Towards a waste-free biorefinery: A cascade valorization of bamboo for efficient fractionation, enzymatic hydrolysis and lithium-sulfur cathode

Abstract

High-value potential and low-cost has propelled lignocellulose in the spotlight of sustainable energy. How to exert the complete conversion is the linchpin of biomass chemistry that asserts a waste-free biorefinery, therefore, the cascade use of three building blocks in lignocellulose is laid at the core area of a booming direction for the extension of bioproducts. Herein, we report a biorefinering initiated by dilute acid and alkaline hydrogen peroxide for successively upgrading bamboo into xylooligosaccharides (XOS), lignin, glucose and lithium-sulfur cathode. The total yield of XOS (44.9 % of low degree of polymerization, DP 2–6) has accounted for 54.4 wt% of hemicelluloses and 12.16 wt% of the virgin bamboo after dilute acid hydrolysis. To probe into the potential of depolymerizing alkaline H2O2-extracted lignin into aromatics, its molecular structure was fully explored for pointing out that the lignin was comprised generally of β-aryl ether groups and hydroxyl units. By hydrolyzing hemicelluloses and subsequently extracting lignin, the chief building-blocks can be further valorized from the independent process units. The two-stage pretreatment peeled off amorphous fractions and then ruined compact architecture, which led to the enhancement of cellulose enzymatic hydrolysis from 16.5–89.3%. A nitrogen doping of biochar (CC) from cellulose enzymatic residue was synthesized serving as lithium-sulfur cathode (CC@S) that retained 526 mA h g−1 after 200 cycles at 1 C with an average coulombic efficiency and capacity decay per cycle being 97.35 % and 0.14 %. The present study delivers a waste-free route that endows the feasibility for reforming biomass to chemicals, biofuels and energy storage devices.