*Sustainability through participation of international science communities* Involving a significantly large and continuously growing community of scientists and engineers through collaborative research projects over long periods ensures the long-term sustainability of a science project or programme. The reasons are

* The personnel costs are distributed over many contributing organisations and countries.

* A stable generation of scientific products [180, 181] (i.e., books, peer-reviewed articles, pre-prints and technical reports, proceedings and presentations) can be guaranteed.

* The knowledge can be effectively transferred into lasting education curricula through publications and direct training over generations.

* Impact can be generated through the training of early career professionals (see previous section).

High value is mainly achieved by ensuring that the science products generated directly by the research project or programme are taken up effectively and cited by an even larger second-tier community. Open Access publication of trusted (peer-reviewed) publications is a pre-requisite to generating research infrastructure sustainability through scientific product generation. Finally, the concept of Open Innovation that involves a large number of knowledge domains around a scientific core mission will ensure that the probability of knowledge generation that is stimulated through the challenges of the science mission will eventually spill over to society in domains that are immediately relevant to them [182].

*Sustainability through industrial spillovers* Industrial spillovers from science projects generate benefits directly for industry and society [183–185].<fnref n="18" /> This impact pathway is most effective if science projects construct their instruments and infrastructures in collaboration with industrial partners [186–188]. It works best when companies work closely with the research project to develop technologically intensive solutions and deliver non-standard services [189]. This approach is more laborious than a conventional client-supplier relationship, as it requires exchanges of ideas and knowledge, the development of integrated processes, the mutual adaptation of working methodologies, and risk sharing. This process, however, leads to the creation of lasting products, services, and processes that industrial partners can leverage in other markets, yielding earnings multipliers exceeding 3 and effects that can last between 5 and 8 years. Lasting territorial effects have also been reliably documented [190, 191].

Sustainability also depends on the design of the science mission: short-lived and non-upgradable programmes will lead to lower and shorter-lasting industrial spillovers than long-lasting programmes that are characterised by periodic upgrades and operational efficiency improvement measures involving industrial partners in continuous challenge-based activities.

Industrial spillovers can also lead to lasting positive environmental externalities. The challenge of reducing the carbon footprint and environmental impact of the construction of a new particle accelerator facility creates an opportunity for industrial innovations in numerous construction-related domains. For instance, it creates a potential of developing or putting in place low-carbon concrete and other construction materials production facilities. It serves as a pilot platform for improved construction techniques, like using natural resources, such as wood and compressed earth. Showcasing the application creates market interest. Developing processes and products for the use of excavated materials can generate benefits significantly beyond the needs of the research infrastructure project, since the management of construction waste is a challenge facing society, and for which conventional construction projects typically have insufficient time and budget. Eco-design-based industrial architecture is another emerging discipline for which particle accelerator facilities are suitable early adopters. Environmental benefits can also be generated in the area of technical infrastructures that are developed with industrial partners. They include:

* More efficient refrigeration systems, which find their application, for example, in gas liquefaction and transport.

* More efficient water cooling systems (adaptive water intake, use of waste water).

* Improved electrical systems (loss reduction via DC-based systems).

* High-speed power control management.

* Short and medium-term energy storage.

* Adaptive and machine learning infrastructure operations.

* Waste heat buffering and supply.

*Sustainability through open information and computing technologies* The development of Information and Communication Technology (ICT) and the generation of widely available data not limited to scientific results (e.g., engineering test data, operation monitoring, system tests, etc.) are essential outputs of particle accelerator-based research infrastructures [192]. Implementing a global data sharing and processing infrastructure has already led to

<footnote n="18">¹⁸Industrial spillover (also known as spinoff) refers to the phenomenon whereby innovations, technologies, or organisational practices developed within a given firm or industry diffuse beyond their original context, generating positive externalities that enhance productivity, competitiveness, or innovation capacity in other firms or sectors, typically without direct market transactions or compensation.</footnote>
the creation of numerous openly accessible software packages, platforms, and online services, which are also utilised
in environments outside high-energy physics. They range from scalable data storage and distribution middleware to
data analysis and visualisation, as well as data management and workflow systems. Also, openly accessible software
has been developed with a value that extends beyond scientific collaborations. Examples include innovative Cloud
computing services (e.g., Helix Nebula Science Cloud serving five scientific research domains), meeting and event
management software (e.g., Indico), particle/matter interaction modelling and analysis (e.g., GEANT4, FLUKA
and ACTIWIZ) and electronic library and information access software (e.g., Invenio and Zenodo). Long-term data
preservation is another technological domain of high societal relevance that is gaining importance, primarily driven
by fundamental science research infrastructures.

Particle accelerators and high-energy physics research projects are strongly encouraged to create an inventory
of potential ICT tools that can be made available openly and free of charge for societal use. The feasibility of
quantifying the societal impact of these solutions relies heavily on accounting for software uptake and uses (e.g., the
number of installations and the number of times it has been integrated into commercial and other open software
packages) over sustained periods of time. Today, there is a lack of such accounting, which makes quantitative
estimation of the societal impact challenging and labour intensive. However, it is important to establish systematic
monitoring and evaluation since ICT tools developed in the science environment have a major impact factor with
significant and tangible value potentials [193, 194].

Open and freely available software developed and maintained by science projects and programmes are sus-
tainability enablers for research infrastructures. Their investment and continuous development and maintenance
costs are marginal with respect to the societal benefits they can generate over decades. Future particle accelerator
projects and programmes should focus on properly managing and promoting ICT developments and make sure
they are taken up by society through a technological competence leveraging process and sustained online presence
in potential user domains.

*Sustainability through cultural goods* Creating an interest in science among all citizens is part of the mission of any research infrastructure. Projects and organisations can develop a broad variety of activities to attract lay people, for instance, through permanent and travelling exhibitions, open days, guided tours, engagement with schools and teachers in joint workshops, citizen science projects, websites, social media, engagement with video bloggers, online and TV documentaries, art internships, common art projects, feature movies, books, science fairs, presence in radio and TV shows and much more. The limit of cultural good creation is the limit of the imagination of an ever-changing and diverse group of creative people that are best employed over sustained periods of time. Each of these cultural goods has the potential to generate value for society. Creating a sustained interest in the science project breaks down barriers and fear of people who are outside the science community.

It is important for particle accelerator and physics projects to engage laypeople in playful and entertaining ways
rather than aiming at education and teaching, which is a different socio-economic impact pathway. The two should
be kept separate, although effective cultural good creation and engagement raise the possibilities for explaining
the underlying science in a second step.

The identification of value for cultural goods can be very different for each good. Therefore, future projects and programmes will need to focus initially on a few cultural pathways. If the estimated value of a pathway turns out to have sufficient potential, it should be further developed with a view to sustainable engagement. Continuous monitoring of the value should be carried out.

The value of on-site visits represents a cultural good of science infrastructures that can generate substantial tangible economic value in a sustainable way [195, 196]. Such visits include the discovery of the environment and nature [197, 198]. It should, therefore, be the first to be considered for development.

Social media presence has the most impact on online cultural goods today and should therefore also be considered
with priority [117]. It is particularly important to create a sustained interest in science and to explain in which
ways science impacts the environment and people’s everyday lives. Different means of communication are needed
for different generations and socio-economic groups [199].

Finally, citizen science projects on the periphery of the physics science mission are effective tools to engage lay people and to reinforce the environmental and territorial compatibility of the research infrastructure. An example is the initiatives to create biodiversity inventories of the surface sites, to improve the quality of habitats on and around sites.

*Sustainability through positive environmental externalities* Any future particle-accelerator-based project has the potential to create positive environmental externalities that can compensate for the residual, unavoidable negative environmental effects that cannot be reduced further. Before developing compensation and accompanying measures, negative effects on the environment have to be avoided. If they cannot be avoided, they should be reduced as far as is compatible with achieving the goals and objectives of the infrastructure within accepted cost and schedule constraints.
National and international legal and regulatory frameworks define boundary conditions for the avoidance, reduction, and compensation approach. The recently adopted update of the law for research and innovation in Switzerland, for instance, explicitly requires the consideration of the national and regional climate protection plans and energy-related aspects [200]. Other countries, such as France, have already encoded the fight against climate change, resource and biodiversity protection, circular economy, and sustainable territorial development in the environmental protection laws (L110-1 of [146] and [201]) that govern the authorisation of new projects [201]. Hence, ‘environmental’ is always to be interpreted in a wide sense. The greenhouse gas emission reduction goals defined by the Paris Agreement are to be integrated in new projects at EU level and following its translation into the national laws [202].

If properly planned, evaluated and monitored, collective compensation can even lead to a net positive effect [203]. Switzerland does not foresee such an approach and requires compensation based on equivalent surface and quality in principle within the affected canton [204–206]. Despite this constraint, the overall environmental performance may still be neutral or positive from a socio-economic assessment point of view if the positive environmental externalities are properly evaluated and integrated in the net present value of the project.

Some typical examples of positive environmental externalities that particle-accelerator facilities can integrate in their designs from the onset are:

* Re-creation of agricultural spaces by transferring top soil to low quality land plots and wasteland.

* Creation of green spaces with covered roads, fertilising wastelands and backfilled quarries, creation of parks, greening of roofs, reforestation around sites, creation and quality improvement of natural habitats and wetlands.

* Increase of biodiversity by the creation of new habitats on the research infrastructure’s domain.

* Improvement or creation of new ecological corridors, green and blue continuities.

* Creation of forests with trees and plants adapted to climate change.

* Introduction of forest management in view of protection from wildfires.

* Improved water management of existing, but low-quality water courses.

* Creation of water reservoirs.

* Creation of raised hedges to fight soil erosion and create new habitats.

* Creation of soft or multimodal mobility concepts for use beyond the research facility.

* Creation and improvement of natural habitats and nature protection zones on the research infrastructure sites.

* Carbon footprint reduction by helping to avoid fossil fuel use through waste heat supply.

* Supply of raw water for non-drinking purposes by supplying purified wastewater when not used by the research facility.

* Increase of renewable energy resource capacities through long-term power purchase agreements and energy purchase communities.

* Development of products and processes that leverage circular economy principles and low environmental impact technologies that spill over into the industrial domain (e.g., in the areas of electrical substations, construction materials, architecture solutions, power transmission and buffering, industrial cooling).

* Dismantling of infrastructures which are no longer used to create environmental and societal value.

### 4.4.2 Innovation and R&D

Particle accelerators and experiment detectors at the collision points of particle colliders are projects which use cutting-edge technologies over periods spanning several decades. As a consequence, they tend to develop and use technologies that do not exist at the time of design. This process continues throughout the operation as detectors are upgraded. The required technical advances may be designed in-house and/or in partner institutions (such as universities) in conjunction with external companies. The development can take the form of joint design or procurement of technologies to be developed by the company. In both cases, industries profit from a technological knowledge transfer which may lead to technological breakthroughs, patents, or new business opportunities [207, 208]. Such processes are encouraged and accompanied by dedicated knowledge transfer (KT) centres at the participating organisations [209–212]. As enabler of the science mission, such technological advancement is a valuable output, which significantly affects the social sustainability of a project.

*Other sustainability potentials* International science projects such as the FCC also provide possibilities to develop soft skills and international cooperation. Such projects bring nations closer together as they aim to pursue a common, peaceful goal. As recently seen with the ceremonies of CERN’s 70th anniversary, heads of state and ministers come to visit the site and have bilateral discussions that may or may not be related to the scientific mission of the project or even to science. National news outlets have reported on the event, focusing on the common project and these side aspects. Often, who discusses with whom is seen as more important than the event itself. Collaboration leading to more collaboration, there is a societal interest to bring decision makers together to discuss issues of the world in an informal setting. Spinning off from particle accelerator scientific research, the
<figure><img src="image_193.png" /><figcaption>**Fig. 4.5** Expression to determine the net present value (NPV) of an investment project considering economic, societal and environmental aspects</figcaption></figure>

SESAME project in Jordan [213] was set up with international collaboration in mind, as much or even more than the proposed scientific project. The Heidelberg, CNAO and MedAustron light-ion cancer therapy facilities are concrete examples of the direct transfer of knowledge, expertise, skills, and technology from fundamental particle physics and particle accelerator research to meaningful societal application. A future circular collider can achieve all this for Europe and beyond.

## 4.5 Comprehensive sustainability performance assessment based on Cost-Benefit Analysis

The approach (Fig. 4.2 is to create an inventory of negative cost and positive benefit items including externalities and convert them into monetary terms that are combined to determine a net present value (NPV) of the investment at the end of a chosen observation period (see Fig. 4.5). The ratio of the benefits of a project relative to its costs (BCR) including externalities and the so-called internal return rate (IRR) are two measures that can be derived from this analysis to provide valuable insight in the sustainability of the undertaking. The IRR is the discount rate that would bring the NPV of the entire project over the observation period to zero. An investment can be considered sustainable if it is financially feasible (net cash flow is non-zero) and profitable from a socio-economic perspective. A positive BCR has been determined through a comprehensive socio-economic impact assessment under the most conservative assumptions, including total costs, externalities, and benefits, and an IRR that is greater than the cost of obtaining the required capital. These results support the overall sustainability of the project.

In line with the guidelines on cost estimation of research infrastructures [214], the following items need to be established:

1. Unit of analysis with clear scope and boundary descriptions.

2. Reference period with a start and an end date of the observation based on the expected useful life (note that this period may be different from the physical life of the infrastructure and may lead to residual asset values).

3. Base year, i.e., the point in time when the quantitative estimation is made that does not necessarily coincide with the start date of the investment or the project operation. Past values are capitalised and future values are discounted with respect to the base year using the same mathematical formula. Conversion rates of the unit of measure with respect to other relevant currencies are to be recorded for the base year.

4. Unit of measure for costs and benefits in a specific monetary currency.

5. Approach for converting in-kind contributions into monetary terms.

6. Definition and description of the counterfactual scenario.

7. Project-specific Social Discount Rate that is justified by an economist expert advisory committee.

8. Structure of capital and operation expenditures.

9. Structure of negative externalities considered.

10. Structure of positive impacts (benefits) considered.

In addition to full financial costs, negative externalities must be integrated in the assessment, as far as they can be reasonably identified, accounted and converted in monetary terms.

Concerning potential impacts on the climate, the methodology includes the accounting of project-relevant emission factors, the estimation of the net greenhouse gas (GHG) emissions (a negative externality) and emissions avoided (positive impact or benefit) compared with a counterfactual baseline scenario. The resulting amount of generated and avoided GHG emissions, in tonnes of carbon dioxide equivalent (tCO₂(eq)), must be converted into monetary terms using a shadow price of carbon. In line with the EC technical guidance on the climate proofing of infrastructure, [215], for the shadow cost of carbon, it is recommended to use the values established by the
European Investment Bank (EIB) as the best available evidence on the cost of meeting the goals of the Paris Agreement [216].<fnref n="19" />

Input-Output analysis [217] is a methodology that only captures economic linkages and determines the value-added of an investment and can be used to estimate the effect on the job market and in which domains and geographical regions the economic activations take place. This tool is regularly used by governments and at the international level (e.g., EU, OECD) for empirical economic research and structural analysis and is therefore widely known. However, it is purely an economic instrument that should only be used as follows:

* As a complementary tool to document economic linkages, permitting the development of international in-cash and in-kind contributions.

* To identify project-relevant industrial sectors.

* To develop targeted common activities and synergies.

* To understand the job market implications.

* To develop regional specialisation policies.

* To develop focused training and skilled labour mobility plans.

Recently, the FCC study implemented the economists' recommendation to carry out a complementary analysis of the public perception [176] using a stated preference and Willingness-To-Financially-Participate (WTP) approach [218]. Such a survey can help to reveal if the full costs and cumulative impacts of a research infrastructure or scientific investment are at least justified with respect to the perception of the public.

The establishment of a risk registry, risk assessment, and evaluation of residual risks is crucial for new science missions and research infrastructure projects and programmes. It should include economic, social, and environmental domains in addition to standard topics such as financial and project management-related matters. Selected chapters are to be analysed using a simplified appraisal process with a limited and self-contained CBA or a multi-criteria analysis (MCA). Presenting several variants and versions of the project and individual segments together with their full financial costs, economic, social, and environmental performance levels is considered good practice in project appraisal and has been implemented by this study.

The results of the integrating and wider sustainability analysis are reported in a condensed summary form using the following key performance indicators:

**Net Present Value (NPV)** is the discounted sum of all future benefits less the discounted sum of all future costs over the appraisal period as a whole. To properly estimate the NPV, realistic estimates are required of the streams of benefits and costs over the appraisal period that can reasonably comprise around 30 years. Beyond this time frame, quantitative socio-economic estimates become challenging. The key to determining both these streams is knowledge of the times at which the various elements would come into play. Investment costs will typically be incurred prior to the date of opening, whilst operating costs (for example, personnel and resources for operation and maintenance) and user benefits would arise after the year of opening. User benefits, operating costs and revenues can be estimated from model runs for two or more years and the stream of benefits can be derived by interpolation and extrapolation between the benefits for the modelled years.

**Benefit/Cost Ratio (BCR)** is given by the ratio of the discounted sum of all future costs and benefits. The BCR is, therefore, a value-for-money measure, which indicates how much net social benefit could be obtained in return for each unit of investment. Although the values are monetised, i.e., converted into monetary units in this approach, they do not necessarily represent financial investments (e.g., the monetary shadow cost of carbon is not a paid amount of money. It represents a monetary cost to restore the effects linked to the quantified, potentially emitted carbon dioxide equivalent). Formulae for the NPV and BCR will be found in CBA textbooks, a good example of which is Pearce and Nash (1981).

**Internal Rate of Return (IRR)**. Whereas the NPV and BCR measures require a test discount rate to be specified, the IRR reports the average rate of return on investment costs over the appraisal period. This can be compared with the test discount rate to see whether the project yields a higher or lower return than is required to break even in social terms. Calculation of the IRR and issues surrounding it is discussed in Pearce and Nash, Chap. 4 and in other cost-benefit textbooks.

## 4.6 Limitations

While Sect. 4.5 outlined the comprehensive sustainability performance assessment based on cost-benefit analysis (CBA), it is equally important to acknowledge the methodological limitations of this approach in the context of research infrastructures.

<footnote n="19">¹⁹The Paris Agreement is a legally binding international treaty on climate change. It was adopted by 196 Parties at the UN Climate Change Conference (COP21) in Paris, France, on 12 December 2015. It entered into force on 4 November 2016.</footnote>
<figure><img src="image_194.png" /><figcaption>**Fig. 4.6** The Rumsfeld matrix [224] applied to the identification of costs and benefits of research infrastructures</figcaption></figure>

Particle accelerator facilities are characterised by a diverse set of investment and operation cost items, negative externalities, benefits and positive externalities. Research infrastructures dedicated to fundamental science generally do not generate direct financial revenue. Unlike commercial ventures, they do not sell a product or service that generates income and therefore cannot be evaluated in terms of profit generation.<fnref n="20" /> This makes it challenging to evaluate their performance using standard business metrics, such as return on investment or earnings.

This situation presents challenges for conducting project appraisals and assessing long-term sustainability through traditional financial methods. In the absence of direct financial returns, the value of such projects must be reflected in their broader socio-economic impact. Thus, the assessment relies on identifying and, where possible, quantifying societal benefits relative to costs and externalities.

One way to address this limitation is through the evaluation of the *public good value*, i.e., the benefit of providing a science infrastructure as a non-rival, non-excludable good to society at large. In the FCC study, the public good value in the countries likely to participate financially was estimated and found to exceed the sum of all known and quantified costs. This supports, from a societal perspective, the justification for such an investment. As with the LHC, it is also expected that participation would extend beyond CERN Member States, as international collaboration has historically underpinned such large-scale science projects.

As recommended by the OECD [219, 220], the French government [221], the UK government [222], and the European Commission [142, 223], a comprehensive sustainability assessment should consider all relevant elements: total costs, total benefits, negative externalities, positive impacts, and environmental benefit potentials. In practice, not all elements are equally relevant for every investment project, not all can be reliably quantified or monetised, and some remain unknown (Fig. 4.6). Both costs and benefits are affected by uncertainties (Fig. 4.7). The results presented in this chapter must be interpreted in this light. Although the EC CBA Guide [107] recommends a Monte Carlo-based uncertainty analysis, this approach requires probability distributions for each cost and benefit component, which are themselves difficult to obtain with confidence.

The comprehensive socio-economic study therefore describes as precisely as possible the scope, assumptions, and methods used to quantify and monetise costs and benefits, together with the results obtained. This includes acknowledging that not all externalities can be fully captured, and that ex-ante analyses always project future conditions into today's socio-economic environment with associated uncertainty ranges.

Rationalising comprehensive sustainability assessment using standard cost-benefit analysis [225] helps to identify limiting and enabling aspects and can guide the iterative design of research infrastructures. Time is explicitly accounted for, which is essential when considering environmental effects. While methods to quantify costs and negative externalities are well developed, approaches to capture and monetise benefits and positive externalities are less standardised and often project-specific, requiring tailored methods and models.

Sustainability should not be seen narrowly as the internal viability of the project alone, but more broadly in terms of its interactions with external economic, social, and environmental factors. The 17 high-level development objectives (with more than 160 sub-objectives) of the 2015 UN Sustainable Development Goals (SDGs), shown in Fig. 4.8, illustrate the breadth of these factors. The FCC study has not yet conducted a full mapping to the SDGs, but such an analysis should be developed in the next design phase, including the project authorisation stage. Meanwhile, the SDGs can serve as a reference catalogue of potential impacts to be considered, both positive and negative, alongside quantitative CBA results. CERN has already implemented such approaches in its periodic environment report, which relies on the GRI framework [226].

<footnote n="20">²⁰Financial profit is the net income earned after deducting all explicit costs from the total revenue.</footnote>
<figure><img src="image_195.png" /><figcaption>**Fig. 4.7** Examples for the accounting of full costs and benefits for an integrated sustainability analysis. Only the identified cost and benefit items that can be converted into monetary terms were considered in this specific assessment. Exhaustive coverage of all negative and positive externalities is challenging and must be accepted in all socio-economic impact assessments</figcaption></figure>

<figure><img src="image_196.png" /><figcaption>**Fig. 4.8** The UN Sustainable Development Goals (SDGs)</figcaption></figure>

Finally, the choice of the Social Discount Rate (SDR) influences the integration of costs and benefits. Different SDR values can be used to perform sensitivity analyses and to test the robustness of the overall net present value. For this study, only a single SDR value has been applied.

# 4.7 Lifecycle analysis

## 4.7.1 Context

As the global focus on combating climate change intensifies, reducing greenhouse gas (GHG) emissions has become a top priority. Infrastructures spanning transport, construction, and scientific instruments play a critical role in this transition. A lifecycle analysis is an essential tool to analyse the sources of emissions that affect the climate, to understand the drivers, and to optimise the project in view of improved environmental compatibility.

The topic is comprehensive and complex, determined by many uncertainties and by the fact that the different segments of the project are only gradually known as the concept development and design advance. A long-term project like the future circular collider does not deliver detailed designs of the technical infrastructures and particle accelerator components until shortly before procurement. Detectors that constitute the scientific experiments will only be built and procured as a collaborative effort at a much later stage. To be able to leverage the technical advances, detailed designs are only developed when the particle collider equipment is well known, procured, and potentially already being installed.

In addition to this time dependency, LCA and the associated carbon budget assessment strongly depend on the procurement scenario and the scenario of specific technologies. Therefore, the FCC study has taken the approach of focusing first on the best-known project segment, the environmental footprint of civil construction based on the current concept.
The study also included the estimate of the Scope 2 footprint for operation, i.e., the carbon emissions that would be associated with the consumption of energy. Also, a specific procurement hypothesis had to be assumed for this analysis.

It must be understood that the results presented herein are subject to further evolution throughout the lifecycle phases of the project, should a decision to pursue it be taken. In particular, they do not consider certain negative externalities related to the construction of the particle accelerators and experiments, optimisations, which are possible with the use of further advanced technologies, materials, products, local production, responsible sourcing and procurement and the outcomes of commercial negotiations during the procurement processes. Consequently, continuous socio-economic performance monitoring, incorporating eco-design based on an iterative Plan-Do-Check-Act cycle, is important and should be established before entering a preparatory project phase.

The analysis carried out using the European LCA Norms ISO/EN 14040 and ISO/EN 14044 aimed to estimate the carbon budget of the infrastructure construction that would serve two subsequently installed particle colliders. It aims to establish a credible benchmark, leveraging the use of European norm EN 15804+A2 and French FDES norm standardised Environmental Product Declarations (EPDs) of materials and products available today. This approach ensures a comprehensive assessment in line with the European standard and norm EN 17472, which provides requirements and guidelines for calculating and reporting GHG emissions associated with infrastructure projects. The work also included the recommendations of Cerema for the evaluation of greenhouse gas emissions for road projects, the Swiss ‘Koordinationskonferenz der Bau- und Liegenschaftsorgane der öffentlichen Bauherren’ (KBOB) and French ‘Les données environnementales et sanitaires de référence pour le bâtiment’ (INIES) databases for ecological product footprints, and the ecoinvent (ecoinvent is an internationally active, mission-driven organisation devoted to supporting high-quality, science-based environmental assessments) database for products and materials where no EPDs were available. The work revealed some realistic pathways to further reduce the consequences of the construction and gave some recommendations on future aspects that need to be considered during the subsequent design phase.

The results are integrated in the integrating, wider socio-economic impact assessment by converting the results of the LCA into monetary terms using the recommended approach of the EIB and the European Norms EN 14007 and EN 14008.

### 4.7.2 Methodology

The work for the estimation of the construction-related greenhouse warming potential included the following steps:

1. Component identification: Compilation of the detailed inventory of materials based on the bill of quantities for the subsurface construction, the 4 experiment sites and the technical sites. The current conceptual design was considered for this step. The products chosen are used throughout the infrastructure's lifecycle.

2. EPDs acquisition: Sourcing of EPDs for each material identified, ensuring compliance with EN 15804+A2, the foundational basis for EN 17472. The materials are selected based on expert knowledge of the local environment and product availability and hence, represent state-of-the-art solutions.

3. Software tool: Selection of a certified tool compatible with French and Swiss Environmental Product Declaration - One Click LCA®, ensuring robust and accurate calculations.

4. Data entry: Imported data into the tool and entered project-specific data, including material quantities and lifecycle phases, transport for excavated and construction material.

5. Calculations: The tool was used to estimate the carbon budget, drawing on EPDs data to evaluate GHG emissions for each lifecycle phase.

6. Result analysis: Analysed the results to pinpoint major emission sources, comparing them against benchmarks and reduction targets.

7. Formulation of recommendations: Based on the results and the identification of the key impact drivers, a set of recommendations was formulated that is to be taken into consideration in the subsequent design phase to further reduce the environmental footprint of the construction.

For the estimation of the Scope 2 emissions, the following steps were taken:

1. Consumption identification: estimation of the electricity consumption for the baseload and for each operational phase and establishment of an operational schedule.

2. Procurement hypothesis: Establish a credible scenario for procuring the energy based on an external expert consultancy with a focus on sourcing energy from renewable energy sources.

3. Quantification: Quantification of the associated climate effect by using the accredited French ADEME 21 database.

<footnote n="21">21 ADEME stands for Agence de la Transition Écologique, which translates to Agency for Ecological Transition. It is a French public agency under the supervision of the Ministry for the Ecological Transition and the Ministry for Higher Education and Research.</footnote>
<table><caption>**Table 4.1 Summary of the LCA-based carbon budget of the construction process**</caption><thead><tr><th>Item</th><th>Footprint</th></tr></thead><tbody><tr><td>Subsurface</td><td>477,390 tCO<sub>2</sub>(eq)</td></tr><tr><td>4 technical sites</td><td>17,546 tCO<sub>2</sub>(eq)</td></tr><tr><td>4 experiment sites</td><td>31,735 tCO<sub>2</sub>(eq)</td></tr><tr><td><strong>Total</strong></td><td><strong>526,671 tCO<sub>2</sub>(eq)</strong></td></tr></tbody></table>

<table><caption>**Table 4.2 Summary of the LCA-based carbon budget of the construction process**</caption><thead><tr><th>Indicator</th><th>Value</th></tr></thead><tbody><tr><td>Potential contribution to ozone layer depletion</td><td>19.3 kg CFC 11 eq</td></tr><tr><td>Potential acidification</td><td>929 t SO<sub>2</sub> eq</td></tr><tr><td>Potential eutrophication - fresh water</td><td>96 t (PO<sub>4</sub>)<sup>3-</sup></td></tr><tr><td>Potential eutrophication - marine</td><td>12 t N</td></tr><tr><td>Potential eutrophication - land</td><td>2.1 x 10<sup>6</sup> mol N</td></tr></tbody></table>

4. Formulation of recommendations: Based on the results and the identification of the key impact drivers, a set of recommendations was formulated that are to be taken into consideration in the subsequent design phase to further reduce the environmental footprint of the operation.

In both cases, the results were converted into monetary terms using the EIB-established shadow price for carbon. The results were integrated over time and discounted using the 2.8% Social Discount Rate established for the assessment project.

### 4.7.3 Results

*Construction phase* The LCA [59] provided a breakdown of GHG emissions across various lifecycle phases and materials. It is essential to note that the results were achieved using the most advanced, state-of-the-art products and materials currently available on the market. The results are, therefore, credible, and the carbon-related climate footprint can be further reduced as more advanced technology can be included in the project. The key emission sources are reinforced steel (14%), precast concrete (49%) and concrete (23%). The climate effects due to the use of electricity have been included in this analysis. It is assumed that the electricity required for the entire construction process can be obtained from renewable energy sources via local suppliers in France and in Switzerland. The official carbon footprints of today's renewable energy mix in the two host countries have been used in the study (see Table 3.5). The results obtained highlight opportunities for emission reduction by establishing technical requirements for the infrastructure with carbon reduction in mind, careful selection of materials which meet the requirements, construction process optimisation, and energy efficiency improvements. The GHG impacts of the initial and benchmark scenarios are given in Table 4.1.

The value obtained corresponds roughly to 3 years of CERN's annual carbon budget [78] or to one-third of the carbon budget of the Olympic Games in Paris, 2024 [79].

Further environmental performance indicators obtained with the LCA are shown in Table 4.2. Compared to classical, non low-carbon construction processes, the most relevant indicator is marine eutrophication, which can be linked to the use of recycled steel.

The results also enable a comparison to be made between the construction of subsurface structures and conventional structures, such as road and metro tunnels, and tram lines. The latter is characterised by significantly higher carbon footprints as a result of the much stricter requirements that public use imposes. For comparison, the construction of the U5 underground line in Berlin (Germany), a typical small-scale metro line, has a carbon footprint of 80,000 tCO₂(eq) per km. The footprint of a typical tramway line has between 7600 and 10,850 tCO₂(eq) per km. The linear part of a future circular collider subsurface structures has a carbon footprint of about 5300 tCO₂(eq) per km (see Fig. 4.9).

Based on the findings, the following levers were identified to reduce GHG emissions:

* Document technical requirements for the structural surface and subsurface elements that capture the strict minimum needs to fulfil the scientific research programme.

* Develop an eco-design that meets the established requirements with carbon reduction in mind.

* Make structural modifications by reducing the inner line thickness of subsurface structures by 5 cm, leading to a reduction in the quantity of precast concrete and rebar steel of 16%.
<figure><img src="image_197.png" /><figcaption>**Fig. 4.9** Comparison of carbon footprint between a small-scale underground metro line, a tramway line and the FCC. [59]</figcaption></figure>

* Substitute materials, using low-impact materials wherever possible, leading to a further reduction of GHG emissions.

* Optimise the construction process to minimise emissions, including local sourcing of raw and recycled materials and production of construction materials.

* Fully electrified construction processes and transport.

* Reuse excavated materials, for instance, in concrete production.

**Climate effects due to energy use during operation** To estimate the climate effects related to the use of energy (Scope 2) during the operation phase, the electricity requirements have been estimated for the baseload and for each individual operation phase (Z, WW, ZH, t). During the operation phase, the energy needed to power the infrastructures, particle accelerators, and experiments will be sourced entirely from the French electricity grid, managed by the national grid operator RTE. A portfolio of multiple electricity contracts and power purchasing agreements (PPA) facilitates the diversification of the electricity mix and sourcing it from different operators who can provide certificates of origin, leading to market-based carbon footprint reporting. A preparatory study with two independent external consultants identified that on a short timescale, before 2030 60% of the required energy could already be obtained from renewable energy sources and in a time frame of 15 years (around 2040) a portfolio to cover 80% of the needs with renewable energies can be established. For 2050, when the FCC is envisaged to operate, a coverage of 90% is assumed with a residual supply of 10% nuclear energy. For the purpose of the socio-economic performance assessment, a conservative maximum use of 80% energy from renewable energy sources has been used, thus over-reporting the carbon equivalent footprint. To estimate the carbon intensity of the project scenario, the official values of the French National Environment and Energy Management Organisation (ADEME) were used, leading to a mix with a carbon intensity of about 15 tCO₂(eq) per GWh. For the calculations in the socio-economic performance assessment, a more conservative degressive carbon intensity starting with 26 tCO₂(eq) per GWh in 2024, 19.10 in 2046 and 18.41 in 2050 assuming a constant decrease in the emission factor of 4% have been used. Again, this approach leads to an over-reporting of the carbon equivalent footprint. Table 4.3 provides the Scope 2 indication of the carbon budget for each particle collider operation phase with beam for scientific research and the total footprint for all operation and shutdown phases for two different carbon footprint assumptions leading to a range for the expected carbon footprint: 15 tCO₂(eq) per GWh and 25 tCO₂(eq) per GWh.

Integrating the energy consumption requirements over the years of operation leads to an integral carbon budget that corresponds to about 2.5 years of CERN’s annual carbon footprint today. For comparison, the Meta company known for its products Facebook, Instagram and WhatsApp operates currently at least three data centres in the United States with electricity consumptions between 1.2 and 1.4 TWh per year [227]. Their individual, location-based Scope 2 emissions are significantly above, 350,000 tCO₂(eq) per year.

**Shadow cost of carbon** The conversion of the carbon budget aligns with the overall goals for climate protection and temperature limits established by a community of nations in the Paris Agreement. The European Investment Bank (EIB) has calculated a so-called ‘shadow price for carbon’ that represents the costs that humankind needs to associate with climate protection measures to achieve the agreed goal. The shadow price of carbon increases over the years, making one tonne of CO₂(eq) more expensive for society each year. The discounted value of the monetary conversion of the construction and operation-related carbon footprint is about 342 million euros. This amount is added to the integrated socio-economic assessment on the cost side of the balance and is used to estimate the
<table><caption>**Table 4.3** Summary of the operation-related Scope 2 carbon emission footprint using two different market-based carbon intensity assumptions for the electricity purchased. Note that the integral carbon footprint also covers Scope 2 emissions during shutdown periods</caption><thead><tr><th>Phase</th><th>Duration</th><th>GWh/year</th><th>Footprint all years at 15 tCO<sub>2</sub>(eq)/GWh</th><th>Footprint all years at 25 tCO<sub>2</sub>(eq)/GWh</th></tr></thead><tbody><tr><td>Z</td><td>4 years</td><td>1100</td><td>66,000 tCO<sub>2</sub>(eq)</td><td>110,000 tCO<sub>2</sub>(eq)</td></tr><tr><td>WW</td><td>2 years</td><td>1300</td><td>39,000 tCO<sub>2</sub>(eq)</td><td>65,000 tCO<sub>2</sub>(eq)</td></tr><tr><td>HZ</td><td>3 years</td><td>1500</td><td>67,500 tCO<sub>2</sub>(eq)</td><td>112,500 tCO<sub>2</sub>(eq)</td></tr><tr><td>t̄</td><td>5 years</td><td>1770</td><td>132,750 tCO<sub>2</sub>(eq)</td><td>221,250 tCO<sub>2</sub>(eq)</td></tr><tr><td><strong>Total</strong></td><td></td><td>20,350</td><td><strong>305,250 tCO<sub>2</sub>(eq)</strong></td><td><strong>508,750 tCO<sub>2</sub>(eq)</strong></td></tr></tbody></table>

<table><caption>**Table 4.4** Shadow cost of carbon under in currency unit per tonne CO₂(eq) for various jurisdictions. Rates in the first row are also published as European Union law 2021/C 280/01. Note that the 1.5% near-term Ramsey Discount Rate is applied to the US indicated rates</caption><thead><tr><th>Organisation</th><th>Unit</th><th>2020</th><th>2025</th><th>2030</th><th>2035</th><th>2040</th><th>2045</th><th>2050</th><th>2060</th><th>Source</th></tr></thead><tbody><tr><td>EIB and EU</td><td>Euro 2016</td><td>€80</td><td>€165</td><td>€250</td><td>€390</td><td>€525</td><td>€660</td><td>€800</td><td>n/a</td><td>[228]</td></tr><tr><td>EIB and EU</td><td>Euro 2024<sup>†</sup></td><td>n/a</td><td>€208</td><td>€316</td><td>€492</td><td>€663</td><td>€833</td><td>€1010</td><td>n/a</td><td></td></tr><tr><td>SGPI France</td><td>Euro 2018</td><td>€87</td><td>n/a</td><td>€250</td><td>n/a</td><td>€500</td><td>n/a</td><td>€775</td><td>€1203</td><td>[149]</td></tr><tr><td>UBA Germany</td><td>Euro 2023</td><td>€240</td><td>n/a</td><td>€254</td><td>€253</td><td>n/a</td><td>n/a</td><td>€301</td><td>n/a</td><td>[229]</td></tr><tr><td>UK (high)</td><td>GBP 2020</td><td>£361</td><td>£390</td><td>£420</td><td>£453</td><td>£489</td><td>£527</td><td>£568</td><td>n/a</td><td>[230]</td></tr><tr><td>EPA USA</td><td>USD 2020</td><td>$340</td><td>n/a</td><td>$380</td><td>n/a</td><td>$430</td><td>n/a</td><td>$480</td><td>$530</td><td>[231]</td></tr></tbody></table>

net present value of the future research infrastructure at the end of its scientific operation programme. Table 4.4 shows the shadow cost of carbon currently recommended for project appraisal by the European Investment Bank (EIB) and its time-adjusted value to be used in 2025.

## 4.8 Socio-economic performance

### 4.8.1 Context

The goal of the comprehensive socio-economic impact analysis including a wider set of components such as environmental externalities is to get a better understanding of the cost drivers and potential benefits (as indicated in Fig. 4.2). This approach has been adopted to plan for a sustainable scenario. The analysis can also reveal under which conditions the overall socio-economic performance can be positive, i.e., represent a long-term sustainable investment for the society. Carrying out such analysis from the onset enables the project to incorporate the findings in the subsequent design phase, where it is easier to plan for sustainability enablers than during construction or when the infrastructure is already in operation.

The socio-economic analysis relies on a working hypothesis of the investments and resources engaged for the project by an international collaboration. Therefore, the work is based on a total project cost estimate including all investment costs, operation costs, and relevant negative and positive externalities for the entire observation period carried out in 2024. This estimate may differ from project cost estimates carried out later or presented elsewhere, since it represents a snapshot of the estimates taken in June 2024 and it includes global personnel engagements such as those of the international collaborations and monetised negative environmental externalities. The total costs required for the socio-economic analysis include the investment costs (capital and operation expenditures) as well as monetised externalities such as environmental costs and the shadow cost of carbon. Therefore, those costs figures must not be used to determine the financial needs to implement the project. They represent the total cost of the science missions for society for the entire observation period. The same holds for the reported benefits: they represent a collection of identified, quantified and monetised positive effects for society and are not limited to direct economic effects. Neither costs nor benefits can be exhaustively covered due to uncertainties, available resources, and time limitations. However, the herein reported results are sufficiently comprehensive and detailed

<footnote>† Adjusted based on EU-27 GDP deflator 100.0 in 2016 and 126.3 in 2023. It measures the amount to which the real value of an economy's total output is reduced by inflation.</footnote>
<figure><img src="image_198.png" /><figcaption>**Fig. 4.10** Number of persons engaged in the project over the years throughout all project phases</figcaption></figure>

to establish a stable Benefit-Cost Ratio that is unlikely to decrease further with the introduction of additional, minor cost and negative externalities. The socio-economic performance requires periodic updates as the project is defined better and in more detail and as models and resources to estimate additional benefits become available.

A comprehensive report on the socio-economic performance analysis [121] details the data, assumptions, methodologies and outcomes of the first socio-economic impact analysis for the first phase of the integrated FCC research programme: the FCC-ee lepton collider based on only two interaction points. The analysis spans the entire lifecycle of FCC-ee, encompassing its design, the construction of the surface and subsurface structures, the creation of the technical infrastructures, the particle accelerator and experiment detector construction, the operation and the gradual beam energy upgrade phases. The entire analysis spans a duration of 41 years (2024 to 2064), starting with pre-investment study expenses, the financial investment decision and lasting until the end of the operation phase. The methodological approach is based on the regulatory guidelines issued by the European Commission (EC) [232], the European Investment Bank (EIB) [228], the European Strategy for Research Infrastructures (ES-FRI) guidelines [214] and the French Secrétariat général pour l'Investissement (SGPI) [149]. The guidelines adopted are compatible with those in other countries of the European Research Area, for instance, in the UK [222]. The study also considers the latest literature, works, and results of empirical research on the economic quantification of impacts associated with research infrastructures.

In evaluating the FCC-ee project, costs and benefits are expressed in comparison to a scenario where the project is not implemented. In this counterfactual scenario, the LHC would continue its operation until its anticipated end of life around 2040, and no new particle-collider would be constructed. CERN would continue its operation of the existing particle accelerators (e.g., AD, ELENA, LINAC4, PS) and the experimental infrastructures linked to them. It is based on the methods of standard cost-benefit analysis (CBA). All costs and benefits are incremental, i.e., expressed as a difference between the costs and benefits of the operation of the existing infrastructure after the shutdown of the LHC and the costs and benefits that the FCC-ee would induce Consequently, the approach captures the net change, focusing on causally related effects that can be reliably attributed to the FCC-ee project.

This social cost-benefit assessment carried out assumes an FCC-ee project with four experiments, collectively involving approximately 260,000 person-years over the project's lifespan. The engagement of people is expected to reach its peak of about 15,500 people during the operation phase (Fig. 4.10). This diverse group comprises scientists, engineers, technicians, administrative staff, doctoral and post-doctoral researchers, undergraduate students, master degree level students and apprentices. Of the total participants, approximately 11% is assumed to be active on the particle accelerators and technical infrastructures, while the remaining 89% will be engaged in the detectors and experimental physics.

## 4.8.2 Results

The initial socio-economic impact assessment based on 2 experiment collaborations, limited to the investment costs, operation costs, and core benefit pathways, yielded a positive net present value at the end of the FCC-ee operation phase [121]. The subsequent complementary assessment carried out in 2024 [233] used an even more conservative calculation based on an update of the project configuration, considered only a reduced set of well-justifiable benefit pathways, and extended the analysis to wider effects and negative environmental externalities:

* Revised investment and operation costs, reflecting the price evolution of goods and services between 2018 and 2024.

* Four experiment collaborations (instead of two as assumed in the initial assessment).
<table><caption>**Table 4.5** Social cost-benefit assessment of the FCC-ee project expressed as an incremental benefit with respect to a counter-factual scenario in which no collider project is implemented after the end of the HL-LHC operation. The results of the ‘wider’ socio-economic analysis include noteworthy negative externalities and environmental benefits</caption><thead><tr><th>Cost/Benefit</th><th>Undiscounted</th><th>Discounted</th></tr></thead><tbody><tr><td><strong>(A) Costs</strong></td><td></td><td><strong>19,666 MCHF</strong></td></tr><tr><td>Investment costs (for 4 experiments, injector and t<span style="text-decoration: overline">t</span> stage)</td><td>16,215 MCHF</td><td>10,171 MCHF</td></tr><tr><td>Personnel costs</td><td>16,802 MCHF</td><td>7544 MCHF</td></tr><tr><td>Operation costs (materials, consumables, services)</td><td>4410 MCHF</td><td>1879 MCHF</td></tr><tr><td>Dismantling costs</td><td>228 MCHF</td><td>72 MCHF</td></tr><tr><td><strong>(B) Negative externalities</strong></td><td></td><td><strong>354 MCHF</strong></td></tr><tr><td>Shadow cost of carbon</td><td>634 MCHF</td><td>342 MCHF</td></tr><tr><td>Loss of agricultural income, biodiversity & habitat</td><td>7.6 MCHF</td><td>4.1 MCHF</td></tr><tr><td>Social cost of project-related, induced noise</td><td>0.02 MCHF</td><td>0.02 MCHF</td></tr><tr><td>Social cost of project-related, traffic-induced air pollution</td><td>0.9 MCHF</td><td>0.6 MCHF</td></tr><tr><td>Social cost of project-related, traffic-induced GHG externalities</td><td>9.8 MCHF</td><td>7 MCHF</td></tr><tr><td>Social cost of ionising radiation</td><td>1.3 MCHF</td><td>0.6 MCHF</td></tr><tr><td><strong>(C) Core benefits</strong></td><td></td><td><strong>23,974 MCHF</strong></td></tr><tr><td>Scientific production</td><td>6507 MCHF</td><td>2813 MCHF</td></tr><tr><td>Early career researcher training</td><td>20,687 MCHF</td><td>4986 MCHF</td></tr><tr><td>Industrial benefits for suppliers</td><td>17,577 MCHF</td><td>9569 MCHF</td></tr><tr><td>Onsite visitors</td><td>4538 MCHF</td><td>2129 MCHF</td></tr><tr><td>Online and social media</td><td>229 MCHF</td><td>102 MCHF</td></tr><tr><td>Open software (experiments and detectors)</td><td>7428 MCHF</td><td>4375 MCHF</td></tr><tr><td><strong>Total costs including negative externalities</strong></td><td>(A + B)</td><td><strong>20,020 MCHF</strong></td></tr><tr><td><strong>Total core benefits</strong></td><td>(C)</td><td><strong>23,974 MCHF</strong></td></tr><tr><td><strong>Reference net present value (NPV)</strong></td><td>(C) – (A + B)</td><td><strong>3954 MCHF</strong></td></tr><tr><td><strong>Reference Benefit Cost Ratio (BCR)</strong></td><td></td><td><strong>1.20</strong></td></tr></tbody></table>

* Revised social discount rate (2.8%).

* Introduction of noteworthy environmental negative externalities.

* Revision of the major benefit pathway monetisation, including additionally gathered data.

* Strict limitation of benefits to core benefit pathways.

Table 4.5 presents the most certain and stable results of this additional social cost-benefit assessment, showing the core cost and benefit pathways. A set of wider benefit pathways may occur, provided that dedicated planning and implementation are incorporated into the project designs and appropriate contextual conditions are in place (see Table 4.6). To aggregate the value of measured benefits and compare them with costs and negative externalities, a social discount rate (SDR) was established specifically for the project. Instead of relying on existing SDRs suggested by international organisations, this project-specific rate accounts for the level of development and preferences for consumption and investments in countries contributing to the CERN budget and the very long duration of the project. The SDR value assumed is 2.8%. The result, strictly limited to costs, noteworthy negative externalities, and core benefits, indicates a positive net present value of approximately 4 billion Swiss francs for the project, resulting in a benefit-cost ratio (BCR) of approximately 1.20. This value must not be interpreted as a fixed and certain number. A positive BCR under highly conservative assumptions provides confidence that the project scenario can achieve an overall beneficial contribution to society. Depending on the project design and implementation measures to support benefit generation and control costs and externalities, the BCR may be lower or higher. Continuous tracking of the impact generation throughout subsequent project phases and monitoring during the project implementation and operation are required to assure an overall positive performance.
<table><caption>**Table 4.6** Additional benefit potentials not considered in the calculation of the reference net present value and benefit cost ratio</caption><thead><tr><th>Cost/Benefit</th><th>Undiscounted</th><th>Discounted</th></tr></thead><tbody><tr><td>(D) Residual asset value for a subsequent collider project</td><td>−7911 MCHF</td><td>−2480 MCHF</td></tr><tr><td>(E) Wider benefit potentials</td><td></td><td><b>6916 MCHF</b></td></tr><tr><td>Open information platform</td><td>5053 MCHF</td><td>2681 MCHF</td></tr><tr><td>Open collaborative software</td><td>7516 MCHF</td><td>3487 MCHF</td></tr><tr><td>ICT spin-offs</td><td>832 MCHF</td><td>409 MCHF</td></tr><tr><td>Creation of renewable energy sources through contracts</td><td>227 MCHF</td><td>117 MCHF</td></tr><tr><td>Supply of waste heat</td><td>313 MCHF</td><td>132 MCHF</td></tr><tr><td>Avoided greenhouse gas emissions (GHG) by supply of waste heat</td><td>170 MCHF</td><td>74 MCHF</td></tr><tr><td>Rewilding (habitats and biodiversity)</td><td>0.4 MCHF</td><td>0.2 MCHF</td></tr><tr><td>Contributions to regional emergency services</td><td>31 MCHF</td><td>16 MCHF</td></tr><tr><td>Net present value including residual asset value</td><td>(C) − (A + B + D)</td><td><b>6446 MCHF</b></td></tr><tr><td>Total core and wider benefit potentials</td><td>(C + E)</td><td><b>30,890 MCHF</b></td></tr></tbody></table>

The findings of the studies carried out over a time frame of about seven years suggest a positive socio-economic net performance of the FCC-ee project. This result serves to demonstrate the long-term social sustainability of the proposed new scientific research infrastructure. The analysis so far has helped identify the main impact pathways with the goal of supporting the design of the research infrastructure for sustained socio-economic impact generation. The findings reported here are, however, not exhaustive. Concerning costs, the estimates are likely to evolve further during the design phase until an investment decision is made provisional and will be subject to updates. The approach taken to integrate the analysis of impacts on the environment, economy, and society at large is in line with EU practice in policy and infrastructure impact assessment. Further complementary socio-economic analysis, given additional time and resources, would permit additional positive impacts to be uncovered and quantified, strengthening the robustness of the benefits already estimated. Studies by Flyvbjerg et al. [234–236] highlight a common trend of underestimating costs, overestimating revenues, and misjudging environmental and economic impacts and the unintentional introduction of bias. Literature, therefore, supports carrying out an uncertainty analysis, especially in large-scale infrastructure projects. To achieve this, the existing deterministic framework of the CBA can be expanded with a probabilistic model, covering costs and benefits. This approach will provide a more comprehensive view of the project’s expected outcomes.

### 4.8.3 Cost and benefit coverage

Good coverage of the main cost and benefit pathways has been achieved with the presented socio-economic assessment, although exhaustive coverage of a large research infrastructure is limited by the knowledge about impact pathways, models to quantify them, time, personnel and budget. The assessment carried out includes the full investment costs for the civil structures, the injectors, the booster, and the collider up to tt stage and 4 experiment detectors. Full personnel costs comprising CERN paid and personnel supplied by the international collaborations to the programme were accounted for. Full materials, maintenance, consumables, and service costs for the operation phase were included in the costs. Finally, the dismantling costs of the main ring booster and collider were also included. This part does not include the disposal of equipment that would be classified as radioactive waste. Such an estimate can be done only once the technical designs have been completed. It does also not consider the residual market value of the metals that would lead to a gain after dismantling.

The establishment of a proper residual value for a proposed investment is a key element for input to the financial sustainability analysis of such a project. According to the guide to the European Commission Cost-Benefit Analysis of investment projects, the discounted value of any net future revenue after the time horizon of the project has to be included in the residual value. The guide indicates that it is “the present value at year *n* of the revenues, net of operation, costs, the project will be able to generate because of the remaining service potential of fixed assets whose economic life is not yet completely exhausted”. In line with this EC guideline (p. 45, [223]) which economist practitioners use, the residual value is highlighted as a value with a negative sign in the cost account. If there is a ‘use value’ for the assets, then the residual value is greater zero. If not, the residual value is considered zero.
Both scenarios were considered in the analysis. Since the proposed infrastructure can serve two particle colliders in sequence, the residual asset value is considered in this assessment. Due to the very long timespan associated with the integrated programme, this social benefit-cost assessment, however, only concerns the first phase, the lepton collider FCC-ee. A residual asset value at the end of the FCC-ee operation phase is calculated that can be made available as a ‘gift’ to a potential subsequent hadron collider project (FCC-hh). The residual asset value becomes zero if no subsequent particle collider is installed that can profit from the built-up assets. This approach has also been taken for the social cost-benefit assessment of the Large Hadron Collider [192]. The calculation of the reference net present value (NPV) for the lepton collider FCC-ee project is carried out in a very conservative way: it does not include the residual asset value at the end of the observation period. For the purpose of showing that further societal impacts are possible and that an integrated programme consisting of a lepton collider (FCC-ee) followed by a hadron collider (FCC-hh) is preferable, this benefit can be included in a wider NPV.

The materialisation of negative externalities and benefits depends largely on the design of an impact-creation framework and external conditions.

Negative externalities such as the carbon footprint and the associated shadow cost of carbon depend on the procurement actions taken for the construction, the power purchasing agreements concluded for construction and operation, and the national carbon pricing at the time of generating the carbon footprint. The shadow cost of carbon indicated considered the construction and operation of the research infrastructure. The costs for the accelerators and detectors could not be included at this time since they rely on the availability of a technical design and a procurement scenario.

The effects of potential disturbances such as noise and induced traffic linked to the construction depend significantly on the actual number of people that would be affected. Additionally, certain impacts are challenging to predict at this early stage because of a lack of forecast models for certain benefit pathways, because they could not be identified, because of a lack of time and resources, or simply because of large uncertainties. Examples include the wider positive externalities that can emerge from developing novel products and processes for re-using excava- vated materials, advancing technologies for low-carbon construction materials, generating local synergies with the municipalities hosting surface sites, the unanticipated creation of high-value technology spinoffs, and the invention of entirely novel technologies.

This analysis focused on the direct benefits currently known and foreseeable based on past factual evidence, for instance, from the LHC and the European XFEL projects. It was concluded as soon as a high level of confidence was achieved in demonstrating a break-even point between benefits and total costs, including noteworthy negative externalities. Conservative assumptions were made for all estimates. Where a causal relationship between positive or negative effects and the project could not be reliably established, the item was entirely left out. For cost and benefit items for which commitments remain to be formulated (e.g., the development of dedicated open software platforms to support knowledge dissemination and international collaboration, the conclusion of renewable energy contracts or PPAs, the supply of waste-heat, projects to re-create and strengthen the lost habitats, contributions to the operation of regional emergency services), the elements were labelled to be considered as a ‘wider’ societal impact. They were included in the calculation of a wider net present value only.

The economic benefits of visitors rely on the existence of a visit programme, dedicated visit points, infras- tructures and guides. The reported benefits of onsite visitors are incremental with respect to the counterfactual scenario in which no future particle collider project is implemented. This means, it captures the likely benefits on top of the effects generated by visitors that come to CERN after the end of the HL-LHC programme. This counterfactual case is envisaged to be less impactful, since CERN without a new flagship project at a global scale is assumed to be less attractive for visitors, as recent surveys of CERN visitors carried out in the first quarter of 2025 reveal. Some benefits are intangible in nature, such as advances in scientific knowledge, impacts related to science diplomacy, ethical considerations, and trust in science. Although benefits created by open software and collaborative platforms have significant value potential, it is challenging to estimate which, when and in which ways such benefits reach society without a dedicated innovation creation and transfer programme in place for such technologies.

Several further wider benefits have been envisaged, but were not pursued further at this stage due to re- source and time constraints associated with unambiguously clarifying the demand. They include, for instance, the strengthening of the local and regional electricity and communication networks, the creation of soft mobility, the contribution to the improvement of public transport, the creation of housing and schooling facilities, and the development of local businesses and services. However, the study included the development of a framework to start elucidating the demands for such wider benefit potentials with the municipalities in the perimeter of the project. Ongoing and future socio-economic analysis will shed more light on those opportunities once the demands are better understood.

### 4.8.4 Cost and negative externalities

For the cost-benefit calculations, the FCC has been considered as a design-to-cost project, with a total investment including 4 experiments and the tt stage, projected at approximately 16.2 billion Swiss francs (undiscounted) with
an uncertainty range of −5% to +20%. This figure encompasses studies, preparatory activities, design work, civil construction works, creation of technical infrastructures, all particle accelerators (injectors, booster and collider) and all investment costs related to the four experiment detectors.

Personnel costs include all human resources involved in the project throughout all lifecycle phases, irrespective of the organisation employing them. The total personnel costs are composed of wages, indirect costs and employer-related costs without overheads. They are averages for different personnel categories in the different countries participating in the project. In total, personnel costs make up about 16.8 billion Swiss francs (undiscounted) and 7.5 billion Swiss francs (discounted).

Operation costs refer to all expenses (both in-kind and outflows) that are needed for running, maintaining, and repairing the research infrastructure throughout the entire scientific exploitation (e.g., electricity, water, spares, and human resources for maintenance and repair). The likely scenario for the operational costs amounts to a total of 4.4 billion Swiss francs undiscounted with a range due to uncertain costs of resources (e.g., electricity and water), supplies and service contracts. The discounted costs are around 1.9 billion Swiss francs. This corresponds to an average annual undiscounted cost of about 250 million Swiss francs and about 105 million Swiss francs discounted over the operational time that spans from commissioning to the end of operation.

The cost figures used for this analysis, along with the projected number of project users must be regarded as a working hypothesis that serves for estimating the socio-economic performance, that helps to identify key impact pathways. It also helps in understanding which benefit potentials may still have potential for further development. They are formulated based on the understanding of the project at the time of the analysis and are expected to undergo further revisions and refinements as the design progresses.

Estimates of the following cost items covering the period from the investment decision to the end of the FCC-ee operation phase have been included in the analysis presented:

* Capital expenditures for civil construction, technical infrastructures, all particle accelerators (injector, booster, collider) including the upgrade to tt operation and four experiments.

* Cost of acquisition of all land for the surface sites, accesses and nature enhancement around the sites.

* Cost of access road creation or refurbishing.

* Creation of off-site infrastructures required for construction and operation (e.g., accesses, water supply, water treatment, local electricity connections).

* Full personnel cost estimates (CERN and the international collaboration) required for the design, construction and operation phases covering the particle accelerators, technical infrastructures and experiments.

* Typical operation costs (consumables, water and energy, maintenance, repair).

* Dismantling cost of the lepton collider and its specific technical infrastructures that cannot be reused for a subsequent hadron collider.

* Negative residual value of the infrastructures for a subsequent particle collider project.

In addition to the items mentioned so far, a portion of the investments in reusable and durable assets, such as superconducting radiofrequency systems, electricity infrastructure, civil structures, and basic technical infrastructure, will be used in a subsequent particle collider project. According to the EC guidelines on Cost-Benefit Analysis (p. 45, [223]), this residual value is reported as a discounted value with a negative sign in the cost part. The residual value of the initial phase assets is significant and contributes to the sustainability of the integrated FCC programme. The estimated discounted value stands at approximately 2.5 billion Swiss francs, equivalent to 24% of the total investment.

Estimates of the following negative externalities have been included in the analysis presented:

* Cost of managing excavated materials as part of the investment cost.

* Shadow cost of carbon for civil construction and the energy used for operation.

* Cost of rewilding measures in the vicinity of the surface sites (e.g., preservation and improvement of wetlands, creation of trees to compensate for forest clearance and the creation of meadows and grasslands) as part of the investment cost.

* Economic loss (direct, indirect, upstream and induced downstream) caused by the consumption of agricultural land for a period of 30 years.

* Economic value of the cleared forest.

* Economic value of loss of habitat and biodiversity.

* Societal cost of construction and operation-related noise.

* Societal cost of added traffic and air pollution induced by the transport of excavated materials.

* Societal cost of additional ionising radiation.

* Societal cost of radioactive waste as part of the operation cost.

### 4.8.5 Impact pathways

The following impact pathways have been included in the analysis either as core elements or as potential wider benefits:
<figure><img src="image_199.png" /><figcaption>**Fig. 4.11** Expected distribution of FCC-ee scientific products over time</figcaption></figure>

* Value of scientific content production.

* Increased market value of early-stage scientists and engineers.

* Value of on-site tourism.

* Value of online presence and social media activities.

* Value of industrial spillovers involved in the construction of infrastructures, accelerators and experiments.

* Market value of ICT spin-offs based on the frequency of past and current spin-off company creation at CERN.

* Societal value of open software products.

* Market value of waste heat supplied and the societal value of carbon emissions avoided.

* Market value of additional renewable energy sources created as a result of long-term power purchasing agreements.

* Market value of treated waste water.

* Societal value of improved and recreated wetlands, meadows, grassland and forests.

* Economic value of compensated agricultural spaces.

* Societal value of regional emergency and fire-fighting services required for the new research infrastructure.

The following impact pathways are considered highly reliable and form, therefore, a set of core benefits on which the conservative net present value is based:

1. Value of produced and cited scientific publications.

2. Lifetime salary premium of early-career researchers and engineers aged under thirty.

3. Incremental value for suppliers due to follow-up contracts that result from their activity in the project.

4. Value of on-site visitors based on the travel cost method and local spending.

5. Leisure time value of people consuming project-related online and social media content.

6. Estimated value of open software developed in the area of particle detectors and experiments, used by other scientific institutes and industries.

The first impact pathway assessed is the value derived from scientific content production. It stems from the knowledge flow generated by scientists and engineers engaged in the collider and its experiments, resulting in a diverse range of scientific products, including journal articles, working papers, conference proceedings, and presentations. These products can have a lasting impact, extending beyond the high-energy and particle physics community, and potentially influencing other knowledge domains to address broader societal challenges. Scientific techniques were employed to estimate scientific production and its propagation from the FCC-ee project. The methodology involved analysing historical patterns observed in comparable physics research programmes like Tevatron, LEP, and LHC. The economic concepts of opportunity cost and value of time were employed to determine the social value of scientific products. This approach considered the time spent by individuals, depending on their involvement and responsibilities, in an experiment collaboration for producing these outputs and valued it based on their average hourly salaries. This method was applied to estimate the social value of scientific products produced by researchers directly involved in the research programme (so-called 'tier 0' products), those citing the initial tier 0 knowledge (so-called 'tier 1' products), and products citing tier 1 outputs (so-called 'tier 2' products). Between 34,000 and 38,000 scientific products are expected to be directly produced in the course of the FCC-ee project (tier 0 publications), with an additional 538,000 to 618,000 tier 1 and 2 products likely to be generated based on that corpus until the year 2083 (see Fig. 4.11).

Considering that about 55% of the time spent by researchers is dedicated to scientific research activities and the production of the production of scientific outputs, but only about 22% can be attributed to FCC-ee specific scientific products, the estimated benefit from scientific production is around 6.51 billion Swiss francs undiscounted and about 2.8 billion Swiss francs discounted. This valuation accounts for the diminishing value of tier 1 and tier
<figure><img src="image_200.png" /><figcaption>**Fig. 4.12** Lifetime salary of early-career researchers by sector of employment</figcaption></figure>

2 products compared to tier 0 products, as knowledge propagates through subsequent waves of production and the initial input from FCC-ee progressively diminishes.

The second impact pathway studied is the value of early career research and engineer training, which reflects the project’s role in imparting knowledge, fostering skills development and building capacities for individuals actively engaged in the research programme throughout its lifecycle. The value stems from the fact that persons who were engaged in large-scale, multi-sectoral high-tech and science projects at CERN represent a higher value to their eventual employers than persons who do not have such training experience. This is reflected by higher starting wages and faster-growing salaries. The effect remains until the person retires, and it leads to an overall incremental added value with respect to peers without such an experience. The analysis specifically evaluated the benefits accrued by technical students, doctoral students, post-doctoral researchers, and associated scientific and engineering personnel up to a cut-off age of 30. The analysis did not include the training value for apprentices and other highly qualified personnel with limited-term contracts, temporary labour and contracted workers. The benefit has been quantified by estimating the lifelong career development improvements for participants upon entering the labour market after gaining work experience within the research programme. Previous studies, further validated through a survey involving approximately 2600 individuals, indicate that the lifetime salary benefit for an early-stage researcher working at FCC-ee ranges from a minimum of 2% to 10% for the average period of stay in the research infrastructure (3.78 years) (see Fig. 4.12). The total undiscounted socio-economic benefit is assessed at around 20.7 billion Swiss francs, and the discounted value is around 5.0 billion Swiss francs.

The third impact pathway explores the benefits generated by the project for industrial suppliers engaged in the construction of the infrastructure, the particle accelerators, and detectors. The benefit stems from increased financial performance of the suppliers a few years after they have received contracts in the frame of the project. The effect of being a supplier in a large-scale project, in particular in domains that are characterised by project-specific designs, developments, and adaptations of off-the-shelf products and services, is linked to the gain of experience, increase in efficiency, and a broadened market access. In essence, the impact stems from a knowledge gain acquired through close collaboration with the research infrastructure. This knowledge, in turn, contributes to the creation and improvement of new processes, products, and services that suppliers can leverage in other markets and domains. It leads to additional contracts that the supplier is able to conclude because of that knowledge gained. This cause-effect-impact chain has been exhaustively analysed over some decades, and it has been found to be robust and stable. A profit multiplier has been determined, standing at 1.96 for procurement of items with low or moderate level of technology intensity and 3.06 for procurement with high level technology intensity. Applying this multiplier to the investments that are likely to generate further industrial spillovers, the undiscounted benefits are estimated at 17.6 billion Swiss francs. The discounted benefits are estimated at 9.6 billion Swiss francs (see Fig. 4.13).

The fourth impact pathway concerns the benefits generated by on-site visitors. Before 2020, 150,000 visitors per year came to CERN. In 2024, after the opening of the new Science Gateway visitor centre, the number increased to about 350,000 external visitors (not counting visits of persons participating in CERN projects, company visits and visits of employee families, accounting to about 40,000 additional persons). While in the period before the Science Gateway the participation was equally distributed among group visits and individuals, the significantly increased capacity to welcome unguided visits led to a change in the distribution. Today about 76% of people visit CERN individually and 24% come as part of groups that enjoy the possibility to also visit experiment facilities, in particular the ones linked to the LHC. 55% are classified as ‘CERN motivated’ visitors, whose primary purpose
<figure><img src="image_201.png" /><figcaption>**Fig. 4.13** Time profile of FCC-ee industry benefits for suppliers, compared with the high-tech investments costs (Swiss francs, undiscounted - baseline scenario)</figcaption></figure>

of the trip was to visit CERN, while 45% are “region motivated” visitors, who travelled to the area for other reasons and took the chance to also visit CERN. The absolute number of persons that are part of visit groups remained relatively stable. Two campaigns of guided systematic interviews with on-site visitors before and after the opening of the Science Gateway permitted a robust multi-year spending behaviour of the visitors to be established (see Fig. 4.14). In total, more than 4000 individuals were interviewed, and only about 3550 responses with self-consistent and credible answers were retained for the analysis. The average stay of persons in the region is 3.75 days, indicating that once they have visited CERN they extend their visit to further destinations in the vicinity.

The local spending associated with the visit ranged between 625 Swiss francs for group visitors and 713 Swiss francs for individual visitors, with a mean of 691 Swiss francs for all visitors. Based on the survey, sampling from the obtained visitor spending distribution, the sum of the local spending due to 350,000 annual on-site visitors translates to a tangible economic benefit for the region of about 250 to 350 million Swiss francs per year. This figure does not, however, capture the socio-economic benefit related to the FCC-ee. Based on this current survey, only a certain fraction of future visitors can be attributed to an FCC. As outlined initially, the analysis limits benefit potentials to the incremental effects, i.e., the difference between the effects of on-site visitors that can be attributed to the existence of the FCC and the evolution of CERN without the FCC. For this reason, the following assumptions were applied to estimate the incremental socio-economic benefit for the FCC-ee:

* Conventional CERN visits: an increasing share of these visitors is attributed to FCC-ee, starting at 0% in 2024 and gradually rising to 50% by 2064.

* Visitors to the FCC-ee construction sites and the four experimental sites: these visitors are fully attributed to FCC-ee, as they would not have been accounted for in a scenario without FCC-ee.

* Visits to the decommissioned LHC tunnel: adhering to a conservative approach, these are not attributed to FCC-ee since they would be justified even in the absence of the FCC-ee.

* Visits to FCC experiment visitors centres.

* About 10% of all visitors are coming to the CERN main site.

* Open-day visitors: these are attributed to FCC-ee only for the additional capacity created by the new accelerator; all other visitors are excluded from the count.

Based on these assumptions, it is estimated that out of almost 19 million visitors throughout the entire observation period, only about 5.5 million are assumed to be attracted by FCC-ee (see Fig. 4.15), while the remaining will be motivated more by the overall CERN activity and longstanding worldwide reputation of scientific excellence.

Considering that only the incremental benefit is reported here, the difference between the number of visitors that CERN would welcome without and with an FCC-ee is about 13.5 million over the observation period.

The benefit for on-site visitors was monetised using the travel cost method, which incorporates the costs borne by visitors to travel to CERN and FCC, the economic value of time spent travelling, along with local expenditures connected to their visit based on two actual surveys carried out at CERN over two years (pre- and post COVID). The discounted benefit generated by about 5.5 million onsite visitors attributable to FCC-ee is estimated to be approximately 2.1 billion Swiss francs.

The fifth impact pathway analysed concerns virtual visitors who consume webpages and social media. Due to the limited availability of data, the analyses concerned only websites and social media channels that are di-
<figure><img src="image_202.png" /><figcaption>**Fig. 4.14** Distributions of the spending of all on-site visitors, individual visitors and visitors that come to CERN as part of groups</figcaption></figure>

rectly managed by CERN. The estimate, therefore, significantly underestimates the actual benefits generated by
numerous online content that would be made available on a global scale.

The estimated number of online visitors is based on historical data collected by CERN's communication group regarding visits to the main CERN website and social media accounts. Assumptions were made about the number of visits specifically related to FCC-ee. This estimate has been revised to reflect changes in the project's timeline and to ensure consistency with the revisions made in the estimation of onsite visitors, particularly regarding the share of FCC-ee attribution. It is assumed that the highest attributable share of visits is approximately 50%, aligning with the assumption made for CERN visitors.

In the scenario without the FCC, it is assumed that the number of online visits to websites and social media will follow the same patterns as the on-site visitors in the absence of the FCC-ee. In the scenario with the FCC, the number of online visits corresponds to the trend of growth of scientific publications due to the projected FCC-ee research programme. The share of online visits attributable to the FCC-ee starts as a marginal share of the total CERN online visits. The main jump in online visits is expected to occur with the start of operation. This share is expected to grow further during the operative phase. The number of online visitors is expected to reach its maximum several years after 2050 and the end of operation. In these years, the share of the total CERN online visits associated with the FCC reaches conservatively about 50% and remains constant. This assumption is in line with survey results to onsite visitors about the reason to visit CERN today. Based on these assumptions, for the FCC-ee over the 2024–2064 period, impressions are estimated at 1.7 billion, engagements at 79 million, and CERN website visits at 175 million. These estimates are highly conservative and do not take into consideration future social medial developments and online platforms are likely to appear, but whose existence can today not be anticipated.
<figure><img src="image_203.png" /><figcaption>**Fig. 4.15** Number of on-site visitors attracted by FCC-ee over the period 2024-2064 used for estimating the impact estimation</figcaption></figure>

The monetisation of these visits is based on the actual observation of an online presence of a little over 3 minutes. Distributions are applied to different media types, such as social-media interactions and consuming online video snippets related to FCC. The value of time spent is determined using the ‘opportunity cost’ method, which suggests that time spent on social media and websites represents a missed opportunity to engage in other potentially profitable activities. Since not all virtual visitors are necessarily part of the economically active workforce, the opportunity cost of time was estimated by using per capita GDP (instead of wages), adjusted based on the geographical distribution of virtual visitors. The total undiscounted cultural benefit for online visitors is estimated to be approximately 229 million Swiss francs, which corresponds to 102 million Swiss francs discounted.

The sixth core impact pathway encompasses free and open-source software, systems, and platforms causally linked to the research programme. It is assumed that in particular software related to the experiment and detector projects generates incremental societal value due to the adoption by other science projects, research institutes, and companies with particular needs that cannot be easily satisfied by commercially available software. While the first user base is typically found in the physics, astronomy, and medical research domains, companies using such software can be very diverse. Recent examples of using software from the LHC experiments range from space-borne earth observation systems through medical imaging and mining to shipping container traffic and stock-market transaction analysis. In essence, in any application where massive amounts of data need to be processed, patterns need to be identified in background dominated environments, time-critical applications demand custom solutions, and data processing efficiency is key to success, the developments of particle physics scientists and engineers are sought after. Increasingly, these software systems also underpin advances in artificial intelligence (AI) and machine learning, both as training grounds for novel algorithms and as sources of specialised tools for large-scale, high-dimensional data analysis, thereby widening the spectrum of industrial and societal spillovers. This is an area of active and ongoing development.

The estimation of this benefit pathway is based on the use of actual particle detector modelling and simulation software, for which the use outside the core community could be tracked over recent years. It serves as a ‘proxy’ for comparable developments for which the need during the development of FCC detectors and experiments has been confirmed. Like software package analysis, new software can find use beyond the core community, thereby generating a spillover benefit for society. A number of developments will concern the use of artificial intelligence in this area, configurable hardware, edge computing, and ever-evolving data communication technologies. Several of these developments are admittedly associated with uncertainties, but as the past has shown, it is likely that the collaborations around the FCC-ee experiments will be able to make significant contributions in the ICT domain.

For detector modelling and simulation software, approximately 50 research centres, space agencies, and companies were identified using software developed for the LHC experiments. This included 38 institutions beyond CERN that contributed in some way to the developments. Examples include but are not limited to the Fermi National Accelerator Laboratory, SLAC National Accelerator Laboratory, the Centre for Medical Radiation Physics, and the European Space Agency. Additionally, 12 other laboratories, institutes, and companies use such software without contributing to its development. They include, for example, NASA, General Electric, Philips, Siemens, Varian, Boeing, and General Motors. CERN does not systematically track the number of users and installations, but data available in 2023 suggest a current user community of about 95 contributing institutes (excluding CERN). Assuming the ratio of 3:1 between contributing and non-contributing institutions remains stable, the total number
of non-contributing users is estimated to be around 30. In the absence of more reliable data, this estimate is
considered reasonable and conservative.

The benefit is estimated as the avoided cost for the external users, and it is based on the cost of production of comparable new software. It was estimated that the production cost of existing detector modelling and simulation software was about 44.2 million Swiss francs up to 2013, covering the first 20 years of its development starting in 1994. CERN contributed about 50% of this cost (22 million Swiss francs), with the remaining amount funded by other external contributors. The estimates are based on the hypothesis of comparable cost figures for FCC-ee related software and assuming CERN’s contribution remains at 50%. The avoided cost for each contributing organisation is the total estimated production cost minus their specific contribution, while the avoided cost for non-contributing users is the full production cost. It is assumed that new software would be first released after 5 years of development with developments continuing over the years, even during the operation phase, due to the continued interest by academia and industry.

In this scenario, the total cumulated avoided cost representing the total undiscounted benefit is estimated to be about 7.4 billion Swiss francs. The discounted benefit is about 4.4 billion Swiss francs. This benefit, in fact, would stand for a range of potential software developments that cannot be explored in detail at this early stage. It is advised that any future development foresees an open access mechanism for such software, actively promotes such software in areas outside the particle physics community in science and industry and, most importantly, includes a systematic tracking of active users to help make socio-economic impact estimates more accurate and reliable.

4.8.6 Wider benefits

A number of wider benefits have been analysed in detail in addition to the core benefits presented in the previous section. Due to uncertainties that are linked with the possibilities to actually turn the wider benefit potentials into tangible impacts, they are not considered in the calculation of the reference baseline net present value. The analysis and quantification of those benefit potentials is, however, based on factual observations of past effects and outcomes and is therefore solid with respect to monetisation. As with the core benefits, highly conservative working assumptions have been established, and only effects that can be credibly justified have been included. Therefore, a second net present value is presented that includes those wider benefits. To turn such potentials into tangible impacts, the preparatory implementation phase of the future project needs to include dedicated work that plans for such benefit creation. Voluntary objectives and commitments are needed by the project owners to put instruments in place to actually turn the potentials into impacts. Last but not least, monitoring and tracking will need to be put in place to follow up on the impact generation.

The following wider benefits have been studied and are briefly presented in this section:

1. Open information platform

2. Open collaborative software

3. Company spin-off generation in the information and communication technologies (ICT) sector

4. Build-up of renewable energy sources

5. Supply of waste heat

6. Avoidance of greenhouse gases by substituting traditional heat energy sources with recovered and supplied waste heat

7. Improvement and creation of habitats and increase of biodiversity

8. Strengthening of emergency services

A future, global collaborative research project relies on a long-term, open scientific and technical information platform that permits the community to make its knowledge widely available so that it becomes findable, accessible, interoperable and reusable (FAIR principle). CERN has a long-term track record in putting such infrastructures in place, the World Wide Web being the most prominent one. This technology subsequently permitted the development and making available of additional services, such as the CERN Document Server (CDS), which is based on the in-house developed Invenio platform. This development has led to the creation of the Zenodo service, which the European Commission has endorsed as the catch-all repository for all EU-funded research. Today CERN operates this platform that is entirely part of the European Open Science Cloud (EOSC) for the European Commission. By continuing to be at the forefront of big science, CERN can have a lead role in scientific and technical information provision in Europe and at a global scale. The launch of a new large-scale science mission, the FCC, justifies not only the continuation of ongoing developments, but will likely also lead to the development and implementation of a new generation of information systems, in line with past occurrences. Such a platform may offer functionalities that go beyond pure document and data management and long-term data preservation. It may offer services that are today impossible to conceive. In order to estimate the potential value of such a future development, the value of the Zenodo platform was estimated as a conservative reference with minimum functionality offered to society today. This was possible, because historic data of sufficient quality for relevant periods could be identified. An econometric model was constructed to estimate the socio-economic impact of the virtual information repository,
designed to fulfil collaborative information storage and usage requirements. The estimated monetised value is derived from measurable benefits associated with comparable repositories, encompassing data storage, online usage, and downloads, net of the present value of its development, operation and maintenance costs.

The undiscounted value over the FCC-ee observation period of such a platform is 5 billion Swiss francs, and its discounted value is about 2.7 billion Swiss francs. To turn such an impact potential into reality, several pre-conditions apply: the global community participating in the project has to have a demand for such a platform, the community must be committed to use the platform, communities beyond the high-energy and particle physics domain must adopt the platform (as was the case with the Zenodo platform being endorsed by the European Commission). The fundamental requirements rely on an intent to play the role of developing and operating an information platform for several user communities. Long-term sustained resource engagement and a plan to disseminate the developments beyond the core community are also needed.

Another typical case for open platforms in the history of CERN's large international collaborations is the creation of tools that support collaborative work. The 'Integrated Digital Conference' (Indico) event management system is one example of such development. It revolutionised the management of physical and virtual meetings, lectures, conferences and led to a comprehensive documentation of collaborative work and can be considered a key enabler of global collaborative projects. Since its start of development in 2002, the platform has spilled over to numerous academic and international organisations worldwide. A future large-scale project not only has very similar needs, but will create demands beyond those that are satisfied with this platform today. The integration of collaborative writing, sketching, AI support for meetings and minute taking, translation among different languages, collaboration management, video conferencing, recording and media publication, real-time messaging, shared workspaces, integration with document management, approval and selected information distribution processes are just a few selected examples for which the need is already starting to appear in the frame of the studies related to the FCC.

For these reasons, the current Indico platform was chosen as a conservative, representative example of a collaborative platform that can enable and improve future collaborative work in the frame of a large-scale project. The value generated from developing a new service to facilitate the worldwide collaboration involved in the FCC project in terms of meetings, calls, and event management was assessed by considering the willingness to pay (WTP) by private users for a comparable toolset, totalling 7.5 billion Swiss francs undiscounted and 3.5 billion Swiss francs discounted. Since the potential of such a new ecosystem relies on a commitment for development, the adoption by communities beyond high-energy and particle physics, the value was only considered as a wider benefit.

The knowledge-transfer office records of the last two decades have shown that a stable number of companies have been created every year by persons who were engaged in CERN's flagship particle collider project and the international experiment detector collaborations. A prominent example includes Proton AG with over 400 employees and more than 100 million customers, offering secure e-mail and VPN as an unparalleled service to other providers. Other examples are Advacam which specialises in imaging devices for various industrial applications based on particle detector technology, LightEye working on LiDAR technology for long-range wind speed measurements to improve aviation safety and PlanetWatch which specialises in data acquisition of environmental data. Based on these factual historical data, it is assumed that FCC-ee would generate approximately two new spin-off companies in the information and computing technologies (ICT) sector alone each year from the design and preparation phase until the end of the observation period. Considering the probability of company survival each year and the annual market value of companies in the ICT sector, the socio-economic benefit is estimated to be at least 832 million Swiss francs undiscounted and 409 million Swiss francs discounted. This figure does not include the economic benefits that are generated by numerous micro enterprises and independent consultants that carry out their activities thanks to the experience and skills they acquired in the frame of large-scale particle accelerator and experiment detector projects.

Some selected environmental benefits that the project could generate were also assessed. They include the voluntary goal of supplying the infrastructure with electricity from renewable energy sources. Entering specific energy supply contracts and long-term power purchasing agreements (PPAs) can serve as a lever to build up new renewable energy sources since the power supplier can secure long-term funding of new renewable energy investment projects before making a financial investment decision. A scenario of a portfolio of complementary energy supply contracts for the FCC construction and operation has been analysed in terms of this value-generation pathway. Assuming that after 2050, society is largely de-carbonised and conservatively, no growing demand for such a funding instrument is assumed on a time horizon of more than 30 years, the reported benefit remains limited: 227 million Swiss francs discounted and 117 million Swiss francs discounted. The development of a renewable energy portfolio can, in principle, begin with an investment decision for a new particle collider project and with a commitment of the project to engage renewable energy sources. In this case, the potential benefit can rapidly turn into a tangible economic benefit. It is suggested that this benefit be revised by that time and reconsidered under the evolving project implementation boundary conditions.

A large part of the energy used to operate the particle collider and its experiments is converted into heat. Traditionally, the heat is dissipated via water-based cooling systems that connect to evaporation towers. A study
has been conducted to prove the feasibility of recovering and re-using waste heat. Recovery and supply of waste heat is a concept that is built into the design of the particle collider from the onset. Recovered waste heat will be supplied via district heating networks to consumers in the vicinity of the FCC-ee sites. The environmental benefit stems from the fact that the energy used by the FCC research infrastructure is reused and supplied for heating and cooling purposes, avoiding the use of alternative, mainly non-renewable, sources with higher carbon intensity such as gas, wood, oil and conventional electricity mix. The environmental benefit of waste heat reuse is derived from the avoided GHG emissions in the project scenario, where CERN supplies waste heat—produced using a cleaner electricity mix—to district heating networks serving consumers near the FCC-ee sites. This is compared to the emissions from alternative heating and cooling methods typically used in the CERN region. The total benefit is estimated at 170 million Swiss francs undiscounted, corresponding to 74 million Swiss francs after discounting.

However, turning this potential benefit into tangible socio-economic impacts requires the adaptation of the operation schedule to the demand curve, agreements with district heating operators to establish and operate networks, and customers who commit to using the heat. Since such developments are typically time-consuming, entail territorial developments that last one to two decades, and depend also on local developments around the future surface sites, the benefits are not included in the core net present value calculation. In addition, the potential benefits emerging from the avoidance of greenhouse gas emissions by replacing conventional heat sources are uncertain for the timescale after 2050, when in principle the economy aims at being largely de-carbonised. Together the benefit potentials, i.e., the costs saved by using waste heat instead of conventional heat sources and avoiding greenhouse gas emissions, add up to about 313 million Swiss francs undiscounted and 132 million Swiss francs discounted. Once a decision to move forward with a project has been taken, a revision of these impacts can take place, since a stronger commitment from the project owner also enables regional stakeholders to plan for waste-heat district heating networks and this eventually will lead to significantly increased benefit potentials.

The project only consumes land due to the development of eight surface sites, but it also opens opportunities to create new natural spaces in the immediate vicinity of the sites. Creating or improving those habitats to integrate the surface sites well in their environments can strengthen the natural spaces around the sites, protecting them from further artificialisation and helping to improve the biodiversity, partially compensating for the effects of the loss of space. While today rewilding projects are foreseen in connection with the surface sites, they have not yet been discussed with the local stakeholders and they have not yet been designed. Therefore, this benefit remains potential and is not included in the calculation of the core net present value. The rewilding of habitats and biodiversity could represent an undiscounted value of 0.4 million Swiss francs corresponding to 0.2 million Swiss francs discounted.

The future particle collider will be embedded in a territory that spans an area of roughly 30×30 km. Care has been taken to select locations for surface sites that are in the vicinity of major transport routes. Nevertheless, the current concept implemented at CERN to provide emergency, rescue and fire-fighting services to surface sites of existing particle accelerators from a central fire brigade at CERN becomes unfeasible for a future infrastructure of the FCC scale. Therefore, the safety concept foresees a strong and lasting collaboration with local emergency services. This concept can be based on support with equipment, training, and personnel made available by the research infrastructure. It could help to increase the expertise and skills of local emergency services, contribute with state-of-the-art equipment, strengthen the number of specialists in the region and increase the cooperation and coordination among different emergency services. This benefit potential has an undiscounted value of about 30 million Swiss francs and represents a discounted value of about 16 million Swiss francs. Since it relies on the development and implementation of a safety concept and plan at the territorial level which can require significant amounts of time and adjustments that make the concept implementable, the benefit is not included in the core net present value calculation today.

Furthermore, two other classes of benefits described in the subsequent sections have not been directly included in the overall formula to determine the project's net present value: the economic creation of value added and the public good value.

*Complementary analysis of economic value added* The economic value added has been estimated in addition to the socio-economic impact by analysing the economic linkages (indirect, direct and induced) during the entire 30-year period covering design, construction and the operation phase of the FCC-ee using the established Input-Output Table methodology [237]. The study estimated the economic and employment effects that are connected to the construction and operation of the new research infrastructure. They are not included in the incremental cost-benefit analysis, since they do not represent the creation of new economic goods and services beyond the research infrastructure, but they lead to economic value added due to the activation of numerous economic sectors in the frame of the research infrastructure-related activities.

These effects primarily arise from the construction of civil structures, particle accelerators and colliders, technical infrastructures, experiments, operating expenses, and personnel-related consumption. This economic analysis was conducted for an infrastructure with two experiments and has not been updated to reflect the current baseline.
Using an economic input-output model, the cumulated expenditure of about 21 billion Swiss francs over a 30-year construction and research operation period could be connected to some 800,000 person-years of employment opportunities, corresponding to almost 30,000 jobs per year via global value-adding chains. In addition to about 6000 directly project-related science, engineering, administration, and management jobs globally, more than 20,000 jobs are needed to provide the goods and services for construction and operation. The host countries, Switzerland and France, and especially the canton of Geneva and the Departments of Ain and Haute-Savoie could benefit most from the operation phase-related expenditures. In total, around 13,000 jobs would be filled or created annually on average in France and Switzerland.

An initial, construction-related investment of 12.1 billion Swiss francs directly generates 5.4 billion Swiss francs of value added globally, generating almost 80,000 person-years of employment, i.e., more than 8000 jobs per year over a ten-year investment period. Including the indirect effects in the production process, value added linked to the investment rises to 11.6 billion Swiss francs, leading to about 180,000 person-years of employment or 18,000 jobs per year during the investment period. Widening the system boundaries to include depreciation (i.e., the capital stock firms need to build up or replenish in order to cope with the FCC-related production), the FCC-related value added grows to more than 14 billion Swiss francs and leads to more than 230,000 person-years of employment opportunities or 23,000 jobs per year during the investment phase. All types of companies, large, medium and small, can enjoy the benefits from the value added. The countries that can profit from these benefits depend on the procurement strategy chosen. The construction sector benefits the most, as almost half of the investment volume can be attributed to civil engineering. Along the cycle, however, its share steadily declines, while the shares of most other sectors rise.

The operation of the FCC generates value added by paying wages and social security contributions and through the depreciation of the investment. No (net) operating surplus is considered since CERN, a purely scientific research organisation, is not profit-oriented. The direct value added during the operation phase is estimated at around 455 million Swiss francs annually. For operation, a mix of inputs (intermediate goods and services) is needed, whose procurement will provide suitable firms with the opportunity for sales and employment and thus generate about 165 million Swiss francs of indirect value added annually. The total direct, indirect and induced value added during the operation phase of more than 620 million Swiss francs per year supports 8400 jobs, the majority in France and Switzerland. The buildup and supply of renewable energy sources for the operation of the research infrastructure would raise Europe's value added by another 500 million Swiss francs, securing an additional 7400 person-years of employment in Europe. By economic sector, the structure of the consumption effects is markedly different from the effects of the investment and operating expenditures: real estate activities, (retail) trade, personal services and the hospitality sector are the main beneficiaries of the consumption of project-related employees.

The lower limit for annual tourism spending due to the project in the wider Geneva region is at least 130 million Swiss francs per year. Switzerland and France share the bigger part of the total effects, with around 1700 jobs linked to visitors only. Another 500 jobs are European; the rest – around 600 – are filled outside Europe. Globally, tourism effects would sustain about 2700 jobs.

The consumption of electrical energy in the frame of long-term power purchasing agreements would generate a direct value added due to the capacity build-up activities of about 200 million Swiss francs, linked to 3500 person-years of employment. Including intermediate inputs and investments needed to produce and install the equipment, the contribution to Europe's value added rises to 510 million Swiss francs, securing 7400 person-years of employment in Europe. Worldwide added value effects related to the electricity supply sector amount to 620 million Swiss francs or 11,600 person-years of employment.

These figures must be interpreted with some caution. Most importantly, the indirect jobs are derived under the assumption of a steady state. The estimates do not project major economic variables into the future (exchange rates, price levels and productivity being the most important ones). Therefore, the effects are estimated as if the FCC were constructed and operated today. This should not be considered a shortcoming, as it helps decision makers to grasp the effects of the estimates more easily when referring to a familiar frame of reference – the economy as it is today. The resulting figures on value added are less compromised by this simplification, due to the fact that the evolution of economic key performance parameters cannot be forecast on the timescale of an FCC project with construction starting in the mid-2030 s and coming into operation in the late 2040 s. The employment figures linked to the expenditures represent reliable upper bounds since labour productivity is expected to rise. Even under changing economic conditions, the FCC would remain what it is today – a major undertaking for the scientific community and society at large, with likely significant scientific, technological, engineering and economic impacts.

The analysis shows that the costs that a project like the FCC entails are also connected with tangible economic impacts in terms of sales opportunities for firms and employment opportunities for scientists and non-scientists alike. By concentrating on a core set of transmission mechanisms only, these results constitute a lower bound for the expected economic effects. Therefore, even though the narrow economic linkages of the construction and operation are not larger than would be expected for a project of this size, the potential for spillovers into quite unrelated areas of technology and business is certainly much more pronounced – for example, only a few projects would have the touristic attractiveness, not to mention their technological and scientific potentials.
Also, by estimating the regional structure of the effects linked to the construction and operation of the FCC, the analysis has shown that the connection between contribution to CERN, direct contracts, and indirect benefits is not always clear-cut. For example, China and the United States, which are not member states of CERN, are estimated to have sizeable economic benefits due to their prominent roles in global value chains. This information could form the basis for negotiations between CERN and countries such as China on intensifying and formalising closer collaborations in the future, which would be beneficial for both parties.

*Public good value* To gauge the volume of the societal benefits, a comprehensive survey was conducted among nearly 10,500 individuals across nine countries [176], including both CERN member and non-member states potentially contributing to the future particle collider project at CERN. The survey aimed to assess public awareness of CERN and its research activities, to evaluate the perceived value of a new research infrastructure, like FCC, to the public, and to compare this monetised value with the per-capita annual contributions made by CERN member states.

The public good value should not be integrated in the estimate of the project’s net present value, since the perceived value of the project, i.e., the value that taxpayers associate with the project, is orthogonal to the actually estimated incremental benefits. Measured through the willingness to pay, the public good value also depends on the knowledge of the project, its costs, negative externalities, and likely incremental benefits. Hence, the value of it is affected by some cognitive biases, such as, for instance, an information bias. The presence of such bias is not negative and cannot be avoided. They are part of the mechanism that permits people to associate a value to an asset to which they have no direct access.

Results indicate that 41% of the respondents are aware of CERN and its mission, which, although lower than some other international organisations like NASA, remains generally positive. Over 80% of respondents believe that scientific research at CERN advances our understanding of the universe and contributes to improving quality of life. The hypothetical willingness to participate financially in the development of the new research infrastructure project was assessed, revealing varying distributions by country. Median values range from 2 Swiss francs per person per year in France to 20 Swiss francs in Switzerland, both CERN member states. For non-member states, the median willingness to pay (WTP) varies from zero in Japan to 24 in the USA (although the mean value for Japan is 10 Swiss francs, meaning that a significant fraction of the Japanese adult population values that type of scientific research). The total value was estimated by multiplying the estimated per capita yearly WTP by a total adult population of about 380 million persons over 30 years in the CERN Member States, starting with the first relevant investments.

In all observed cases, the perceived public value in CERN’s member states is higher than CERN’s annual operational budget of 1.4 billion Swiss francs. The average per capita contribution in these states is approximately 2.5 Euro per year or about 5 Euro per income taxpayer per year. The total estimated WTP for a future collider project at CERN surpasses the estimated total costs of the FCC by a factor of 20 and exceeds its quantified benefits by over 11 times.

These findings robustly support the conclusion that the decision to invest in a future particle collider programme at CERN can be considered justified from a societal perspective since the people who potentially fund the endeavour assign more value to it than it costs in total.

### 4.8.7 Conclusions

The socio-economic impact analysis is based on a social cost-benefit assessment conducted on the first phase of the FCC programme, spanning a time frame of 40 years from the financial investment decision to the end of operation. The FCC-ee has quantified costs, negative externalities and conservative benefit potentials and wider benefit potentials across various domains. Costs of about 20 billion Swiss francs discounted and negative externalities of about 354 million Swiss francs can be compared to the benefits that this research infrastructure can generate. The total present value of the monetised core socio-economic benefits associated with the FCC-ee research infrastructures has been conservatively estimated at a discounted value of 24 billion Swiss francs. Additional wider benefits amount to about 7 billion Swiss francs discounted. The infrastructures would represent a residual value of about 2.5 billion Swiss francs for a subsequent hadron collider, made available as a ‘gift’ to this second project.

The conservative estimate for the net present value (NPV) of the project over its entire observation period is about 4 billion Swiss francs, yielding a positive benefit-cost ratio of about 1.20. Including the residual asset values can bring the NPV to about 6.5 billion Swiss francs. Extending the estimates with wider benefit potentials, the project provides an opportunity to reach an even higher NPV. However, achieving such a performance requires the design, planning, and implementation of benefits, as well as generating measures with commitments and continuous monitoring and tracking at the level of CERN and international collaboration. Proper risk management and cost control must be in place to manage costs and negative externalities.

Costs were based on the currently available investment cost estimates and on the experience of operating CERN’s particle accelerator and collider complex over the last two decades. The most noteworthy negative externalities
were identified, quantified and monetised using lifecycle analysis methodologies and guidelines at the European level for wider socio-economic impact assessment and project appraisal. Cost values were currency and time value adjusted for 2024 as the base year.

Benefits have always been appraised through a conservative methodology, drawing on the current understanding of the project, insights garnered from analogous past research infrastructures, and socio-economic impact analyses on the LHC [192] and the HL-LHC [118] that were carried out as pre-cursors, anticipating the need to eventually produce an FCC socio-economic impact study.

Additionally, recent data collected between 2020 and 2024 has played a crucial role in shaping these estimations. To ensure a comprehensive perspective, data gathering efforts included over 16,000 individuals through online surveys. This diverse group included members of the public, visitors to CERN, users of platforms like Zenodo and Indico, as well as former researchers.

In a likely scenario between optimistic and pessimistic assumptions, the quantified benefits exceed the total costs associated with the design, construction, and operation of FCC-ee, resulting in a net positive socio-economic impact for the project.

Should a financial investment decision be taken to proceed with a construction project, it will be necessary to update the assessment during the coming years and to compile all the materials necessary to obtain funding from participating countries and seek authorisations from the host states.

The approach used in this analysis intentionally entirely excludes the uncertain and unforeseeable impacts of knowledge increase generated by the science mission on society because of their inherent unpredictability.

The assessment of the public good value of the research infrastructure for the public offers an insight into the overall benefits of a future particle collider project at CERN for society, gauged through the public's perspective and willingness to financially contribute to a project's implementation. The insight that the perceived value of a future research infrastructure project exceeds the costs of the FCC is important evidence that the public values such scientific research more than it actually costs and thus helps obtain the Social Licence to Operate (SLO).

While recognising the need for refinement, this analysis serves as a tool to inform decision-making, optimise user engagement, identify and mitigate risks, and enhance social acceptability for the FCC-ee project. The findings emphasise that the FCC-ee project holds the promise of positive impacts not only for the scientific community but for all of society, thereby contributing to the project's long-term sustainability.

## 4.9 Returns to participating countries

### 4.9.1 Overview

Several economic analysis organisations (e.g., LSE [179], WIFO [238]) have been consulted to analyse how potentially participating nations can increase the likelihood of benefiting from financially contributing to the project. An example set of those proposals is compiled in this section.

There exists a consensus among experts that international organisations, including CERN, generate significant economic and societal impacts beyond their core activities in their host countries and their participating nations.

One existing concept to ensure a continuous return to the participating countries is the International Liaison Officer (ILO) approach for integrating national companies in the procurement processes of the international organisation. This approach was studied by economists, and it was found that for a future large-scale project, a more structured and comprehensive approach could lead to better returns for the participating nations.

The recommended measures [179] to ensure good returns to the financially participating nations revolve mainly around three topics:

1. Industry benefits

2. Training benefits

3. Cultural benefits

One lever to ensure good returns is to increase the sustainability of spreading the benefits of procurement, by enabling more firms across the various regions to successfully participate in future collider-related procurement and to tap into the value chain created by the contracts. This concerns:

* Levelling the playing field so that more firms can participate in the procurement process, for example by adopting standard tendering procedures (e.g., publishing opportunities on the EU TED platform using NACE codes) or by unbundling large contracts into smaller lots, thereby facilitating the participation of SMEs (see Sects. 3.3 and 3.5 in Ref. [179]).

* Supporting SMEs as these are the firms that are most likely to face barriers in the procurement process.

* Embedding more firms in the procurement value chain.

* Decarbonising the procurement supply chain through aggregated energy supply contracts or power purchase agreements (PPAs) and energy communities that permit pooling renewable energy contracts for groups of suppliers and larger procurements.
Another lever is to foster brain circulation. CERN is an attractive place for people from across the world to study and work. However, many of these talented individuals end up remaining abroad once their project involvement ends, leading to what is often referred to as brain drain for their country of origin. In order to ensure that more places benefit from human capital formation in a virtuous process of brain circulation, the following policies can help:

* Understanding the local needs for talent so that Member States and their regions can target the repatriation of people better.

* Attracting CERN alumni through tailored initiatives.

* Boosting connectivity so that sending and receiving regions benefit from human capital development.

A further lever is to extend the benefits of tourism and to increase it to more regions. With the new Science Gateway, each year 300,000 to 400,000 people visit CERN. However, most of the benefits accrue in a small geographic perimeter in Switzerland and France, where CERN is located. One way for more regions to tap into this is to ensure that the larger FCC perimeter benefits from the on-site visits. Then, further developments can take place to turn CERN into a gateway for science tourism.

Economists have developed proposals that can be considered in the project development phase to help partic-
ipating nations to reap the most from the opportunities that a new large-scale project offers. One possibility for
a contributing country would be to establish a national organisation with dedicated staff that aims to develop
the most suitable matches between the country's competencies and interests and the project. This activity goes
beyond classical industrial liaison. It aims to integrate schools, universities, research centres, companies of all sizes
and national funding agencies through development policies and concrete actions with the project. This requires
in-depth knowledge about the project, ensuring that the organisation's personnel is involved long-term to be able
to build up durable links and gain comprehensive knowledge of the landscape of national competency and capacity.
While the remit of such an organisation would be broader than existing liaison structures, its format could build
on comparable initiatives such as CERN's Industrial Liaison Officers (ILOs) and the EU's National Contact Point
(NCP) networks, which are explicitly referenced in the policy recommendations of both the LSE [179] and WIFO
[238] reports as effective examples of small, dedicated coordination mechanisms.

The direct revenue from procurement contracts is only considered the tip of an iceberg of potential impacts.
Long-term returns can exceed those from direct contracts by far. They include:

* Repatriation of people and acquisition of highly skilled and trained personnel from the project.

* Training nationals at all levels for limited periods abroad.

* Using the project as a pilot factory, demonstrating technologies, bringing technologies to market and entering new markets.

* Build durable transnational value chains, using the project as a motor for national innovation, leveraging national funds.

* Connect companies of different sizes.

* Break up research silos by bringing universities and institutes from different disciplines together around a single science project.

The entire concept aims to overcome the information asymmetries that privilege only a few companies and universities that benefit from historical links, which enable them to benefit from CERN’s large-scale science projects.

All efforts to plan for a good return on investment for financially participating countries rely on a systematically established analysis, tracking, and regular evaluation of socio-economic performance that can adapt the project. Sufficient evidence exists regarding the socio-economic benefits of CERN’s activities through various pathways; however, a gap remains in understanding what is needed to increase and sustain these effects. Making data gathering and evaluation an integral part of the FCC project can help set goals for data collection and the methodological approaches to measure these effects.

The recommendations documented by LSE and WIFO for ensuring good returns for participating nations provide specific and tangible examples of successful cases for each policy recommendation based on past initiatives. A significant advantage of several proposals is their standalone nature: they can be implemented individually. Many of them can also be implemented independently by countries and regions, allowing them to reap benefits from a project without involving other participating nations.

4.9.2 Local employment opportunities

A future research infrastructure with additional territorial development can lead to territorial benefits through direct employment, goods and services supply, as well as indirect and induced job opportunities in a wider perimeter than currently covered by CERN’s activities. Indirect and induced impact not only concern the value chain of regionally supplied goods and services, i.e., further materials and service suppliers to satisfy the needs of
FCC suppliers and jobs that satisfy the needs that emerge from the presence of personnel associated with FCC construction and operation in the vicinity of the surface sites. The federation of certain activities that relate to the construction and operation, i.e., services that are research infrastructure enablers at certain locations, can also create new and durable territorial employment opportunities. Such services include, for example, during the construction project planning, project management, construction site preparation and operation, and business services (e.g., accounting, human resources, IT, land plot management). Services for the operation phase include, for instance, surface site surveillance and safety, technical operation services, technical maintenance, operation of visit facilities and general business services, as is the case with the construction phase.

The economic impact potentials, in particular the employment-related effects, are still under study and development of the relevant supplies and services as well as the locations where they would be supplied. Preliminary analysis points to opportunities in the range of 1000 to 2000 jobs over a sustained period of time until the end of the century. The effects are mainly linked to household expenses generated by those persons, representing per year about 219 million euro for the region Auvergne-Rhône-Alpes. Direct tax-related benefits are estimated to be in the range of 2.6 (regional) to 3.3 (national) million euros per year. Indirect and induced tax-related impacts range between 3.6 (regional) and 4.1 (national) million euros. The main sectors that would benefit from these are trade, housing, specialised construction works, civil engineering and public works, commerce, manufacturing and specialised equipment, materials processing, financial and insurance services, chemical processing, energy production and distribution, cultural goods and services, restoration, and telecommunications.

These preliminary results should be taken with caution, as the project scenario, construction, and operational organisation are at a very early stage and are subject to ongoing development.

### 4.9.3 Opportunities for impact generation

The following policy recommendations to generate regional returns in a global project are examples drawn from studies conducted by independent economic research organisations.

* Participating nations build up national support organisations to connect various actors (companies, universities, research centres, innovation hubs, national funding agencies) to the new research project to leverage beyond pure contract acquisition as much as possible:

- Piloting technologies.

- Bringing technologies to market.

- Training people.

- Exploit the scientific research opportunities.

- Leverage national funding for developments motivated by the new project.

- Attracting highly qualified and trained people via job fairs.

- Transferring knowledge from the project to universities and companies.

* Move to a standard tendering approach, which includes adopting standard keywords and codes and publishing tendering opportunities to a wider audience, such as in the Supplement to the Official Journal of the European Union (TED). This can reduce search costs for firms and increase the opportunities for small and medium enterprises (SMEs).

* Use the standard international NACE<fnref n="22" /> code system to ensure that companies receive requests for participation that match their competencies well and to ensure that countries can make an efficient match of their specialisations to the project's needs.

* Establish dedicated support centres within local business association offices in regions with concentrated clusters of firms active in the project relevant sectors. These centres will offer specialised support to regional SMEs aspiring to engage in the procurement process.

* Unbundle large contracts to enhance the possibility of SMEs to participate in the procurement process while making the supply chain more resilient.

* Set aside lower value contracts for SMEs, if they meet competitiveness criteria for quality and price.

* Conduct value chain mapping for the different technologies required to understand the spatial distribution of procurement activities and for regions to better understand the local competitiveness opportunities.

* Set up Local Content Units (LCUs) as separate bodies or functions to be developed within existing regional development agencies in areas where important CERN suppliers are located. They may also be established and coordinated directly by CERN as a 'local economic impact acceleration unit'.

* Create alliances between regions with project-relevant sectors to facilitate interregional collaboration and the sharing of knowledge.

<footnote n="22">²²The Statistical Classification of Economic Activities in the European Community, commonly referred to as NACE (for the French term 'nomenclature statistique des activités économiques dans la Communauté Européenne'), is the industry standard classification system used in the European Union.</footnote>
* CERN could facilitate energy supply contracts or aggregate power purchase agreements (PPAs) by acting as an anchor tenant or encouraging the creation of consortia. Alternatively, energy supply contracts or PPAs can be created for larger procurements and groups of suppliers can be created in the frame of dedicated supplies. Also, energy communities that exist in other countries are an effective example of obtaining electricity for production and manufacturing purposes from renewable energy sources. Conditions can be included in procurement requirements.

* Regions identified as talent contributors should conduct a comprehensive analysis of the type of skills that the region needs to attract with a special focus on profiling homegrown talent that has left the region to join CERN.

* Create and promote opportunities through grants and fellowships targeting high-skilled individuals to move to their regions.

* Provide repatriation incentives to return to their home region for individuals who stayed at CERN.

* Engage with CERN staff and alumni abroad through knowledge exchange and entrepreneurship programmes, mentorship schemes and awards.

* Together with tourism boards and other research facilities, develop science tour packages that feature additional scientific attractions across Europe and technology hubs in combination with other activities.

* Establish a funding stream for sustained socio-economic impact evaluation and data collection from the outset of the FCC project.

* Operate an Open Data portal that attracts social scientists to use CERN to continue to evaluate the socio-economic impact of investment in science.

## 4.10 Requirements and constraints for a preparatory phase

The subsequent design and preparatory phase requires a more detailed design of the technical infrastructures, based on systematically identified and properly structured and documented requirements for the particle collider and the experiments. This documentation must be used to conduct a life cycle analysis (LCA) in accordance with the standards and best practices already employed for the analysis of the construction footprint.

Due to the absence of a detailed design, the long time scales, and the need to develop a particular procurement scenario for a study, a more high-level approach can be taken for the estimation of the potential climate effects of the particle accelerators and experiments. However, much care must be taken to avoid an approach that is too simplistic and only focuses on the generic analysis of the carbon footprint of the assumed materials. As far as possible, full systems should be considered; where this is not feasible, reasonable assumptions about the manufacturing, assembly, and installation processes must be made and included in the analysis.

Concerning the use of renewable energy, it is important to establish an energy procurement team that can anticipate the development of supply contracts or purchase agreements. The team needs to develop a strategy and prepare for establishing an energy supply portfolio, taking into account the test, commissioning, and operational phases. The preparation for procuring energy for the construction phase is to start as soon as possible. A time frame of ten years is considered adequate for the preparatory and procurement process of renewable energy for the operation phase.

The potential of waste heat supply and reduction of water consumption depends on national stakeholders putting district heating networks in place and working with CERN on water treatment and supply of treated water at a regional level. Therefore, dedicated local designs, operational plans and pilot schemes will need to be put in place before the research infrastructure is assumed to enter the operation phase. A time window of 20 years is adequate, considering authorisations, financing, the establishment of local operators and the connection of consumers to the district heating network.

With respect to landscape integration, the development of rewilding projects, the use of excavated materials and the design of compensatory actions need ample time for working with local and regional stakeholders. This also requires the allocation of dedicated project-internal resources to establish contracts with external partners and to work together with them, the communities, and public administration. Several years should be allocated for building up these capacities. Hence, a schedule that provides flexibility in working with local and regional stakeholders is needed, thereby avoiding the build-up of excessive pressure. Such pressure can be counterproductive to achieving mutual agreements and consensus on territorial development projects, as well as generating socio-economic benefits at all levels.

## 4.11 Recommendations for a preparatory phase project

This section presents a set of recommendations that have been derived from the work presented in this analysis. Their purpose is to ensure that the benefits can be monitored and regularly reported so that the updated findings can be integrated in the infrastructure's design, construction, and operation phases.

The socio-economic study showed that a break-even of costs and benefits can be achieved with the FCC-ee research infrastructure with the impact pathways documented so far. However, the potential can only be
fully exploited if a continuous tracking of socio-economic impacts is integrated in the infrastructure's design, construction, and operation phases. To achieve this objective, nine recommendations have been made to the FCC project owners by the expert group of economists (CSIL, LSE, WIFO, University of Milano, Economic University of Vienna) who have been involved in the socio-economic studies so far.

1. **Allocate adequate personnel and material resources for the impact identification, design, planning, implementation, monitoring, and assessment** to help fully leverage the impact potentials and make FCC a socio-economically sustainable endeavour. The personnel need to be empowered so that the results of the impact assessment and the impact generation recommendations are accommodated in the design where appropriate, that they are implemented, and that they are continuously and systematically monitored. Also, the analysis should be carried out with the help of all participating project members. This requires that the socio-economic impact assessment is implemented across the entire organisation, with the direct involvement of the highest managerial level and reporting directly to CERN's key stakeholder, the Council. This approach is expected to secure the sustainability and effectiveness of the process, as well as help enhance project acceptance among financially contributing countries.

2. **Encourage participants to publish scientific and engineering works via gold open access channels** (as opposed to self-publishing) and reputable outlets (as opposed to depositing information in preprint servers only). This ensures proper identification of work for tracking purposes and increases the likelihood of their uptake. This socio-economic impact assessment study has revealed challenges in identifying all the scientific output associated with the research infrastructure activities. It is essential to track the scientific production of researchers involved in experiments and monitor citations across papers and other scientific products. However, scientific outputs lacking proper unique digital identifiers and citation references, as is often the case with workshop proceedings and presentations available on platforms like the CERN-developed Indico [239], cannot be adequately identified and considered for socio-economic valuation. These types of outputs should, whenever possible, be replaced or supplemented by citable reports or papers. Establishing strategic partnerships with leading publishers, as exemplified by the SCOAP3 [240] project, is a suitable approach to ensure the presence of citable publications. Open-access platforms used for dissemination could integrate download, citation and reference tracking if they do not already offer those functions (e.g., Zenodo [241] and ArXiv [242] currently lack these functions). Furthermore, additional research is necessary to expand the monitoring and tracking of scientific content beyond scientific and engineering articles and presentations to include books to better understand the societal uptake of knowledge acquisition within the FCC programme.

3. **Foresee a framework to monitor the movement of people after they leave the project**, to facilitate the analysis of future career developments. Every individual contributing to the project for a minimum duration should be encouraged, on a voluntary basis, to engage in a comprehensive monitoring programme. Thanks to mechanisms to reconnect with them periodically, this initiative would entail long-term follow-up and periodic collection of a set of basic information concerning their current work position.

4. To ensure the effective analysis of industrial spillovers generated during project implementation, **incorporate systematic monitoring of the incremental economic impacts on suppliers** resulting from procurement actions over multi-year periods. Given that these effects may not manifest immediately and can extend beyond the duration of the procurement contract, it is crucial to obtain feedback from the companies involved. This necessitates the establishment of a comprehensive procurement monitoring framework that facilitates ongoing engagement. Such a framework should include provisions for storing information on the individuals initially involved in the contract, enabling periodic follow-up after the contract's conclusion. Additionally, it should facilitate the collection of essential information regarding the spillover effects on the company generated by the procurement experience with CERN. This can be achieved through mechanisms such as short online surveys designed to gather pertinent data. By implementing this approach, the FCC programme can gain valuable insights into the long-term economic impacts of its procurement activities, fostering continuous improvement and enhancing collaboration with industrial partners.

5. **Information and Communication Technologies (ICT) have been identified as a key impact pathway that should be better leveraged** through society-targeted transmission actions, accompanied by systematic monitoring of uptake. CERN and the FCC represent a globally unparalleled environment for the development of software and platforms to serve the needs of global collaborations, which are in high demand across societal and industrial sectors as well. By identifying the specific requirements of such collaborations and initiating dedicated development projects, the potential for widespread adoption beyond the FCC project can be created. Examples include collaborative event management, document creation, communication (both one-to-one and one-to-many), file sharing, information management, social networks, remote operation, cybersecurity, distributed computing, and data processing. CERN and its member states should ensure that the technologies developed are accessible at no charge to users outside the high-energy and particle physics community, while also guaranteeing long-term maintenance and improvement. This requires making software and tools available on platforms that support download and installation tracking. The lack of such data has been identified as one of the limiting factors hindering the accurate estimation of ICT impacts.
6. With respect to the impact of spin-off companies, there is a need to establish a systematic method for tracking companies founded by former participants in the FCC programme, monitoring their evolution over time, and assessing their economic value. The establishment of new companies that leverage knowledge acquired through the FCC programme represents a significant societal benefit. Notably, spin-offs often emerge from participants’ amalgamation of different skills and experiences rather than the direct exploitation of a single licensed technology. In particular, the technologies developed in collaborative R&D projects cannot be attributed solely to CERN, and CERN does not track the technologies of its collaborating partners. However, to accurately gauge the economic and societal benefits generated, a voluntary, systematic tracking mechanism is essential.

This tracking framework should facilitate a comprehensive assessment of the impact of spin-off companies. It could include the establishment of a centralised database to record information about spin-off companies (such as their founders, country, industry sector, products/services offered), and have the possibility to periodically contact them to provide updates on their companies' progress.

7. The study revealed the relevance of economic benefits due to on-site visitors. To ensure sustainable monitoring of the on-site tourism impact pathway, CERN and the FCC collaboration should **establish a unified framework to continuously collect essential data on visitors to CERN's exhibition centres, the experiments and any other relevant visit site.** A systematic tracking mechanism for visitors is indeed necessary to accurately report on the effects of on-site visitors. Visitors should be requested to provide a small set of basic information, including their country of origin, mode of transport to Geneva, the main purpose of the visit, duration of stay, visitor spending, and feedback on the exhibitions and the visit sites (e.g., their level of satisfaction). By implementing this monitoring framework, it will be possible to effectively track and evaluate the cultural impact of on-site visitors, as well as enable continual enhancement of visitor experiences.

8. The **identification and quantification of environmental benefit potentials and the development of dedicated projects should be intensified.** The identification and analysis of environmental benefits are important for social acceptability and for achieving a net-zero balance of the scientific research activities for society. This requires the establishment and empowerment of economic and environment experts in the upcoming project preparatory phase, as well as intensified cooperation with industrial partners and Host State services, to ensure a reliable identification of potential environmental benefits and costs associated with the project. In addition to the creation of renewable energy sources and the reuse of waste heat and excavated materials, further opportunities may be uncovered through additional research and extended discussions with project stakeholders. For instance, impact pathways related to water usage, land management, biodiversity conservation, and transport infrastructure need thorough investigation. Assessing potential negative environmental impacts is equally important. Understanding and mitigating adverse effects, such as pollution, is critical for achieving sustainable outcomes and ensuring the responsible use of natural resources.

9. **Continuous monitoring of the so-called 'common good value' has been identified as a suitable approach to validate the investments against the expectations of funders, ultimately the taxpayers.** This effort should be strengthened by conducting regular surveys across all potential funding countries, thereby deepening the understanding of how social acceptance can be not only sustained but also enhanced.

A framework for streamlining this process has been developed within this project, enabling the activity to continue with only marginal additional resources. Expanding data collection to additional countries beyond those already surveyed can provide insights into the factors influencing the people's perception of the FCC science mission. The findings should be regularly shared with CERN management and the Council and summarised for broader dissemination to all stakeholders, including the public, through channels such as CERN's social media platforms and its main websites.

**Funding information** Open access funding provided by CERN (European Organization for Nuclear Research).

**Data availability** The authors declare that the data supporting the findings of this study are available within the paper and/or its supplementary information files.

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