The growing challenges related to environmental protection, energy transition, and sustainable waste management have placed methanization and waste valorisation at the heart of global scientific and industrial priorities. Methanization, as a biological process that converts organic waste into biogas and digestate, represents a strategic pillar for the development of renewable energies and the reduction of greenhouse gas emissions. At the same time, the valorisation of municipal, agricultural, and industrial waste offers major opportunities for creating circular, low-carbon systems that contribute directly to regional and national development. This Scientific Day aims to bring together researchers, professionals, industrial actors, and decision-makers to discuss the latest advances, share innovative practices, and promote collaborative approaches for sustainable waste management and efficient bioenergy production.