GHG Accounting for sustainable mega-events: How lessons learnt during the Milan Expo 2015 world fair could lead to less carbon-intensive future mega-events

World Fairs such as the Expo events are major events organized to generate tourism revenues, attract people and investments, but which result in environmental impacts that need to be accounted in a reliable and comprehensive way. In particular, accounting the greenhouse gases of a mega-event and comparing the emissions of different events is a very challenging task due to the large amount of data to be collected and to the lack of a specific methodology. In this paper, the quantification of greenhouse gas emissions and removals of Milan Expo 2015 international exposition is presented. Calculations, performed according to the international standard ISO 14064-1, includes office activities, construction of expo site and pavilions, operations and decommissioning process. Detailed information on data collecting methods and sources is shown in the paper. Furthermore, the obtained GHG results normalized to the number of visitors were compared to other mega-events, i.e. the latest Olympic Games, FIFA World Cups and Shanghai Expo 2010. With all the limitations described in the paper, the results showed a total impact of World Expos of about one ton of CO2-eq per square meter of exhibition and averagely 60 kgCO2-eq/visitor. Olympic Games and FIFA World Cups have an average impact respectively of 400 kgCO2-eq/visitor and 600 kgCO2-eq/visitor. The performed analysis was presented in the form of requirements and guidelines with the aim of refining the existing standard methodology highlighting the specific aspect of mega-events and transferring the findings to future world fairs.