Putting the environment at the heart of CERN

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Dr. Fabiola Gianotti, CERN's Director-General (Image: CERN)

Welcome to CERN’s second public environment report, covering the period 2019-2020. This was a challenging time for all of us, as the COVID-19 pandemic brought much of the world to a halt. For CERN, it was also the second long shutdown (LS2) of the Large Hadron Collider (LHC) and our entire accelerator complex – an extended period of maintenance and upgrades across the Laboratory. From an environmental-management perspective, long shutdowns are particularly intense periods, as equipment at the end of its life is replaced, thereby offering opportunities to align with the latest environmental standards. The COVID-19 pandemic meant that we had to adapt our plans, and I’m pleased to report that we managed to do so with just a few months’ delay to the schedule.

LS2 saw the completion of the LHC Injectors Upgrade project (LIU), which has readied the injector chain for the high-luminosity phase of LHC operation (HL-LHC), scheduled to get under way in 2028. The oldest accelerator still in operation at CERN dates back to 1959, and others to the 1970s. LIU was an opportunity not only to enhance their performance, but also to improve their environmental credentials. During the LHC’s first long shutdown, a new powering scheme for the Super Proton Synchrotron (SPS) accelerator allowed the machine’s energy consumption to be reduced by 40 GWh/year, and during the period covered by this report, a similar scheme was deployed as part of the refurbishment of our East Area experimental hall, which has led to a 90% reduction in energy consumption.

LS2 was also an occasion for maintenance and upgrades of our experiments. In our last environment report, we undertook to reduce scope 1 emissions of greenhouse gases by 28% by 2024. Although the pandemic prevented us from advancing as much as we had planned, we were able to start installing new cooling systems for major particle detectors to replace high-global-warming-potential gases with more environment-friendly ones. The experiments have also been repairing leaks in their gas-based detectors and investigating environmentally friendly gas mixtures.

An important milestone in 2020 was the publication of an update to the European Strategy for Particle Physics, which puts environmental protection at the heart of particle physics in Europe and of any future project at CERN. It states: “The environmental impact of particle physics activities should continue to be carefully studied and minimised. A detailed plan for the minimisation of environmental impact and for the saving and re-use of energy should be part of the approval process for any major project.”

One tangible example of this principle in action is the completion in 2020 of a plant to recover waste heat from the LHC to heat a new residential development in nearby France. This will not be a one-off: plans for a new computer centre include heat recovery to heat the buildings of CERN’s Prévessin site, and studies are under way to evaluate the heat-recovery potential of other points around the LHC. Heat recovery will be built into any designs for future facilities at CERN.

The production of CERN’s first public environment report in 2020 enabled us to establish reporting frameworks and set concrete goals. This second report is about turning words into action. Over the 2019-2020 period, initial objectives identified by the CERN Environmental Protection Steering Board (CEPS) were formalised, financed and implemented – one example being the construction of a retention basin for the Prévessin site to protect local watercourses from accidental pollution and to mitigate the consequences of extremely heavy rainfall.

In this document, we report on our scope 3 emissions for the first time, presenting data relating to business travel, personnel commutes, catering, waste treatment and water purification. Procurement is expected to constitute the largest part of the Organization’s scope 3 emissions. A procedure for evaluating scope 3 emissions due to procurement, along with a project to assess how to green CERN's procurement, are in preparation. This will be covered in a future report. This represents an important step in understanding and controlling our overall emissions.

At CERN, we aspire to contribute to the achievement of some of the environment-related UN Sustainable Development Goals (SDGs) by improving our performance and forging partnerships with others. Among the goals we have identified as areas where CERN can make an active contribution are Affordable and Clean Energy (SDG 7) and Industry, Innovation and Infrastructure (SDG 9). We are actively working on new technologies, such as superconducting power transmission lines, that could make a significant contribution to achieving these goals.

Due to the COVID-19 pandemic, CERN’s way of working changed dramatically over the period covered by this report, with most personnel working from home and our usually highly mobile user community unable to travel to CERN. While everyone is looking forward to the end of the pandemic, the positive environmental benefits of less travel and traffic will feed into new methods of working for the long term.

CERN is fully committed to environmental protection and transparent reporting. It is also committed to developing technologies that could help society to improve the health of the planet. This document provides a record of our performance, describes our objectives for improvement and reflects a proactive approach to environmental protection across the Laboratory and among CERN’s worldwide scientific community. That the environment is a CERN priority has been clear since we committed to public reporting, and this has been consolidated since the publication of our first report last year. In particular, a materiality analysis helped us to identify and prioritise goals for improvement. It is an exercise that we will revisit regularly, ensuring that protecting the environment remains at the heart of CERN’s decision making and all aspects of everyday life at the Laboratory.

Fabiola Gianotti, Director-General

Highlights - CERN and the environment in 2019

During the period covered by this report, 2019-2020, CERN’s accelerator complex was in its second long shutdown. Due to this shutdown, several environmental indicators show a different pattern from the previous reporting time frame of 2017-2018. These highlights only include 2019 indicators, given that 2020, with the COVID-19 pandemic, was not representative of a normal year.


428 GWh

In 2019, CERN consumed 428 GWh of electricity and 68 GWh of fossil fuel. CERN’s electricity consumption during this period was about 64% lower than when the accelerator complex is running.

The Laboratory is committed to limiting rises in electricity consumption to 5% up to the end of 2024 (baseline year: 2018), while delivering significantly increased performance of its facilities. CERN is also committed to increase energy re-use.



78 169 tCO2e

In 2019, CERN’s direct greenhouse gas emissions (scope 1) were 78 169 tonnes of CO2 equivalent (tCO2e) which is less than half of the amount emitted annually over the period 2017-2018 when the accelerators were running.

Indirect emissions arising from electricity consumption (scope 2) were 10 672 tCO2e. In addition, indirect emissions from water purification, waste treatment, business travel, personnel commutes and catering (scope 3) were 12 098 tCO2e.

CERN’s immediate target is to reduce direct emissions by 28% by the end of 2024 (baseline year: 2018).



57% recycled

In 2019, CERN eliminated 5589 tonnes of non-hazardous waste, of which 57% was recycled.
The Laboratory also eliminated 1868 tonnes of hazardous waste.

CERN’s objective is to increase the current recycling rate.



2006 ML

In 2019, CERN drew 2006 megalitres (ML) of water, mostly from Lake Geneva. This is about 47% less than in operational years.

The Laboratory is committed to keeping its increase in water consumption below 5% up to the end of 2024 (baseline year: 2018), despite a growing demand for water cooling of upgraded facilities.



16 species of orchids

In 2019, a new species of orchid was discovered on CERN’s sites, bringing the total to 16 species.

CERN land includes 258 hectares of cultivated fields and meadows, 136 hectares of forest and three wetlands.

Full report & glossary

Explore the environment report online or download it as a PDF here.

Questions regarding this report may be addressed to Environment.report@cern.ch.