This book presents the selected papers from the 2023 5th International Conference on Environmental Sciences and Renewable Energy (ESRE 2023), which was held as a hybrid conference during June 19–21, 2023, in Vienna, Austria. The book includes first-rate, original research on various aspects of environmental sciences and renewable energy, offering perspectives from industrial and research communities to address current challenges in related fields. In the field of environmental science, wastewater and sludge treatment, air pollution and control, global environmental change, and ecosystems management are discussed. In the area of renewable energy, several hot topics are presented including solar energy, energy conservation and recovery, and hydrogen generation and application. This book supports the transfer of vital knowledge to next-generation researchers, students, and practitioners in academia and industry.