Fossil Fuels
The Hidden Climate Costs of Exporting US Liquefied Natural Gas
An exclusive Inside Climate News analysis found that a single year of greenhouse gas emissions from tankers carrying LNG from the United States more than cancels out the annual reductions achieved through driving all the electric vehicles currently on U.S. roads.
By Phil McKenna, Peter Aldhous
April 16, 2025
Energy Intelligence, a liquefied natural gas tanker, docks at Venture Global’s Calcasieu Pass LNG export terminal in Cameron, La. on Feb. 26 to refill its cargo holds before departing for Eemshaven in the Netherlands. Credit: Phil McKenna/Inside Climate News
Energy Intelligence, a liquefied natural gas tanker, docks at Venture Global’s Calcasieu Pass LNG export terminal in Cameron, La. on Feb. 26 to refill its cargo holds before departing for Eemshaven in the Netherlands. Credit: Phil McKenna/Inside Climate News
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CAMERON, La.—For a ship the length of nearly three football fields, Energy Intelligence seemed to turn on a dime. With tugboats pushing and pulling at its bow and stern, the 295-meter liquefied natural gas tanker pivoted 180 degrees in the brackish waters of the Calcasieu Ship Channel in late February, preparing to refuel for a trip to the Netherlands.
Its journey is part of a seismic shift that in the past decade has seen the U.S. go from an LNG importer to the world’s largest exporter, fueled by an ongoing boom in hydraulically fractured natural gas. New U.S. export terminals and expansions currently under construction will nearly double existing export capacity in the coming years, while even more projects have been approved.
Scientists have warned that LNG production involves significant greenhouse gas emissions at every step in the process, from methane leaks at wells to the burning of the gas by end users. But there’s been little attention to the impact of emissions from the tankers that ship LNG from the U.S. to other countries.
That too is substantial, an Inside Climate News analysis found. A single year of greenhouse gas emissions from tankers carrying LNG from the United States more than cancels out the annual emissions reductions achieved through all the electric vehicles currently on U.S. roads.
To estimate the climate pollution from vessels exporting U.S. LNG, Inside Climate News analyzed federal export data, information from the International Gas Union on the ships’ capacities and propulsion systems and ship tracking data supplied by the maritime analytics provider MarineTraffic.
The first-of-its-kind analysis totaled emissions for two one-year periods: between April 1, 2017 and March 31, 2018, shortly after large-scale exports from the U.S. began with the opening of the Sabine Pass export facility in Louisiana, and again between April 1, 2023 and March 31, 2024.
Inside Climate News found that total greenhouse gas emissions more than quadrupled from about 4.1 million metric tons of CO2 equivalent for 224 return journeys in 2017-2018 to around 18.4 million tons for 1,265 journeys in 2023-2024. To put the latter figure in perspective: It equals the annual greenhouse gas reductions from swapping 5.8 million gasoline-powered vehicles with an equal number of electric vehicles.
That’s around 50 percent more than all the light-duty EVs currently registered in the United States.
It’s “a big deal,” said Mark Brownstein, the Environmental Defense Fund’s energy transition senior vice president.
“Methane from human activities drives nearly a third of the warming that the planet is experiencing right now,” he said. “Every molecule of methane, whether lost at the well site, the pipeline, the ship or the power plant is working to accelerate warming at a time when the climate crisis is bearing down on countries around the world.”
The Inside Climate News analysis drew on methods described in a scientific study published in 2023, which accounted for the age of each ship, its specific propulsion system, the distance the tanker traveled, the capacity of its LNG tanks and the time each ship spent maneuvering and docked.
Importantly, these calculations accounted for both the release of CO2 from vessels’ engines and emissions of unburned methane that passes through the engines of tankers that are fueled by gas boiling off from their cargo tanks. Across the entire fleet involved in U.S. exports of LNG, this “methane slip” accounted for more than half of all CO2-equivalent emissions.
Video taken with an optical gas imaging camera reveals emissions of methane, and potentially other volatile organic compounds, being released from the smokestack of the Energy Intelligence liquefied natural gas tanker in Cameron, La. in late February. Carbon dioxide is typically released along with methane, however the OGI camera used doesn’t detect CO2. Credit: Oilfield Witness
Methane, the primary component of LNG, is the second leading driver of climate change after carbon dioxide. On a pound for pound basis, it’s far more effective than CO2 at warming the planet in the 20 years after it’s released. And because methane remains in the atmosphere for a relatively short amount of time compared to carbon dioxide, reducing methane emissions is widely viewed as the fastest way to combat climate change.
The portion of emissions from shipping is modest relative to the total climate pollution associated with LNG. A recent peer-reviewed study suggests that shipping accounts for 6 percent of LNG-associated greenhouse gas emissions, with the vast majority coming from production wells and end use, when gas is burned for heating or to produce electricity.
The study concluded that the total climate pollution associated with exported U.S. LNG is higher than that of coal produced in the importing countries. Natural Allies for a Clean Energy Future, a group that supports the natural gas industry, funded a July 2024 report that did not go through academic peer review and came to the opposite conclusion.
Putting the ICN finding in the context of vehicle use makes it all the more striking, said Ade Samuel, an energy analyst at the Natural Resources Defense Council.
“When you compare it to these numbers of the emissions released from gasoline-powered vehicles, I think it really gives you a sense for how significant the emissions of LNG on the full lifecycle basis are,” Samuel said.
The American Petroleum Institute, which represents the U.S. oil and gas industry, and Natural Allies for a Clean Energy Future both declined to comment on the ICN analysis.
Out of Sight, Out of Mind
While much has been made of methane releases at wells, pipelines and compressor stations in recent years, emissions of methane and CO2 from ships transporting LNG have gone largely unnoticed. Part of the reason is the physical distance of tankers at sea from human observers.
A gap in satellite capabilities is also partly to blame. Satellites can easily detect plumes of methane from oil and gas facilities on land, but the technique, which relies on bouncing light off the ground, has proved more challenging over water.
In addition, tankers passing through international waters occupy an accountability “no man’s land” when it comes to quantifying both the release of methane and CO2 from ships, said Alison Kirsch, a senior energy analyst for the Sierra Club.
“Shipping emissions are not really taken into account by either the exporting country or the importing country,” Kirsch said. “The shipping phase of emissions sort of falls to the wayside.”
The Inside Climate News analysis also revealed a secondary reason for the increased emissions in 2023-2024, beyond the rapid ramp-up in exports: Tankers are making longer journeys to countries in Asia and the west coast of South America, due to companies increasingly routing LNG vessels around the southern tip of South America or South Africa rather than passing through the Panama Canal. Drought–induced low water levels in the canal limited ship traffic through the waterway starting in early 2023.
One vessel bound for Singapore, meanwhile, turned around in the Mediterranean and headed around the tip of South Africa rather than passing through the Suez Canal in November 2023, shortly after Houthi rebels in Yemen began to attack international shipping in the Red Sea. GasLog Partners, the owner of the vessel, did not respond to requests for comment.