Nord Stream methane release highlights scale of emissions

Berlin, Germany (SPX) Jan 16, 2025
In late September 2022, damage to the Nord Stream pipelines led to an unprecedented release of nearly 500,000 tonnes of methane into the atmosphere. This represents the largest single event of methane emissions ever recorded, according to analysis by the International Methane Emissions Observatory (IMEO) under the United Nations Environment Programme (UNEP). The findings involved nearly 70 scientists from 30 research organizations, with the German Aerospace Center (DLR) and the Technical University of Braunschweig conducting the only airborne measurement campaign of the event, organized rapidly with IMEO support.

The campaign, carried out in early October 2022, identified the large-scale release of methane initially dissolved in seawater near the leaks. Measurements taken by the University of Gothenburg and the Voice of the Ocean research foundation tracked the spread of this dissolved methane across the Baltic Sea, spanning from Denmark's Zealand region to Poland's Gulf of Gdansk. The findings have been published in *Nature* and *Nature Communications* in three comprehensive studies.

"Nine days after the pipeline damage, significant methane levels were detected up to 45 kilometers from the leak sites," said Friedemann Reum of the DLR Institute of Atmospheric Physics, who led the flight measurement campaign. "Although the pipelines had emptied by this time, measurements from 5 October 2022 showed emissions of 19 to 48 tonnes of methane per hour. The data revealed how methane initially dissolved in the Baltic Sea was transported by ocean currents before releasing into the atmosphere. Our airborne observations directly confirmed the outgassing process and helped quantify the amount of methane involved."

The airborne measurements provided a wide-scale overview of methane outgassing. These observations aligned closely with flow models estimating the total methane dissolved in seawater, based on smaller-scale marine measurements by the University of Gothenburg and Voice of the Ocean. According to these models, 9,000 to 15,000 tonnes of methane were dissolved in seawater before surfacing.

The total methane release from the Nord Stream event, estimated between 445,000 and 485,000 tonnes, accounted for 0.1 percent of all human-caused methane emissions in 2022. This volume equals 1.2 percent of annual emissions from the natural gas sector and 0.3 percent of emissions from agriculture. "This analysis underscores the importance of integrating multiple observation and estimation techniques to accurately quantify methane emissions," said Andrea Hinwood, Chief Scientist at UNEP. IMEO's approach combined pipeline pressure data, tower-based measurements, satellite imagery, marine observations, and DLR's airborne data to produce its estimates.

Methane detection by air and sea

The flight measurement campaign, conducted on 5 October 2022, utilized the HELiPOD towed probe developed by the Institute of Flight Guidance at the Technical University of Braunschweig. Researchers undertook two helicopter flights near the Polish coast using the HELiPOD, which was equipped with a methane sensor from DLR. This unique instrument, towed on a 25-meter cable, can accommodate various sensors to measure atmospheric data, particles, fine dust, and gases. For this mission, the HELiPOD provided critical data on methane levels in the atmosphere.

"The HELiPOD's flexibility and advanced sensor suite enabled rapid deployment and collection of essential data," explained Peter Hecker, Head of the Institute of Flight Guidance at TU Braunschweig. "Its ability to adapt to different research needs, combined with robust data processing systems, makes it an invaluable tool for studying emissions worldwide."

Global methane database initiative

Methane, responsible for about one-third of greenhouse gas-driven warming, is the second most impactful greenhouse gas after carbon dioxide. The Intergovernmental Panel on Climate Change (IPCC) has called for a 30 percent reduction in methane emissions by 2030 to meet the 1.5 degrees Celsius global temperature goal. To aid in this effort, IMEO is building a global public database of methane emissions, integrating data from various sources. DLR has contributed to IMEO's mission through multiple flight campaigns in key methane-emitting regions, including oil and gas production zones in Africa and Europe's coal mining areas.

Research Report:Methane emissions from the Nord Stream subsea pipeline leaks