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Report: Combined-Cycle Plants Release Far Less CO2 Than Coal

boulderPower plants that use natural gas and a new technology to squeeze more energy from the fuel release far less CO2 than coal-fired power plants do, according to research by NOAA and the University of Colorado, Boulder.

The so-called “combined cycle” natural gas power plants also release significantly less nitrogen oxides and sulfur dioxide, which can worsen air quality. Since more and more of our electricity is coming from these cleaner power plants, emissions from the power sector are lower by 20, 30 even 40 percent for some gases since 1997, according to Reduced Emissions of CO2, NOx and SO2 from US Power Plants Due to the Switch from Coal to Natural Gas with Combined Cycle Technology, which has been published in the journal Earth’s Future.

Researchers analyzed data from systems that continuously monitor emissions at power plant stacks around the country. Previous aircraft-based studies have shown these stack measurements are accurate for carbon dioxide and for nitrogen oxides and sulfur dioxide. Nitrogen oxides and sulfur dioxide can react in the atmosphere to form tiny particles and ozone, which can cause respiratory disease.

To compare pollutant emissions from different types of power plants, the scientists calculated emissions per unit of energy produced, for all data available between 1997 and 2012. During that period of time, on average:

  • Coal-based power plants emitted 915 grams (32 ounces) of CO2 per kWh of energy produced;
  • Natural gas power plants emitted 549 grams (19 ounces) COper kWh hour; and
  • Combined cycle natural gas plants emitted 436 grams (15 ounces) CO2 per kWh hour.

The researchers reported that between 1997 and 2012, the fraction of electric energy in the United States produced from coal gradually decreased from 83 percent to 59, and the fraction of energy from combined cycle natural gas plants rose from none to 34 percent.

That shift in the energy industry meant that power plants, overall, sent 23 percent less CO2 into the atmosphere last year than they would have, had coal been providing about the same fraction of electric power as in 1997. The switch led to even greater reductions in the power sector’s emissions of nitrogen oxides and sulfur dioxide, which dropped by 40 percent and 44 percent, respectively.

In September 2012, GE announced that it had secured $1.2 billion of orders for its FlexEfficiency 60 combined-cycle power plant, a plant that the company called the “most efficient power plant of its kind.”

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2 thoughts on “Report: Combined-Cycle Plants Release Far Less CO2 Than Coal

  1. This lends support to the idea of natural gas as a ‘bridging’ technology that can decrease CO2 emissions in the near-term while we continue to develop truly clean sources of energy like wind and solar. And in turn, that implies that the trend to produce more natural gas via fracking should generally be supported rather than opposed. Yes, fracking is bad for several reasons, including possible water contamination, overall use of large amounts of water, and continued release of fossil-fuel CO2 – but it also clearly has short-term benefits as it replaces older, inefficient, and CO2-intensive use of coal for electricity production. It’s a mixed bag, certainly – and it does not represent any acceptable long-term solution; but neither is it the monstrous nemesis that some make it out to be.

  2. Natural gas is the natural bridge energy source! And it is home-grown, lowering trade deficits, creating jobs at home. Frack technology and horizontal drilling of intervals miles below the surface of the earth is what has unlocked this resource. Fracking has been around since the 1940’s. Hundreds of thousands of wells have been fracked, with not a single documented case of groundwater contamination. Opposition to fracking is based on ignorance and hysteria. Why not ban elevators? About 30 people a year are killed in elevator accidents and thousands are injured. As far as groundwater use in fracking is concerned, mining activities in Texas (which includes fracking AND coal and other mining activities) account for only 1.6% of the State’s total water use, and much of fracking’s water comes from surface water. Municipal and irrigation account for almost 83% of Texas’ water use. The small amount of water being used for oil and gas drilling and fracking is very telling, as Texas accounts for right at half the drilling activity in America. Natural gas is a natural fit for our energy future.

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