In the battle for the climate, carbon dioxide (CO2) is consistently cited as enemy number 1. Not surprising, as its emissions contribute 80% of global warming. The other enemy is methane (CH4), which represents the remaining 20% and whose emissions have skyrocketed since 2006. Although the fight against this polluting gas has long been put aside, it nevertheless comes to the fore again. . and most recently thanks to the announcement by US President Joe Biden on September 17 of a project to reduce CH4 emissions in partnership with the European Union.
By chance, researchers from Stanford University (United States) publish two new studies on Monday, September 27, in the Philosophical Transactions journal of the Royal Society A. The first presents a plan for coordinating research aimed at capturing and eliminating methane. of the atmosphere. . The second details a computer model of the considerable effect such an approach could have on reducing temperature. According to this work, eliminating the equivalent of about three years of man-made methane emissions would reduce global surface temperatures by about 0.21 degrees Celsius. Results that confirm those obtained by scientists from the Intergovernmental Panel on Climate Change (IPCC), who indicate in their latest report that a drastic reduction in CH4 emissions by 2050 could “gain” 0.3 ° C.
Methane, 81 times more powerful than CO2
The origin of this work is based on a simple observation: the concentration of methane in the atmosphere has increased more than double that of CO2 since the beginning of the industrial revolution. Above all, it has skyrocketed since the 1980s and even more since 2006. According to the sixth IPCC report, global temperature has risen on average 1.09 ° C compared to the end of the 19th century and methane emissions contribute to the height. . 0.5 ° C of the total.
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Removing it from the atmosphere would lower temperatures faster than removing CO2. “In fact, it is 27 to 28 times more powerful than CO2, which means that, compared to CO2, the same amount of CH4 in the atmosphere heats 27 to 28 times more than CO2,” explains the professor. Rob Jackson of the Stanford School of Earth Energy. and Environmental Sciences, lead author of the first study and co-author of the second, interviewed by L’Express. It would also improve air quality and prevent around tens of thousands of deaths each year. “Methane is what is called a ground-level ozone precursor, which means that more CH4 in the atmosphere produces more ozone,” adds Sam Abernethy, an applied physics student, supervised by Rob Jackson, co-author of the two studies, also interviewed by L’Express. Ozone, which is also a greenhouse gas, causes respiratory diseases that cause around one million deaths a year globally, significantly reducing its presence would prevent up to 50,000 premature deaths a year, according to a study published in 2021 “.
Global average methane concentration in the atmosphere since 1983, according to the United States Agency for Atmospheric and Ocean Observation.
The sources of methane emissions are varied and more numerous than the sources of CO2. Approximately 40% comes from natural sources and 60% from sources linked to human activities. Natural sources include microbes in the soils of wet and flooded areas such as swamps and mangroves, geological sources such as the natural outgassing of methane trapped underground, and even … termites! This percentage could also rise soon due to the melting of Arctic permafrost brought on by global warming, which will help release methane synthesized by bacteria so far trapped under this frozen soil.
But most of the world’s methane emissions are man-made. The main culprits are agriculture, including the rearing of ruminants that emit methane during their digestion (belching and farts), but also manure production, not to mention rice paddies, which emit methane when flooded. Waste disposal and extraction of fossil fuels also contribute substantial emissions, as does the transportation and exploitation of fossil fuels from coal, natural gas, and oil.
What technologies to use?
In the first study, the researchers looked at the best strategies for capturing methane. They first compared technologies aimed at removing CO2 and methane, then selected the best ones while outlining a plan to coordinate research, development and acceleration of production. According to the scientists, their work will help improve the analysis of methane removal factors, in particular through emission site-specific simulations. If the authors recognize that the development of technologies for the removal of methane is not easy at all due to its low concentration in the atmosphere, they point out that technologies are emerging, such as that linked to zeolites, a type of mineral capable of ‘absorbing this gas ; photocatalysis, which consists of destroying gaseous compounds by degrading them on the surface of a catalyst; or the development of amendments, materials that modify and improve the quality of agricultural soil.
According to the researchers, more research should be done on the cost, efficiency and energy requirements of these technologies, but also to determine the possible obstacles to their implementation, the benefits and the possible negative side effects. “Removing carbon dioxide from the atmosphere is a multi-billion dollar investment and dozens of companies have been created,” says Rob Jackson. We need similar investments to phase out methane. “He and his team also insist on the significant economic rewards. Market prices for carbon offsets, which involve offsetting one’s CO2 emissions by financing projects to reduce other emissions or sequester carbon, reach $ 100 or more per ton, so each ton of methane removed from the Atmosphere could be worth more than $ 2,700. “Today there are offsets for methane, particularly gas capture from coal mines, but current prices are much lower than the values we mentioned, both for CO2, which is still far from being $ 100 per ton removed, just for CH4, “says Rob Jackson.
Limit global warming to 1 ° C
In their second study, researchers from the UK’s national weather service, the UK Met Office, created a computer model that simulates various scenarios that measure the effect of methane reduction on falling temperatures by varying the amount of methane. removed or when discarded. They also took into account the lifespan of methane in the atmosphere, which is shorter than that of CO2, as some of the removed methane would have “naturally” disappeared anyway.
In a high emissions scenario, the researchers’ analysis suggests that a 40% reduction in global methane emissions by 2050 would result in a temperature decrease of approximately 0.4 ° C. In a low emissions scenario, a removal of methane of the same magnitude could reduce the maximum temperature by 1 ° C by 2050. They add that capturing the equivalent of three years of methane emissions would reduce temperatures by about 0.21 degrees Celsius. “This new model helps us better understand how methane removal changes global warming and human air quality,” says Sam Abernethy.
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In addition to capturing methane, which at this stage remains an illusion, other scientists have considered other solutions. Changing the diet of ruminants could, for example, make it possible to reduce their methane emissions, as well as the recovery of agricultural residues to produce biogas or even the modification of irrigation protocols for rice fields. Biogas from surface landfills could also be recovered and reused. Regarding fossil fuels – gas, oil – one of the solutions would be to burn the escaping methane, or recover it for use, but also to repair old gas distribution circuits, in order to limit leaks.