Integrated biorefinery process for dual production of fermentable sugars and functional humic acids from...

In traditional lignocellulosic biorefineries, lignocellulose undergoes pretreatment followed by enzymatic hydrolysis to produce fermentable sugars, often leaving behind lignin rich residual biomass underutilized. In this study, we present a novel and integrated approach for the comprehensive utilization of lignocellulosic biomass as fermentable sugars and functional humic acids. First, corn stover was subjected to a mild densification pretreatment with Ca(OH)₂ (DLCA(ch)), facilitating efficient enzymatic hydrolysis and yielding 172.09 g/L of sugars at 30 % solid loading. Further, the enzymatic hydrolysis residues were subsequently converted into artificial humic acid (AHA) through a mild artificial humification process at 50 °C, catalyzed by potassium hydroxide (KOH) alone or in combination with urea. This process achieved a high AHA yield of 44.17 %, with a final concentration of 78 g/L. The AHA synthesized with KOH and urea (KU-AHA) predominantly consisted of medium molecular weight fractions (30-100 kDa) and exhibited enhanced nitrogen incorporation due to the involvement of urea. Additionally, KU-AHA demonstrated comparable effectiveness to natural humic acid in promoting plant growth, leading to an 13.40 % increase in plant height, an 11.82 % increase in root length. This integrated approach not only maximizes the utilization of lignocellulosic biomass but also provides a sustainable and efficient pathway for residue valorization.