Carbon footprint in Higher Education Institutions: a literature review and prospects for future research.

Higher Education Institutions (HEI) or universities, as organisations engaged in education, research and community services, play an important role in promoting sustainable development. Therefore, they are increasingly linked to the initiative of calculating their carbon footprint (CF), which is a tool to assess sustainability from the perspective of greenhouse gas (GHG) emissions. The aim of this study is to carry out a systematic review of the current situation of CF assessment in academic institutions by analysing different key elements, such as the time period, methodologies and practises, calculation tools, emission sources, emission factors and reduction plans. The review protocol considered articles published until March 2021. Of the articles reviewed, 35 are aimed specifically at calculating the CF of HEI, while the remaining articles consist of review, activity-specific CF assessment or GHG emission reduction articles. Clear differences have been identified when results are compared for the normalised CF (average of 2.67 t CO2e/student, ranging from 0.06 to 10.94) or the percentage of carbon offsetting, only considered in 14% of the studies and ranging from 0.09 to 18%. The main reason for this is the lack of standardisation as regards the time metric (year, semester), functional unit (student, employee, area) and data collection boundary (scope 1, 2, 3), the emissions sources and emission factors, mainly for scope 3 (water consumption and treatment, waste treatment, office, ICT and laboratory consumables, commuting and travel, construction materials, canteens, etc.), and the inclusion or not of the effect of carbon offset projects to offset the CF (aim of the project and absorption sources and factors). However, despite the differences, a reduction over time is clearly observed. Therefore, CF in HEI requires further improvements and solutions to a number of challenges, including the definition of representative emission sources, the creation of a robust emission factor database and the development of tools/methodologies that cover all the needs of this type of organisation.