Microbes, not fossil fuels, produced most new methane: study

Microbes, not fossil fuels, produced most new methane: study

Subject: Environment

Section: Climate change

Tag: Greenhouse gases, Methane, Global methane Pledge

Context:

• Historically, methane levels rose until the 1990s, stabilized, and then began increasing again in 2007.
• Current methane concentrations are estimated to be three times higher than they were 300 years ago.

Evolving understanding:

• Methane, the second most abundant anthropogenic greenhouse gas after CO2, is significantly more potent, having a global warming potential 28 times greater than CO2 over a century and even higher over two decades.
• Its sources include cattle-farming, landfills, wastewater treatment facilities, rice cultivation, and some industrial processes.
  • Energy, agriculture and waste sectors are the primary emitters of methane, responsible for 30 per cent of the earth’s warning.
• It is only recently that policymakers have started to prioritize methane in global warming discussions.
• This shift was highlighted at the 2021 U.N. climate talks where the ‘Global Methane Pledge’ was introduced, aiming to reduce methane emissions to slow global warming.
• New research has revealed that the primary source of atmospheric methane is microbes, rather than the burning of fossil fuels, indicating an evolving understanding of methane’s sources and impacts.

Sources of methane:

• Scientists have identified two primary sources of methane: biogenic and thermogenic.
  • Thermogenic methane is released during the extraction of fossil fuels like natural gas and oil from beneath the Earth’s crust.
  • Biogenic methane, on the other hand, is produced by microbes known as archaea, or methanogens.
• These single-celled organisms, distinct from bacteria and eukaryotes, thrive in oxygen-poor environments such as animal digestive tracts, wetlands, rice paddies, landfills, and lake and ocean sediments.
• Methanogens are crucial to the global carbon cycle, converting organic matter into methane, a potent greenhouse gas.
• However, human activities such as agriculture, dairy farming, and fossil fuel production have amplified methane emissions.
• Different isotopes of methane, produced by both biogenic and thermogenic processes, help scientists trace the most active sources.

Modelling with a supercomputer:

• The carbon-13 isotope is important in distinguishing the sources of methane.
• Methane molecules containing fewer carbon-13 atoms typically indicate a biological origin, while a higher presence suggests thermogenic sources like fossil fuels or geological activities.
• The study suggests that the observed discrepancies in methane emissions might be linked to increased cattle-rearing in Latin America and rising emissions from waste in South and Southeast Asia, as well as in Latin America and Africa.
• Additionally, the number of wetlands globally has also grown. While satellite data has previously highlighted anaerobic archaea microbes as major methane contributors, Mr. Patra points out that satellite data, reliant on models, cannot accurately measure changes over time and are subject to uncertainties.

Global Methane Pledge

• Launched at the UN COP26 climate conference in Glasgow.
  • So far, over 90 countries have signed this pledge, which is an effort led jointly by the United States and the European Union.
• The pledge was first announced in September by the US and EU, and is essentially an agreement to reduce global methane emissions.
• One of the central aims of this agreement is to cut down methane emissions by up to 30 per cent from 2020 levels by the year 2030.
• Among the signatories is Brazil — one of the five biggest emitters of methane, which is generated in cows’ digestive systems, in landfill waste and in oil and gas production.
  • Three others —China, Russia and India — have not signed up.
  • Australia has said it will not back the pledge.
• According to the latest Intergovernmental Panel on Climate Change report, methane accounts for about half of the 1.0 degrees Celsius net rise in global average temperature since the pre-industrial era.

Source: TH