The increasing generation of organic wasteOrganic waste from agricultural, municipal, industrial, and household activities presents both a critical environmental challenge and a valuable opportunity. In the pursuit of a sustainable and circular economyCircular economy, biorefineries have emerged as transformative systems capable of converting diverse waste streams into high-value products such as biofuels, bioplastics, platform chemicals, fertilizers, and bio-based materialsBio-based materials. This chapter explores the pivotal role of biorefineries in advancing circular economy principles by shifting the linear waste-disposal paradigm toward a regenerative model of resource recoveryResource recovery and reuse. The study begins by defining the conceptual framework of the circular economyCircular economy and examining how biorefineries align with its goals. It then delves into the various thermochemical and biochemical technologies employed in modern biorefineries, including pyrolysisPyrolysis, anaerobic digestionAnaerobic digestion, fermentationFermentation, and integrated process systems. Different types of feedstocks, ranging from agricultural residuesAgricultural residues and food wasteFood waste to sewage sludge, are evaluated for their suitability and conversion potential. The chapter also highlights the spectrum of value-added products derived from these feedstocks. It assesses their environmental and economic impacts using tools such as life cycle assessmentLife Cycle Assessment (LCA) (LCA) and cost–benefit analysis. Further discussion addresses policy support, business models, and community engagement strategies necessary to scale biorefineryBiorefinery solutions. By identifying current challenges and future directions, this research underscores the potential of waste valorisationWaste valorisation through biorefineries as a key enabler of sustainable developmentSustainable development, resource efficiency, and climate resilience in the global bioeconomy.