Book excerpt: This book, the conference proceeding, contains invited articles and contributory papers from the 9th International Conference on Energy Engineering and Environmental Engineering, organized by Beijing Jiao Tong University in Sanya, China, on December 9–10, 2022. It includes contributions from researchers and practitioners working in the area of energy engineering, hydrogen, hydrogen carriers technology environmental engineering, climate change & global warming, and related fields. The articles cover the topics such as new energy production, storage, transmission, electrolysis, electrolyzes chemical, thermochemical, electrochemical hydrogen, energy environmental protection, and environmental sustainability. The content caters to research scholars, students, industry professionals, companies, government bodies, and policymakers, who work in the field of energy and environmental engineering.