Constantly increasing global warming induced by greenhouse gas (GHG) emissions has led to a promotion of energy efficiency in almost every sphere of life. There have been several attempts to combat global warming and climate change, such as the introduction of the Kyoto Protocol in 1992, or the United Kingdom's Climate Change Act in 2008. To this end, measuring GHG emissions has become an important starting point. Thereby, the term "carbon footprint" was introduced. It refers to the amount of CO2 or greenhouse gas emissions (expressed in CO2 equivalents) generated by a product, company, or even a country. However, there is still no universally accepted definition of carbon footprint. All definitions are related to human activities, though a consensus on which GHG emissions to take into account in measurement has still not been reached. The GHG Protocol developed by the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD) represents a global and widely accepted methodology for GHG accounting. It classifies GHG emissions into three scopes: Scope 1 emissions refer to direct emissions, Scope 2 emissions include indirect emissions from the generation of purchased energy consumed by the reporting company, and Scope 3 emissions encompass all indirect emissions occurring in the value chain of the company (not already been included in Scope 2 emissions). According to WRI and WBCSD, Scope 3 emissions have recently become the largest source of emissions and the most significant opportunity for GHG reductions. When talking about carbon footprint in higher education institutions, organisational carbon footprinting is applied. Although this is a significant sector in the EU, with 19.6 million students and 1.5 million people teaching in tertiary education in 2016, there is still no international standard for carbon footprinting. Furthermore, some higher education institutions have already committed to reducing their carbon emissions. Different methodologies have been applied for the purpose of measuring the carbon footprint in the sector, and it has been concluded that Scope 3 emissions are rising and becoming more difficult to quantify. An additional problem refers to the optional reporting on Scope 3 emissions, making it more difficult to compare those emissions between companies. Thereby, it is necessary to improve the methodology used for measuring Scope 3 emissions. Researchers have also concluded that the main source of emissions in higher education institutions comes from energy (electricity). One of the best ways for higher education institutions to reduce their environmental impact is to incorporate online learning as a means of education. Online learning, along with technological improvements and the use of renewable energy sources, would significantly reduce the carbon impact of student and staff travel. Promoting environmental sustainability by higher education institutions would have a significant role in shaping the opinions of future generations, and it should be a priority.
