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The mischievous methane molecule

The mischievous methane molecule

Molecule-for-molecule, methane traps more heat than carbon dioxide but is thankfully prevalent in lower concentrations in the atmosphere.

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Last Updated : 10 April 2024, 23:26 IST
Last Updated : 10 April 2024, 23:26 IST
Last Updated : 10 April 2024, 23:26 IST
Last Updated : 10 April 2024, 23:26 IST
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At the global climate summit, the 28th Conference of the Parties (COP28), held in Dubai in December last year, methane got a lot of attention. What is all the fuss about? Methane is a gas molecule comprising one carbon and four hydrogen atoms. It is produced any time organic matter decomposes, such as from waste in a landfill, in standing water like marshes and paddy fields, from animal manure, and in cow’s flatulence. It is also the primary component of the natural gas that many of us use for cooking. Leakage of unburned methane from natural gas systems as ‘fugitive emissions’ is also a major contributor to atmospheric methane.

And, relevant to the focus at COP28, methane is a powerful greenhouse gas (GHG) that traps the energy of the sun, leading to global warming.

Molecule-for-molecule, methane traps more heat than carbon dioxide but is thankfully prevalent in lower concentrations in the atmosphere. In order to report multiple GHGs with a single composite number, the amount of each GHG is multiplied by an index called global warming potential (GWP) that captures the heat-trapping capacity of that gas. The total is reported in metric tons of carbon dioxide equivalents. By definition, carbon dioxide has a GWP of 1.0. 

Different gases remain in the atmosphere for different amounts of time. Therefore, the GWP index is specific to the time period over which the warming potential is measured. The most commonly used index for methane is a GWP100 of 27.9, i.e., it is 27.9 times worse than carbon dioxide in terms of heat-trapping over a 100-year period. 

The harms of climate change critically depend on our ability to decarbonise in the next two decades. Hence, climate scientists are increasingly tilting towards using GWP20 indices. In the case of methane, that index is a whopping 81.2. Yes, over the next 20 critical years, each tonne of methane released today will trap as much heat as 81.2 tons of carbon dioxide! 

At COP28, Durwood Zelke, president of the Institute for Governance and Sustainability, said, “Methane is the blowtorch that is boiling the planet. Turn it off, and you immediately turn down the heat.”

Indeed, focusing on the next 20 years, methane is about one-third of the global emissions problem and nearly half of GHG emissions in India! Worldwide, methane emissions come from agriculture (40%), fossil fuels (35%), and waste (20%), while in India, the proportion is skewed towards agriculture (81%), fossil fuels (8%), and waste (11%). In other words, if we do not tackle methane, and in particular methane from agriculture, India does not have a chance of achieving net zero in India.

At COP28, former vice president of the United States, Al Gore, launched Climate TRACE, of which he is a co-founder. Climate TRACE uses satellites and remote sensing technology to measure GHGs with unprecedented precision. An open emissions database of more than 352 million assets was unveiled. This is good news for climate scientists, environmental activists, and those companies, such as Tesla, Boeing, and Polestar, that seek to decarbonise their supply chains. It is bad news for the fossil fuel industry, which has been under-reporting fugitive emissions. In countries with piped natural gas, there is system-wide leakage, including the well head, compressor stations, transmission pipes, and distribution pipes — so much so that the clean-burning nature of natural gas is more than nullified by fugitive leakage. One might as well be burning coal from a GHG point of view.

In the US, 2.5% to 3% of the natural gas in the system leaks, leading to fugitive leakage, which accounts for 54% of all methane emissions. Thanks to all the recent attention, renewed attempts are now underway to reduce this leakage. 

The challenge in India is different. Methane emissions are dominated by agriculture. Importantly, 42% of Indian employment is on farms, which are typically small and financially strapped. Although India has the most cattle in the world and the most acreage of rice fields in the world, productivity has remained stubbornly low and methane emissions high. 

How is it possible to reduce methane from farming quickly and dramatically while working with often impoverished farmers on small parcels of land? Read our next article in the series to find out.


(Visweswariah is VP, cure100.org, and Muralidharan is an R&D specialist, IIT Madras. This is the third in a series of seven articles on climate change and net zero.)

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