Total greenhouse gas (GHG) emissions from burning natural gas obtained using hydraulic fracturing to stimulate wells and those from burning coal obtained from mountaintop removal may be similar or even greater in the case of natural gas, a Cornell University professor has claimed.

“There is an urgent need for a comprehensive assessment of the full range of emission of greenhouse gases from using natural gas obtained by high-volume, slick water hydraulic fracturing (HVSWHF),” wrote ecology and environmental biology Professor Robert W. Howarth in a draft paper published in mid-March.

GHG emissions from gas obtained using HVSWHF are estimated to be 60% more than for diesel fuel and gasoline, Howarth wrote. “These numbers should be treated with caution. Nonetheless, until better estimates are generated and rigorously reviewed, society should be wary of claims that natural gas is a desirable fuel in terms of the consequences of global warming.”

In scrutinizing the GHG footprint of gas, Howarth turned his attention to emissions that occur during the development, processing and transport of natural gas, “due to the use of fossil fuels to build pipelines, truck water, drill wells, make the compounds used in drilling and fracturing, and treat wastes, and the loss of carbon-trapping forests.” He wrote that the leakage of methane during the production, transport and processing of natural gas “is probably a far more important consideration.”

Howarth conceded that comparing the overall GHG emissions of gas and coal “is difficult as the energy needs and greenhouse gas emissions from mining and transporting the coal are not well known.” Assuming that coal’s associated emissions are equal to one-third of those from its direct combustion — as Howarth did with gas — total emissions from coal would be “very slightly less than the estimate for natural gas,” he wrote.

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