Non-CO2 Greenhouse Gases

Congressional Climate Camp 2023

Find out more about the briefings in this series below:

Budget and Appropriations

Public Polling on Climate Change

Non-CO2 Greenhouse Gases

Implementing the Inflation Reduction Act and Infrastructure Investment and Jobs Act

Ready to make a difference in climate policy? But not sure where to start? We have you covered. The Environmental and Energy Study Institute (EESI) invites you to join us for our start-of-the-new Congress briefing series, Climate Camp. We will go over the basics of the legislative process, highlighting key areas and opportunities for climate mitigation and adaptation policy. 

Although carbon dioxide (CO2) is the most commonly discussed greenhouse gas, there are many other gases that also contribute to global warming, including methane, nitrous oxides, and fluorinated gases. Our third session in EESI’s Congressional Climate Camp series discussed how these gases play a part in climate change, as well as solutions for limiting their effects. Presenters highlighted federal and international policy actions, including the Kigali Amendment to the Montreal Protocol, that address the warming potential of non-CO2 greenhouse gases.

Highlights

KEY TAKEAWAYS

Non-carbon dioxide (non-CO2) greenhouse gases are overlooked contributors to climate change. Reducing these emissions can deliver fast climate, economic, and health benefits. Half of all warming contributions today come from non-CO2 greenhouse gases. Cutting short-lived climate pollutants, including methane, hydrofluorocarbons, ozone, and black carbon, can avoid four times more warming by 2050 than decarbonization policies alone. The United States is a founding member of the Climate and Clean Air Coalition, an intergovernmental coalition of countries and non-state partners that have come together to scale up action to reduce black carbon and methane. RMI’s Oil and Gas Solutions Initiative, Climate TRACE, and Carbon Mapper are global mapping efforts that track methane, CO2, and other greenhouse gas emissions using satellite and country data. Measuring, monitoring, and quantifying emissions begins the process of tracking, accounting, and attributing them to certify and regulate emissions. For more information on this topic, read EESI’s article series on non-CO2 greenhouse gases.

 

Gabrielle Dreyfus, Chief Scientist, Institute for Governance and Sustainable Development

• Non-carbon dioxide (CO2) greenhouse gases are overlooked contributors to climate change. Reducing these emissions can deliver fast climate, economic, and health benefits.
• The Intergovernmental Panel on Climate Change’s (IPCC’s) 6th Assessment Report suggests that half of all warming contributions today come from non-CO2 greenhouse gases. Cutting short-lived climate pollutants, including methane, hydrofluorocarbons (HFCs), ozone, and black carbon, can avoid four times more warming by 2050 than decarbonization policies alone.
• Many of the processes emitting non-CO2 greenhouse gases also result in energy waste. This is particularly true of methane leaks, which amount to 110 million metric tons per year. Reducing methane leaks will lead to both climate and economic benefits.
• Nitrous oxides, methane, HFCs, ground-level ozone, and black carbon are all ‘super climate pollutants,’ meaning that they are tens to thousands of times more potent at trapping heat in the atmosphere than CO2.
• Short-lived climate pollutants remain in the atmosphere for less time after being emitted than CO2, which stays in the atmosphere for hundreds of years.
  • Methane resides in the atmosphere for 11.8 years,
  • Atmospheric HFCs have an average lifetime of 15 years,
  • Ground-level ozone has a lifetime on the order of weeks, and
  • Aerosolized black carbon lasts for only a few days.
• Because of their short lifetimes, reducing short-lived climate pollutants will have a much more immediate impact on global temperatures than an equivalent reduction of CO2.
• Effective climate policy should employ a dual strategy to simultaneously reduce both categories of greenhouse gases, with a sprint to cut short-lived climate pollutant output and a marathon to reach net-zero CO2 emissions.
• The 1987 Montreal Protocol is an effective example of an international policy that was primarily designed to address ozone-depleting substances, but also functions to reduce non-CO2 greenhouse gases. It phased out the production of chlorofluorocarbons (CFCs), which are non-CO2 greenhouse gases. The Kigali Amendment, ratified by the U.S. Senate in September 2022, calls for the phase out of HFCs (which replaced CFCs). This simultaneously reduces the risk of skin cancer by closing the ozone hole and helps avoid 1-2 degrees Celsius of warming from these gases.
• Continued use of HFCs in air conditioners and refrigerators means that even as production is phased down, millions of tons of the product remain in use and could be leaked into the atmosphere without sufficient management and recycling processes. A 2022 Environmental Investigation Agency report notes that lifecycle refrigerant management is an opportunity to cut the equivalent of 90 billion tons of CO2 emissions.

 

Susan Anenberg, Chair, Environmental and Occupational Health Department, Milken Institute School of Public Health, George Washington University; Director, GW Climate and Health Institute

• Short-lived climate pollutants are both climate-warming agents and health-damaging pollutants. Black carbon, in particular, contributes substantially to the burden of premature mortality around the world. Its global warming potential over 100 years ranges from 1,055 to 2,020 times that of CO2. Meanwhile, methane is both a greenhouse gas in its own right—86 times more potent than CO2—and a precursor to tropospheric ozone, which poses significant health risks as a component of smog. Because it can stay in the atmosphere for about a decade, methane’s impacts are rather evenly distributed around the world.
• The best resources for policymakers interested in the health consequences of air pollution are the U.S. Environmental Protection Agency's (EPA's) integrated science assessments.
• The only way to stay below the 2 degrees Celsius warming target [set by the Paris Agreement] is by mitigating both long-lived greenhouse gases, like CO2, and short-lived climate pollutants.
• Particulate matter, made up of black carbon, sulfate aerosol, and organic carbon, can have a variable effect on the climate. Organic carbon and sulfate aerosols have a cooling effect, but the more black carbon is present, the less the particulate matter has a  net cooling impact. The Clean Air Act has led to substantial reductions in sulfate emissions. While extremely beneficial for public health, this has also caused a loss of cooling potential.
• Diesel exhaust, biomass burned in cookstoves, and burning coal and biofuels are the largest sources of black carbon, meaning that developing countries are frequently the highest emitters. Mitigation options exist, including strategies like eliminating biomass cookstoves, using diesel particulate filters, and banning open burning of municipal waste. However, these efforts need to be scaled up globally.
• The United States is a founding member of the Climate and Clean Air Coalition, an intergovernmental coalition of countries and non-state partners that have come together to scale up action to reduce black carbon and methane. Over the past decade, they have seen rapid results, including partner cities transitioning municipal bus fleets from diesel to electric vehicles.

 

Debbie Gordon, Senior Principal, Climate Intelligence, RMI

• The IPCC found that climate warming from methane rivals that of CO2.
• The waste, oil, and gas sectors produced almost half of U.S. methane emissions in 2020. The livestock sector is responsible for about 36 percent of U.S. methane emissions.
• Natural gas is between 70 and 90 percent methane.
• Impurities are emitted with methane, including carcinogens such as benzene, toluene, xylene, and ethylbenzene.
• Methane is a climate issue, an air pollution issue, and an environmental justice issue.
• Modeling oil methane emissions challenges the notion that all oil has the same emissions profile, and the same is true for gas. The physical, chemical, and environmental properties of both gas and oil differ depending on their place of origin and how they are processed. Oil and gas must be analyzed to find the worst actors, worst oils, and worst gases to ensure that emissions are as effectively reduced as possible.
• RMI has modeled about 70 percent of the world’s oil and gas assets, which can be explored using the interactive tool, Oil Climate Index plus Gas (OCI+).
• Modeling finds that about half of oil and gas methane emissions are due to methane leakage; this gas leaking is indicative of environmental issues and of lost economic value.
• RMI’s Oil and Gas Solutions Initiative has expanded emissions visibility to drive decarbonization. Measuring, monitoring, and quantifying emissions begins the process of tracking, accounting, and attributing them to certify and regulate emissions. Other initiatives that complement this effort include Climate TRACE and Carbon Mapper, which are global mapping efforts that track methane, CO2, and other greenhouse gas emissions using satellite and country data.
• The oil and gas sector is the second-largest source of human-made methane, but more importantly, it has the highest potential for emissions reduction: methane’s economic value motivates companies to not leak it. Currently, over three percent of produced gas is leaked directly into the environment, and those leaks are more damaging to the climate than emissions from burning coal.
• There is a two-step approach to waste methane mitigation: first, develop decision-support tools that garner on-the-ground support, then develop policies to establish mandatory performance standards and create financial instruments.

 

Eric Davidson, Professor, Appalachian Laboratory, Center for Environmental Science, University of Maryland

• CO2 accounts for 79 percent of all greenhouse gas emissions, with methane making up 11 percent and nitrous oxides composing another seven percent. However, when examining the 20-year global warming potential of these gases, methane represents 24 percent of all warming.
• The agriculture industry is responsible for 15 percent of all warming, and emits 40 percent of all methane, 75 percent of all nitrous oxide, and 10 percent of overall emissions.
• Enteric methane, which is methane generated by the intestines of ruminants like cows and sheep, is a significant source of agricultural greenhouse gas emissions.
• Feed additives, such as 3-NOP or red seaweed, may be able to block some methane-forming enzymes in the ruminant digestive process. These could create up to a 30 percent reduction in per-cow methane emissions, but are not currently formulated for grazing animals, which is the majority of cows in the United States.
• Food production is extremely closely tied to nitrogen pollution. The nitrogen system in agriculture is a ‘leaky pipe,’ where humans only consume about 14 percent of the nitrogen put into crops and four percent of the nitrogen put into animal production. The rest of it goes directly into the environment as both water and atmospheric pollutants.
• Nitrous oxide emissions are growing far faster than even the worst IPCC projections. Current mitigation efforts are not working.
• There are four “Rs” that guide optimal fertilizer use on croplands in the United States: the right source, the right rate, the right time, and the right place. As a result, U.S. emissions are increasing only modestly even though food production has increased. But emissions are not going down.
• Research and development will help to reduce nitrous oxide emissions, including studying nitrogen fertilizers that are synthesized using renewable energy processes, crop breeding for greater nitrogen retention in root systems, and feeding livestock with synthetic amino acids as a substitute for nitrogen-intensive feed crops.
• Net-zero climate goals by 2050 require at-scale solutions to methane and nitrous oxide emissions by the year 2040. That means beta testing should be in place by 2030, giving a real urgency to the timeline of technological development.

 

Q&A:

 

Q: How can strategies to mitigate non-CO2 greenhouse gas emissions and other pollutants also deliver CO2 mitigation benefits and vice versa?

Dreyfus

• The same piece of technology, like an air conditioner, that is being redesigned to use alternatives to short-lived climate pollutants—such as low global warming potential HFCs—is the same air conditioner that can be made more efficient, reducing the electricity used to run the appliance, which reduces CO2 emissions.
• When we calculate the life cycle climate performance for air conditioner technology, it is necessary to look at both the emissions associated with the use of the appliance and the gas within the appliance.
• Around 70 to 80 percent of air conditioner emissions are associated with energy use.
• Today, most air conditioners are at the minimum efficiency allowed despite available technologies that would make them much more efficient.
• There are climate-friendly refrigerant alternatives that can improve air conditioner efficiency and handle humidity better.

Anenberg

• Anytime we burn anything, we are emitting CO2 as well as air pollution at the same time.
• There are many ways to reduce the amount of fuel that is burned in a variety of sectors.
• In the transportation sector, diesel trucks and buses emit black carbon and CO2. If we reduce the amount of diesel that is burned, then both CO2 and short-lived climate pollutants would be reduced.
• U.S. buses and trucks are relatively clean in terms of black carbon emissions, but electrifying buses would further reduce emissions of nitrogen oxides, CO2, and other air pollutants and improve public health.

Gordon

• The oil and gas sector uses a lot of its own product for production, shipping, processing, and refining. Stopping “stuff” from being burned, so oil and gas companies can sell it instead, applies heavily to this sector.
• If the natural gas and diesel used within this sector were replaced with renewable energy, the industry would make more profits while reducing CO2 emissions and the leakage of methane.
• In landfills, rotting organic material causes methane emissions, and the transportation of food waste to landfills contributes to CO2 emissions. A new culture around composting and reducing food waste would help reduce both methane and CO2 emissions.

Davidson

• Globally, the production of nitrogen fertilizers contributes about two percent of global CO2 emissions.
• If nitrogen fertilizer is used more efficiently, we can reduce CO2 emissions; the current technology to synthesize fertilizers is also energy-intensive.

Dreyfus

• To best address methane emissions, the United States needs to use targeted strategies—not just strategies that treat methane reduction as a co-benefit of targeting CO2.
• There are policies that target both, but methane-specific policies are important.

 

Q: What role does methane play as a precursor to ozone, and what other kinds of gases are involved in this process?

Anenberg

• Ozone is not emitted directly but instead is a secondary pollutant that is formed in the atmosphere by reactions of precursors [a compound that produces another compound when a chemical reaction occurs].
• To reduce ozone, we must consider its precursors that can be targeted.
• Methane produces ozone on a global scale.
• Nitrogen oxides and volatile organic compounds produce ozone on a regional scale.

Gordon

• Much of the equipment in operation to target ozone precursors was designed with the inaccurate belief that methane does not cause smog.
• With the knowledge we have now that methane does contribute to smog, there are opportunities to retrofit equipment and shut off legacy assets.

Dreyfus

• The atmosphere can oxidize chemicals like methane, which is how it gets removed from the atmosphere. The main molecule that does this oxidation is the hydroxyl radical, which you can think of as the atmosphere’s cleaning agent.
• This is important to understand in the context of broadening use of hydrogen. If we have a hydrogen economy that is leaky, that hydrogen is going to eat up the hydroxyl radical and reduce the overall oxidative capacity in the atmosphere, which would extend the lifetime of methane and other gases and increase their warming potential.

 

Q: What are the potential impacts of increased production and emissions of hydrogen on atmospheric methane?

Dreyfus

• We must consider how much hydroxyl radical—which reacts with both hydrogen and methane—is available in the atmosphere.
• The more gaseous hydrogen humans add to the atmosphere, the more hydroxyl radical it will react with. When there are fewer free hydroxyl radicals in residence in the atmosphere, the lifetime of potent greenhouse gases like methane will be longer and therefore they will have a greater warming potential.

Gordon

• Hydrogen leakage is a considerable problem that we have not surmounted.

 

Q: Which sectors will find it easiest to reduce non-CO2 greenhouse gas emissions? Which sectors will find it hardest?

Davidson

• The livestock sector is responsible for significant methane emissions, and solutions in this sector are essential to achieving U.S. methane reduction goals.
• There are promising technologies on the horizon for this sector, and the implementation of these technologies could also have co-benefits such as food security and economic productivity.

Gordon

• Carbon Mapper is launching the first two public-private, nonprofit satellites at the end of the year, and this satellite will analyze super-emitters that often go unnoticed.
• Certifying operations by acting as a third-party observer can provide validity to company and country commitments like achieving net-zero greenhouse gas emissions.
• The financial sector that lends money to industry is concerned about who they are in business with, which will provide a level of accountability.

Anenberg

• Both non-technical and technical solutions should be considered in tandem.
• There are ways to accomplish reductions in non-CO2 greenhouse gases that are not technical, such as changing diets and choosing to bike and walk over driving.

Dreyfus

• The United States needs to invest in and research methane removal.
• Counties need to move from voluntary frameworks such as the global methane pledge to sectoral agreements such as supporting low-emission methane and creating a market for stopping methane leaks.

 

Q: How has the shifting economics of oil and gas impacted methane venting?

Gordon

• Oil and gas are produced together as they are in the ground together but, historically, oil extraction systems have been designed to produce liquids to sell at a premium and discharge the gas into the atmosphere.
• Many offshore platforms are designed to vent their gas like this because methane is explosive when contained.
• However, gas is now poised to reach one trillion dollars in global trade next year, and it is increasing in value. This means it is much less likely to be leaked purposefully because producers can sell it and make a profit.
• With gas going global, more infrastructure is being built for gas. It must be built without leaks to ensure that this global infrastructure push does not release more gas into the atmosphere.

 

Compiled by Tyler Burkhardt and Lynlee Derrick and edited for clarity and length. This is not a transcript.