METHANE EMISSIONS

Why in the News?

Recently, ISRO scientists released a first-of-its-kind comprehensive analysis paper on the methane emissions over multiple Indian locations using satellite data.

More about News

• Considering its high global warming potential, the monitoring of source locations is inadvertent.
• The study employed data from NASA’s Earth Surface Mineral Dust Source Investigation (EMIT) and European Space Agency’s Sentinel-5P TROPOMI.
  • The EMIT instrument measures surface mineralogy, targeting the Earth's arid dust source regions.
  • The TROPOMI instrument is a space-borne, nadir-viewing, imaging spectrometer covering wavelength bands between the ultraviolet and the shortwave infrared.
• This paper tries to showcase the potential of spaceborne monitoring systems to effectively identify and monitor methane point sources.
  • The advantage of using an imaging spectrometer is that it enables the detection of highly localised sources of methane which can be used for identifying leaks coming from very localised sources.

Key findings of the paper 

• Regional Emission hotspot: 17 unique plumes were identified in the states of Maharashtra, Rajasthan, Punjab, Gujarat and Assam. 
• Emission source point: Solid waste landfill sites, sewage treatment plant, wetlands/marshy agriculture, city sewage outlet, oil and gas field, oil refinery and textile industry.
• Increase in Methane Emission from municipal solid waste landfills: The net annual emission of India from municipal solid waste landfills is estimated to be 1084 Gg (Giga-gram) in 2015, whereas it was 404 Gg in 1999-2000.
• Aids carbon emission: Out of the total carbon emissions in India, 14.43% is attributed to CH4.
  • The major share of this percentage is contributed by enteric fermentation and rice cultivation areas of agriculture. 

About Methane   

• Methane (CH4) is a hydrocarbon that is a primary component of natural gas.
• It is also a potent greenhouse gas (GHG) responsible for approximately a third of the warming being experienced today.
• It is a powerful and short-lived (GHG), with a lifetime of about a decade and a Global Warming Potential about 80 times greater than that of carbon dioxide (CO2) during the 20 years after it is released into the atmosphere (IPCC).
• Methane emissions lead to ground-level ozone pollution which causes approximately a million premature deaths per year globally, reduces crop productivity and harms ecosystems. 
• The majority of human-driven methane emissions come from three main sectors:
  • Agriculture (40%): Enteric fermentation from livestock rearing and rice cultivation.
  • Fossil fuels (35%): Leakage from natural gas, oil and gas field, mining, etc.
  • Solid waste and wastewater (20%): Dumpsites, landfills, etc.
• Proven technologies and practices could reduce emissions from the major sectors by approximately 45% by 2030.
  • Most of these technical solutions can be implemented at a negative or low cost, especially in the fossil fuel and waste sectors.
• Potential of spaceborne monitoring for methane emission: Generally accurate quantification of anthropogenic emission sources including solid waste disposal sites, O&G industry, mining areas, etc. is challenging due to constantly changing conditions and management practices. 
  • Remote sensing of these vulnerable sources allows for top-down monitoring of emissions and can provide valuable information on the dynamics of methane emissions.
  • Imaging spectrometer enables detection of highly-localised sources of methane which can be used for identifying leaks coming from very localised sources.

Limitation of spaceborne monitoring systems

• Spectral interference: Methane has spectral absorption bands overlapping with other atmospheric constituents, particularly water vapour.
  • Differentiating the spectral signatures of methane from those of other gases can be challenging, especially in humid environments.
• Low spatial and temporal resolution: Instruments like TROPOMI, SCIAMACHY, AIRS, GOSAT designed for global methane monitoring and do not have the spatial resolution necessary to detect small-scale methane sources or to pinpoint exact emission locations.
  • Low Temporal Resolution or frequency of revisit, making it difficult to monitor rapid changes in methane emissions
• Ground based validation: While both spaceborne and airborne imagery requires ground-based measurements that are essential but can be resource-intensive.
  • Even if methane is detected, determining its source can be challenging without additional data. 
• Instrumental limitations: Instruments (whether ground-based or on remote platforms) have detection limits, sensitivities, and specificities that can constrain their ability to reliably detect methane under all conditions.
• Atmospheric variability: Satellites might miss methane emissions from regions that are frequently cloudy. Since, methane has a relatively short atmospheric lifetime, which means its concentrations can vary rapidly in time and space.
• Temporal measurement: Methane has a relatively short atmospheric lifetime, which means its concentrations can vary rapidly in time and space.
  • This variability requires frequent and accurate measurements to understand and manage emissions effectively
• Background Methane Concentration: since methane is present throughout the atmosphere, detecting localised increases or 'plumes' requires distinguishing these from the background levels. This can be particularly challenging for small emissions or in regions with high background methane concentrations.

Way ahead

Data integration is one major focus where combining data from various sources, including satellite, airborne, and ground-based measurements, can provide a more complete and accurate picture of methane emissions for very local to global level. Advances in sensor technology, data analytics, and international cooperation are critical to improve our ability to detect, quantify, and manage methane emissions.