A recent study from Cornell University indicates that liquefied natural gas (LNG) has a greenhouse gas emissions profile that is 33% more harmful than that of coal when the entire process from extraction to shipping is considered.
Robert Howarth, the study’s author and a professor of ecology and environmental biology, stated, “Natural gas and shale gas both negatively impact the climate, but liquefied natural gas (LNG) is even worse. LNG is derived from shale gas, and producing it requires supercooling it to a liquid state, followed by transportation in large tankers. This process demands energy.”
The research titled, “The Greenhouse Gas Footprint of Liquefied Natural Gas (LNG) Exported from the United States,” was published on October 3 in the journal Energy Science & Engineering.
Howarth noted that the methane and carbon dioxide emissions generated during the extraction, processing, transportation, and storage of LNG contribute to about half of its overall greenhouse gas impact.
According to the study, over a 20-year period, the carbon footprint of LNG is one-third greater than that of coal when evaluated based on global warming potential, which assesses the atmospheric consequences of various greenhouse gases. Even over a more lenient time frame of 100 years, LNG’s carbon footprint matches or surpasses that of coal, Howarth added.
The study’s findings have relevant implications for LNG production in the U.S., which became the world’s leading exporter following the lifting of the export ban in 2016. Almost all of the rise in natural gas production since 2005 has come from shale gas. Howarth explained that the LNG being exported is sourced from shale fields in Texas and Louisiana.
The liquefaction process, involving cooling natural gas to minus 260 degrees Fahrenheit, facilitates its transport on tanker ships.
However, this shipping method carries an environmental cost. LNG transport ships equipped with two- or four-stroke engines produce lower carbon dioxide emissions than those powered by steam. Nonetheless, as these engines utilize LNG during transit, methane escapes as exhaust, contributing additional emissions to the atmosphere.
Methane is significantly more damaging to the environment than carbon dioxide—over 80 times more potent—meaning even minimal emissions can greatly affect climate change, according to Howarth.
He pointed out that the newer LNG tankers, even with their improved efficiency and reduced carbon dioxide emissions, still have higher greenhouse gas emissions compared to steam-powered vessels due to the escape of methane in their exhaust.
During the liquefaction of natural gas, significant methane emissions occur—estimated to be around 8.8% of the total when assessing overall warming potential. The methane emissions from tankers can vary between 3.9% and 8.1%, based on the specific ship used.
Howarth emphasized, “Most methane emissions arise during the extraction of shale gas and its liquefaction. This is all exacerbated just to deliver LNG to the market.”
“Thus, liquefied natural gas will consistently exhibit a larger climate footprint compared to natural gas alone, irrespective of the arguments supporting it as a transitional fuel,” Howarth stated. “Ultimately, it is still significantly worse than coal.”
This research received funding from the Park Foundation.
