The emissions during the life cycle of shale natural gas are roughly equivalent to that of conventional natural gas, and both emit roughly half that of coal – a new research by the Joint Institute for Strategic Energy Analysis, in the U.S. has found.
The researchers have noted that hitherto efforts to estimate the amount of GHG emissions that occur during the entire lifecycle of shale gas have varied, generally due to differing assumptions by those making the effort, baselines used for comparison and system boundaries. This is why they have come up with a new way to measure such emissions, using a meta-analytical procedure they’ve dubbed harmonization, which they believe offers a true picture of such emissions.
However, Dr Robert Howarth, of Cornell University, has reached a very different conclusion. In the paper, published in the journal Energy Science & Engineering, he argues that gasses actually have a larger greenhouse gas footprint than coal or oil, which are usually thought of as the more polluting fossil fuels.
In his study, Dr Howarth demonstrates that while the burning of natural and shale gas emits less carbon dioxide than coal and oil, they emit far more methane. This is significant because in its pure form, methane is a far more potent greenhouse gas than CO2.
Vikram Rao in his book “Shale Gas – The Promise and The Peril” quotes data indicating that, when combusted, methane produces about 45% less carbon dioxide than coal in producing the same amount of electricity. Yet while over the period of 25 years, the global warming potential of methane is 72 times that of carbon dioxide, over the period of 100 years, methane is about 25 times more potent than carbon dioxide in its global warming proclivity.
This is close to the US Environmental Protection Agency estimates which indicate that “Pound for pound, the comparative impact of [methane] on climate change is over 20 times greater than [carbon dioxide] over a 100-year period.”
Dr Howarth came to his conclusions after studying data and analysing greenhouse gas footprints from a 20-year period.
“Methane is such a potent greenhouse gas that these emissions make natural gas a dangerous fuel from the standpoint of global warming over the next several decades,” he said.
Scientists have long warned about fugitive methane emissions accompanying shale gas extraction. A separate study from Cornell University pointed to casing and cement impairment in oil and gas wells as the main source of methane leaks, while an earlier study prepared jointly by Purdue and Cornell universities, shows that shale gas wells also emit high levels of methane during the drilling process; a stage previously not associated with greenhouse gas emissions.
“Society should wean ourselves from all fossil fuels and not rely on the myth that natural gas is an acceptable bridge fuel to a sustainable future” said Dr Howarth.
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