Dr. Ruan’s research focuses on renewable energy and environment technologies for sustainable development and circular economy. Specifically, he has conducted research and published his findings in the areas of biomass and solid wastes such as plastic wastes pyrolysis and gasification for chemicals, materials, fuels and energy production, municipal, agricultural, and industrial wastewater treatment and utilization through novel anaerobic digestion, microalgae cultivation, and hydroponics, airborne and other pathogen disinfection and pollutant control, innovative catalytic non-thermal plasma, low temperature microwave and pulse microwave, photocatalytic intensive pulse light, and NMR/MRI technologies research, development and applications in nitrogen fixation, food safety assurance, and food quality improvement, and food engineering and various value-added processing, etc. Dr. Ruan is a Fellow of ASABE and a Fellow of IFT, and a top-cited author with an h-index of 69, i10-index of 303, and over 19,000 citations.