An optimal conversion cascading of distinct lignocelluloses to maximize bioethanol productivity and bio-adsorption capacities of Cd2+/Cr(VI) and red/blue dyes selective for complete biomass recycling

Although agriculture and forestry provide enormous lignocellulose resources, it remains to explore a novel technology for efficient biomass conversion into renewable bioethanol followed with complete recycling for valuable bioproduction with zero- waste release. As classic chemical (acid and alkali) pretreatments could cause chemical waste liberation, this study performed optimal pretreatments with hot-FeCl3 for sequentially enhancing biomass enzymatic saccharification in three bioenergy crops, which led to achieving hexoses yields raised by 4–7 times compared to the controls. By employing engineered yeast strain for xylose co-fermentation, the highest bioethanol yield was achieved at 18 % (% dry matter) in Miscanthus sample. The remaining enzyme-undigestible residue was thermal-chemically converted into high-porosity biochar capable of upgraded organic dyes adsorption. The yeast-fermentation residue of wheat was further incubated with classic oxidative chemicals for desirable biosorbent assembly with the highest Cd2+ adsorption capacity (25 mg/g), whereas the fermentation residue of Eucalyptus was mixed with its pretreatment liquid to generate another optimal biosorbent for maximum Cr(VI) adsorption (20 mg/g) among all biosorbents (7–13 mg/g) examined to date. A novel hypothetic model is thus proposed about how distinct lignocelluloses are convertible and selectable for high-yield bioethanol and high-performance bioproducts, providing insights into the optimal lignocellulose utilization under green-like processes.