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Methane Pollution is the emission of methane from anthropogenic and natural sources on Earth. Methane pollution is of particular interest because it is one of the atmosphere's most potent greenhouse gases and because of its impact on climate change.

Methane pollution can come from a variety of sources including coal mining and burning, natural gas, petroleum extraction, agriculture, rice cultivation, biomass burning, landfills, human waste, wetlands, termites, and the oceans. Approximately 71% of methane pollution globally is from anthropogenic sources.

History

Starting in 100 B.C. and going to 1600 A.D. there was a steady increase in atmospheric methane. This 31 million tons per year increase has been attributed to human activity. The Roman Empire and other civilizations were growing and started to domesticate cows, goats, and sheep. The Han Dynasty in China was also growing and increasing its rice production. Both livestock and rice paddies emit methane, thus the increase in atmospheric levels. Then with the industrial revolution, methane levels rose exponentially.

Main Sources

Natural Gas, Petroleum Systems, and Coal Mining

Coal production and burning, combined with natural gas and petroleum production, make up the largest anthropogenic source of methane.

These systems together make up approximately 19% globally. Much of the methane pollution from natural gas and petroleum systems is a byproduct of hydraulic fracturing and natural gas extraction, in which methane is the main component. This is due to methane being leaked unintentionally or sometimes intentionally to reduce pressures in the system. Overall emissions methane emissions from 1990 to 2009 experienced a decrease due to advances in efficiency.

Methane released from coal mining is sourced from underground mining, surface activities, and post-mining activities. These sources declined in emissions from 1990 to 2002 due to natural gas consumption, but have remained steady since then.

Enteric Fermentation

Enteric fermentation makes up approximately 16% of methane emissions globally. Enteric fermentation is essentially belches and flatulence that comes from ruminant animals, or animals with a dual stomach to allow for digestion of cellulose-enhanced plants and grains, such as cattle. The vast majority of enteric fermentation in the United States (95%) comes from beef and dairy cattle. These emissions increased 33% from 1984 to 2004 in developing nations.

Rice Cultivation

Rice cultivation makes up 12% of methane pollution, although it makes up approximately 50% of the global population's primary food. The rice paddy is essentially a man-made wetland, which is an environment particularly beneficial to the growth of methane-producing microbes which decompose organic matter.

Biomass Burning

Biomass burning makes up approximately 8% of methane pollution globally. It mostly stems from large scale burns of woodlands, savanna, and agricultural waste. The burning of biomass may be done for shifting agricultural use and to control the growth of grass, weeds, and litter. Some populations in developing countries also use biomass burning as a fuel and heat source.

Solid Waste and Landfills

Solid waste and landfills contribute 6% to methane production globally. This happens when microbes act upon the waste and breakdown the materials. The gas emitted from landfills as about 50% methane and 50% carbon dioxide. Fortunately, there are many solutions for recapturing of this gas to reuse it as a heat or fuel source.

Human Sewage and Wastewater

Human sewage and wastewater make up 5% of methane pollution globally. This is most prevalent in developing counties with little or no collection and treatment of wastewater. The biggest methane producers from this source include China, Nigeria, Mexico, and India.

Animal Waste

Animal waste makes up 5% of global methane pollution. This is mostly associated with industrial and automated dairy and swine farms that use liquid manure management systems, which is cheaper than solid management systems. This is most prevalent in the United States, where is makes up 9% of the annual methane emission. Liquid manure systems make up 80% of manure emissions despite being a much smaller proportion.

Wetlands are the largest source of Methane globally.

Natural Sources

Wetlands are the greatest contributor to methane emissions, both naturally and anthropogenically, giving off 22% of global emissions. This is due to the abundant organic matter in wetlands anaerobically decomposed by methanogens.

Termites make up 4% of global methane emissions. Their consumption of cellulose results in their giving off of methane. They are mostly concentrated in tropical grasslands and forests.

Oceans make up 3% of global methane emissions due to methane emitting microbes that can be found in organic-rich sediments.

Environmental Impacts

Large Scale

In the environment, methane is a green house gas. Behind carbon dioxide, methane is the second most emitted green house gas, however it is more dangerous. Its global warming potential is 25 times more than carbon dioxide. This heightened danger lasts a shorter period of time as methane only lasts in the atmosphere 12 years before it breaks down. At first, 1 pound of methane emitted into the atmosphere is equivalent to 25 pounds of carbon dioxide, but over time the warming potential for methane decreases.

Compound	Emissions %	Lifetime (years)	100 Year Global Warming Potential
Carbon Dioxide	82%	30-95	1
Methane	10%	12	25
Nitrous Oxide	5%	114	298
Fluorinated Gases	3%	Large Range	Large Range

Small Scale

Landfills release large amounts of methane gas as waste decays. Any large methane gas buildup can pose an explosion hazard, which can damage the surrounding environment as well as force mandatory evacuations in at-risk areas. There is also risk of methane leakage into streams and other water sources from these landfills. Any leakage can cause disease, eutrophication, and other environmental problems. Locally increased levels of methane also contributes to background tropospheric ozone levels. This can raise local temperatures and pose health risk, especially near the equator.

Anthropogenic Mitigation Efforts

Presently, most efforts to decrease methane emissions _target four key industries: oil and gas, agriculture, landfills, and coal mines. Methane gas that would have otherwise been emitted into the atmosphere is instead captured - usually requiring relatively newer technology. Because methane is the primary component of natural gas, this recovered methane can then be used for power generation, heating or manufacturing. This strategy reduces greenhouse gas emissions directly, by capturing the methane that would otherwise have been released into the atmosphere; and indirectly, by then using that to generate power - replacing the demand for power that would likely otherwise have been derived from sources that emit greenhouse gases, like coal or oil. In this way, the recovery and productive use of methane emissions can be important in mitigating climate change.

Policy and Legislation

Strategy to Reduce Methane Emissions

This is a U.S. methane mitigation plan released in March 2014 as part of the Obama Administration’s Climate Action Plan. It aims to cut methane emissions the four key sectors, as well as improve methane monitoring and measurement.

Oil and Gas

In a subsequent January 15th report, the Obama Administration announced a goal to decrease methane emissions from this sector by 40-45 percent from 2012 levels by 2025.To reach these cuts, the EPA is currently in the process of creating methane standards for new and significantly modified oil and gas production sites, as well as for gas processing and transmission sites. The EPA has said these rules will be proposed in 2015, and after a public comment period will be finalized in 2016. The agency plans to suggest certain technology upgrades and best practices to that can efficiently recover methane from venting and leaks across the oil and gas supply chain, such as those at oil well completions, pneumatic pumps, well sites, gathering and boosting stations and compressor stations. Since the report has been published, the Department of Energy has hosted a series of roundtable discussions with various stakeholders to discuss how to modernize the natural gas transmission and distribution systems to reduce methane emissions. Culminating in July 2014, these meetings produced an Initiative to Modernize Natural Gas Transmission and Distribution Infrastructure which includes an action plan for industry and stakeholders.

Agriculture

This section of the strategy is completely voluntary (devoid of regulations) and primarily encourages the adoption of biogas technology, also known as ‘biodigesters.’ These facilities anaerobically digest manure - recovering the methane that would have otherwise been emitted in order to produce biogas. Biogas contains 50-70 percent methane, and is a renewable energy source. Power generated by biogas can be used on site or sold to generate revenue. The EPA released a “Biogas Opportunities Roadmap” in August 2014, a collaboration between the USDA, EPA, DOE and the dairy industry. It found ample opportunity for biogas systems in the U.S. - currently there are only 239 livestock biodigesters in action, which alone produce enough energy to power the equivalent of 70,000 average American homes and reduce methane emissions equivalent to 2 million metric tons of carbon dioxide. Yet there is potential for at least 11,000 additional systems to be implemented. If realized, the EPA poses that enough energy to power more than 3 million American homes could be produced, and methane reductions would be equivalent to 4 to 54 million metric tons of carbon in 2030. The roadmap also explains how agencies will promote biogas utilization, strengthen biogas markets and improve interagency and industry communication surrounding biogas technology.

Landfills present a valuable opportunity for methane pollution mitigation

Landfills

The strategy aims to reform landfills to encourage better capture of the methane emitted, which can then be used as an energy source. In June 2014, the EPA proposed updates to the current (1996) standards for new municipal landfills (New Source Performance Standards), as well as opened up public comment on updating the guidelines of existing sources. The finalized updates are expected sometimes this year.Landfill gas that is captured can be used for electricity and/or heat generation. To capture the methane, landfills may need to install a gas collection system that could include with wells, wellheads, piping, trenches, blowers, flares, and a gas treatment system.

Coal Mines

Compared to the three other key sectors, less action has been taken thus far in mitigating methane emissions from coal mines. However in April 2014 the Bureau of Land Management began accepting public comment on a proposed program that would capture, sell and/or dispose of waste mine methane from mines on federal land. No update on the status of this program is available. Internationally, waste mine methane is used for power generation, district heating, boiler fuel, town gas, and is sold to natural gas pipelines. In the U.S., it is injected straight into the natural gas pipeline system.

Monitoring and Measurement

A major component of the strategy is to improve accuracy in the monitoring and measurement of methane emissions. The plan aims utilize both bottom-up methods which measure emissions from specific sources and activities, and top-down approaches that analyze atmospheric methane concentrations. The U.S. emissions are recorded in a bottom-up inventory called the Greenhouse Gas Inventory (GHGI), which includes activity factors (e.g. number of gas wells), emissions factors (e.g. emission levels per well), and reductions data (e.g. number of devices or technology that reduce emissions). The strategy aims to strengthen this program. Since the strategy was released, the Department of Energy has kickstarted an initiative to develop low-cost, highly sensitive technologies to measure methane emissions from oil and gas sources. The agency has made $30 million available and has selected 11 projects to focus on. Efforts are also being made to strengthen our national monitoring network through the National Oceanic and Atmospheric Administration (NOAA) by expanding infrastructure. Further, NOAA, the World Meteorological Organization, NASA and the DOE are working together to compile the largest network of greenhouse gas measurements. Updated publications of measurements and projections will be continually released.

EPA Voluntary Partnership Programs

The EPA has established voluntary partnership programs that encourage industry to adopt the technologies needed for methane capture and emission reduction. Being a partner in these partnerships also includes reporting of methane emission levels, as well as which technologies are being utilized, in order to share knowledge and information amongst partners. There is a program to correspond with each of the four key sectors: Natural Gas STAR, AgSTAR, Landfill Methane Outreach Program and Coalbed Methane Outreach Program. In recent developments, the EPA has said it has plans to expand on the Natural Gas STAR program in 2015 by initiating new stakeholder partnerships.

Global Methane Initiative

This is a voluntary, multilateral partnership program founded by the U.S. EPA in 2004 that encourages mitigation of emissions by capturing methane and subsequently using it for power generation. Currently 43 countries are partners to the program, representing 70 percent of global emissions. By joining, nations agree to 1) identify cost-effective opportunities to recover methane emissions for energy production, 2) address legal, regulatory, financial and institutional barriers to project development, and 3) foster cooperation amongst Partner countries and the private sector.

Voluntary Industry and Business Actions

Methane Flaring

Flaring in North Dakota

Methane and other gases are emitted from oil wells when drilling for natural gas and oil. It is either too expensive to capture and recover these gases, or the technology doesn't exist and it is too difficult. The leaking gas is instead flared to burn some of it off. This still releases methane into the atmosphere, just not as much as could be without flaring. However, it is estimated that 40% of lost gas could be recovered with existing technologies. Flaring is also used when building a new drill site to reduce any explosion risk.