16. January 2025 | Press releases:

Nord Stream pipelines: methane emissions analysed after damage

  • Leaks in the Nord Stream pipelines in 2022 released the largest amount of the greenhouse gas methane to date caused by a single event.

  • The released amount of 445,000 to 485,000 tonnes of methane corresponds to 0.1 percent of man-made methane emissions in 2022.

  • DLR provides the only airborne data on the methane emissions from the leaks.

  • Focus: Earth observation, aeronautics, aerospace, climate change, maritime safety

At the end of September 2022, the damage to the Nord Stream pipelines caused almost half a million tonnes of methane to be released into the atmosphere. This is the largest amount of the greenhouse gas methane ever released by a single event. This is the conclusion of an analysis by the International Methane Emissions Observatory (IMEO) of the United Nations Environment Programme (UNEP). Nearly 70 scientists from 30 research organisations contributed to the analysis. The German Aerospace Center (DLR), together with TU Braunschweig, conducted the only airborne measurement campaign of the leaks organised at short notice. These flight measurements in early October 2022 showed large-scale outgassing of methane initially dissolved in seawater and provided confirmation of the total amount. Measurements in the waters of the Baltic Sea between the Danish island of Zealand and the Gulf of Gdañsk off Poland by University of Gothenburg and the Voice of the Ocean research foundation have also shown how methane dissolved in the sea has spread over several months. The results have now been published in three studies in Nature and Nature Communications.

“Nine days after the damage to the pipelines, we found large amounts of methane in the air around the leaks, up to 45 kilometres away. By this point, however, the pipes had already emptied and the methane had been blown away,” explains Dr Friedemann Reum from DLR Institute of Atmospheric Physics, who led the study of the flight measurement campaign. “But the data from 5 October 2022 showed that 19 to 48 tonnes of methane were still being emitted every hour. What we were seeing was methane that had first dissolved into the water at the leak sites. From there, it was further transported by ocean currents before being released into the air. Our measurement flights provided direct evidence of the outgassing of dissolved methane into the atmosphere. This enabled us to complete the picture of how much methane leaked from the pipelines into the Baltic Sea and what happened to it afterwards.”

The flight campaign provided a large-scale snapshot of the outgassing of the initially dissolved methane. The results are largely consistent with current models. These models have been used by University of Gothenburg and Voice of the Ocean to estimate the total amount of methane dissolved in seawater based on the spatially limited methane measurements in the water. According to these estimates, 9,000 to 15,000 tonnes of the greenhouse gas from the pipelines initially dissolved in the water before reaching the surface.

The 445,000 to 485,000 tonnes of methane released from the leaks in the Nord Stream pipelines accounts for 0.1 per cent of man-made methane emissions in 2022. In terms of methane emissions from the natural gas sector in 2022, this is equivalent to 1.2 per cent. In terms of methane emissions from agriculture in 2022, it is 0.3 per cent. “The analysis shows that it is important to consider complementary monitoring and estimation methods to characterise methane emissions. This was key to assessing the amount of methane emitted during the Nord Stream leak,” says Dr Andrea Hinwood, senior scientist at UNEP. To estimate the emissions from the Nord Stream leak, IMEO used technical calculations based on information about the pressure in the pipelines and various sources of methane data, such as measurement towers, satellites, marine observations and the airborne measurement data from the DLR.

“Sniffing” out methane over the sea

The airborne measurement campaign, which was organised at short notice, took place on 5 October 2022 in close cooperation with the Institute of Flight Guidance (IFF) at TU Braunschweig. In total, the researchers were able to carry out two helicopter flights with a towed probe from the Polish coast near Kolberg. The IFF operates the helicopter-borne HELiPOD probe, which is equipped with a wide range of atmospheric measurement technology. The HELiPOD flies as a sling load on a 25-metre tether below the helicopter. For the flights in autumn 2022, it was additionally equipped with a methane instrument from the DLR Institute of Atmospheric Physics. The Braunschweig office of the German Federal Agency for Technical Relief (THW) provided important support in the short-term logistical preparation of the measurements. The helicopter was provided by the Polish company Helipoland. “We are pleased that the provision of the HELiPOD towed probe has made these measurements possible. This unique research instrument can be flexibly equipped with a wide range of sensors and can be deplyed almost anywhere in the world. With a length of around five metres and a take-off weight of up to 300 kilograms, it can carry a wide range of instruments to measure air quality, particles and fine dust, surface properties, and gases such as methane. In conjunction with a highly developed system for processing and storing measurement data, important research data can be obtained,” explains Prof. Dr.-Ing. Peter Hecker, Head of the Institute of Flight Guidance at TU Braunschweig.

Global public database on methane emissions

Methane is responsible for about a third of global warming caused by greenhouse gases, making it the second most important anthropogenic greenhouse gas after carbon dioxide. The IPCC urges that methane emissions be reduced by at least 30 per cent by 2030 to keep global warming within the 1.5 degree Celsius limit. To support the development of effective measures to reduce methane emissions, IMEO is establishing a global public database on methane emissions under the auspices of the UN Environment Programme. DLR has already carried out several IMEO flight projects, including over major oil and gas producing regions in Africa and the Arabian Peninsula, as well as over European coal mining areas.