Saleh Al Arni is a Professor in the Department of Chemical Engineering at the University of Hail, Saudi Arabia. He received a Laurea (Master’s equivalent) in Chemical Engineering from the University of Genoa, Italy, in 1996, followed by a Ph.D. in Technologies and Economics of Processes and Products to Safeguard the Environment from the University of Genoa and the University of Catania in 2000, and a second Ph.D. in Chemical Sciences, Technologies and Processes from the University of Genoa in 2008. He has worked in research and teaching at the University of Genoa, King Saud University, and the University of Hail, and was also a visiting researcher at the University of Genoa. His research interests include biomass conversion, thermochemical hydrogen production, waste-to-energy, environmental biotechnology, wastewater treatment, bioremediation, and renewable energy systems; more recently, his work has also covered energy storage, thermal systems, and sustainable process technologies. He has served as a peer reviewer for several international journals and has received multiple research grants and awards, including recognition among Stanford University’s World’s Top 2% Most-Cited Scientists for three consecutive years (2023–2025).