In August, the U.S. Energy Information Agency made a surprising announcement. U.S. carbon emissions had fallen to their lowest level since 1992. In the first five months of this year, it said, they dropped 14% compared to the same period in 2007.
There were several reasons, said experts. Small ones: increasing use of renewables, energy efficiency, and a slow economy. And one big one: a switch away from coal for electricity production to natural gas. In 2005, coal accounted for about 50% of U.S. power generation. In March this year, it was down to about a third. Some said gas accounted for as much as three-quarters of the emissions improvement.
Yet, according to new research, it’s questionable how much gas actually contributes to the fight against climate change. It may be the gas boom is cutting emissions here. But much of the coal-related output is still going into the atmosphere. Even though the U.S. is burning less coal, it’s not actually leaving it in the ground, says Manchester University’s Tyndall Centre For Climate Change Research. Instead, we are increasingly exporting the stuff, chiefly to Europe and Asia.
From being a net importer of coal in 2005, the U.S. exported 26 million tons of coal at the beginning of this year. Tyndall shows that "more than half of the emissions avoided in the U.S. power sector may have been exported as coal."
"Research papers and newspaper column inches have focused on the relative emissions from coal and gas," says co-author John Broderick. "However, it is the total quantity of CO2 from the energy system that matters to the climate."
The report points to the weakness of national carbon caps, and the need for a global agreement on emissions. "Without a meaningful cap on global carbon emissions, the exploitation of shale gas reserves is likely to increase total emissions," says the report. "For this not to be the case, consumption of displaced fuels must be reduced globally and remain suppressed indefinitely."
The U.S. gas industry greeted the EIA’s emissions announcement warmly. America’s Natural Gas Alliance said: "Greater utilization of America’s vast supplies of natural gas for cleaner electricity have reduced U.S. power sector carbon emissions to levels not seen in two decades." ANGA’s website says gas has 56% of the CO2 emissions of coal.
ANGA continues to pooh-pooh research by scientists at Cornell claiming "fugitive" methane emissions from the drilling process increases gas’s carbon profile. Tyndall says more work needs to be done looking at the whole lifecycle, rather than just the combustion part.
While the drop in U.S. carbon emissions is a good thing, there are several reasons to be cautious about natural gas’s environmental benefits.