Environmental Sustainability in Stadium Design and Construction: A Systematic Literature Review

: Large stadiums are highly visible assets for large-scale ‘mega-events’, inspiring built environment professionals to innovate in structure and aesthetics. In recent years environmental performance—or environmental sustainability—has been increasing in focus, with events such as the Olympics calling for ‘green games’ and countries committing to reducing built environment carbon emissions. This paper presents a systematic literature review of large stadiums’ environmental sustainability discourse over the last ﬁve years related to design and construction. Using the PRISMA methodology, 18 relevant conceptual and empirical research papers were distilled from 159 extracted papers. Energy consumption and material composition were the most discussed topics. Emergent technologies and processes were also extensively discussed regarding signiﬁcant embodied energy and indoor air-quality improvements, and greenhouse gas emissions reductions. There was a lack of best practices, or whole life cycle considerations, and minimal demonstration of other attributes of environmental sustainability. This paper provides a baseline to assess progress on environmental sustainability for the built environment sector. A practical deﬁnition is presented for Environmentally Sustainable Stadiums (ESS) and a checklist is provided to support leading practices in design and construction. This paper is relevant for built environment professionals and asset owners and managers considering new-build and refurbishments.


Introduction
The first modern Olympic games in 1896 is considered as the starting point for the era of 'mega-events', with large scale visitor attractiveness, mediated reach, cost and transformative impact [1].Within the sporting industry, the Olympics and the FIFA Football World Cup are regarded as the largest mega-events globally, acting as catalysts for transformative development in host cities for local development and urban revitalization [2][3][4][5][6].Large stadiums are built for hosting these mega-events, with FIFA's stadium requirement including a minimum 40,000 capacity for hosting a World Cup quarter final, 60,000 for hosting a World Cup final and a minimum 80,000 capacity to conduct opening and closing ceremonies [7].Associated infrastructure, event management and travel by competitors and visitors have been criticized for having negative environmental impacts.For example, the predicted carbon footprint of the recent 2022 Qatar World Cup was estimated to be around 3.6 million tonnes [8].Preparation of the 'permanent-venue' (i.e., stadiums) is estimated to comprise 72% of these GHG emissions [7].The stadiums built for mega-events often become a financial burden to the stadium owners and the local community after the event due to underutilization and lack of maintenance, and are therefore left abandoned and become white elephants [2].
The strategic positioning of large stadiums as community facilities long after the megaevents goes some way to supporting the value proposition of expending such emissions, considering a stadium's long service life [9].There are still significant opportunities to address mega-event resource usage and carbon emissions through addressing the environmental performance of stadium infrastructure.Initiatives that address the different environmental sustainability categories such as materials, energy, water and light, along with new design and construction methods such as multi-purpose stadiums (e.g., AT&T Stadium in the US) and modular infrastructure (Strahov Stadium in Prague, Stadium 974, Qatar), can help to enhance the overall environmental sustainability outcomes of a stadium [10].Considering aspirations such as the United Nations Sustainable Development Goals (UNSDG) and Paris Agreement [11], the challenge is to ensure that large stadiums are environmentally sustainable while also providing a hub for community development and resilience.Such a holistic goal requires considering the full life of a stadium, spanning planning, design, construction, operation, maintenance, post-event game use, through to end-of-life demolition or repurposing [12].

Novelty of the Study
There is limited literature addressing mega-event infrastructure and sustainability as most academic papers document sustainability in general terms.Furthermore, stadium design and construction lag behind other building types in the adoption of green building methods due to its unique characteristics.For example, adoption of passive design strategies which can improve thermal comfort and reduce cooling energy loads can be seen in other type of buildings such as residential buildings as retrofit options but is limited in stadium infrastructure [13].Additionally, papers that investigate how to design, construct and maintain a large stadium which is environmentally sustainable throughout its life cycle are limited.
In 2014 the International Olympic Committee (IOC), put forward Agenda 2020 and the International Federation of Association Football (FIFA) introduced mandatory green building certification for all new and renovating official World Cup stadiums from 2018.These new requirements, along with recent building codes and other legislation, may play a significant role in raising the bar on sustainability initiatives in stadium design and construction.As a result, more environmental sustainability initiatives are being considered in large stadiums and subsequently academic papers which focus on one or more environmental sustainability initiatives or technologies have started to be documented.For example, improving thermal comfort and balancing energy usage in stadiums can be seen as one of the emerging areas in sustainable stadium infrastructure.Studies using Computational Fluid Dynamics (CFD) that focus on aforementioned areas, such as the combined usage of air curtains and roof cooling supply slot in large stadiums to prevent the infiltration of hot air from outside and reduce the cooling system's energy consumption [14] and the use of PVC film-based black coated fabric as a shielding material in the cavity of an ethylene tetrafluoroethylene (ETFE) air pillow ceiling system to reduce the transmission of sunlight and maintain a lower indoor temperature and thereby to reduce energy usage [15], are gaining momentum.
However, there is still a relative absence of papers that investigate the various aspects of environmental sustainability of a large stadium's life cycle and how different environmentally sustainable features are being integrated during the design and construction of large stadiums.This highlights a gap between the understanding about what is known about environmentally sustainable stadiums and the state of play within which large stadiums are currently working.

Significance of the Study
Infrastructure construction is an important and influential area to improve environmental sustainability in stadiums [16].The objective of this study was to collate and review recent developments in the design and construction of large sports venues, considering, 'How are large stadiums currently being designed and constructed for environmental sustainability?'.To guide the review, the authors explored four questions: (1) What is being defined as an 'Environmentally Sustainable Stadium' (ESS); (2) major drivers ensuring ESS outcomes; (3) major resource saving measures and engineering features embedded in stadium design and construction to improve environmental sustainability; and (4) how environmental sustainability assessment tools and green building certification systems are being used in the design and construction of stadiums towards sustainable outcomes.

Contribution to New Knowledge
In this paper the authors present the findings of the review, exploring what an environmentally sustainable stadium (ESS) constitutes, identifying major drivers for ESS design and construction, and the most common resource saving areas in the design and construction of large stadiums.The paper analyses how effective new environmentally sustainable initiatives are in reducing the environmental impacts of large stadium design and construction.Additionally, this paper evaluates the application of different environmental sustainability assessment tools and green certification systems used in large stadium projects.Finally, the paper reconceptualizes the concept of environmental sustainability in large stadiums by proposing an ESS definition and checklist.Through this, this systematic literature review sets a solid foundation for future research in this field.

Materials and Methods
Systematic literature reviews (SLR) follow a transparent scientific design going beyond other type of reviews which are usually limited by an ad hoc literature selection [17].An SLR is comprehensive, structured, explicit and reproducible, guided by a well-defined methodology [18].SLRs help to reveal the areas where knowledge is lacking which is vital to guide future research.The authors also acknowledge the potential limitations and challenges of SLRs, including the risk of bias, grey literature exclusion and limited number of databases as the sources.To overcome these potential limitations, the authors used electronic databases for searching, and management products such as Endnote, Covidence and NVivo to organize and analyse the data retrieved.This also added efficiency to the processes, enabling the research team to edit and discuss the data remotely in real-time.This SLR was also completed by a team with mixed methodological expertise.
This SLR adopted the methods outlined by Xiao and Watson (2019) [19] and Braun and Clarke (2006) [20] for conducting systematic literature reviews and thematic analysis, comprising two steps.Step 1 is SLR protocol development and Step 2 is SLR execution [21].The SLR protocol development consisted of four steps: purpose definition, formulation of research questions, keywords and database selection.A summary of the process is presented in Figure 1.This SLR followed the 'Preferred Items for Systematic Review Recommendations' (PRISMA) protocol described by [22].A summary of the process is presented in Figure 2.This SLR followed the 'Preferred Items for Systematic Review Recommendations' (PRISMA) protocol described by [22].A summary of the process is presented in Figure 2.This SLR followed the 'Preferred Items for Systematic Review Recommendations' (PRISMA) protocol described by [22].A summary of the process is presented in Figure 2. Step by step flow of information of the systematic literature review using the PRISMA approach.Adapted from [22].
The primary objective of this study was to identify the recent developments in the design and construction of large stadiums for improved environmental sustainability and to uncover the research gaps in designing and constructing environmentally sustainable stadiums.The following overarching research question was developed to address these aims, 'How are large stadiums currently being designed and constructed for environmental sustainability?'

Keywords Selection, Search Strings, Strategy and Article Search
To begin the systematic literature review process, two initial steps are vital; (1) creating the search strategy and (2) finalizing the literature sources [23,24].These literature sources were located by searching the results of defined search strings in various electronic databases [24].In this SLR, three key terms were identified ('sustainable', 'stadium' and 'design') and these were used to develop search strings for the literature search.These keywords together with their synonyms and closely related terms were identified and connected using different Boolean operators such as 'OR', 'AND' and 'NOT' to create Boolean search strings.The search strings used in this SLR comprised the following statements: (sustainab* OR "environment* sustainab*" OR "environment* friendly" OR ecofriendly OR resilient OR "green certif*" OR "circular economy" OR "resilient infrastructure*" OR "green infrastructure*") AND (stadium* OR "sport* facilit*" OR "sport* arena*" OR "sport* stadium*") AND (design* OR construct* OR build* OR architect* OR engineer* OR infrastructure*)

Database Selection
Databases were selected according to their relevance and coverage of the field, with a mix selected to get the best possible results and to cross check if the searches were comprehensive.Scopus, Web of Science, ProQuest, Sage, Ebsco, Ovid, Informit and Wiley Online were the selected databases for data collection.The search considered peer reviewed academic journal articles written in English.A preliminary search for publications using the identified key search terms in these databases resulted in more than 39,000 publications, as shown in the Supplementary Materials.
A heading and abstract-level review of a random sample of approximately 400 of these papers found that most were not central to stadium design and construction and, among the rest, the majority were not directly relevant to the aims of this SLR.To identify the most relevant papers, articles were limited to those published in the last five years (2017-2021), building on Sotiriadou and Hill (2015) [25] and Aquino and Nawari (2015) [26], and considering the IOC's Agenda 2020 and FIFA's mandatory green building certification for all official World Cup stadiums from 2018.Within this context, the author team concluded that the most innovative developments in environmental sustainability of stadiums are happening in recently constructed stadiums and/or stadiums that are under construction.A few other filters were also used in the process, as shown in Table 1 below.

Study Selection and Data Screening
A total of 159 academic articles were extracted from the literature search and screened.A minimum of two reviewers conducted the initial screening, full text screening and final analysis of relevant papers, using the inclusion and exclusion criteria presented in Table 2.
The initial Title and Abstract screening and Full Text Screening were conducted using Covidence [27].A total of 22 articles were deemed suitable for inclusion in this review, however four of these were excluded while doing the final screening and quality assessment of the papers.The final list of 18 papers is summarised in Table 3 below.It is noted that one paper is a review paper of secondary sources; however, this paper is included in the study as it critically assesses the infrastructure development associated with the 2018 PyeongChang Winter Olympics, synthesizing official statistics and information from civic organisations, media reports, etc., and therefore it provides an excellent case study analysis of a mega-event construction project.The authors acknowledge that the academic papers do not necessarily provide a statistical representation of the number of stadiums that are adopting environmentally sustainable initiatives internationally.However, they do provide an insight into the types of environmentally sustainable initiatives, and we acknowledge that academic literature lags behind industry practice.This gap between academic literature and industry practice is mentioned in the conclusion of the paper as something that is needing to be addressed.Papers written in any language other than English Table 3. Papers reviewed in this SLR.

Paper Title Reference
A thin line between a sport mega-event and a mega-construction project: the 2018 Winter Olympic Games in PyeongChang and its event-led development [4] Analysis of the influence of cooling jets on the wind and thermal environment in football stadiums in hot climates [14] CFD optimisation of a stadium roof geometry: a qualitative study to improve the wind microenvironment [28] Challenges and key factors in planning legacies of mega sporting events: Lessons learned from London, Sochi, and Rio de Janeiro [29] Circular economy application for a Green Stadium construction towards sustainable FIFA world cup Qatar 2022 [30] Climate vulnerability as a catalyst for early stadium replacement [31] Construction of the Evaluation System of Sustainable Utilization of Large Stadiums Based on the AHP Method [12] Environmental management of sport events: a focus on European professional football [32] Examination of sustainable features of stadiums as an integral part of sustainable urban development: the case of Turkey [6] How circular design can contribute to social sustainability and legacy of the FIFA World Cup Qatar 2022™?The case of innovative shipping container stadium [33] Investigating alternative development strategies for sport arenas based on active and passive systems [34] Modern Stadium Design: an adaptive renovation or urban renewal.[35] Research on the Indoor Physical Characteristic of the Ceiling of China National Aquatics Center under the Demand of Olympic Games [15] Reusing Stadiums for a Greener Future: The Circular Design Potential of Football Architecture [36] Rwanda Cricket Stadium: Seismically stabilised tile vaults [37] The Object-Oriented Politics of Stadium Sustainability: A Case Study of SC Freiburg [38] Using Simulation-Based Modeling to Evaluate Light Trespass in the Design Stage of Sports Facilities [39] Water savings and reduction of costs through the use of a dual water supply system in a sports facility [40]

Thematic Analysis
The selected 18 articles were imported to NVivo 12 software version 1.6 to analyse the content [41,42].The authors began the thematic analysis with a deductive approach, then initial coding was conducted addressing the research questions, coding into a-priori nodes.New nodes were generated for coding any new data found from the sources that did not align with the initial nodes.Sub nodes were also created under the main nodes for collating similar data [20].For example, a main node called engineering features included sub-nodes for materials, energy, water, light and air quality.Axial coding, where data were linked together in new ways to reveal new codes and categories as well as to find new relationships and connections between codes and categories, was also performed [43].Thematic analysis to collate different codes into potential themes and patterns to provide descriptive and analytical findings from the data was then conducted after completing the coding process.This step involved in the NVivo coding and coding outcomes is shown in Figure 3.
sub-nodes for materials, energy, water, light and air quality.Axial coding, where data were linked together in new ways to reveal new codes and categories as well as to find new relationships and connections between codes and categories, was also performed [43].Thematic analysis to collate different codes into potential themes and patterns to provide descriptive and analytical findings from the data was then conducted after completing the coding process.This step involved in the NVivo coding and coding outcomes is shown in Figure 3.

Descriptive Analysis
This section describes the research context, journals, range and frequency of journal articles, research methods and types of sports venues of the 18 academic literature papers found from Scopus, Web of Science, ProQuest, Sage, EbscoHost, Ovid, Informit and Wiley Online.

Journal Paper Characteristics
Figure 4 presents the journals in which the articles were published along with the number of publications.Within the eighteen articles, three were published in Sustainability followed by International Journal of Sports Marketing and Sponsorship and Environmental Impact Assessment Review (two articles each) as shown in Figure 5. Online.

Journal Paper Characteristics
Figure 4 presents the journals in which the articles were published along with the number of publications.Within the eighteen articles, three were published in Sustainability followed by International Journal of Sports Marketing and Sponsorship and Environmental Impact Assessment Review (two articles each) as shown in Figure 5.  Calls for improving environmental sustainability of large stadium design and construction emerged with FIFA's requirement for all official World Cup stadiums under construction or renovation to be green building certified from 2018 and the IOC's Agenda 2022 [44,45].This paper also builds on the work of Aquino and Nawari (2015) [26], who investigated different techniques adopted for sustainable stadium design and construction, and Sotiriadou and Hill (2015) [25], who pointed out that addressing the negative Calls for improving environmental sustainability of large stadium design and construction emerged with FIFA's requirement for all official World Cup stadiums under construction or renovation to be green building certified from 2018 and the IOC's Agenda 2022 [44,45].This paper also builds on the work of Aquino and Nawari (2015) [26], who investigated different techniques adopted for sustainable stadium design and construction, and Sotiriadou and Hill (2015) [25], who pointed out that addressing the negative impacts of sports facilities and events on the environment are yet considerably under-researched topic in field of sports.
As shown in Figure 6, since 2018 there has been a constant increase in the number of articles published which suggests there is an increasing trend in environmentally sustainable design and construction of stadiums.Among the eighteen articles, 50% (nine articles) were published in 2021.Calls for improving environmental sustainability of large stadium design and construction emerged with FIFA's requirement for all official World Cup stadiums under construction or renovation to be green building certified from 2018 and the IOC's Agenda 2022 [44,45].This paper also builds on the work of Aquino and Nawari (2015) [26], who investigated different techniques adopted for sustainable stadium design and construction, and Sotiriadou and Hill (2015) [25], who pointed out that addressing the negative impacts of sports facilities and events on the environment are yet considerably underresearched topic in field of sports.
As shown in Figure 6, since 2018 there has been a constant increase in the number of articles published which suggests there is an increasing trend in environmentally sustainable design and construction of stadiums.Among the eighteen articles, 50% (nine articles) were published in 2021.

Overview of Paper Contents
Figure 7 denotes the geographical distribution of stadiums studied in this SLR.One of the papers reviewed in this SLR examined 20 stadiums in Turkey which is denoted in dark blue colour in the location map followed by Qatar, United States, China and South Korea with 3 case study stadiums each.The method of study used to conduct the research is almost equally distributed among the 18 articles.Fifty percent (nine articles) of articles adopted quantitative research methods, eight articles adopted qualitative research methods and one paper reported a mixed method design.All the qualitative research papers used a case study research approach of one or more stadiums to understand and analyse the research problem.
All nine quantitative papers adopted empirical research to observe and measure the environmental sustainability features of stadiums.Among these, five papers used computer simulation approach in their research method and three papers used life cycle assessment to conduct the environmental impact analysis.Within the 18 articles, 11 articles studied an existing stadium.The papers on existing stadiums either adopted an environmentally sustainable retrofit or adopted a qualitative study on the stadium's environmental aspects.The other seven empirical papers conducted research focusing on newly constructed stadiums.Eight of these articles mentioned a mega sporting event and six articles mentioned professional sports league or a large sporting event.
There are only limited documented data about other stadium properties, such as thermal properties.One example that can be noted is the boundary conditions set for the stadium model in [14].In this stadium model, the material for stadium's wall was set as concrete and the surface temperature was assumed as 10 • C higher than the outdoor air temperature [14].In addition to this, other climate information of the major case study locations, such as high and low temperatures, chance of clearer skies and average daily incident shortwave solar energy, have been generated using the online site called Weather Spark and are provided as Supplementary Material.
dark blue colour in the location map followed by Qatar, United States, China and South Korea with 3 case study stadiums each.The method of study used to conduct the research is almost equally distributed among the 18 articles.Fifty percent (nine articles) of articles adopted quantitative research methods, eight articles adopted qualitative research methods and one paper reported a mixed method design.All the qualitative research papers used a case study research approach of one or more stadiums to understand and analyse the research problem.All nine quantitative papers adopted empirical research to observe and measure the environmental sustainability features of stadiums.Among these, five papers used computer simulation approach in their research method and three papers used life cycle assessment to conduct the environmental impact analysis.Within the 18 articles, 11 articles studied an existing stadium.The papers on existing stadiums either adopted an environmentally sustainable retrofit or adopted a qualitative study on the stadium's environmental aspects.The other seven empirical papers conducted research focusing on newly constructed stadiums.Eight of these articles mentioned a mega sporting event and six articles mentioned professional sports league or a large sporting event.
There are only limited documented data about other stadium properties, such as thermal properties.One example that can be noted is the boundary conditions set for the stadium model in [14].In this stadium model, the material for stadium's wall was set as concrete and the surface temperature was assumed as 10°C higher than the outdoor air temperature [14].In addition to this, other climate information of the major case study locations, such as high and low temperatures, chance of clearer skies and average daily incident shortwave solar energy, have been generated using the online site called Weather Spark and are provided as Supplementary Material.
Table 4 below summarises the state, climate properties and end use of the stadiums studied in this review.To promote sustainable development and to optimise environmental outcomes, it is critical to develop environmentally sustainable stadiums (ESS).The majority of the papers describe environmental sustainability in general, focusing on reporting as few as one environmental sustainability category.The review identifies the lack of a holistic system which clearly defines the various interconnected aspects of environmental sustainability in stadiums.
There is only one author definition available in the reviewed literature for 'sustainable stadiums.'This is a pragmatic definition of stadium sustainability stating that "a stadium is sustainable when the material public's environmental, social, and economic interests are reconciled in the stadium as a matter of fact" [38].Other than this, one other paper describes sustainable use of sports venues as the reduction of damage caused to the natural and social environment while maximizing the efficient use of stadiums which can be achieved with the effective implementation of green development throughout the stadium life cycle from its site selection to post match operations [12].In addition to this, the Union of European Football Associations (UEFA) guide to Quality Stadiums put forward the idea of sustainable stadiums and points out that energy, water and materials are three major areas of sustainable buildings.'Sustainability in Stadiums' of the UEFA also denotes that reductions in energy usage, waste and carbon emissions, as well as promoting the use of local and recycled natural resources, should be the main objectives when designing a stadium [6].
A comprehensive definition for an environmentally sustainable stadium (ESS) or what characteristics an ESS constitute is lacking in the academic literature.The authors propose the following definition for an ESS: A stadium which can be utilised or modified for the different functions of the community it serves that consumes minimal natural resources and reverses any environmental damages already made, thereby contributing to the mitigation of greater environmental issues throughout its life cycle.This definition of an ESS has three main parts.A stadium can be defined as environmentally sustainable, first, if it can be easily modified or adapted not only for different types of sports competitions but also for the different needs (cultural events, disaster management, etc.) of the community where it stands, it can serve the community through extended benefits (renewable energy production, storm management, catering services, etc.) and it provides a lasting legacy which can also benefit future sustainable events; second, if it consumes minimum natural resources, including water, energy, materials, land, etc.; and third, if it can come up with ways to reverse the environmental damages already made and, through effective operations, can contribute to solve greater environmental concerns, such as climate change, GHG emissions, deforestation and natural disasters such as drought, flood, etc.

ESS Drivers
Recent trends in the sports sector demonstrated in the papers shows that major sporting events and associated infrastructure, particularly stadiums, are moving towards higher levels of environmental sustainability.Sports organisations such as IOC, FIFA and UEFA have necessitated the importance of adopting environmentally friendly strategies in order to be able to host events such as the Olympics and the World Cup.Transforming the design and construction of large stadiums is considered vital to reduce any adverse environmental outcomes resulting from hosting mega sporting events.New initiatives and requirements put forward by these organisations, along with other national and/or local regulations and goals, can be seen as the major drivers for the design and construction of environmentally sustainable stadiums, as summarised in Table 5 below.

•
Requirements of international standards regarding sustainability and environmental management.

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ISO 20121:2012-First international standard specifically aimed at the events sector.ISO 20121 provides the framework for identifying and reducing the potentially negative social, economic and environmental impacts of events.• GRI: G4 Guidelines on Sustainability Reporting Event Organizers Sector Supplement. [32] In addition to these requirements and standards, climate vulnerability, human wellbeing and comfort, mitigation of the direct environmental impact or footprint of the sporting events and the potentiality offered by these events to promote more sustainable rebuilding and long-term legacies are also major drivers for ESS.National and local sustainability goals and policies such as the 13th Five-Year Plan for Sports Development in China, the Korean light pollution prevention Acts and Qatar National Vision 2030 are the other drivers found in the literature that are helping stadium design and construction [12,33,39].

ESS Resource-Saving Measures in Design and Construction
Guidance regarding ESS design and construction is summarised in Table 6 and discussed in the following paragraphs.Alternative designs reduced the horizontal and vertical illuminances by 74.5% and 72.2%, respectively, in M city stadium and 30% and 30.6% in K city stadium. [39] • Energy: As the attractiveness of mega-events is increasing, the size of stadiums is also getting large, resulting in increased energy demand.Complimentary activities and areas such as restaurants, retail centres and museums integrating into the stadium space further increase energy consumption for stadiums.Therefore, one of the major challenges for stadiums is to minimize its substantial energy use for various purposes which include (but are not limited to) lighting, air-conditioning and maintaining aerothermal comfort within stadiums.This can be achieved by making the stadium resilient to the changing outside temperatures.Using cooling jets at different positions within the stadium to optimise the aero-thermal conditions, optimising roof configurations to optimise wind comfort within the stadium [28] and application of highly reflective coatings and shielding materials to minimise the effects of sunlight and to stabilise the indoor environment [15,34] are examples of major strategies discussed in the literature aiming to improve energy outcomes.

•
Materials: As massive structures, stadiums need huge quantities of materials to build.Among different materials, construction of stadiums consumes large quantities of concrete, which emit significant amounts of CO 2 and use huge quantities of raw materials for production.Therefore, the concept of sustainable construction is gaining prominence in the field of venue construction.Education City Stadium in Qatar, one of the venues for the 2022 Qatar World Cup, used site excavated boulders with concrete mix to fill its under-raft foundation, while RAA stadium, another 2022 Qatar World Cup venue, used reusable shipping containers to construct its main structure.Both stadiums are leading examples of sustainable construction practices which resulted in reduced use of raw materials, less landfill waste, less greenhouse gas emissions and a reduction in overall project costs [30,33].Another interesting study comes from the East African country of Rwanda, where the Rwanda Cricket Stadium was built by the process of thin tile vaulting consisting of six layers of compressed soil-cement tiles made from site excavated earth and two layers of geogrid reinforcement for seismic stabilisation.Waste produced from tile making and vault guide work have been used in other major building works such as flooring, countertops and doors, ensuring maximum usage of waste materials [37].

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Lighting: Light trespass and skyglow from large stadiums are harmful to the surrounding natural ecosystems and residential areas.Large stadiums require various lighting methods, depending on the size, configuration and the type of sports they are built to house.Currently, light pollution from stadiums is evaluated after the stadium is constructed.Techniques to predict and quantify light trespass and skyglow during the planning phase of a stadium can help to detect most pollution causing design elements and early assessments can be used to design alternative lighting options preventing light pollution.One of the papers from the review outlined a light pollution prediction method which can be used in the planning phase.This paper proposed alternative lighting design options to reduce light pollution by altering the height, type and number of lighting fixtures in two case study stadiums in Korea using computer simulations in Sketch up, AGi32 and The Relux Program [39].

•
Water: From the construction to the day-to-day operations, large stadiums use significant amounts of water, and sustainably managing water usage is of primary importance at this time of climate change, water pollution and ever-increasing water demand.The academic literature provides an excellent example of rainwater harvesting in a Euro 2012 stadium in Poland.A dual water supply system of public water supply for potable water uses such as catering kiosks, washbasins, showers, and medical rooms and an onsite rainwater harvesting system for non-potable water uses such as turf irrigation, flushing toilets and urinals was implemented in the stadium aiming to optimize water consumption, resulting in both environmental and financial gains [40].Water management using rainwater harvesting can also play an important role in stormwater management as well as in protection of water bodies in cities [40].

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Adaptability: Large stadiums mainly built for 'mega' events often become a financial burden to the stadium owners and the local community after the event due to underutilisation, lack of maintenance and abandonment [2].Stadiums that can be easily adapted or transformed into different forms based on the needs of the events they host, and that can blend into the surrounding natural environment, are effective solutions to the aforementioned problems.A case study of Z stadium in China put forward a modern stadium plan based on the concepts of adaptive renovation and urban renewal.According to the renovation plan, the outside area of the Z stadium will be transformed into an open space which combines well with the surrounding environment and contains modern fitness facilities, parking lots and parks, whereas the indoors area will be divided into three parts which are capable of adapting to a range of sports competitions and other functional needs of the stadium users [35].

ESS Assessment Tools and Certification Systems
Green certification systems and sustainability assessment tools are still in their beginning phase for large stadium design and construction.Currently, there are no strict regulatory structure, certification system or sustainability assessment tools in place particularly for large stadiums which would force stadium owners, decision makers, designer experts and sports organizations to build environmentally sustainable stadiums.In 2018 FIFA made green building certification mandatory for all World Cup stadiums which significantly increased the efforts to design and construct environmentally sustainable stadiums and can be considered as a reason behind recent developments in the field [33].
There are only two papers in this review which mention certification systems for stadiums [6,33].One of the research papers developed a sustainability assessment tool called the "Sustainable Stadium Assessment Tool (SSAT)".The SSAT is proposed specifically for stadiums to assess their sustainability characteristics.This tool has been used to evaluate the social, economic and environmental sustainability of twenty stadiums established between 2008 and 2018 in Turkey which were built according to FIFA standards.The stadiums were classified as platinum, gold, silver or bronze according to the scores obtained in different sustainability areas.For example, the categories under environmental sustainability are water, energy, waste and materials and components, and only two stadiums showed platinum level sustainability properties [6].The other paper which analysed the life cycle of the RAA stadium in Qatar mentions the green certification requirement of FIFA stated in the "Technical Recommendations and requirement" for stadiums.According to this paper, World Cup hosting stadiums should incorporate green design strategies resulting in material and energy reduction and must be eligible for Leadership in Energy and Environmental Design (LEED) certification.

Discussion
This SLR demonstrates the extent of knowledge regarding environmental sustainability in large stadiums and current environmental measures being adopted to provide a baseline from which the built environment sector can consider design and construction phase improvement opportunities going forward.Through the 18 articles in this systematic literature review, the descriptive analysis verified the relevance and the qualitative nature of the topic, and it is found that despite the growing research in stadium environmental sustainability, it is still in an exploratory phase.Many recent developments and technology are not well described in the academic literature; for example, innovations such as fully demountable stadiums including Stadium 974, timber stadiums such as the Eco Park, the world's first timber stadium, and Climate Pledge Arena, the world's first arena to earn a net zero carbon certification.Thematic analysis explored the characteristics and definitions for an environmentally sustainable stadium (ESS) and the different resource saving areas stadium developers and managers can consider for improved environmental sustainability.Furthermore, tools used to assess stadium sustainability were located (e.g., SSAT).The emergent key findings of this SLR are discussed in the following sections.

Improving Environmental Sustainability Outcomes for Large Stadiums
Environmental sustainability is of critical importance in the life of a large stadium as development of these complex, mostly permanent and expensive structures require the use of scarce natural resources not only to construct, but also to operate and maintain.Large stadiums accommodate large-scale public gatherings, and the events they host carry large carbon footprints, imposing significant impacts on the natural environment when left unchecked.However, as community infrastructure, stadiums can act as effective platforms to raise awareness about different social, economic and environmental issues [46].Furthermore, these structures are also easily imitated and therefore can showcase what is possible in the field of built environment, encouraging transformational design breakthroughs in other infrastructure.Therefore, building an ESS which uses minimal natural resources in development and construction, produces less construction and operational waste, consumes minimal resources to operate and maintain, integrates into the surrounding community, and promotes community and ecological regeneration is vital for mega-events as well as hubs for community development and resilience.

Incorporating Macro-Sustainability Categories in ESS
According to the literature, improving environmental sustainability outcomes have focused on to date on two major sustainability categories: Energy and Materials with Energy as the highest priority.Minimising energy consumption and improving aero-thermal comfort for stadium users are the most commonly found initiatives in the literature reviewed.'Materials' are given second priority within sustainable construction practices; in particular, application of locally sourced materials and use of waste materials for construction are attracting research interest.However, only one paper focused on water saving potential in stadiums and similarly only one paper studied light pollution caused by stadiums.However, these are important areas of concerns, particularly water conservation, to achieve environmentally sustainable outcomes in stadiums by reducing resource wastage [15].According to the literature, reviewed studies researching noise pollution and indoor air quality are lacking even though these are major environmental problems caused by stadiums that are connected to urban development and are vital to solve environmental problems in urban areas.

Prioritising Sustainability Governance, Certification and Assessment Tools
Through the literature review it was evident that papers that document or study green certified stadiums are very limited.Certification of sports stadiums were mostly recommendations and done largely on a voluntary basis until recent years and there is also a clear lack of the use of green building rating tools and certification systems in stadium design and construction.
To date, no green building certification system or environmental sustainability assessment tool has been created specific for stadiums that can assess and ensure the environmental sustainability of large stadiums.Therefore, stadium design and construction are lagging behind other conventional buildings in the adoption of green building methods due to their unique characteristics.Widespread use of green certification systems and environmental sustainability assessment tools in stadiums is of significant importance as these tools help indicate the significance of environmental sustainability in the context of a stadium's whole life cycle by providing a comprehensive assessment of environmental performance [47].A strict regulatory structure or an independent body to develop, monitor and enforce environmental sustainability standards and requirements for stadiums can force stadium owners, decision makers, designer experts and sports organizations to build stadiums that are environmentally sustainable.This can also assist to make host cities and stadium management accountable for their environmental sustainability goals and actual practice [48].

Considering Stadium 'Whole of Life' Performance
When creating an ESS, rather than focusing on a single phase in a stadium's lifecycle, it is important to take a holistic perspective that ensures environmental sustainability throughout the life cycle of a stadium; that is, in each of the phases from the concept, site selection, planning, construction, operation and finally decommissioning.Within each of these phases, particularly at the front end, the whole of building life of stadium should be considered as part of the ESS discussion.Lee (2021) [4] highlighted the practical importance of constructing a stadium with a postgame utilization plan in the preparation stage by indicating the importance of undertaking a proper market analysis and consideration of local demands for the stadium in the planning or concept phase so that the stadium can be effectively used and managed in the post-event period.Zhu et al. (2020) [12] put forward a postgame utilization evaluation system for large stadiums, focusing on sustainable utilization and considering the design, construction, operation and management phases of the stadium.

Documenting Academic Information for Capacity Building and Future Research
There is a lack of academic literature tracking current industry-leading practices, which can negatively influence the progress in the field of capacity building and research.The lack of documented information regarding the most recent technology developments and environmental sustainability initiatives happening in large stadium design and construction can result in a lack of evidence that has been translated into educational materials to help train the workforce.Likewise, documentation of current best practices is vital for further research in the field by academics.
Exploring the different resource saving areas and environmental sustainability factors and understanding the absence of a holistic method to evaluate the overall environmental sustainability of a stadium project, the authors herein introduce a short version of a checklist for Environmentally Sustainable Stadiums (ESS) which is shown in Table 7.This checklist consists of two steps.Step 1: General Questions and step 2: Specific questions related to different environmental sustainability fields.For any harm caused, are there enough compensation measures in place to balance the harm occurring to the biodiversity from building the stadium? 16 Will this stadium have any strategies in place to maximise the environmental and financial gains through the stadium infrastructure (e.g., subleasing of space during non-event days, electricity generation and feeding to the grid, etc.)?Is this project aiming for any green certification system?Are windows and roof lights positioned so that they can make the best use of daylight?

•
Are there any measures adopted to minimise light trespass from the stadium to surroundings?• Does this stadium have any eco-friendly lighting options?

•
Were the materials and components used in the stadium selected after comparing their environmental profiles?

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Were locally and sustainably (recycled or secondary materials) produced materials used wherever possible?• Does the timber used in the stadium comes from legal and sustainable sources?

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Were the materials used resilient with only minimum intermittent maintenance needed?

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Were the components that need replacement over time selected based on their ability to get recycled or reused?

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Will the waste materials from construction processes be reused or recycled?

Water
• Are there any rainwater harvesting systems installed, or the feasibility for such examined?• Are there any facilities for treating and reusing water within the stadium?• Are surface water runoffs saved for further use or directed safely to other water channels?

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Are there any water meters installed to monitor water consumption?

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Is the stadium using any other modern water-saving or water recycling technology?(e.g., water-saving sanitary fittings)

Limitations of the Study and Implications of Future Research
This study provides a reference for industry experts and academics in the stadium design and construction industry by considering environmental sustainability.However, this SLR did not include grey literature which includes industry reports, books, reports published by sports organizations, conference proceedings and newspaper or magazine articles.Noting the gap between academic literature and emerging technology in industry, we recommend that future studies should include industry-based studies and reports to ascertain the level of contribution to environmentally sustainable stadium design and construction.In addition, this SLR focused on the design and construction phases of a stadium and will contribute significantly to the body of knowledge of Environmentally Sustainable Stadium (ESS) if future studies can focus on the operation and demolition phases of the stadium.Finally, the stadiums reviewed in this SLR are large stadiums primarily built for mega-events.There might be innovations that are being applied to stadiums for better environmental sustainability outcomes at small scale stadiums or other types of sports facilities internationally which are not studied in this SLR, and therefore future studies should include this.
The proposed future research directions are based on the extensive literature review; the identified gaps are represented in Figure 8 and can be summarized into three main points as below:

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Prioritize research on areas that have received less focus, such as noise pollution, light pollution and indoor air quality.

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Better clarification on features and characteristics of an ESS, and development of a holistic system to build stadiums as community infrastructure and not as standalone buildings.

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Development of a framework or guideline for the effective application of green certification systems and sustainability assessment tools in stadiums.

Conclusions
This systematic literature review synthesises state-of-the-art stadium design and construction methods and initiatives that can be applied for improved environmental sustainability outcomes.Energy and materials are the most widely focused environmental sustainability categories in stadium design and construction.Mega-events candidacy requirements and recommendations put forward by sports organisations such as FIFA and national sustainability goals can be seen as the main drivers for transitioning stadium de-

Conclusions
This systematic literature review synthesises state-of-the-art stadium design and construction methods and initiatives that can be applied for improved environmental sustainability outcomes.Energy and materials are the most widely focused environmental sustainability categories in stadium design and construction.Mega-events candidacy requirements and recommendations put forward by sports organisations such as FIFA and national sustainability goals can be seen as the main drivers for transitioning stadium design and construction for improved environmental sustainability.Due to these requirements, green certified stadiums are becoming major game changers, with more stadiums aiming for a sustainability certification.However, there is still a long way to go for stadiums to change from awkward structures in the community to focal points of community development and urban regeneration, and to become megaphones to talk about how big pieces of infrastructure can achieve sustainability and climate goals.
The stadium of the future will not just be about the games it hosts; it will be more about the fan experience and the community it exists in.Therefore, next generation stadiums need to find ways to reduce the impacts of environmental damages that current stadiums have already made in the surrounding community and environment.To make this happen, it is important to go beyond reducing environmental impacts and make actively positive contributions to the environment and the surrounding community.This paper offers an important baseline that can be used in the future to measure progress.Areas of focus (e.g., water use) for future research and the need for a holistic perspective are indicated.A checklist is offered, aiming to extend stadium sustainability discourse to achieve the vision of stadiums of the future, and to help stadiums evolve as environmentally sustainable community infrastructure during and after the event.The study findings will equally assist academics and practitioners from public and private sectors interested in designing, constructing and maintaining large stadiums as environmentally sustainable infrastructure.

Supplementary Materials:
The following supporting information can be downloaded at: https:// www.mdpi.com/article/10.3390/su15086896/s1.Table S1: Initial data search results before applying filters.Figures S1-S6 shown below compare different climate characteristics of the major locations of the case study stadiums from the papers (created using the online tool Weather Spark).
Author Contributions: A.E.F., M.W. and C.D. were involved in conceptualization, methodology, and writing-original draft preparation.A.E.F. and M.W. were involved in formal analysis.S.C. and S.R.-T.contributed to writing-review and editing.All authors have read and agreed to the published version of the manuscript.

Figure 2 .
Figure 2.Step by step flow of information of the systematic literature review using the PRISMA approach.Adapted from[22].

Figure 3 .
Figure 3. Flow diagram that represents the step by step of the SLR process.

Figure 3 .
Figure 3. Flow diagram that represents the step by step of the SLR process.

Figure 4 .
Figure 4. Data analysis steps used in NVivo and coding outcomes.Figure 4. Data analysis steps used in NVivo and coding outcomes.

Figure 4 . 24 Figure 5 .
Figure 4. Data analysis steps used in NVivo and coding outcomes.Figure 4. Data analysis steps used in NVivo and coding outcomes.Sustainability 2023, 15, x FOR PEER REVIEW 10 of 24

Figure 5 .
Figure 5. Number of articles published in different journals.

Figure 5 .
Figure 5. Number of articles published in different journals.

Figure 6 .
Figure 6.Frequency of articles published over the period of 2017-November 2021.3.1.2.Overview of Paper ContentsFigure7denotes the geographical distribution of stadiums studied in this SLR.One of the papers reviewed in this SLR examined 20 stadiums in Turkey which is denoted in

Figure 6 .
Figure 6.Frequency of articles published over the period of 2017-November 2021.

Figure 7 .
Figure 7. Location map of the case study stadiums from the papers reviewed.

Figure 7 .
Figure 7. Location map of the case study stadiums from the papers reviewed.

Figure 8 .
Figure 8. Existing gaps and future research directions.

Table 1 .
Data search results after applying filters.

Table 2 .
Inclusion and exclusion criteria used in screening papers.
• Papers that feature environmental sustainability only in the operational or demolishing phase of stadium

Table 4 .
State and end use of stadiums internationally.

Table 4
below summarises the state, climate properties and end use of the stadiums studied in this review.

Table 4 .
State and end use of stadiums internationally.

Table 5 .
Requirements/actions put forward by different organisations.
[4,14,15]its charter in 2011 to reduce the negative impacts of Olympic Games on natural environments.•Olympic2020Agenda:Encourageshost cities to use temporary venues, existing venues and detachable venues for Olympic Games.•Legacy plan in the bid book.[4,14,15]

Table 6 .
Environmental sustainability initiatives experimented recently in large stadiums that are found in the literature.