The global event industry's rapid growth has led to significant greenhouse gas emissions, posing a challenge to climate change mitigation goals. In 2017, business events involved over 1.5 billion participants, generating $2.5 trillion in spending. The carbon footprint per participant can reach up to 3000 kg CO2 equivalent, comparable to the yearly GHG emissions of the entire United States. While sustainability measures and virtual conferences have been promoted, the optimal format for future conferences (in-person, virtual, or hybrid) remains debated. Critics of virtual conferences cite fatigue, loss of informal interactions, and time zone challenges. Supporters highlight accessibility, inclusivity, and sustainability. Hybrid conferences offer a potential compromise, yet quantitative understanding of their environmental impacts is lacking. Previous research often oversimplified the environmental footprint of virtual conferences by neglecting aspects beyond transportation emissions. This study aims to quantify the life cycle environmental impacts of different conference modes and analyze the trade-offs between in-person interactions and carbon footprint. It addresses the critical gap in understanding the environmental impacts of hybrid conferences and the geographical effects of hub selection and participant assignment.

Prior life cycle assessments (LCAs) of conferences mainly focused on in-person events, with transportation identified as the primary environmental hotspot. The carbon footprint varied widely (92–3540 kg CO2 equivalent per capita) due to differing assumptions about conference size, location, participant distribution, and transportation modes. Studies comparing in-person and virtual conferences reported carbon footprints ranging from 0 to 5.87 kg CO2 equivalent per capita, with inconsistencies stemming from varying assumptions about energy consumption from technology and other emissions. Several studies considered multi-site conferences but lacked optimization of hub locations. Notably, none comprehensively assessed the environmental sustainability of hybrid conferences with spatially optimized hubs and participant assignments.

This study employs a holistic LCA approach, incorporating spatial analysis, following the ISO 14040 standard. The four LCA phases included goal and scope definition, life cycle inventory (LCI), life cycle impact assessment (LCIA), and interpretation. The 2020 American Center for Life Cycle Assessment virtual conference served as a case study. The LCI considered food preparation, accommodation, preparation, execution, information and communication technology (ICT), and transportation. Data on food consumption were obtained from FAOSTAT. Energy and water consumption for accommodation were based on existing literature, and waste management pathways were obtained from the U.S. Environmental Protection Agency. For ICT, an environmental impact assessment framework for Internet services was used, encompassing infrastructure, network, and server energy consumption. Transportation distances were calculated using Google APIs, considering different transportation modes based on distance thresholds. The LCIA used carbon footprint, cumulative energy demand (CED), and 17 ReCiPe midpoint indicators. Hub selection and participant assignment were optimized using a facility location model to minimize total travel distance. Two sets of hybrid scenarios were examined: Maximum Virtual Participation (MVP) scenarios, with constraints on virtual participation levels, and Maximum Travel Distance (MTD) scenarios, with constraints on maximum travel distances. Sensitivity analyses were conducted to assess the uncertainty of results.

The study found that transitioning from in-person to virtual conferencing significantly reduced the carbon footprint by 94% and CED by 90%. For the virtual conference, food preparation dominated most impact categories (agricultural land occupation, terrestrial ecotoxicity, water depletion), followed by electricity consumption for accommodation and video-conferencing. ICT was another environmental hotspot, particularly regarding metal depletion. Adding conference hubs to in-person conferences reduced the carbon footprint and CED by half, but they still remained significantly higher than virtual conferences. Analyzing hybrid scenarios, the MVP scenarios clearly showed trade-offs between carbon footprint and in-person participation levels. Achieving a two-thirds reduction in the carbon footprint of in-person conferences was possible with less than 50% virtual participation. The MTD scenarios showed that setting a relatively small maximum travel distance (e.g., <3000 km) was effective in reducing the carbon footprint of hybrid conferences. Sensitivity analyses indicated that the carbon footprint of in-person scenarios was highly sensitive to the characterization factors and distances of air transportation. For virtual conferences, daily participation, dietary type, and ICT-related electricity consumption were highly sensitive parameters.

The findings highlight the substantial environmental benefits of transitioning to virtual or optimized hybrid conference formats. The significant reduction in carbon footprint and energy use associated with virtual conferences is undeniable. The effectiveness of hybrid models depends on careful optimization of hub locations and balancing in-person and virtual participation. The study demonstrates that a significant reduction in the environmental impact of conferences is achievable while maintaining a substantial level of in-person interaction. The results underscore the importance of considering the trade-off between the desire for in-person networking and the need for environmental sustainability. The study's findings provide valuable insights for policymakers and conference organizers in developing strategies for reducing the environmental impact of future events. The identified environmental hotspots inform the need for improving energy efficiency and resource utilization in the ICT and transportation sectors.

This study demonstrates the significant potential of virtual and optimized hybrid conferences to mitigate the environmental impact of academic and professional gatherings. The substantial reduction in carbon footprint and energy consumption achieved through the transition to virtual formats underscores the importance of considering environmental sustainability in conference planning. Optimizing hybrid conference designs through careful selection of hub locations and balancing in-person and virtual participation offers a path toward minimizing environmental impact while preserving the benefits of in-person interaction. Future research should explore the long-term implications of the increasing reliance on virtual conferencing technologies and investigate further refinements to hybrid conference designs to maximize sustainability.

The study relied on a single case study (the 2020 ACLCA virtual conference), limiting the generalizability of findings to other conferences with different participant demographics or geographical distributions. The model used for optimization may not perfectly capture real-world travel decisions by participants. The study did not fully account for all potential environmental impacts associated with virtual conferencing, such as the production of devices and post-conference activities. Uncertainty exists regarding the future energy efficiency improvement rate of the ICT sector and the precise composition of food consumption during conferences.