A recent UN report suggested that the world is on track to warm more than 2C, well above what countries had agreed on with the Paris Agreement. Extreme weather events like heatwaves and rainstorms are on the rise, bringing destruction across the world, with no country spared. Among other necessary and urgent steps, curbing methane emissions has received attention as a quick win to slow down global heating. We take a look at the major sources of methane in the atmosphere and the available cost-effective measures to cut emissions worldwide.
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Why Should We Care About Methane Emissions?
According to the latest Emission Gap Report by the United Nations Environment Programme (UNEP), inadequate climate actions in recent decades may lead to a 2.8C global temperature rise by the end of the current century. This modelled temperature rise is considerably higher than the 1.5C target the world committed to when signing the Paris Agreement. Atmospheric methane is a potent greenhouse gas with 84-86 times higher in global warming potential than carbon dioxide across a 20-year period.
What Are the Major Sources of Methane in the Atmosphere?
Understanding which processes contribute the most is the first step before intervening or deploying measures to control rising emissions. The Global Methane Assessment (GMA) conducted by the joint effort of the United Nations Environment Programme and Climate and Clean Air Coalition revealed that anthropogenic methane accounts for 60% of the total methane emission, with 90% coming from three main sources: agriculture (40%), fossil fuel (35%), and waste (20%).
Agriculture is by far the biggest source of anthropogenic methane, with about 32% of total emissions originating from enteric fermentation and manure management, while the remaining 8% is attributed to rice cultivation. Cattle are an enormous contributor that accounts for more than 70% of the total livestock emissions among other kinds of animals including buffalo, sheep, goats, pigs, and chickens. Animal husbandry is also a source of methane emissions from feed production and manure deposition.
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Methane discharged from the fossil fuel industry is attributed to oil and gas extraction, pumping, and transport of fuels, altogether contributing to about 23% of total anthropogenic emissions. Coal mining – including active and abandoned mines – released another 12% as part of the total fossil fuel-derived emissions. Within oil and gas extraction, gas venting and fugitive emissions are the main cause of methane emissions. Gas venting is a practice that pumps out unwanted gas – a fossil fuel predominantly composed of methane – to maintain safe conditions in the oil and gas extraction process. While gas venting is a deliberate methane release, fugitive emissions are unintentional releases of gas across the fossil fuel supply system. The majority of the methane escape comes from downstream processes, which include refining, transmission, and distribution of gaseous products.
As the third most methane emitter, the waste sector generally releases methane from landfill and sewage treatment. Landfilling organic waste is known to generate landfill gas, which mainly contains methane gas from anaerobic bacteria. Landfills intrinsically create an anoxic environment for the methane-generating bacteria to thrive. This bacteria consume organic matter from waste and produces methane as a by-product. Sewage treatment facilities, on the other hand, introduce anaerobic processes to reduce sludge volume or sludge thickening.
The geographical distribution of the emissions varies across different sectors, where the fossil fuel and agricultural industries are prominent in particular regions. In the fossil fuel industry, China is the largest contributor to coal mining-related emissions, while Russia and North America are the biggest part of the oil and gas methane emissions. Within the agriculture sector, livestock emissions mainly originated from Latin America, followed by South Asia. While most of the emission from rice cultivation comes from Southeast Asia, Korea, and Japan, followed by South Asia and China. Methane from the waste sector is performed differently where the emissions are more geographically distributed across the continents.
Apart from human-related emissions, methane also comes naturally and mainly from freshwater and wetland. Similar to the emission from waste, bacteria generally produce methane in an oxygen deficit environment.
Beyond existing atmospheric methane, a potential source of methane from the Permafrost has received widespread attention given its enormous quantity being stored. Permafrost holds 1,400 billion tons of carbon which is almost double of methane currently in the atmosphere. Rein in emissions is therefore a critical move to prevent permafrost thaw from causing an outbreak of methane gas.
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What Can Be Done to Reduce Methane Emissions in the Atmosphere?
More than 100 nations signed the Global Methane Pledge (GMA) at COP26 in Glasgow last year, committing to cut down global methane emissions by at least 30% in 2030 from 2020 levels.
While the world’s biggest emitters, including China and India, have not signed the pledge, the Chinese envoy Xie Zhenhua agreed to deliver additional measures to cut down methane from oil and gas, agriculture, and waste with a drafted action plan presented at the 27th United Nations Climate Change Conference (COP27), which took place last month in Egypt.
The GMA summarised cost-effective measures to limit methane emissions with respect to methane-intensive sectors. Action to be in the agriculture sector include feeding changes and supplements to reduce enteric fermentation in livestock as well as improving manure management by installing biogas digester and reducing manure storage time.
The fossil fuel sector, on the other hand, requires better control of leak events by inspection, detection, and repair, capture and reuse of vented gas, and treatment of abandoned mines.
Regarding waste management, necessary steps include separating reusable and recycling materials from the rest, recovering energy from landfill gas, and zero landfill of organic waste. Similar to manure management in farms, sewage treatment plants should also be equipped with biogas facilities to recover and utilise it as a type of energy supply.
Engaging in the aforementioned actions would not only reduce methane outputs but also increase productivity, save costs from improved resource management, and promote better environmental quality.
The United Nations has also launched a methane detection and notification platform, known as Methane Alert and Response System (MARS). MARS integrates data from methane-detecting satellites to identify methane plumes and emission hotspots, informing governments and companies to take appropriate action, as well as monitoring mitigation progress.
Conclusion
Limiting methane emissions is no magic bullet to halt global warming. Nonetheless, it would definitely buy us some time to decarbonise every other sector before the climate crisis becomes irreversible. The latest UN Emission Gap Report has warned us that there is a closing window of opportunity given to recent off-tracking global political actions. Climate action does not require rocket science and technologies have been available and affordable to reverse the devasting consequence of climate change.
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