After an eight-year downward trend, carbon dioxide (CO2) emissions in the United States have started to includes with the return of more coal-fired generation in 2013, compared to last year, the Environmental Integrity Project (EIP) said in an analysis. However, a separate report said greenhouse gas (GHG) emissions are at mid-1990s levels and the role of natural gas remains critical.

In a new report, Arlington, VA-based Center for Climate and Energy Solutions (C2ES) and University of Texas at Austin researchers stressed that the potential for climate benefits from natural gas use can be maximized only if further steps are taken throughout the gas system to reduce methane leaks, a potent source of GHG, in its report, “Leveraging Natural Gas to Reduce GHG Emissions.”

The C2ES report drew praise from the American Gas Association and National Grid CEO Tom King, noting the report sees gas and renewables as being complementary. “With gas prices expected to remain low for the foreseeable future and with an abundance of domestic supply, natural gas provides a cost-effective, low-carbon fuel source to aid overall economic growth and curb demand for imported oil,” King said.

“Further reductions can be achieved by substituting natural gas for coal and oil in the transportation, manufacturing and building sectors,” C2ES said in its 87-page report. The researchers acknowledged that zero-carbon energy sources, such as solar, wind and nuclear, remain “critical” to lowering GHG emissions, but they cautioned that longer term, “simply substituting natural gas will not achieve the deeper emissions cuts needed. Strong support also is needed to perfect and deploy technologies to capture carbon emissions from coal- and gas-fired power plants and bury them underground.”

The center’s report makes a strong case for expanding natural gas use in the power generation sector; using it to complement intermittent renewable sources of power, such as wind and solar; using it more in commercial buildings to obtain additional overall energy efficiency, increasing use as a transportation fuel; additional use in manufacturing and in distributed generation technologies; and finally, through an expanded natural gas infrastructure nationally.

“It is important to better understand and more accurately measure the GHG emissions from natural gas production and use in order to achieve emissions reductions along the entire natural gas value chain,” said the C2ES report.

While electricity demand was essentially flat over the past eight years, unusually low natural gas prices in recent years led to gas-fired generation reaching a new peak last year of 1.23 billion MWh, an increase of 60% compared to its level in 2005, EIP said. At the same time, coal-fired generation declined 25%.

“Natural gas releases about half as much CO2 as coal when burned for electricity, but its price can swing widely, and that volatility encourages companies to hang on to dirty and inefficient coal plants,” said EIP Project Director Eric Schaeffer. “As natural gas gets more expensive, coal is finding its way back into the U.S. electricity generation picture, and that means higher carbon dioxide emissions.”

U.S. power companies have plans to retire an estimated 45 GW of coal-fired capacity through 2016. While increased renewables and moderate demand, along with higher costs for meeting federal clean air requirements, all help reduce CO2 levels, a change in natural gas prices upward by itself could “encourage plant operators to squeeze more generation out of remaining coal plants,” Schaeffer said.

In a separate analysis EIP said, “Global warming emissions from coal-based electricity are projected to continue to increase throughout 2013 as rising natural gas prices encourage more use of coal.” The higher carbon emissions levels are not expected to be anything close to what they were a decade ago, the analysis said. EIP projects the upward trend in CO2 emissions will continue the rest of this year, based on data from the U.S. Environmental Protection Agency (EPA) and the Energy Information Administration (EIA). There was a 7.1% increase in carbon emissions from coal during the first quarter, compared to the same period last year, said EIP, a nonpartisan organization established a decade ago by former EPA attorneys.

EIP interprets the latest EIA projections as calling for a 34% increase in gas prices above last year’s levels while coal prices remain flat. This makes coal attractive to power companies with the capacity to switch to move to the cheaper coal-fired generation, according to EIP. This would have a tendency to reverse the trends that pushed carbon emissions levels down during the past eight years. EIA attributed the decline to a combination of greater reliance on gas-fired generation, rapid wind power development, moderate demand growth and the closure of old coal-fired generation plants.

EIP and the federal agencies did not indicate why over the longer haul these same trends will not continue. Carbon emissions vary widely from state to state, EIP’s analysis said, citing data from the EPA’s Air Markets Program Database. Kentucky, Wyoming, West Virginia, Indiana and North Dakota, which rely on coal-fired generation, were the top emitting states for CO2/MWh of power generated. The five lowest were Idaho, Washington, Vermont, Oregon and Connecticut.

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