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Are there risks to transporting carbon dioxide in pipelines?

CO2 pipeline accidents have been rare, but as with pipelines carrying oil, natural gas, or hazardous chemicals, if ruptures are allowed to happen they can be very serious.


July 10, 2024

The United States is currently home to about 5,000 miles of pipelines that carry carbon dioxide around the country (compared to about 3 million miles of pipeline for natural gas).1 Today, CO2 is mostly transported for oil and gas drilling: companies pump CO2 underground to loosen more fossil fuels from the ground, a tool called “enhanced oil recovery.” But if many more CO2 pipelines are built in the future, it will likely be because they can help address climate change. CO2 is a climate-warming greenhouse gas, and through a technology called carbon capture and storage, it can be collected from smokestacks or removed from the air itself. We can then transport this CO2 through pipelines to storage locations, and bury it underground where it won’t warm the planet.

Are these CO2 pipelines safe? “​​Nothing is risk-free. But we have lots and lots of pipelines criss-crossing the United States,” says Howard Herzog, a Senior Research Engineer at the MIT Energy Initiative. “Compared to at least the materials in those pipelines, transporting CO2 is relatively safe.” The U.S. maintains about 75,000 miles of pipelines that carry other hazardous liquids, including toxic or flammable ones like ammonia and propane, and more than 84,000 carrying crude oil.2

Researchers have found that the failure rates for CO2 pipelines are similar to those for pipelines carrying oil and gas—which is to say, failures are relatively rare, but are worth taking serious precautions to prevent. From 1986 to 2021, the U.S. recorded around three accidents related to onshore CO2 pipelines per year.3 (Although it’s important to remember that our small network of CO2 pipelines means we have limited safety data.) And while big ruptures could release large amounts of CO2, which would be both dangerous to people and a problem for the climate, the data shows smaller leaks have been much more common. From 1994 to 2021, leaks accounted for 48 percent of CO2 pipeline incidents while ruptures accounted for 3 percent.3

Serious ruptures can happen, though—for instance, if a natural disaster, like an earthquake or flood, disrupts the integrity of a pipeline. This is what happened in the only mass-exposure event from a CO2 pipeline failure to date, when a landslide damaged an underground pipeline carrying CO2 near the village of Satartia, Mississippi, in 2020.

If a pipeline is compromised, CO2 can leak from it. CO2 is transported at high pressures in a “supercritical” liquid phase, but in the open air, it turns to gas as it rushes out of a ruptured pipe. Dry ice—the solid form of CO2—may also form at the opening, which could further damage the pipeline.

As a gas, carbon dioxide is heavier than air. When large amounts of it are released, it hugs the ground and can displace oxygen—including in people's lungs. “The biggest risk is it being an asphyxiant,” says Herzog. Whether that happens depends on the amount of CO2 that escapes, the landscape of the region, and the weather. In addition to asphyxiation, breathing in concentrated CO2 can cause headaches, dizziness, sweating, increased heart rate, and other maladies. If people can get to fresh air, these symptoms typically pass (although treatment with oxygen is recommended)—but if high levels of CO2 sit in low-lying areas on a windless day, or build up indoors, people could be hurt or killed. After the rupture in Satartia, forty-five people went to the hospital for treatment.

If other substances are mixed with the CO2, that can also present dangers. The rupture that impacted Satartia, for instance, also released hydrogen sulfide, a toxic chemical that can cause convulsions, coma, and even death. “I think with high probability it was the hydrogen sulfide that sent people to the hospital,” says Herzog. “Patients reported a green gas and rotten egg smell, which could only be hydrogen sulfide, and this is a highly toxic chemical. Fortunately, CO2 pipelines carrying toxic materials are the exception, not the rule. As CO2 pipelines get built for carbon capture and storage, as opposed to enhanced oil recovery, there will be no reason to transport toxic chemicals in them.”

In April 2024, another section of CO2 pipeline in Mississippi, owned by the same company as the Satartia pipe, also failed, though the cause is still being investigated.

Building CO2 pipelines far from people, and ensuring emergency procedures are in place, can reduce risks if ruptures do happen. Prior to the rupture in Satartia, there had been one injury associated with carbon pipelines in the U.S. in the last two decades.4

Regulations and careful management can also help make pipelines as safe as possible, says Herzog. Operators must “dry” CO2 and monitor it for impurities, including even water, before it enters a pipeline, so that reactions in the pipe don’t produce acids that may cause corrosion.5 Checking valves and fittings regularly should let companies know whether equipment is damaged or leaking. And regulators have a responsibility to make sure companies follow these practices, monitor for leaks, and accurately report them. (Research has shown oil and gas pipeline leaks across the U.S. have gone undetected in the past.6)

As carbon capture becomes more common, companies are expected to build out many more pipelines—up to 66,000 miles of them by 20507—to ferry CO2 around the country. To avoid future failures, the U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration recently began the process to create new rules for CO2 pipelines and emergency preparedness.8 Those regulations will be important, because many scientists agree we will need to remove some carbon from the atmosphere to meet the world’s climate targets and minimize the harms of climate change. The transport of carbon for underground storage will need to be safe and effective at scale if we expect to include carbon removal in our toolkit of climate solutions.


Thank you to Hans of Sydney, Australia, for the question.

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1 "Natural Gas Explained." Energy Information Administration, March 2024.

2 "Annual Report Mileage for Hazardous Liquid or Carbon Dioxide Systems." U.S. Department of Transportation, Pipeline and Hazardous Materials Safety Administration, July 2024.

3 Vitali, Matteo et. al, "Statistical analysis of incidents on onshore CO2 pipelines based on PHMSA database." Journal of Loss Prevention in the Process Industries, Volume 77, July 2022, doi:10.1016/j.jlp.2022.104799

4 Parfomak, Paul W., "Carbon Dioxide Pipelines: Safety Issues." Congressional Research Service, June 2022.

5 Hoa, Le Quynh et. al, "On the Corrosion Mechanism of CO2 Transport Pipeline Steel Caused by Condensate: Synergistic Effects of NO2 and SO2." National Library of Medicine, Volume 12, Issue 3, February 2019, doi:10.3390/ma12030364

6 Sherwin, Evan D. et. al, "US oil and gas system emissions from nearly one million aerial site measurements." Nature, Volume 627, March 2024, doi:10.1038/s41586-024-07117-5.

7 Larson, Eric et. al, "Net-Zero America: Potential Pathways, Infrastructure, and Impacts." Andlinger Center for energy + the environment, Princeton University, October 2021.

8 "Pipeline Safety: Safety of Carbon Dioxide and Hazardous Liquid Pipelines," Office of Information and Regulatory Affairs, 2023.