Greenhouse Gases

The Nord Stream, a natural gas pipeline running from Russia to Germany under the Baltic Sea, has suffered from different leaks (4 at the time of writing) since last Monday, 26^th September. The pipeline was not in use when the leaks emerged, as Gazprom shut it down indefinitely on 2^nd September 2022. Nonetheless, methane was present in the conduit and is now emitted almost directly into the atmosphere.

While examining the causes of the leaks would be beyond the scope of this article, it is crucial to understand the implication of methane release in the atmosphere and its impact on the environment and climate.

The Umweltbundesamt – UBA, the German Environment Agency, estimated that between 300,000 and 350,000 tonnes of methane are being emitted from the Nord Stream. However, the exact number is difficult to determine. To put these figures in context, the International Energy Agency (IEA) estimated the methane emissions in 2021 to be 580 Million tonnes (Mt), of which 350 Mt (approximately 60% of the total) come from anthropogenic activities [1]. Therefore, the highest UBA estimate of 350,000 tonnes of methane from the Nord Stream corresponds to 0.1% of the anthropogenic and just ~0.06% of the total methane emissions for 2021.

While these numbers seem negligible, the implications on climate are considerable. Methane is one of the most effective greenhouse gases (GHGs) in the atmosphere. While the usual lifetime of methane (few years) in the atmosphere is much smaller than carbon dioxide (hundreds of years), its impact is much more significant. To quantify the effects of different GHGs, the Intergovernmental Panel on Climate Change (IPCC) uses a metric called the Global Warming Potential (GWP). The GWP determines the impact of a tonne of a given GHG emitted over a time window (usually 20 and 100 years) in terms of CO₂ equivalent. Methane has a GWP of 28 over 100 years [2]. In other words, each tonne of methane emitted is equivalent to 28 tonnes of CO2. In these terms, it is straightforward to understand how 350,000 tonnes of methane from Nord Stream correspond to 9.8 Mt of CO₂. The latter value corresponds to as much as 3% of the yearly UK CO₂ emissions [3].

One of the most common uses of methane is heat production by combustion. Therefore, it is natural to wonder what would have been the impact of the same amount of methane released now in the Nord Stream if it had been burnt. Chemistry helps answer this question. Methane combustion is the reaction between methane (CH₄) and oxygen (O₂) in the air. This reaction produces CO₂, water (H₂O), and energy. Therefore, the impact of burning 350,000 tonnes of CH₄ is the same as emitting 350,000 tonnes of CO₂ directly into the atmosphere. This value is much lower, precisely by a factor of 28, than the 9.8 Mt determined previously, while also producing energy.

The additional methane introduced into the atmosphere due to the Nord Stream leaks helps emphasise an already critical situation regarding methane emissions. While carbon dioxide (i.e. burning methane) emissions are always preferable to direct methane emissions, they still represent GHGs emissions. As such, it should be reduced to mitigate global warming. Moving towards renewable and more sustainable ways of producing energy is critical to avoid emissions of GHGs, whether directly or indirectly, and having to pay the environmental price when episodes such as the leaks in the Nord Stream occour.

References:

[1] IEA (2022), Global Methane Tracker 2022, IEA, Paris https://www.iea.org/reports/global-methane-tracker-2022

[2] Myhre, G., D. Shindell, F.‐M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.‐F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.‐K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

[3] Crippa, M., Guizzardi, D., Solazzo, E., Muntean, M., Schaaf, E., Monforti-Ferrario, F., Banja, M., Olivier, J.G.J., Grassi, G., Rossi, S., Vignati, E., GHG emissions of all world countries – 2021 Report, EUR 30831 EN, Publications Office of the European Union, Luxembourg, 2021, ISBN 978-92-76-41547-3, doi:10.2760/173513, JRC126363.