Total methane emissions have declined since 1991, but methane emissions from livestock are up

The recently passed Inflation Reduction Act includes a number of provisions meant to reduce greenhouse gas emissions in the US.

Part of that effort is $29.6 billion in funding for programs directly related to reducing methane emissions.

As a greenhouse gas, methane is 25 times as effective as carbon dioxide at trapping heat in the atmosphere. It’s the second largest source of greenhouse gas emissions in the US, after carbon dioxide.

What is methane and why is it harmful to the environment?

Methane^[1] is a gas that comes from a variety of both natural and human-influenced sources. The gas plays a role in some natural processes of digestion and decay. Natural gas is also mostly made of methane.

As a greenhouse gas, methane in the air can trap heat within the earth’s atmosphere and affect the earth’s temperature and climate.

Because some greenhouse gases are more potent than others, the Environmental Protection Agency (EPA) standardizes the way it measures greenhouse gas emissions. Instead of reporting the actual volume of emissions for each gas, it tracks the volume of carbon dioxide that would have the same effect on the atmosphere. This means that one metric ton of methane would be reported as about 25 metric tons of carbon dioxide equivalent, since methane is more potent.

Methane emissions account for about 11% of the nation’s greenhouse gas emissions.

How much methane is released in the US?

According to the EPA, the US emitted 650 million metric tons (MMT) of methane^[2] in 2020, 17% lower than in 1991. Methane emissions dropped at a faster rate than total greenhouse gas emissions, which declined 7% over the same period.

While methane emissions dropped between 1991 and 2020, the country’s population increased by 31%. This means that on a per-person basis, methane emissions are 37% lower than in 1991.

Despite this decline in methane emissions, the EPA says that atmospheric concentrations of the gas are still more than twice what they were 200 years ago.

What are the biggest sources of methane emissions?

The top three sources of methane emissions in the US are enteric fermentation in livestock, natural gas systems, and landfills. Together, these sources account for 67% of all methane emissions.

Enteric fermentation is part of the digestive process of some animals, including cows, buffalo, sheep, and camels. Bacteria in the stomach and large intestine cause fermentation that helps these animals digest certain plants that other animals can’t digest. Methane is a byproduct of this process and is exhaled, belched, or excreted. The amount of methane produced is affected by factors such as the type and amount of feed used, how often animals are fed, and the animals’ health and activity levels.

Methane is also created during the production of natural gas and petroleum. It’s produced during the decomposition of municipal solid waste in landfills or wastewater treatment facilities. Methane is also released as a byproduct of coal mining, rice cultivation, and some fossil fuel combustion.

The top eight sources^[3] of methane accounted for 94% of all methane emissions in 2019, the most recent year for which data broken down by source is available.

Most of the decline in methane emissions between 1991 and 2019 came from declines in emissions from landfills (down 35% since 1991), coal mining (down 51%), and natural gas systems (down 14%). Emissions from some methane sources, including enteric fermentation and manure management, have increased since 1991.

Which states have the highest methane emissions?

Wyoming, West Virginia, North Dakota, and South Dakota all had methane emissions in 2019 of higher than 10 metric tons per person.

The largest source of methane varies for the states with the most emissions.

For example, coal mining plays a large role in Wyoming and West Virginia’s methane emissions. In contrast, South Dakota’s methane emissions come primarily from livestock.

The top four states are part of a broader group in the middle of the country where methane emissions are higher than the rest of the US. Some of these states create an identifiable strip running from around Montana and the Dakotas down to Oklahoma and Texas. Oil or gas extraction, mining, or agriculture are major parts of the economy in this group of states. Each of those sectors is connected to methane emissions.

States in this group emitted 5.1 metric tons of methane per person^[2] in 2019, compared with 1.3 metric tons per person for all other states.

What does the Inflation Reduction Act do to address methane emissions?

The reconciliation bill passed by Congress in August 2022 explicitly addresses methane emissions through provisions costing about $30 billion between 2022 and 2031. The funds are focused on four areas: agriculture, natural gas and petroleum, electricity generation, and general regulations.

The bill allows the Secretary of Agriculture to fund diet and feed management projects to reduce livestock methane emissions. It also pays agricultural facilities for achieving environmental outcomes. It charges fees on methane emissions exceeding certain thresholds. It also assists in purchasing agricultural conservation easements, or agreements for landowners to give up the right to certain types of development on their property to achieve certain conservation purposes^[4]. These programs will cost a total of $18.1 billion through 2031.

Relating to natural gas systems, the reconciliation bill creates a methane emissions and waste reduction incentive program for petroleum and natural gas systems. The bill appropriates $1.6 billion to the EPA to provide financial and technical assistance to owners and operators of natural gas and petroleum facilities to help them in monitoring and reducing greenhouse gas emissions. It also instructs the EPA to collect fees on methane emissions from petroleum and natural gas facilities that exceed certain thresholds.

The bill appropriates $9.7 billion for loans or other financial assistance to rural electric systems to achieve the greatest possible reduction in methane and other greenhouse gas emissions. It also provides $320 million in funding for general methane emissions monitoring and makes properties that capture methane for use as renewable energy eligible for a business energy investment tax credit.

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