Methane emissions rates from natural gas systems are lower than EPA estimated

Following up on a post last week – about overall methane emissions falling even while natural gas production has soared – it’s worth noting the latest University of Texas contribution to the understanding of methane emissions.

This is another chapter in a long-running, comprehensive study of methane emissions from natural gas production that has been undertaken by UT researchers, with the aid and support of the Environmental Defense Fund and 10 participating energy companies (including ExxonMobil’s subsidiary XTO Energy).

In July 2013, UT researchers confirmed that methane emissions from hydraulic fracturing at natural gas well sites are actually quite low. Their real-world data improved upon the assumptions and estimates that had previously been provided only by theoretical models.

For its latest efforts, the UT team expanded its research to focus on two specific methane emissions sources tied to hydraulic fracturing operations – liquid unloadings and pneumatic sources. The former refer to the process of removing gas and liquids from the wellbore; the latter are devices that control valves and other equipment at the well site. The technical aspects of each are described in this release from UT.

Findings for this latest phase were released earlier this month when the UT team’s peer-reviewed research was published in Environmental Science and Technology.

Once again it’s good news.

The new study confirms that overall methane emissions rates from natural gas systems are lower than the Environmental Protection Agency’s model-based estimates.

In addition, it turns out that the overall methane leakage rate of 0.38 percent from oil and gas production is a further 10 percent reduction from the original rate reported in the first UT study published last year.

Of course, there is always room for improvement. One encouraging finding from the study is that the largest portion of methane emissions appears to be coming from a small number of sources, in much the same way that a small percentage of older cars is responsible for the largest share of automotive-exhaust pollution.

That should help identify ways to further reduce the already low levels of methane emissions from natural gas sites in a targeted, cost-effective manner.