Bridge Out: Bombshell Study Finds Methane Emissions From Natural Gas Production Far Higher Than EPA Estimates

A major new study blows up the whole notion of natural gas as a short-term bridge fuel to a carbon-free economy.

Natural gas is mostly methane (CH4), a potent heat-trapping gas. If, as now seems likely, natural gas production systems leak 2.7% (or more), then gas-fired power loses its near-term advantage over coal and becomes more of a gangplank than a bridge. Worse, without a carbon price, some gas displaces renewable energy, further undercutting any benefit it might have had.

Fifteen scientists from some of the leading institutions in the world — including Harvard, NOAA and Lawrence Berkeley National Lab — have published a seminal study, “Anthropogenic emissions of methane in the United States.” Crucially, it is based on “comprehensive atmospheric methane observations, extensive spatial datasets, and a high-resolution atmospheric transport model,” rather than the industry-provided numbers EPA uses.

Indeed, the Proceedings of the National Academy of Sciences study by Scot Miller et al takes the unusual step of explicitly criticizing the EPA:

The US EPA recently decreased its CH4 emission factors for fossil fuel extraction and processing by 25–30% (for 1990–2011), but we find that CH4 data from across North America instead indicate the need for a larger adjustment of the opposite sign.


How much larger? The study found greenhouse gas emissions from “fossil fuel extraction and processing (i.e., oil and/or natural gas) are likely a factor of two or greater than cited in existing studies.” In particular, they concluded, “regional methane emissions due to fossil fuel extraction and processing could be 4.9 ± 2.6 times larger than in EDGAR, the most comprehensive global methane inventory.”

This suggests the methane leakage rate from natural gas production, which EPA recently decreased to about 1.5%, is in fact 3% or higher.

This broad-based look at methane emissions confirms the findings of 3 recent leakage studies covering very different regions of the country:

  • NOAA researchers found in 2012 that natural-gas producers in the Denver area “are losing about 4% of their gas to the atmosphere — not including additional losses in the pipeline and distribution system.”
  • A 2013 study by NOAA found leaks from oil and gas exploration and extraction in the L.A. basin representing “about 17% of the natural gas produced in the region, similar to the leak rate estimated by the California Air Resources Board using other methods.” Almost all the gas produced in the basin is “associated” with oil production (rather than, say, fracked). Associated gas is still about a fifth of total U.S. gas production.
  • Another 2013 study from 19 researchers led by NOAA concluded “measurements show that on one February day in the Uinta Basin, the natural gas field leaked 6 to 12 percent of the methane produced, on average, on February days.” The Uinta Basin is of special interest because it “produces about 1 percent of total U.S. natural gas” and fracking has increased there over the past decade.