Scientists fear methane spewing from the exploded Nord Stream pipeline into the Baltic Sea could be one of the worst natural gas leaks ever and pose significant climate risks.
Neither of the two breached Nord Stream gas pipelines, which run between Russia and Germany, were operational, but both contained natural gas. This mainly consists of methane – the greenhouse gas that is the biggest cause of climate warming after carbon dioxide.
The extent of the leak is still unclear, but rough estimates by scientists, based on the amount of gas allegedly contained in one of the pipelines, vary between 100,000 and 350,000 tons of methane.
Jasmine Cooper, a research associate at Imperial College London’s chemical engineering department, said there was “a lot of uncertainty” about the leak.
“We know there are three explosions, but we don’t know if there are three holes in the sides of the pipe or how big the breaks are,” Cooper said. “It’s hard to know how much is reaching the surface.” But it is potentially hundreds of thousands of tons of methane: quite a large amount is being pumped into the atmosphere.
Nord Stream 2, which was supposed to increase the flow of gas from Russia to Germany, reportedly contained 300 million cubic meters of gas when Berlin halted the certification process just before Russia invaded Ukraine.
That amount alone would be 200,000 tons of methane, Cooper said. If all of it escaped, it would exceed the 100,000 tons of methane released by the Aliso Canyon blowout, the largest gas leak in US history, which occurred in California in 2015. Aliso had the equivalent of heating half a million cars.
“It has the potential to be one of the largest gas leaks,” Cooper said. “The climate risks of methane leaks are quite large.” Methane is a powerful greenhouse gas, 30 times stronger than CO2 over 100 years and more than 80 times stronger in 20 years.”
Professor Grant Allen, an expert in earth and environmental science at the University of Manchester, said it was unlikely that natural processes, which convert small amounts of methane into carbon dioxide, would be able to absorb much of the leakage.
Allen said: “This is a colossal amount of gas, in really big bubbles. If you have small sources of gas, nature will help you by digesting the gas. In the Deepwater Horizon spill, there was a lot of methane attenuation by bacteria.
“My scientific experience tells me that – with such a large impact – methane will not have time to be weakened by nature.” So a significant part will be released as methane gas.”
Unlike an oil spill, gas won’t have as much of a polluting effect on the marine environment, Allen said. “But in terms of greenhouse gases, it’s a reckless and unnecessary emission into the atmosphere.”
Germany’s environment agency said there were no containment mechanisms on the pipeline, so it was likely the entire contents would escape.
The Danish Energy Agency said on Wednesday that the pipelines contain a total of 778 million cubic meters of natural gas – the equivalent of 32% of Denmark’s annual CO2 emissions.
This is almost double the volume originally estimated by scientists. This would significantly increase estimates of methane that has leaked into the atmosphere, from 200,000 to more than 400,000 tons. More than half of the gas has left the pipes, and the rest is expected to disappear by Sunday, according to the agency.
Jean-Francois Gauthier, vice president of measurements at commercial methane-measuring satellite firm GHGSat, said estimating the total volume of the gas emitted was “challenging”.
“There is little information about the size of the breach and whether it is still ongoing,” Gauthier said. “If it’s a significant enough breach, it would empty itself.”
“It is safe to say that we are talking about hundreds of thousands of tons of methane. As for the leak, it is certainly very serious. The catastrophic immediate nature of this – I’ve certainly never seen anything like it before.”
In terms of climate impact, 250,000 tons of methane was equivalent to the impact of 1.3 million cars driving on the road for a year, Gauthier said.