Abstract
Purpose This study aims to integrate methodologies for carbon footprint (CF) assessment in higher education institutions (HEIs) using the Greenhouse Gas Protocol and ISO 14064:2018 standards with a hybrid process-economic approach. The research addresses current gaps in HEI CF assessment, where scope 3 emissions are often unreported, and establishes a framework for systematic quantification across the educational value chain. Methods A hybrid assessment model was developed, combining process-based and economic-based approaches through environmentally extended input–output (EEIO) analysis. The methodology integrates complementary aspects of the GHG Protocol and ISO 14064:2018, enabling the categorisation of emissions across organisational boundaries. The framework was applied to the University of Coimbra (Portugal) as a case study, with data collected from 2019 to 2023 using sustainability reports, financial statements, and mobility surveys. Thirty-six activities were compiled across four ISO 14064 categories and nine GHG Protocol sub-categories. Data quality was assessed using a tiered approach with sensitivity analysis performed through the one-at-a-time method to identify emission hotspots. Results and discussion Analysis revealed that the University of Coimbra emitted 29.53 kt CO₂-eq in 2023, representing a 59.69% increase from 2019, with a carbon intensity of 0.87 t CO₂-eq/person. Scope 3 emissions constituted 78.38% of total emissions, primarily from construction activities (40.35%), commuting (32.18%), and purchased goods (8.05%). Without the hybrid approach, significant indirect emissions would have remained unquantified. The comprehensive assessment revealed the University’s CF to be substantially higher than previously reported figures, which excluded scope 3 emissions. Benchmarking against other Portuguese institutions positioned the University of Coimbra’s carbon intensity (0.87 t CO₂-eq/person) within expected national ranges. Conclusions The hybrid CF assessment methodology effectively captures comprehensive emission profiles in HEIs, particularly revealing previously unreported scope 3 impacts. This pioneering application to a Portuguese university establishes a benchmark for subsequent assessments while highlighting significant institutional emission sources. The framework enables meaningful comparative analyses between institutions and can be readily adapted for national and international HEIs seeking to enhance their sustainability assessments and develop targeted carbon reduction strategies.