WASHINGTON — The amount of carbon dioxide, the leading greenhouse gas, released by the nation's power plants grew by nearly 3 percent last year, the largest annual increase in nearly a decade, an environmental group said Tuesday.
The analysis of government emissions figures covered more than 1,000 plants including those burning coal, natural gas and oil.
States where plants release the most CO2 per megawatt-hour of electricity generated were North Dakota, Wyoming, Kentucky, Indiana and Utah.
The report by the Environmental Integrity Project, a Washington-based advocacy group, said that the 2.9 percent increase in CO2 releases outpaced a 2.3 percent year-to-year increase in electricity production.
"Carbon emissions actually increased faster than (electricity) demand," said Eric Schaeffer, the group's executive director. He said reduced efficiency of older coal-burning power plants that often are some of the largest coal burners may have been one reason for the CO2 increase.
The report said that Texas, Georgia, Arizona, California and Pennsylvania had the biggest one-year increases.
Bill Sang, climate issues director for the Edison Electric Institute, said the increase reflected greater demand for power last year and a shortage of hydroelectric power that forced utilities to shift to fossil fuels.
"We think as much as two-thirds of the (CO2) increase was due to increased demand for electricity," said Sang, whose organization represents utilities that generate 70 percent of the electricity.
Carbon dioxide is the leading so-called "greenhouse gas" that is linked to global warming. It is a product of burning fossil fuels. Power plants account for nearly 2 billion tons of carbon dioxide emissions a year, about a third of the U.S. total.
"The amount that we're emitting today makes any long-term (reduction) goals that much harder to reach," said Schaeffer.
The group used data on 2006 and 2007 carbon dioxide emissions from the Environmental Protection Agency and the federal Energy Information Administration. Emissions levels are dependent on a variety of factors from weather to economic growth or decline.
Earlier this year, President Bush cited a 1.3 percent decline in overall CO2 emissions in 2006, compared to a year earlier. Much of that decline was attributed to a mild winter and cool summer, which resulted in less energy demand for heating and cooling.
The Scherer coal-burning power plant, operated by Georgia Power, produced the most CO2 in 2007, about 27 million tons, and showed a year-to-year increase of 2 million tons, the environmentalists said.
"Any increase in emissions that we have is due to increased electricity production," said Georgia Power spokeswoman Carol Boatright. "Georgia is one of the fastest-growing states in the country. Our demand for energy is growing."
Melissa McHenry, spokeswoman for Ohio-based American Electric Power, which has 25 coal-burning power plants in nine states, said her company showed a 2.8 percent increase in CO2 emission in 2007, but "we also saw a 3.6 percent increase in electricity demand." She said AEP is investing in wind generation and purchasing carbon "offsets" through a carbon exchange program.
According to the environmental group's analysis, the most CO2 in 2007 came from power plants in Texas, 262 million tons; Ohio, 138.6 million tons; Florida, 134.5 million tons; Indiana, 132 million tons; and Pennsylvania, 123.6 million tons. Those numbers did not take into account amount of power produced.