Anaerobic digestion constitutes a sustainable method for waste management and renewable energy generation, addressing significant environmental and societal challenges. The growing global waste crisis and the increasing momentum toward sustainable energy solutions emphasize the critical need to enhance anaerobic digestion technology for improved efficiency and environmental advantages. This process mitigates waste accumulation, enhances energy security, and reduces greenhouse gas emissions, providing a feasible solution within the framework of a circular bioeconomy. Here, we review the principles of anaerobic digestion and biogas production, focusing on agricultural waste and the utilization of biogas for energy within a sustainable framework. We specifically explore biogas applications in rural and industrial settings, assess the environmental impacts, and discuss the regulatory landscape with insights from China and Europe. This study reveals that the strategic implementation of anaerobic digestion can markedly improve energy yield and sustainability, demonstrating how focused policies and advanced technological practices can optimize biogas utilization. The review enhances comprehension of environmental impacts, emphasizing insights from China and Europe as key examples.

The rise of global waste and the decline of fossil fuels are calling for recycling waste into energy and materials. For example, rice straw, a by-product of rice cultivation, can be converted into biogas and by-products with added value, e.g., biofertilizer, yet processing rice straw is limited by the low energy content, high ash and silica, low nitrogen, high moisture, and high-quality variability. Here, we review the recycling of rice straw with focus on the global and Chinese energy situations, conversion of rice straw into energy and gas, biogas digestate management, cogeneration, biogas upgrading, bioeconomy, and life cycle assessment. The quality of rice straw can be improved by pretreatments, such as baling, ensiling, and co-digestion of rice straw with other feedstocks. The biogas digestate can be used to fertilize soils. The average annual potential energy of collectable rice straw, with a lower heating value of 15.35 megajoule/kilogram, over the past ten years (2013–2022) could reach 2.41 × 10⁹ megajoule.