Methane Matters: Let's Learn Why • L I B R A R Y

What is methane?

Methane is the main component of “natural gas,” which is a significant source of heat and energy in the U.S. and globally. It is a colorless, odorless gas that is lighter than air and is chemically composed of one molecule of carbon and four molecules of hydrogen. Methane is generally stable but can be explosive if enough mixes with air. Because of its potential for combustion, natural gas utilities add scents to it as a safety feature.

What does it do to our climate?

Methane is a potent greenhouse gas. Anthropogenic methane emissions are likely responsible for 0.5° C of warming since the industrial revolution. After carbon dioxide, it is the most abundant greenhouse gas in our atmosphere.

Methane has an atmospheric lifespan of about 12 years before it oxidizes and turns into water vapor and carbon dioxide. In contrast, carbon dioxide will stay in the atmosphere for about 100 years. However, the same amount of methane will have a much stronger warming effect because it is more efficient at trapping radiation. Pound per pound, the impact of methane is 28 to 34 times greater than carbon dioxide over a 100-year period. But measured over a 12-year period, it traps atmospheric heat 87 times more effectively than carbon dioxide.

Methane can also react with other chemicals in the air to form ground level ozone, the primary component of smog, which is another powerful greenhouse gas.

Where does it come from?

Methane occurs both in nature and as a product of human activities. In nature, methane is produced by decomposition of plant matter in the wetlands and, to a smaller degree, by termite digestion, volcanoes, and vents in the ocean floor. However, globally, 50-65 percent of total methane emissions come from human activities, which include energy, livestock and other agriculture, land use, and waste management.

Methane gas generates electricity when used in steam and gas turbines. In 2020, methane gas was the largest of all the fossil fuel sources used for electricity, accounting for about 40 percent of electrical generation in the U.S. Recent studies suggest that methane leaks subsequent to energy production are more prevalent and more serious than previously thought. Methane is also found subsequent to other energy production, specifically in oil fields and coal basins, where it is sometimes intentionally “vented” or “flared” into the atmosphere during oil or coal extraction.

Livestock emissions, including manure, account for roughly 32 percent of anthropogenic methane emissions. With the global population approaching 10 billion, the demand for animal protein is expected to increase by up to 70 percent by 2050, so methane emissions from livestock are likewise expected to grow.

Agricultural methane emissions come from plants that are cultivated using flooding, such as rice paddies. Flooded fields prevent oxygenation of the soil beneath, creating the ideal conditions for methane-emitting bacteria. This accounts for another 8 percent of human-caused methane emissions.

Methane emissions from the waste sector account for 20 percent of human-generated methane. Roughly one-third of the food produced for human consumption is thrown away and ends up in landfills. If food waste was its own country, it would be the third-largest emitter of greenhouse gasses, behind only China and the U.S.

How does the drilling and production of natural gas affect the land and water?

Drilling a natural gas well on land, a process known as hydraulic fracturing or fracking, disturbs the ecosystem around the well site. Fracking requires large amounts of water that may affect aquatic habitats and the availability of water for other uses. It produces large volumes of contaminated wastewater at the surface, which requires treatment or injection back into the earth. The drilling activities themselves produce air pollution.

How does methane affect human health?

Methane poses immediate hazards to health when burned indoors in furnaces and stoves. In addition to releasing carbon when it burns, it produces a range of pollutants, particularly when unvented. These include particulate matter, nitrogen dioxide, carbon monoxide, and formaldehyde.

A meta-analysis of 41 studies found that children living in homes with gas stoves had a 42% higher risk of experiencing asthma symptoms, and, over their lifetime, a 24% increase in the risk of being diagnosed with asthma. Children are more susceptible than adults to the effects of nitrogen dioxide as well, which may cause learning deficits, lung infections, cardiovascular illness, and allergies.

In addition to the pollutants created when natural gas burns, a recent study suggests that methane and nitrogen oxides leak from gas stoves. Surprisingly, about 75% of emissions occurred while the stove was off, and were not related to how old or costly the appliance was. The researchers determined that leaking from gas stoves inside U.S. homes has the same climate impact as about 500,000 gasoline-powered cars.

Ground-level ozone, formed from methane, has been linked to one million premature deaths per year.

Methane poses safety risks as well due to its explosive ability. Explosions due to methane have been frequent in coal mines and collieries and have been the cause of many mine disasters.

What would reducing methane emissions do?

Because methane is a short-term driver of climate change, reducing methane emissions now would have fairly immediate impacts and is critical for maintaining global warming below 1.5°C. A global methane assessment (GMA) from the United Nations Environment Programme says that cutting methane emissions by nearly half within the next decade would prevent a 0.3°C rise in the average global temperature in two to three decades. Every year, the subsequent reduction in ground-level ozone would also prevent 260,000 premature deaths, 775,000 asthma-related hospital visits, 73 billion hours of lost labor from extreme heat, and 25 million tons of crop losses. Every ton of methane reduced would provide $4,300 in benefits. The authors of the most recent assessment of the Intergovernmental Panel on Climate Change made clear that of the many priorities for policymakers, few are more urgent than reducing methane emissions.

How much methane can we reduce?

The GMA found that human-caused methane emissions could be reduced by as much as 45 percent within the decade and could be one of the most cost-effective strategies to rapidly reduce the rate of warming.

How do we do it?

The GMA has identified targeted measures that are currently and readily available in the fossil fuel, agricultural, and waste sectors. Roughly 60 percent of these available measures have low mitigation costs, and just over 50 percent of those have negative costs, meaning the measures pay for themselves quickly by saving money.

In the fossil fuel sector, methane can be reduced at both the point of emission and along production/transmission lines relatively easily through leak detection, repair, and recovery of vented gas. Incentives can be used to expand the use of wind, solar, and hydro power for electricity generation. Incentives and standards can also be used to improve the energy efficiency of household appliances, buildings, lighting, heating, and cooling. Consumer awareness of cleaner energy solutions can be improved.

In agriculture, targeted changes in human behaviors are particularly important due to the limited potential of technological measures to reduce methane emissions in this sector. These behavioral changes include the adoption of healthy diets low in meat and dairy content, improved methods for the management of livestock and manure, improved management of rice paddie watering and drainage, and discontinuing crop residue burning.

Waste management can be improved by reducing food waste at the retail and consumer level, reducing food loss along production and supply chains and donating excess food. Methane produced from organic waste can be captured in what are called methane digesters and can be used as a source for electricity and heat. Although this is not a perfect system, compared to the process this waste would undergo in a landfill, the captured methane means there is less of an impact on the environment. Wastewater treatment can also be upgraded to capture and utilize methane in a similar manner.

What is the takeaway?

Urgent steps must be taken to reduce methane emissions this decade, which could rapidly reduce the rate of warming. Given the wide range of health, economic, and environmental impacts from methane, the benefits of acting now are numerous and far outweigh the costs. The existence of readily available, low-cost, targeted measures and methane’s short-lived atmospheric lifespan means significant climate and clean air benefits can be achieved by 2030 if we act now.