In late February, the 295-meter LNG tanker Energy Intelligence made a sharp 180-degree turn in the Calcasieu Ship Channel, preparing for a journey to the Netherlands. This maneuver marked just one step in a larger trend: the U.S. has rapidly transitioned from an LNG importer to the world’s top exporter in the past decade. This shift is driven by a boom in hydraulically fractured natural gas, with new export terminals under construction expected to nearly double the country’s LNG export capacity in the coming years.
However, experts warn that while the production of LNG itself generates significant greenhouse gas emissions—due to methane leaks at wells and the eventual burning of the gas—less attention has been paid to the environmental impact of the tankers transporting LNG. A new analysis by Inside Climate News reveals that the emissions from U.S. LNG tankers are also substantial, surpassing the annual emissions reductions achieved by all the electric vehicles on U.S. roads.
The analysis estimated the climate pollution from LNG tankers using federal export data, ship capacity and propulsion information from the International Gas Union, and maritime data provided by MarineTraffic. It examined emissions during two one-year periods: April 1, 2017 to March 31, 2018, and April 1, 2023 to March 31, 2024, after large-scale U.S. exports began in 2016 with the opening of the Sabine Pass facility in Louisiana.
The findings showed that emissions from LNG tankers more than quadrupled—from 4.1 million metric tons of CO2 equivalent during 224 round-trip voyages in 2017-2018 to 18.4 million tons for 1,265 trips in 2023-2024. To put this into perspective, these 2023-2024 emissions are equivalent to the annual reductions achieved by replacing 5.8 million gasoline-powered vehicles with electric ones—roughly 50% more than the total number of light-duty electric vehicles currently registered in the U.S.
Mark Brownstein, Senior Vice President of the Environmental Defense Fund, called these findings a “big deal,” emphasizing that methane emissions are responsible for nearly a third of the planet’s current warming. He added, “Every molecule of methane, whether lost at the well site, the pipeline, the ship, or the power plant, is accelerating global warming.”
The analysis used methods from a 2023 scientific study that took into account each ship’s age, propulsion system, distance traveled, LNG capacity, and the time spent maneuvering and docked. Importantly, it also considered the release of CO2 from tanker engines and the emissions from unburned methane that escapes through the engines of vessels fueled by gas boiling off from their cargo tanks. This “methane slip” contributed to more than half of all CO2-equivalent emissions across the U.S. LNG export fleet.
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