This chapter explores the valorization of agro-industrial residues, particularly orange peel waste, as a promising source for the development of functional materials within a circular bioeconomy framework. Through a multidisciplinary approach, it examines the physicochemical characteristics and activation processes of these residues to produce high-performance carbonaceous materials, such as activated carbons, that can substitute fossil-based products in diverse applications. The discussion highlights how transforming agricultural by-products into valuable materials supports environmental sustainability, technological innovation, and local circularity of resources. Emphasis is placed on the integration of waste valorization into broader sustainability agendas, aligning with several United Nations Sustainable Development Goals, including Responsible Consumption and Production (SDG 12), by encouraging the use of renewable resources; Industry, Innovation and Infrastructure (SDG 9), through the development of alternative materials and emerging technologies; and Climate Action (SDG 13), by promoting the reduction of greenhouse gas emissions through waste minimization and resource efficiency. This chapter emphasizes the importance of designing new material pathways that not only divert organic waste from landfills but also create high-value solutions for industrial applications, demonstrating that residues are not an endpoint, but a strategic entry point for sustainable development.