Mountain States

New Methane Study Finds Low Emissions from Transmission and Storage Facilities

Researchers at Colorado State University, partnering with the Environmental Defense Fund (EDF), released a new study today focusing on methane emissions from natural gas transmission and storage facilities.  The study finds very low methane emissions that are very much in line with the Environmental Protection Agency’s (EPA) estimates in its Greenhouse Gas Inventory.

Here are just a few quick things that jumped out from the report:

Data show lower emissions than the EPA Greenhouse Gas Inventory

As the researchers explain, they found methane emissions to be lower that EPA’s estimates:

“We estimate total methane emissions from the T&S sector at 1,503 [1,220 to 1,950] Gg/yr (95% confidence interval) compared to the 2012 Environmental Protection Agency’s Greenhouse Gas Inventory (GHGI) estimate of 2,071 [1,680 to 2,690] Gg/yr.” (p. A)

Colorado State University states in its press release, “Because these ranges overlap, the researchers consider the two estimates statistically similar.”

Researchers included “super-emitters” in their data, yet still found low methane emissions 

From the report:

“In addition to the equipment level emissions models, this study also explicitly modeled facility-level “super-emitters”. During the field measurement campaign, two facilities were classified as super-emitters due to elevated emissions observed by tracer flux methods which were not measured using onsite measurements or were inaccurately measured with portable acoustic meters.” (p. D)

In other words, the researchers included facilities known to release large amounts of methane, yet they still found very low overall methane leakage rates from transmission and storage facilities.

Methane emissions well below the threshold for natural gas to maintain climate benefits

The report notes,

“T&S emissions are estimated as 1,503 Gg/yr [+30%/−19%], corresponding to a methane loss rate of 0.35% [0.28% to 0.45%] of the methane transported by the T&S sector in 2012 (based upon 434 Tg of methane contained in a natural gas throughput of 23.8 × 1012 scf, SI, Section 16).” (p. E)

The researchers explain that these results are statistically similar to EPA’s Greenhouse Gas Inventory, which, as they rightly note, also found a very low methane leakage rate overall for natural gas systems.

“Currently, the most complete bottom-up inventory of natural gas system emissions is the 2012 U.S. Environmental Protection Agency’s (EPA) Greenhouse Gas Inventory (GHGI). It estimates an overall system-wide methane loss rate of 6.2 Tg/yr of methane, or 1.3% of methane transported (Supporting Information (SI), Section 16) and that the transmission and storage sector (T&S) is the largest emitting segment of the natural gas industry, accounting for about one third of methane emissions.” (p. A)

Many scientists have observed that, for natural gas to maintain its climate advantages, methane leaks need to be kept between 2 to 3 percent. EDF has long maintained that natural gas is beneficial for the climate “as long as leakage remains under 3.2%.”  With this new study being very much in line with EPA’s Greenhouse Gas Inventory, which found an overall leakage rate for natural gas systems of 1.3 percent, it also demonstrates a rate well below the threshold to maintain climate benefits.

New report corroborates top methane studies finding low emissions

This study is the latest in a long list of reports that have found that as natural gas production has skyrocketed, methane emissions have plummeted.

The Intergovernmental Panel on Climate Change (IPCC) climate assessment  states that hydraulic fracturing “is an important reason for a reduction of GHG emissions in the United States.” The IPCC also noted that even “[t]aking into account revised estimates for fugitive emissions, recent lifecycle assessment indicate that specific GHG emission are reduced by one half” as more power plants are powered by natural gas.

A report by the University of Colorado at Boulder and the National Oceanic and Atmospheric Administration found that methane leakage rates in three of the top natural gas producing areas the United States are consistent with the EPA’s estimate at 1.1 percent of production.

A number of studies spearheaded by EDF have also found low methane emissions including the recent publication of eleven new reports in the journal Environmental Science and Technology.  These studies found that methane leakage rates from natural gas systems in the Barnett Shale area were extremely low – at 1.2 percent.

And, of course, as mentioned above, EPA’s latest Greenhouse Gas Inventory found that methane emissions from the production of natural gas have fallen 38 percent since 2005, all while gas production increased by 26 percent.

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