A hybrid approach to a more complete emissions inventory: a case study of Aarhus University

Abstract There has been a notable absence of procurement emissions in university GHG inventories, which act to inform universities of possible decarbonization pathways only partially. Guided by a methodological trade-offs consensus document presented by a consortium of Danish universities, this study estimates the 2021 emissions of Aarhus University, including procurement. Utilizing a hybrid approach of process- and spend-based methods the results contribute to a trend of hybrid university assessments. Procurement-related emissions (39,692 tCO2e) were estimated using accounting data and EXIOBASE, a multi-regional environmentally extended input-output (MREEIO) model, with all other emissions estimated using physical data and governmental sources (20,273 tCO2e). EXIOBASE draws on a combination of consequential and attributional life cycle assessment, therefore the results are reported separately to maintain the distinctions between methodologies. The accounting data is not optimally matched with EXIOBASE’s categories, yet the comprehensive nature of the method increased the university’s awareness of procurement emissions and presented initial decarbonization routes, along with recommendations for better data quality. Further research is necessary to enable informed decisions towards decarbonization and to allow seamless incorporation of supplier-specific emissions data, which requires greater interdepartmental collaboration to elevate data resolution, and a data ontology that preserves both supplier transparency and proprietary information.