Why detecting methane is difficult but crucial work

In Washington D.C. and its surrounding areas, volunteers and environmentalists are walking the streets and visiting homes to assess air quality conditions. They are equipped with industrial-grade monitoring devices used to detect the presence of various gases. These devices resemble walkie-talkies in appearance.

These devices are equipped with sensors that can reveal the concentration of methane, transforming this invisible gas into concrete numbers on a screen. These numbers can be alarming. In a 25-hour period, community researchers discovered 13 outdoor methane leaks with concentrations exceeding the lower explosive limit. They also found methane leaks inside residences.

A key concern is health issues. Methane and other gases, particularly nitrogen oxides produced by gas stoves, are associated with a higher risk of asthma. Djamila Bah, a tenant leader and healthcare worker with the community organization Action in Montgomery, reported that one-third of the children in the homes tested by the organization suffer from asthma.

Ms. Bah stated, "It's very heartbreaking and shocking when you do the testing and then you realize that some people are living in conditions that they temporarily cannot change."

Methane can pose a hazard to human health, and it is also a potent greenhouse gas. Although methane has a much shorter lifespan in the atmosphere than carbon dioxide (CO2), it is more effective at trapping heat, contributing to approximately one-quarter of the global temperature increase since industrialization.

Methane emissions come from multiple sectors, primarily including fossil fuels, waste, and agriculture. However, methane is not always easy to detect.

Methane can be detected using handheld gas sensors, such as those used by community researchers. It can also be observed using infrared cameras, as methane absorbs infrared light. Monitoring can be ground-based (including vehicle-mounted equipment) or airborne (including drone measurements). Combining technologies is especially effective.

Andreea Calcan, a project management officer with the UN initiative "International Methane Emissions Observatory," stated, "There is no perfect solution." There are trade-offs between technology costs and the scale of analysis, which can extend to thousands of facilities. Fortunately, she has seen an increase in affordable methane sensors over the past decade. Therefore, there is no reason to wait to monitor methane, regardless of scale. She stated that the world needs to address both small-scale leaks and high-emission events.

On a larger scale, satellites are generally good at pinpointing super-emitters: infrequent but high-emission events, such as large oil and gas leaks. Alternatively, they can detect more common, smaller, and more dispersed emission sources, such as cattle farms.

Riley Duren, CEO of the non-profit organization Carbon Mapper, stated that current satellites are typically designed to monitor one scale of emission source. He likened this to film cameras. Telephoto lenses offer higher resolution, while wide-angle lenses offer a larger field of view.

Through a new satellite, Carbon Mapper is focusing on high resolution, high sensitivity, and rapid detection to more precisely detect emissions from super-emitters. In August 2024, Carbon Mapper, in collaboration with NASA's Jet Propulsion Laboratory and earth imaging company Planet Labs, launched the Tanager-1 satellite.

Satellites have difficulty detecting methane emissions in certain environments, such as snow-covered, heavily vegetated areas with poorly maintained oil wells. Low-light, high-latitude, mountainous, and offshore areas also present challenges. Mr. Duren stated that the high-resolution Tanager-1 can address some of these challenges, such as observing through clouds or gaps in forest cover.

He stated, "In oil and gas fields, high resolution may be the key to isolating methane emissions from the wellhead from methane emissions from adjacent pipelines." This helps determine who should be held responsible. Carbon Mapper began releasing emissions data in November, data derived from Tanager-1 observations.

Establishing a complete satellite constellation will take years and will depend on funding. Tanager-1 is not the only new satellite focused on providing methane data. The Environmental Defense Fund's project MethaneSAT, along with private and public partners, also launched in 2024.

Mr. Duren stated that with the increasing maturity of all these satellite technologies, "things that were previously invisible are now becoming visible. As a society, we are still learning about our true methane footprint."

Clearly, we need more information about methane emissions. Some energy companies attempt to evade methane detection by using "enclosed combustors" to mask natural gas combustion. Even with the increasing amount of existing information, translating knowledge into action is not always straightforward. Methane levels continue to rise.

For example, the Methane Alert and Response System (MARS) uses satellite data to detect methane emissions and notify companies and governments. The MARS team collected a large number of methane plume images and manually verified them to train a machine learning model to identify such plumes.

At all locations continuously monitored by MARS, the model checks daily for methane plumes based on their emission history. Analysts then carefully review any alerts. Itziar Irakulis Loitxate, head of remote sensing for MARS at the International Methane Emissions Observatory, stated that because there are so many locations to monitor, "this saves us a lot of time."

In the two years since its launch, MARS has issued more than 1,200 significant methane leak alerts. Only 1% of the alerts have led to a response. However, Ms. Irakulis remains optimistic. Some of these alerts have led to direct action, such as repairs, including cases where emissions stopped even when oil and gas operators did not formally provide feedback.

Ms. Irakulis stated that communication has been improving. "I hope that this 1% figure will increase significantly in the coming year."

At the community level, it is very empowering for residents in the Washington D.C. area to take their own air pollution readings and use those readings to push back against misinformation. Joelle Novey of Interfaith Power and Light stated, "Now that we know more, we can do better."