors used in the EIA report to rank emissions of the gas from all 50 states are the net CO₂ emissions—which are affected by the physical size of the state, its major industries, and the main sources of its electricity—and those emissions as a function of the state’s population.

Fossil-fuel-rich Texas was number one among states for total amount of CO₂ released from energy use in 2010, the EIA study shows. Texas emitted 652.6 million metric tons that year—nearly 12% of the 5.6 billion metric tons released by all states and the District of Columbia combined. California was a distant second with 369.8 million metric tons emitted in 2010.

But both Texas and California are big states with lots of residents. California is the nation’s most populous state, followed by Texas. After EIA combined population numbers with CO₂ emission figures, Texas ranked 15th among states in 2010, with 25.9 metric tons per person. California came in near the bottom at number 48, with 9.9 metric tons per person.

Solidly in the number one slot for per-person emissions in 2010 was Wyoming, the nation’s least populous state. It averaged 118.5 metric tons per state resident. Number two North Dakota, which is the third least populous state, had significantly less, with 80.4 metric tons per person. In comparison, the national average for 2010 was 18.2 metric tons per person, according to EIA.

These sorts of figures help demonstrate just how much CO₂ emissions related to energy use vary across the states. Each state’s situation is unique, says Perry Lindstrom, an EIA industry economist who prepared the report. This means that if decisionmakers opt for policies to lower CO₂ emissions, they will need to consider each state’s particular circumstances, he tells C&EN.

The uniqueness Lindstrom refers to stems from a number of criteria. A major one is the mix of fuels used in the state: Coal releases more CO₂ per unit of energy delivered when burned than does petroleum, and both produce more than natural gas. States vary in what they depend on for fuel. For instance, the report shows that more than 80% of West Virginia’s CO₂ emissions in 2010 came from the burning of coal for electricity. And nearly all of Hawaii’s CO₂ releases—some 92%—stemmed from combustion of petroleum products, as most of the state’s electricity comes from oil-fired plants, EIA points out.

The types of businesses that make up significant portions of a state’s economy also affect the amount of CO₂ released within its borders, EIA says. States heavily dependent on extraction of coal, oil, or natural gas have carbon-intensive economies. They include top 10 per capita emitters Wyoming, West Virginia, North Dakota, and Louisiana. “The activity of producing energy is itself energy intensive,” the report explains.

When a number of factors are combined, EIA’s analysis reveals a complex reality behind states’ emissions numbers. For instance, Wyoming’s top per capita ranking is not just because it has a small population and is a major energy producer. Weather also comes into play. Wyoming’s long, cold winters spur a long season of high demand for energy to heat homes and businesses.

New York, in contrast, had the lowest per capita CO₂ emissions among the 50 states—8.8 metric tons per person. This may seem surprising for a northern-tier state with major demand for heating. But EIA teased out reasons behind this ranking. New York is the nation’s third most populous state, and a major portion of its residents are densely clustered in the metropolitan New York City area.

This region has a number of characteristics linked to lower CO₂ emissions, including extensive mass transit and an economy that is tilted toward what EIA describes as “high-value, low-energy-consuming activities such as financial markets.” What’s more, most housing in the New York metropolitan area consists of multifamily units such as apartment buildings, which are more energy efficient for heating and cooling than are stand-alone homes.

In addition, New York state also gets a significant amount of electricity generated from sources that don’t release CO₂ nuclear power plants and a large 2,353-MW hydropower facility. When it comes to fossil fuels, that state burns much more natural gas than coal, the report adds

EIA points out that its analysis looks at emissions only from the state where a fuel is burned. This is an issue because some states with high per capita emissions send electricity generated within their borders to other states. Wyoming, North Dakota, West Virginia, and Montana are large exporters of electricity generated by coal-fired power plants, EIA says.

In contrast, some states with the lowest per capita CO₂ releases over the years import electricity generated elsewhere, notably California, Idaho, and Massachusetts. If CO₂ releases from power plants were allocated to states that use the electricity, the analysis would paint a different picture in many parts of the country, EIA says.