The World’s Most Potent Greenhouse Gas Has the Potential to be a Good News Story

By Lily Hartzell

Studying climate change is often an overwhelming experience. It can feel like every new piece of information is worse than the last, bringing us closer and closer to planetary devastation. It can be tempting to stop reading altogether, lest the next thing you learn take away all hope.

My capstone has been a happy exception to that pattern. I first learned about sulfur hexafluoride at a conference I attended in Beijing in 2019. The gas, known as SF6, is the most potent greenhouse gas (GHG) on earth. SF6 has 22,800 times CO2’s warming potential over a 100-year period, and it stays in the atmosphere for 3,200 years without degrading. SF6 is primarily used as an insulator in electrical equipment (70% of emissions come from the sector), entering the atmosphere when the equipment leaks or needs to be repaired. This presents a catch-22 for climate mitigation: the more electrical grids are expanded to accommodate renewable energy, the more SF6 will be emitted down the line. The EPA predicts that global SF6 emissions from electric power systems will increase 34% between 2015 and 2030.

My initial reaction was shock. After years of studying climate change, I had never even heard of this gas. It was particularly concerning to think about in regards to China. China is the source of 36% of the world’s SF6 emissions, but has no policies in place to regulate the gas. Its emissions of this gas are expected to increase 151% from 2015 levels by 2030, and by 2050 will be more than four times greater than 2015 levels under a business-as-usual scenario. This is largely due to sustained growth in the electricity transmission industry; which grew by an average of 5.7% per year between 2016 and 2021.

At the time I learned about sulfur hexafluoride, I was working as a freelance journalist focused on environmental issues, and I began to work on an article about SF6. Unfortunately, the pandemic got in the way and the article was never published.

Cut to last spring when I started working with Dean Gallagher to develop a capstone topic. I came back to SF6, hoping to use the skills I had developed in policy analysis to propose a solution. It turns out that what makes the gas so obscure--its concentrated use in one highly technical sector--also makes it low-hanging fruit for climate mitigation. Unlike carbon dioxide, which permeates every aspect of our economy and requires thousands of technical and policy solutions to mitigate, SF6 can be eliminated with just one or two interventions.

The problem is that China has not acknowledged that SF6 emissions are an issue and has shown no interest in regulating them. That does not mean the Chinese government cannot be convinced, however. China is looking for opportunities to capture clean tech market share and boost its international credibility on climate change. In fact, I believe SF6 could be a promising area for U.S.-China collaboration on climate action, something that has been stalled by wider political tensions in recent years.

The United States has successfully reduced SF6 emissions in the last couple decades. The EPA has reduced emissions through the voluntary SF6 Emission Reduction Partnership for Electric Power Systems, established in 1999. Program participants achieved 74% emission reductions between 1999 and 2016, even as SF6 capacity increased. California and Massachusetts have also implemented mandatory SF6 reductions. Both have policies in place to limit SF6 emissions to 1% or less per year for electrical equipment, and California is considering fully phasing out the gas after 2025.

The United States has shown that SF6 emissions reductions can be achieved at low cost, and this promise extends globally. The EPA calculates that China has 34% of global mitigation potential in 2030, much of which can be achieved at little to no cost through improved SF6 handling. 43% of global emissions can be eliminated for less than $20/t CO2eq.

Given this, I propose that the United States work with China and the other largest emitters of SF6 (South Korea, Saudi Arabia, India, and South Africa) to establish an international agreement to reduce and ultimately eliminate SF6 emissions. This should be done through a technical body, such as the Clean Energy Ministerial, to reduce potential for politicization and to allow the EPA to take the lead in sharing best practices for SF6 management. The countries should start by improving handling of the gas, a low-cost measure that can significantly decrease emissions. This will give the private sector time to commercialize and scale the SF6 alternatives already in development. By 2035, any new installations of transmission equipment that includes SF6 should be banned.

Diving into SF6 and ultimately writing a memo proposing a mini-multilateral agreement to address it has been a more hopeful journey than I might have guessed. Here is a problem we can solve: eliminating emissions would be equivalent to taking 100 million cars off the road. Failing to do so will lock in warming for thousands of years to come.

Lily Hartzell is a MALD candidate at the Fletcher School at Tufts University.