Decarbonizing waste: Building tomorrow's biorefinery beyond biogas

Anaerobic digestion (AD) is increasingly recognized as a foundational process in the global shift toward sustainable, circular, and low-carbon systems. Long established for its capacity to convert organic waste into biogas and nutrient-rich digestate, AD now plays a pivotal role in climate-smart production, decentralized energy generation, and resource recovery. Yet its full potential extends far beyond these traditional outputs. Advances in microbial ecology and process engineering are transforming AD into a modular biomanufacturing platform capable of producing high-value compounds. These biomolecules offer renewable pathways for the synthesis of biofuels, single-cell protein (SCP), methanol, microalgal products, and other speciality chemicals, positioning AD at the heart of emerging bioeconomies. This dual capacity, addressing today's urgent need for sustainability and enabling tomorrow's bio-based production system, positions AD as an important technology in future biorefineries. This article appeals to a broad readership seeking to understand AD, which is one of the most mature yet dynamically evolving processes for biological resource recovery. Increasingly positioned as a central platform for future circular bioeconomies and sustainable biomanufacturing, this review specifically focuses on pivotal aspects of next-generation biorefineries, including biomethanation, SCP and methanol production, microalgal-based products, and integrated resource recovery strategies.