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Study: GHG emissions from burning LNG higher than from coal

13 November 2023

A new study authored by Robert Howarth at Cornell University—one of the world’s premier methane scientists—shows that GHG emissions from burning liquefied natural gas (LNG) are at least equal or much higher than those from coal, depending on the LNG transportation scenario.

The paper, titled The Greenhouse Gas Footprint of Liquefied Natural Gas (LNG) Exported from the United States has been submitted to a peer-reviewed journal, but the review process has not yet been completed. A pre-print version of the paper is available from the Cornell University website. The results of the study were reported by The New Yorker and by Die Welt in Germany—a country that relies heavily on imported LNG to bridge the energy crisis.

The main cause of high GHG emissions from LNG are methane losses (“leaks”) during various stages of LNG production and distribution. The study considered all sources of CH4 and CO2 emissions, including upstream and midstream emissions, emissions in the liquefaction process, tanker transport, regasification and distribution, and combustion by final consumer. Methane is a powerful warming agent, more potent than CO2. The study used a 20-year global warming potential value for methane of 82.5 (GWP20) and a 100-year value of 29.8 (GWP100).

The study examined several LNG transportation scenarios, with different amount of methane released during the transit. The results, Figure 1, show that even when the gas is delivered with the most modern ship, taking the most direct route, the GHG emissions from the entire LNG life cycle are 24% higher than those caused by burning an equivalent amount of coal. In the worst case, involving long voyages in old vessels, steam-powered using heavy fuel oil, the emissions are 274% worse compared to coal.

Figure 1. Lifecycle GHG footprints for LNG burned by final consumer (left) and for coal and natural gas (right) for different LNG transportation scenarios using GWP20 = 82.5 for methane

Using GWP100 instead of GWP20, the GHG footprint of LNG and natural gas relative to coal decreases. Even so, GHG emissions from LNG are at least as much as from coal, in the scenario with short voyages and tankers burning LNG, to considerably higher than coal, for the scenario of long voyages by tankers burning heavy fuel oil. Even when using GWP100, LNG is never preferable to coal from the standpoint of greenhouse gas emissions, concluded the study.

Source: The New Yorker | Die Welt


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