This book presents selected, peer-reviewed proceedings of the 4th International Conference on Material, Machines and Methods for Sustainable Development (MMMS2024), held in the city of Da Nang, Vietnam, from September 18 to 21, 2024. The conference establishes a comprehensive understanding of the key elements that drive sustainable development, with a particular focus on materials, machinery, and methodologies. Building on this foundation, the conference seeks to provide a holistic approach that guides policymakers, industries, and researchers in aligning local technological advancements with global sustainable development objectives. This alignment is intended to support informed decision-making that prioritizes greener solutions, particularly in relation to materials, machinery, and methods. The papers presented in Volume 2 of this proceedings book highlight cutting-edge advancements in materials science, machining, and renewable energy technologies. Key topics include butt fusion welding parameters, TiAl6V4 TIG welding properties, and CBN grinding wheel surface ability for precision applications. Studies explore single-point incremental forming, high-entropy alloy performance, and orthopedic trauma brace manufacturing using PETG material. Sustainability features prominently, with research on ACC parameters for electric vehicles, proton exchange membrane fuel cells, and Simulink energy simulations. Advances in biogas-enriched syngas combustion and high-pressure die casting optimization further emphasize energy efficiency. The authors extend their sincere appreciation to the International Organizing and Academic Committees of the Conference for their dedication and invaluable insights, which were instrumental in upholding the high standards of this event. The authors hope that this proceedings book will serve as a rich resource for academics, researchers, engineers, and students, fostering further scientific inquiry and innovation in the pur