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Environmental awareness: Greenhouse gas emissions

With climate change a growing concern, the Organization is committed to reducing its greenhouse gas emissions

Environment campaign: Greenhouse gases
The Prototype 2PACL plant designed by EP-DT-FS: three pump heads coated in ice due to the -53 °C cooling. The plant is a keystone in CERN's endeavours towards replacing fluorinated gases with CO2, for the cooling of the detectors of the large LHC experiments (Image: CERN)

The recent UN Climate Change Conference (COP26) in Glasgow once again stressed the importance of combatting climate change through the reduction of greenhouse gas emissions. CERN is committed to participating in this combat.

The first step in this endeavour is to accurately monitor the Organization’s greenhouse gas emissions following the Greenhouse Gas Protocol’s nomenclature, which breaks down emissions into three scopes: scope 1 refers to the direct carbon dioxide equivalent (CO2e) emissions resulting from an organisation’s facilities, scope 2 refers to indirect CO2e emissions, for example related to the generation and supply of electricity, while scope 3 refers to indirect CO2e emissions occurring upstream and downstream of an organisation’s activities, such as those linked to mobility and waste.

CERN’s direct CO2e emissions (scope 1) arise from the Laboratory’s industrial infrastructure and on-site activities, such as heating, air conditioning and the vehicle fleet, but the vast majority are generated by the gases in the LHC experiments. These large experiments use a wide range of gas mixtures, including fluorinated gases (F-gases), for particle detection and detector cooling purposes. More than 78% of CERN’s direct emissions is due to F-gases, some of which have high Global Warming Potential (GWP)*.

Distribution of CERN's greenhouse gas emissions in 2019 (representative of LS2, before the COVID-19 pandemic) (Image: CERN)

The Organization set itself the objective of reducing its direct CO2e emissions by 28% by the end of 2024 (baseline year: 2018). Because of their major contribution, F-gases are the main focus of these mitigation efforts and CERN has developed an R&D strategy based on gas recuperation, optimisation of current technologies and replacement with more environmentally friendly gases. During LS2, the Organization took important steps towards replacing F-gases with CO2, which has a substantially lower GWP, in detector cooling systems. The experiments also carried out a leak repair campaign and investigated environmentally friendly gas mixtures. Despite the difficulties arising from the COVID-19 pandemic, most planned repairs have been or are being carried out.

The indirect emissions related to CERN’s electrical power supply and consumption (scope 2) are relatively low as the Laboratory procures low-carbon electricity. Nevertheless, the Organization is committed to limiting its increase in electricity consumption to 5% up to the end of 2024. During LS2, CERN consumed about 64% less electricity, which had a knock-on effect on energy-related emissions.

In 2020 and for the first time, CERN assessed its scope 3 CO2e emissions, such as those arising from business travel, personnel commutes, catering, waste and water purification. This estimate marks an important step in understanding and controlling the Laboratory’s overall emissions. Emissions related to personnel commutes and to long-distance flights in the framework of business travel make up the bulk of CERN’s scope 3 emissions. CERN’s goals are to keep individual motorised vehicle commuting constant by 2025, despite a growing scientific community, and to better understand and monitor emissions deriving from the Laboratory’s procurement. A project was launched by the IPT department in 2021 to address this second goal.

More information about CERN’s scope 3 emissions and their reduction priorities can be found in the latest Environment Report.

In addition to setting reduction objectives and mitigation measures, CERN discusses its carbon footprint in international forums, such as the EIROforum, where representatives of eight major research organisations in Europe share their respective experiences.


This article is part of the series “CERN’s Year of Environmental Awareness”.


* Global Warming Potential (GWP) is defined as the cumulative radiative forcing impact of one unit of a given greenhouse gas, relative to one unit of CO2, over a period of time. In practice, it allows comparisons of the global warming impacts of different gases.