Previously, knowing where significant methane emissions were coming from was not something easily determined by multispectral satellite systems. In part, methane was generally not a major focus for remote sensing specialists.
Methane: A Major Greenhouse Gas
Methane is perhaps the most potent of greenhouse gas emissions. While methane does not constitute a large percentage of our atmosphere, the danger is increasing methane emissions, particularly from thawing permafrost, could greatly hasten the pace of global warming.
Currently, most emissions are coming from areas related to the oil and gas industry, including pipelines releasing the gas. Now, a new satellite system can aid in finding major areas of methane emissions so we can work to reduce leaks in order to limit greenhouse gases.
Remote Sensing of Methane Emissions
The TROPOspheric Monitoring Instrument (TROPOMI), which is onboard the Copernicus Sentinel-5 Precursor, has been demonstrated to be effective in detecting methane emissions. The instrument, which has spatial resolution of about 50 square kilometers, uses ultraviolet and visible (270–500 nm), near-infrared (675–775 nm) and shortwave infrared (2305–2385 nm) spectral bands from the TROPOMI passive spectrometer.
Previously, this instrument was used to detect a wide range of pollutants, such as sulfur dioxide or ozone, but it has also demonstrated ability to detect methane over individual industrial-scale sites. The instrument was developed for the European Space Agency (ESA).
Where are Methane Emissions Highest?
In a new research study by a multi-national team of scientists, results have highlighted that methane emissions detected from the TOPOMI instrument show about one-tenth of global methane emissions come from three countries who are classified as ultra-emitters and major oil and gas producers.
Globally, this is Turkmenistan, Russia and the US. Overall, Turkmenistan was measured as having the largest emissions with over million tons of methane between 2019-2020. Iran, Algeria and Kazakhstan were also found to be significant in their methane contributions to overall emissions.
The imagery used in a new study was processed using an algorithm that automatically detects large methane plumes. The largest country emitters pump out more than 25 tons of methane per hour or about 8 million tons a year. Given the potency of methane in affecting climate change, this is a very large and worrying number.
Pipeline Leaks are a Major Contributor to Methane Emissions
While the worst emitters may show a worrying trend, there is hope that the problem may not be too hard to repair. Mainly, the emissions of high quantity are happening at pipeline sites that are leaking or deliberately releasing methane. This happens when pipes need repair and leakages or deliberate release is conducted for methane.
The solution to the problem might be to fix or safely remove the methane, which costs less than $300 per ton to remove. With the new imagery, high emission sites are not only identified but the data can be used to inform companies or sites responsible for these emissions in order to fix the problem as expediently as possible.
Continued Mapping of Methane Emission is Needed
While the new results offer hope that high methane emission areas could be more easily found and immediate action can be taken to mitigate leakages or emissions, more consistent and higher resolution monitoring might be needed. In the US, the methane estimate may actually be low, as smaller sites are likely also significantly contributing to methane emissions. In the study, major oil and gas regions were not even included for the US.
A new satellite, called MethaneSAT, will be launched later this year. It will provide higher sensitivity in measuring methane emissions and will enable more precise tracking of emissions across time. Data from the satellite will also be submitted within days of measurement and sent to organizations responsible for given emissions. The satellite is support by the Environmental Defense Fund and the New Zealand Space Agency.
The spectrometer used will monitor a narrow range within shortwave infrared (SWIR). This band is where methane is most detectable, which will allow more precise emission measurements to be made and from smaller emission sources. This will then allow a more comprehensive assessment on areas that may need to better reduce their overall methane emissions. Perhaps an important aspect of this satellite is that it will be singularly dedicated to monitoring methane, allowing more coverage for sites throughout the year.
With increasing awareness of the importance in rapidly diminishing greenhouse gas emissions, scientists have focused on methane emissions as an area of concern. Recent study has highlighted some major emission areas, mainly to do with pipelines used by the oil and gas sectors. These problems are, in many cases, easy to fix by properly fixing pipelines and not releasing methane. However, to better limit methane emissions, more spatially sensitive satellites such as MethaneSAT, which can also be used to monitor emissions throughout the year, will be needed to monitor more sites and for longer periods.
 For more on TROPOMI, see: http://www.tropomi.eu/ and https://sentinel.esa.int/web/sentinel/user-guides/sentinel-5p-tropomi.
 For more on the study that look at global emissions of methane from satellite imagery, see: Lauvaux, T.; Giron, C.; Mazzolini, M.; d’Aspremont, A.; Duren, R.; Cusworth, D.; Shindell, D.; Ciais, P. Global Assessment of Oil and Gas Methane Ultra-Emitters. Science 2022, 375, 557–561, doi:10.1126/science.abj4351.
 For more on the high methane emission sites, see: https://www.newscientist.com/article/2306715-satellite-images-show-biggest-methane-leaks-come-from-russia-and-us/.
 For more on the new MethaneSAT satellite, see: https://optics.org/news/11/9/26 and https://www.methanesat.org/.