Combined Cycle Energy Technology Led to Emissions Reduction by US Power Plants

A technology being implemented by natural gas power plants in the US has led to a reduction in emissions, according to a new study.

So-called "combined cycle" natural gas power plants are abe to squeeze more energy out of the fuel they produce, as well as release fewer carbon dioxide emissions than coal-fired power plants, according to an analysis in the journal Earth's Future. Essentially, the combined cycle power process works by powering separate components in a power plant with the same heat source. The video below describles the process more in-depth. 

"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," said lead author Joost de Gouw, an atmospheric scientist with NOAA's Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder.

For their analysis, the researchers examined data from the systems that continuously monitor power plant emissions across the US. Among the gasses the systems monitor are carbon dioxide, nitrogen oxides and sulfur dioxide. Carbon dioxide emissions are linked to global warming, while nitrogen oxides and sulfur dioxide can react in the atmosphere to form tiny particles and ozone, which can cause respiratory diseases.

The researchers compared pollutant emissions from different types of power plants by calculating the emissions per unit of energy produced, using power plant emissions data collected between 1997 and 2012.

Three types of power plants were included in their analysis: coal-fired, natural gas and combined cycle natural gas plants.

The researchers found that during the study period, the percent of US energy produced from coal gradually decreased from 83 percent in 1997 to 59 percent by 2012. In the same time period, the energy produced by combined cycle gas power 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 researchers said in a statement. "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."

The research is consistent with other recent reports that suggest that substituting coal for natural gas in power generation will help lower coal-related carbon dioxide emissions.