Accidentally Identifying Methane Super-Emitters From Space

By John Oncea, Editor

NASA’s EMIT mission is mapping the prevalence of key minerals in dust-producing deserts. But — surprise! — it’s also detecting the presence of methane around the world.

Former editor Abby Proch wrote about a year ago about how photonics will help curb methane emissions and slow global warming. In the article, Abby notes that by “updating rules to further limit intentional venting and flaring and reduce unintentional distribution pipeline leaks, the EPA hopes to reduce most types of oil and gas emissions by about 75%.”

She further explains, “Before emissions can be reduced, repairs must be made. And before repairs can be made, leaks must be identified. Methane emissions detection has come a long way since miners took chirpy yellow birds into the depths of the earth. Centuries later, innovation continues to predominate, with novel photonic technologies quickly gaining ground on existing methods.”

Current methods of detecting and measuring methane gas emissions include a flame ionization detector (FID) and an optical gas imaging (OGI) camera. The latter option removes the risk of human exposure to harmful gases but reduces accuracy.

That problem was addressed when Bridger Photonics debuted Gas Mapping Lidar — now its flagship product. “From the scanned lidar data and aerial photos captured simultaneously, our processing and analytics create high-resolution, geo-registered methane plume imagery and leak rate quantification. Effectively, we hand our clients a map with each leak location and emission rate precisely and accurately identified,” Abby quoted Peter Roos, CEO of Bridger Photonics as saying at the time.

Now comes word that an “orbital NASA instrument designed mainly to advance studies of airborne dust and its effects on climate change has proven adept at another key Earth-science function - detecting large, worldwide emissions of methane, a potent greenhouse gas,” according to Reuters.

In a span of four months, NASA identified “more than 50 methane ‘super-emitters’ in Central Asia, the Middle East, and the Southwestern United States” using an imaging spectrometer aboard the International Space Station.

The spectrometer was built primarily to identify the mineral composition of dust blown into the atmosphere from Earth's deserts and other arid regions by measuring the wavelengths of light reflected from the surface soil in those areas. That study, NASA's Earth Surface Mineral Dust Investigation (EMIT) will help scientists determine whether airborne dust in different parts of the world is likely to trap or deflect heat from the sun, thus contributing to the warming or cooling of the planet.

But, in a happy little accident, it turns out that methane absorbs infrared light in a unique pattern that EMIT's spectrometer can easily detect, according to scientists at NASA's Jet Propulsion Laboratory (JPL) near Los Angeles, where the instrument was designed and built. “Some of the (methane) plumes EMIT detected are among the largest ever seen — unlike anything that has ever been observed from space,” said Andrew Thorpe, a JPL research technologist leading the methane studies.

Carbon Mapper Is Putting NASA’s Data To Work

According to NASA, methane from the waste sector makes up about 20% of human-caused methane emissions. A new project from a nonprofit group, Carbon Mapper, will use NASA instruments and data to measure emissions from landfills around the globe.

“Carbon Mapper received a grant from the Grantham Foundation for the Protection of the Environment to support its operations related to the waste-site initiative, including potential funding to cover airborne methane surveys using NASA airborne assets,” writes NASA. “The project will entail conducting an initial remote-sensing survey in 2023 of more than 1,000 managed landfills across the United States and Canada, and in key locations in Latin America, Africa, and Asia.”

To collect data from these regions, researchers will use aircraft-based sensors, including the Airborne Visible/Infrared Imaging Spectrometer-Next Generation (AVIRIS-NG), which was developed at NASA’s Jet Propulsion Laboratory in Southern California. In addition, they will use Arizona State University’s Global Airborne Observatory from the Center of Global Discovery and Conservation Science, which uses another JPL-built imaging spectrometer.

One More Thing

While all of this is certainly encouraging, there are possible issues that need to be addressed. Nature.com published a paper — Evaluating the detectability of methane point sources from satellite observing systems using microscale modeling — evaluating “the efficacy of current satellite observing systems to detect methane point sources from typical oil and gas production (O&G) facilities using a novel very high-resolution methane concentration dataset generated using a microscale model.”

While not addressing EMIT specifically, the study concluded that “two orders of magnitude change in emission rates at the surface results only in about 0.4%, 1.6%, and 47.8% enhancement in the methane column observed by the satellites at 3 km, 1 km, and 50 m, resolutions, respectively. The large, persistent point sources (e.g., liquid unloading events) could be detected using state of art instruments with sufficient resolution (e.g., with 50 m pixels shown here) using the IME methodology.

“However, our results also show that sources associated with normal operations, excluding liquid unloading events, that are rapidly fluctuating, are difficult to accurately quantify provided the limitations in satellite detection limits, precision, overpass timing, and pixel resolution. Our analysis also shows that detection would in principle be limited by the strength of emission source and atmospheric turbulence.”

These findings in no way discredit anything EMIT has accomplished, rather they suggest “a continued need for coordinated space-aircraft/ground measurements to fully characterize all emissions from O&G point sources, as well as the importance of bottom-up/inventory estimates that could provide accurate emissions estimates from the well pads provided they are not misrepresented in terms of facility count and characterization of sources, including the smaller sources that are often undetectable by satellite-based measurements.”