Biomass-to-bioenergy conversion pathways: A systematic review of feedstocks, technologies, sustainability, and emerging directions
Abstract
Biomass is a versatile renewable carbon resource capable of supplying heat, electricity, gaseous fuels, liquid biofuels, and carbon-rich co-products while supporting waste valorization and circular resource use. This review systematically examines biomass-to-bioenergy pathways by linking feedstock characteristics, conversion technologies, energy products, process performance, sustainability, and emerging research directions. Agricultural and forestry residues, energy crops, municipal and industrial biowastes, sewage sludge, and algal resources were evaluated alongside combustion, co-firing, pyrolysis, gasification, hydrothermal conversion, anaerobic digestion, fermentation, transesterification, and integrated conversion systems. The synthesis shows that feedstock moisture, ash chemistry, lignocellulosic composition, elemental properties, and biodegradability strongly govern technology suitability and product distribution. Thermochemical pathways offer rapid conversion and broad product flexibility, whereas biochemical and hydrothermal routes are particularly advantageous for wet and biodegradable feedstocks. Sustainability depends on whole-system performance rather than conversion yield alone, requiring simultaneous consideration of energy and exergy efficiency, life-cycle impacts, techno-economics, logistics, and carbon management. This present review also suggests that major research frontiers should include Artificial Intelligence (AI) and Machine Learning (ML)-assisted modelling, digital twins, advanced catalysis, integrated biorefineries, green-hydrogen coupling, bioenergy with carbon capture and storage (BECCS), and circular waste-to-energy systems. More importantly, a future framework is proposed that integrates feedstock intelligence, adaptive pretreatment, optimized conversion, selective upgrading, carbon management, digital optimization, and life-cycle and economic validation. In general, this review aims to support biomass-to-bioenergy conversion pathways toward scalable, credible, environmentally robust commercial deployment globally.