U.S. LNG shipped to Asia could emit up to 50% less than even the cleanest coal-powered plants, according to Rystad Energy.

Even with the assumption of high methane leakage rates, generally, the value chain of U.S. LNG headed to Asia has a lower emissions footprint than domestic coal used for power, Rystad said in a June 11 research report.

Rystad sees global LNG supply approach 850 Bcm annually by 2030, with around 30% likely coming from the U.S. The research company expects gas demand in Asian markets to remain strong, and sees LNG as a key competitor to coal in power generation.

But the rule that LNG is cleaner than coal is not hard and fast.

“There are some Asian coal power stations that could have lower value chain emissions than some of the high-emitting LNG sources,” according to Rystad.

“There are significant variations between U.S. LNG sources, coal sources … and power plants, as well as uncertainties regarding methane emissions through both value chains,” Rystad said.

New measurement technology suggests methane emissions to be higher than expected in the coal and oil and gas value chains, Rystad said.

But there is still no tried and true method to accurately quantify emissions from a particular energy source.

A lack of granular and high-quality measurement data is a major challenge when assessing the methane emissions associated with the LNG and coal value chains, Rystad said. And satellite monitoring still has its limitations, particularly with its detection threshold, as satellites with global coverage are unable to register smaller methane plumes.

“Accurately quantifying emissions for any energy source is essential to understanding its full environmental impact. As the global focus swings towards methane emissions, and the wealth of credible data grows from more granular satellites and increased on-site measurements, the uncertainty within the methane data will begin to contract,” Rystad Energy senior analyst Patrick King said in the report.