Advances in agricultural crop residue utilization for biogas production and sustainable energy solutions

The valorization of agricultural and agro-industrial residues is critical for advancing the circular bioeconomy and achieving global energy transition goals. This study presents a comprehensive bibliometric analysis of scientific literature on biogas production from these residues to gain insights into the intellectual structure, trends, and influence of this research field. By addressing the central question-What are the emerging research trends, thematic hotspots, and key intellectual contributions in the field of crop residues for biogas production over the last five years?-this paper maps the conceptual evolution and key actors shaping the domain. Based on a dataset of 1004 documents from the Web of Science Core Collection (2021-2025), VOSviewer and the Bibliometrix Rpackage were used to analyse publication volume, collaboration networks, and thematic clusters. This analysis reveals significant and sustained growth in publications, with China and India emerging as the most influential countries, supported by leading institutions such as the Chinese Academy of Sciences. Keyword co-occurrence analysis reveals a shift from a narrow focus on anaerobic digestion to integrated circular economy frameworks. Emerging research hotspots include biorefinery concepts, biochar applications, and the use of life cycle assessment (LCA) to evaluate environmental performance. The findings underscore a maturing field that has evolved from a singular focus on energy generation to a holistic, systems-level approach aligned with Sustainable Development Goals (SDGs), particularly SDG 7 (Affordable and Clean Energy) and SDG 12 (Responsible Consumption and Production).