Simultaneous production of green hydrogen and bioethanol from segregated sugarcane bagasse hydrolysate streams with circular biorefinery design

Abstract

This study represents an integrated and sustainable approach to mine fullest potential of sugarcane bagasse (SCB) for the production of bio-H2 and bioethanol along with organic farming. Experiments were designed in three phases, where feasibility of bio-H2 production was initially evaluated with pure xylose and further validated with real field feedstock (i.e, SCB). Acid pretreatment of SCB with 2% H2SO4 (v/v) yielded xylose rich hydrolysate (21.8 g xylose/100 g SCB), which was subjected to dark fermentation for bio-H2 and VFA production. Heat-pretreated inoculum at pH 7.0 showed maximum bio-H2 fraction of 34.2% (v/v) with corresponding volumetric yield of 204.5 mL H2/g xylose. 5200 mg/L of VFA was noted with butyrate and acetate as the major fermentative metabolites. The unhydrolysed biomass recovered after acid hydrolysis of SCB was further subjected to simultaneous saccharification and fermentation (SSF) for bioethanol production. SSF of cellulose rich recovered biomass with cellulase enzyme showed 86.56% (w/w) depolymerization of cellulose into glucose and production of 241.2 mg ethanol/g treated SCB by Saccharomyces cerevisiae. Lastly acidogenic effluent (AE) from bio-H2 production process was utilized as phosphate solubilizing organic fertilizer for the cultivation of chick pea (Cicer arietinum). Regular supplementation of AE showed beneficial effect on phosphate solubilization in soil and uptake by plants. The obtained results confirm the feasible utilization of segregated streams of SCB for bio-H2 and bioethanol production with integrated organic farming in a closed loop approach. This integrated strategy would extract maximum potential of the agri-biomass feedstock with net-zero waste discharge.