Biochar for Low-Carbon Energy Crop Systems: Bibliometric Trends, Agronomic Evidence, and Soil Carbon Sequestration Pathways from 2007 to 2025

Abstract This bibliometric and critical review examines the evolution of scientific research on biochar application in energy-crop systems, emphasizing biomass productivity, soil quality, and soil carbon sequestration from 2007 to 2025. The bibliometric assessment comprised 409 records retrieved from the Web of Science Core Collection and integrated publication trends, thematic evolution, scientific collaboration networks, and agronomic and environmental evidence. Scientific production increased markedly during the period, despite interannual variability, accompanied by a shift from biochar production and physicochemical characterization toward field-scale agronomic performance, soil–biochar interactions, pyrogenic carbon persistence, life-cycle assessment, greenhouse gas mitigation, and engineered biochars. Physicochemical characterization nevertheless remained essential for interpreting biochar functionality. Field evidence indicates that crop responses depend on feedstock origin, pyrolysis conditions, biochar properties, application rate, soil characteristics, crop species, and experimental duration. Long-term studies and assessments of pyrogenic carbon stability support the potential of biochar to increase soil carbon stocks and contribute to durable carbon sequestration, although the magnitude and permanence of these effects vary across pedoclimatic conditions and management systems. Major research gaps include limited standardization of biochar characterization, insufficient long-term field validation under tropical conditions, incomplete evaluation of the environmental safety of modified biochars, and the absence of harmonized indicators integrating biomass productivity, soil carbon dynamics, greenhouse gas emissions, and carbon permanence. Overall, current evidence supports biochar as a soil amendment and carbon-management strategy for low-carbon bioenergy systems when material properties and application practices are aligned with site-specific agronomic constraints and validated under representative field conditions.