Cornell professors Richard Howarth, Renee Santoro, and Anthony Ingraffea ignited a controversy in 2011 when they published a study claiming that, due to escaped methane, emissions from hydraulically fractured natural gas were worse than coal. Their study showed that the escaped gas amounted to four to eight percent of total gas production, more than twice the EPA’s estimate for the same figure.
Two different studies, one from Cornell and another from MIT, produced their own analyses criticizing Howarth et. al.’s claims on the grounds that their data set was too small, their assumptions incorrect. Both studies concluded that hydro fracturing leaked little gas. But both studies criticized Howarth et. al.’s assumptions by way of offering new assumptions, but no new data or measurements. Nothing was settled.
Carbon dioxide emissions—with the exception of emissions from transportation—come from large, industrial sources. By contrast, methane emissions leak out of hundreds of thousands of sources that include valves, pipes, landfills, and waste pools. In oil and gas production, these emissions, known as ‘fugitive’, are just that; they steal out of the equipment and infrastructure and go uncounted into the atmosphere. The Environmental Protection Agency requires gas production, processing and transmission facilities to report fugitive emissions using emissions using estimates based on a predetermined calculation for leakage rates for each piece of equipment. But actual leakage rates can vary depending on the type of equipment, how it is maintained, the type and pressure of the gas that it conveys, and the geology of the formation from which it is withdrawn. The estimations are necessarily inexact. There are no direct measurements, and so much room for controversy.
Recently, the Environmental Defense Fund attempted to fill the data gap by coordinating a study that took direct measurements of gas flow back from wells. Results showed that wells constructed using advanced technology leaked only 0.42 percent of production—much less than Howarth et. al.’s or EPA’s estimates. But the study settled nothing due to skepticism due to over sample bias—companies that voluntarily cooperate with fugitive emissions studies are likely to be the best actors.
via Methane Leakage and Impact Measurement | The Energy Collective.
Categories: Energy, Natural Gas