Advancing the Lignocellulosic Value Chain within the PERCIVAL Project: Integrated Biorefinery Approaches for Lactic Acid and Biochar Production

The lignocellulosic value chain within the PERCIVAL project focuses on transforming agro-industrial residues into high-value bioproducts through a sustainable circular bioeconomy approach. The process integrates the conversion of the carbohydrate fraction of lignocellulosic biomass into lactic acid and the valorization of the lignin-rich residue into biochar. Steam explosion pretreatment (198 °C, 5 minutes, 55 mM acid catalysis) was optimized for hemicellulose solubilization, achieving high xylose recovery from the xylan-rich fraction. Enzymatic hydrolysis with commercial enzyme blends (Cellic® CTec3 HS) achieved up to 75 wt% cellulose hydrolysis and 86 wt% xylan conversion, generating fermentable hydrolysates. Fermentation of undiluted and undetoxified wheat straw hydrolysate was carried out by Lactobacillus brevis ATCC 14869 under optimized microaerophilic conditions, reaching lactic acid titers of 48.95 ± 0.37 g/L after 60 h, with a yield of 0.49 ± 0.09 g/g, complete glucose consumption, and partial xylose utilization. The lignin-rich residues were thermochemically converted into biochar via slow pyrolysis in a rotary kiln reactor (600 °C, heating rate ~60 °C/min, N2 flow 2 L/min, 3 rpm), with a residence time of about 20 min, yielding 30 wt% char. This integrated biorefinery model demonstrates efficient biomass valorization and minimal waste generation, contributing to sustainable, carbon-neutral bioproduct pathways.