Other Sources of Methane
Work Area: Super Pollutants
While oil and gas methane is the number one industrial source of methane pollution, reductions in other sectors are not only economically justified but necessary to realize emission reductions. Methane emissions come from coal mining operations, landfills, wastewater treatment, and manure management operations. CATF has worked to develop an understanding of methane emissions at coal mines and landfills, and we work to develop and implement policy and regulatory solutions that can be applied both in the U.S. and internationally.
Coal Mine Methane
Globally, coal mining is responsible for 9% of total methane emissions. Reducing these emissions will improve mine safety and local air quality, reduce global warming, and provide a cleaner burning fuel for use at the mine or for sale.
Methane in coal seams, deposits of coal that are visible within layers of rock, is created as part of the same geological process that leads to the formation of coal. Large quantities of methane are typically trapped in or near coal deposits and are released during mining operations. Methane is emitted from a number of sources and operations, including:
- Degasification systems at underground coal mines;
- Ventilation of air from underground mines;
- Abandoned or closed mines;
- Surface mines; and
- Fugitive emissions from post-mining operations.
Underground coal mines are the single largest source of coal mine methane (CMM) emissions. Methane concentrations between 5 and 15 percent in the air of a coal mine represent an explosion hazard, so methane is removed with large-scale ventilation systems that move massive quantities of air through the mines. These systems also release large amounts of very low concentration ventilation air methane (VAM) into the atmosphere. Capturing these low concentrations of methane from VAM in the past has proven difficult, but new technologies have recently been developed and deployed to oxidize the methane in ventilation air rather than venting.
In addition, substantial reductions in methane emissions can be achieved by pre-draining methane from coal seams prior to the coal being mined (known as degasification) and draining methane from post-mining operations (known as “gob”). This reduces the amount of methane released into the mine that would need to be vented, and produces high-quality gas that can be sold.
CMM abatement must play an important role in mitigating the impacts of climate change, but a number of barriers exist that hinder methane abatement from coal mines. These barriers can be policy-related, financial, knowledge-based, or technology-based, and vary between countries. CATF is working to understand the barriers and to develop innovative ways to overcome them.
Methane from Solid Waste
Methane emissions from solid waste result from the decomposition of organic waste in an oxygen free (anaerobic) environment. Globally, dumpsites and landfills account for approximately 11% of methane emissions.
The most effective solution to reduce methane from solid waste is to reduce the amount of food and green waste being sent to landfill. This is primarily accomplished through food waste prevention and organic waste diversion programs. Organic waste that is not sent to landfill can be treated via composting or anaerobic digestion to reduce methane and generate co-benefits. Because the outputs of these treatment technologies are usable products like compost or biogas — which can be used as fuel or combusted to generate electricity — they align well with circular economy goals in place in many cities, regions, and countries.
For waste that has already been generated, emissions reductions can be achieved through the collection and combustion of gas produced within a landfill. Landfill gas can be flared to reduce emissions of methane, combusted to generate electricity, directly used as a heat source in boilers and furnaces, or upgraded to renewable natural gas and injected into pipelines. Effective collection of landfill gas requires control measures, including:
- A bottom liner to inhibit gas migration;
- An effective leachate management system that doesn’t interfere with landfill gas operations. Leachate is liquid formed when water passes through solid waste in a landfill and draws out chemicals and contaminants;
- Proper spacing and maintenance of wells based on an understanding of gas production and flow rates; and
- A cover or cap on top of the waste mass.
Improvements in operational practices and monitoring technologies can also increase the effectiveness of gas collection.
CATF is working to help countries around the world prioritize the waste sector in methane mitigation plans and goals. We advocate for regulations to tighten controls on landfill methane emissions and policies to improve organic waste management. We also support financial instruments and other solutions that can be utilized to scale-up mitigation and drastically reduce methane from solid waste on a global scale.
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