Mapping research on carbon neutrality in WWTPs between 2001 and 2021: A scientometric and visualization analysis

Carbon neutrality is a globally established research topic in wastewater treatment plants (WWTPs); carbon-neutral operations of WWTPs have already started. Carbon neutrality refers to greenhouse gases (GHGs) emissions, and WWTPs have been recognized as one of the largest minor GHGs generators, due to their on- and off-site production of the three primary GHGs. Recently, carbon neutrality in WWTPs has attracted significant attention from the government, industry, and academia, with an increase in the number of research publications. In this paper, we screen 555 unique scientific articles from Web of Science related to this topic and employ Cite Space to conduct a knowledge mapping of the domain. The results visually demonstrate that “Environmental Sciences” was the top category with 378 publications, and “Water Research”, “Journal of Cleaner Production”, and “Science of The Total Environment” were the most representative journals. Chinese research on carbon neutrality has entered a rapid expansion stage with the continuous introduction of China's macro policies towards achieving carbon peaking and carbon neutrality goals. Also, a co-citation literature analysis by Cite Space informed that the cited journals were concentrated in the fields of environment, toxicology, and nutrition. This paper further explains how the research topics have changed over time and analyzes the current research frontiers, including “recovery”, “biogas”, and “China”. We present a novel approach for assessing the research performance on carbon neutrality. The findings here described will support newcomers in identifying the most pioneer publications, journals, and institutions.