LNG Has 2.7X Climate Impact of Coal - US Pauses Approvals

Feb. 12, 2024

Liquefied natural gas (LNG) carries up to 2.7 times the global warming impact of burning coal, according to a draft science paper released on the heels of U.S. President Joe Biden’s landmark decision to apply a climate test to a massive, new LNG export terminal in Louisiana.

The preprint manuscript [pdf] by Cornell University biogeochemist and environmental scientist Robert Howarth acknowledges that coal releases almost twice as much carbon dioxide as LNG when the fuels are actually burned. But LNG’s methane emissions are “substantially higher”, the equivalent of 70.9 to 154 grams of CO2 per megajoule of energy, compared to just 17.3 grams per coal, based on methane’s climate impact over a 20-year span.

After looking at the CO2 and methane that enter the atmosphere across the LNG life cycle—including extraction, liquefaction, tanker transport, regasification, final distribution, and combustion—Howarth concludes that LNG emissions are 12.3% higher than coal when the gas is carried over a shorter distance on a more modern tanker, equipped with an engine that can burn some of the gas en route. LNG carries 2.7 times the climate punch on longer cruises in older tankers that burn heavy fuel oil.

Those distances range from 9,070 kilometres in each direction between the Texas coast and the United Kingdom, to 29,461 kilometres each way between Texas and Shanghai. “Not surprisingly, total emissions go down for the shorter voyage and increase for the longest voyage” across four different types of LNG tankers, Howarth writes.

The paper cites the LNG that evaporates, or is “boiled off”, during transport, loading, and unloading, as well as the 108 to 175 tons of LNG per day that tankers consume while they’re at sea and the unburned methane that some types of tankers emit in their exhaust streams.

The as-yet unpublished paper is still going through peer review, but Howarth told The Energy Mix he’s confident his major conclusions are “straightforward and relatively conservative”, and will “stand firm” through the review process.

“My analysis leads to one strong recommendation: the venting of unburned methane from tanker boil off should be prohibited, and those older tankers that cannot capture and use boil‐off methane should be retired within the near future. These older tankers that burn heavy fuel oil have a very large greenhouse gas footprint,” Howarth says in the paper.

“A broader conclusion is the need to move away from the use of LNG as a fuel as quickly as possible, and to immediately stop construction of any new LNG infrastructure,” he adds. “Proponents of exporting LNG from the United States are wrong when they assert a climate benefit for the use of LNG over coal produced and used domestically in Europe and Asia.”

In fact, the greenhouse gas footprint of LNG is so much larger than coal’s that “short‐term energy needs such as those caused by the Russian invasion of Ukraine are perhaps better met by reopening closed coal facilities, on a temporary basis, than by expanding LNG infrastructure” that will ultimately become a stranded asset as the world decarbonizes, Howarth maintains.

‘Trouble’ for LNG Terminals

Canary Media first reported on Howarth’s paper January 26, the same day the Biden administration announced it would require a climate test before completing regulatory review of the Calcasieu Pass 2 (CP2) LNG export terminal in Louisiana. Two days before the official announcement, the New York Times said the pause could “spell trouble” for CP2 and the 16 other export terminals coming up behind it.

The United States is already the world leader in both LNG exports and oil and gas extraction, with seven export terminals in operation and another five under construction. The pause could extend review of the CP2 project beyond the November general election in the U.S., an outcome that veteran climate writer and activist Bill McKibben called “the biggest thing a U.S. president has ever done to stand up to the fossil fuel industry.”

In the days after the White House announcement, Carbon Brief published a detailed explainer on the factors behind Biden’s decision, the new global LNG capacity currently under development, whether the world needs more U.S. LNG, how U.S. exports affect greenhouse gas emissions, and how the pause will affect U.S. politics. A week later, 23 Republican attorneys general in the U.S. led by West Virginia AG Patrick Morrisey are vowing legal action unless Biden and Energy Secretary Jennifer Granholm resume LNG project approvals.

“The issue is arguably as politically important for Republicans, who are trying to paint the administration’s pause on LNG exports as a de facto ban,” Politico writes. “Biden has also faced pushback from some Democrats: Pennsylvania Sens. John Fetterman and Bob Casey said they would push the administration ‘to reverse this decision’ if the pause ends up affecting natural gas jobs in their state.”

The Problem with Methane

In the paper, Howarth deliberately bases his calculations on methane’s climate footprint over a 20-year span, explaining that the 100-year average widely used in other life cycle assessments was an “arbitrary choice” baked into the 1997 Kyoto Protocol, at a time when climate scientists weren’t yet paying as much attention to methane. Fast forward a quarter-century, and the Intergovernmental Panel on Climate Change now identifies methane controls in oil and gas as one of the cheapest ways to achieve the fastest, deepest emission cuts by 2030.

“The rate of global warming over the next few decades is critical, with the rate of warming important in the context of potential tipping points in the climate system,” Howarth writes. “Reducing methane emissions rapidly is increasingly viewed as critical to reaching climate targets,” prompting many researchers to “call for using the 20‐year time frame of GWP20 instead of or in addition to GWP100.”

Based on that crucial, 20-year span, he adds, “LNG always has a larger greenhouse gas footprint than coal.”

While Howarth has taken his share of criticism for his past analysis, most obviously for using the 20-year time span for calculating methane’s impact, he emphasizes repeatedly in the paper that his calculations are conservative.

“I have a very low emission rate from the pipeline systems in the destination country, which is reasonable if the gas is moved via high-pressure pipeline directly to an electric power plant, but is much too low if the gas were to enter an urban distribution system and be used for heating,” he told The Energy Mix in an email. “In fact, most gas in Europe is used for heating, so the footprint would be substantially larger.”

As well, “I assume no leakage at all from the methane that is boiled off from LNG in storage terminals and during transport by tanker; rather, I assume it is all captured with 100% efficiency and burned for useful energy,” he added. But “over the past year, tankers have often stood by for days at a time (weeks in some cases) before being unloaded, either because of congestion at ports or because operators were hoping for higher prices. There is a lot of methane boil off during this time period,” but “I have ignored this, since it is hard to get quantitative data on how long these holds are, and on the fate of the boil off.”

[Top photo: Robin Lucas/Geograph]