A critical review on conversion technology for liquid biofuel production from lignocellulosic biomass

The growing demand for sustainable energy solutions has intensified interest in lignocellulosic biomass (LCB) as a renewable feedstock for liquid biofuels. This review critically evaluates advancements in LCB-to-biofuel conversion technologies, comparing their efficiency, environmental impact, and economic feasibility. Thermochemical processes such as pyrolysis and gasification offer conversion efficiencies of 28–40 % at relatively low costs (0.55–0.60 USD/L gasoline equivalent) but require bio-oil upgrading. Biochemical pathways produce higher-quality fuels; however, high enzyme costs and microbial toxicity hinder large-scale implementation. Hydrothermal liquefaction (HTL) shows promise with 35 MJ/kg biocrude energy density and 92 % carbon retention, though high energy input and catalyst costs remain challenges. Biobutanol outperforms bioethanol in energy content (29.2 MJ/dm3) and engine compatibility but suffers from microbial toxicity. Biodiesel cuts GHG emissions by 53–61 % but struggles in cold climates. Life cycle assessments indicate significantly reduce GHG emissions, with waste-derived feedstocks mitigating land-use conflicts. Advancing LCB biofuels requires optimizing HTL, enhancing microbial tolerance in biobutanol production, and integrating AI for process improvements. Policy support through subsidies and carbon incentives, along with scalable technology deployment, is key to sustainable biofuel adoption.