Anthropogenic influence on global warming is now undeniably proven scientific fact. Ever-increasing efforts directed towards cleaner technologies are needed given the fact that COVID-19 caused disturbances in global supply chains, and a record increase in natural gas prices led to coal power production revitalization, nuclear renaissance and overall hampering of the energy transition. Cleaner technologies are becoming increasingly important on our path towards sustainable development. Present work builds on contributions from this special issue dedicated to the four Sustainable Development of Energy, Water and Environment Systems Conferences held in 2020 by emphasizing the role of cleaner technologies and detecting research trends. By dissecting recent examples of cleaner technologies in environmental systems, water systems and industrial processes, circular economy principles are obeyed through the application of cleaner technologies, where the material and energy loops are closed through cross-sectoral integration. Digitalization and advanced control concepts are expected to accelerate that integration under the smart paradigm. As technology for decarbonization is maturing and becoming increasingly compatible with the market, the focus is placed more on the social dimension of sustainability.