“…Scholars have focused on the concept connotation (Xiao et al, 2019), calculation methods (Mancini et al, 2016), case studies of carbon footprints (Röös et al, 2013), etc. The calculation methods in these studies can be divided into "bottom-up" methods based on a process analysis and "top-down" methods based on an input-output analysis (Alvarez et al, 2015). The studies cover different scales, such as individuals (Kenny, 2009), families (Steen-Olsen et al, 2016), enterprises (Adewale et al, 2019), industries (Cadarso et al, 2015), cities (Chen et al, 2012), regions (Harris et al, 2012), and countries (Wolfram et al, 2016).…”