Methane Pollution: Understanding The Major Causes

Methane is a powerful greenhouse gas that is emitted from both anthropogenic and natural sources. It is the second-largest contributor to global warming after carbon dioxide, and its concentration in the atmosphere has more than doubled over the past 200 years, largely due to human activities. The main sources of methane emissions are agriculture, fossil fuels, and the decomposition of landfill waste. Natural processes, such as wetlands, lakes, and thawing permafrost, also contribute to methane emissions. Methane pollution has severe impacts on public health and the environment, causing extreme weather events, crop losses, and respiratory issues. Reducing methane emissions is crucial for mitigating climate change and its associated consequences.

Oil and gas production

Oil and gas operations also release methane into the atmosphere through the wasteful practices of intentional flaring and venting, as well as through the unintentional release of fugitive methane emissions. Flaring is the process of burning off excess gas that is released during the extraction of oil and gas. While it is intended to reduce the amount of methane released into the atmosphere, it still results in significant methane emissions. Venting is the process of releasing natural gas into the atmosphere without burning it, and it is also a significant source of methane pollution. Fugitive methane emissions refer to the unintentional release of methane, often due to leaks in equipment or pipelines.

The production and transportation of natural gas, including both associated and non-associated gas, often result in leaks and other unintentional releases of methane. While the composition of gas varies, natural gas typically comprises about 80-95% methane, so leaks can result in large amounts of methane escaping into the atmosphere. These leaks are typically the result of poor maintenance, broken equipment, or other operational issues.

In addition to the direct release of methane, oil and gas production can also contribute to methane pollution through the release of other pollutants, such as volatile organic compounds (VOCs). VOCs are formed during the combustion of natural gas and crude oil, and they can have significant health impacts, including cancer, nervous system damage, and birth defects. People living near oil and gas wells are especially vulnerable to the health risks associated with VOCs and other air pollutants. For example, in Arlington, Texas, many public schools and licensed daycares are located within close proximity to natural gas wells, exposing children to toxic pollution and increasing their risk of asthma attacks, cancer, and other health issues.

Despite the significant impact of oil and gas production on methane pollution, efforts to reduce these emissions have been limited. In November 2021, the EPA proposed new rules for methane emissions from the oil and gas industry, which was a positive step forward. However, methane abatement solutions are often underfunded, and there are challenges in attracting commercial investment for flare and methane reduction projects. Additionally, there is a lack of accepted methane abatement finance criteria, and climate-focused investors are hesitant to support projects aimed at reducing emissions connected to oil and gas production. Nevertheless, there is growing recognition of the importance of integrated flare reduction and gas management in the decarbonization of the oil and gas industry.

Agriculture and animal agriculture

Methane is a powerful greenhouse gas that is 80 times more potent than carbon dioxide over a 20-year period. It has a relatively short lifespan of 7 to 12 years in the atmosphere, compared to carbon dioxide, which can persist for hundreds of years or more. However, methane traps significantly more heat than carbon dioxide, making it a major contributor to climate change.

Animal agriculture's impact on methane pollution is primarily due to the enteric fermentation that occurs during the digestion of ruminant animals, such as cattle, goats, and sheep. This process produces methane, which is released into the atmosphere through flatulence and burps. Additionally, manure management in animal agriculture contributes to methane emissions.

To reduce methane pollution from animal agriculture, scientists are experimenting with alternative feed sources, such as Asparagopsis taxiformis, a type of red seaweed that has shown promising results in reducing methane emissions from cattle. Other initiatives include improving manure management practices, such as covering, composting, or using manure to produce biogas.

In addition to animal agriculture, paddy rice cultivation is another significant source of methane emissions from agriculture. The flooded fields used in paddy rice cultivation prevent oxygen from penetrating the soil, creating ideal conditions for methane-emitting bacteria. Experts recommend alternate wetting and drying approaches, which can halve emissions and reduce water usage by one-third.

Reducing methane emissions from agriculture and animal agriculture is crucial for mitigating climate change. According to the UN Environment Programme, methane has accounted for approximately 30% of climate change since pre-industrial times. By reducing human-caused methane emissions, we can significantly decrease global warming and prevent its worst impacts.

Coal mining

There are several ways in which coal mining activities lead to methane pollution. Firstly, during the coal mining process, methane is released from coal seams exposed in surface or open-pit mines. This release occurs due to seepage from the coal seams and through drainage and ventilation systems used to reduce methane content and ensure safety. Secondly, post-mining activities such as coal processing, storage, and transportation can result in methane emissions. Even after coal production ceases, coal mines continue to emit methane.

Abandoned coal mines, which are no longer actively operated, are another significant source of methane pollution. These mines can emit methane through diffuse vents, ventilation pipes, boreholes, or fissures in the ground. The methane released from abandoned mines, known as abandoned mine methane (AMM), can be deliberately extracted and utilized for power generation or other purposes. However, if not captured and controlled, AMM contributes to methane pollution and poses safety risks due to its explosiveness.

The impact of coal mining on methane pollution is significant, with emissions estimates ranging between 38 and 67 million tonnes of methane per year. Independent studies suggest that actual emissions may be significantly higher than reported by governments, indicating a critical need for improved monitoring and reporting of CMM emissions. Reducing coal consumption and implementing abatement measures, such as degasification systems and methane capture technologies, are crucial steps towards mitigating methane pollution from coal mining.

While there are challenges in reducing methane emissions from coal mining, there are also opportunities for utilizing captured methane. In the United States, recovered CMM is often sold to natural gas pipeline systems, and it can also be used for coal drying, vehicle fuel, manufacturing feedstock, and fuel cells. As coal operations are a major source of methane emissions, addressing this sector is essential for mitigating climate change and achieving global methane reduction goals.

Wastewater treatment

The wastewater sector is a significant contributor to global methane emissions, accounting for about 5-8% of total anthropogenic CH4 emissions. This is primarily due to the anaerobic decomposition of organic waste during the management and treatment of urban wastewater. Municipal wastewater treatment plants emit methane, a potent greenhouse gas, which contributes to climate change.

During wastewater collection and treatment, methane is produced in anaerobic environments where methanogenic archaea convert acetate, H2, or formate to methane and carbon dioxide through anaerobic fermentation and acetogenesis. The growth of biofilms, or biological slime layers, on pipe surfaces also contributes to methane production, even in low-strength or rapidly moving systems. Stagnant flow can create anaerobic conditions that further enhance methane generation.

To mitigate methane emissions from wastewater treatment, various approaches have been proposed. These include chemical dosing methods, such as using oxygen, ferric salts, hydroxide, and free nitrous acid. Additionally, the addition of nitrite has been found to effectively reduce methane emissions. The development of "end-of-pipe" methane abatement solutions, such as methanotrophic air biofilters, can also help capture methane at potential hotspots within the sewer and treatment systems.

Improvements in waste treatment practices, such as the use of biodigesters, can significantly reduce methane emissions and produce renewable energy through biogas generation. Modernizing wastewater treatment facilities with advanced membranes and methane gas sensors can help optimize control operations and improve waste management. These measures not only reduce methane pollution but also enhance air quality and promote a circular economy.

Fossil fuel production

The production and transport of coal, natural gas, and oil are key sources of methane emissions. In particular, the extraction and transportation of natural gas and crude oil from wells have been identified as processes that allow methane to leak into the atmosphere. One study found that about 13 million metric tons of methane leak before it is even used. These leaks have been detected using tools such as NASA's Airborne Visible InfraRed Imaging Spectrometer - Next Generation (AVIRIS-NG), which can determine the amount of greenhouse gases present by measuring the exact wavelengths of light that are absorbed.

Compressor stations along pipelines, which are necessary to compress gas and keep it moving, have been identified as significant sources of methane emissions. In addition, the combustion of fossil fuels, such as coal, natural gas, and oil, releases methane into the atmosphere. Fossil fuel-related emissions of methane have been found to be higher than previously thought, with researchers estimating that they may be twice as high. This is due in part to uncertainties related to a lack of in-situ observations and accurate infrastructure data.

The impact of fossil fuel production on methane pollution is not limited to direct emissions. For example, people living near oil and gas wells are exposed to toxic pollution, including volatile organic compounds (VOCs) that are released alongside methane. These pollutants can cause a range of health issues, including cancer, nervous system problems, and birth defects.

Addressing methane emissions from fossil fuel production is crucial for mitigating climate change and protecting public health. Efforts to reduce these emissions include the EPA's proposed new rules for methane emissions from the oil and gas industry, as well as NASA's mapping initiatives to better understand the sources and impact of these emissions.

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