“…The topic of life cycle assessment [70,85] holds the second position in terms of page rank value, but its low betweenness centrality indicates that it does not serve as a link between other topics. This cluster also contains the following topics: cleaner production [86][87][88], exergy [67,89], recycling [90,91], climate change [92,93], global warming [94], environmental impact [95,96], energy efficiency [97,98], energy transition [99,100], industry 4.0 [101], anaerobic digestion [102,103], bioenergy [104,105], biogas [58,104,105], and solar energy [106,107]. Compared to solar energy, wind energy, and hydropower, bioenergy appears the most frequently in the author's keywords in the article database regarding the application of renewable energy in the circular economy framework.…”