Evaluation and characterization of novel sources of sustainable lignocellulosic residues for bioethanol production using ultrasound-assisted alkaline pre-treatment.

In recent years, research is focused on finding a sustainable and eco-friendly lignocellulosic biomass for the effective production of bioethanol to meet the world's energy demand. The present study investigates the bioethanol production potential of four different lignocellulosic biomass residues viz., Saccharum arundinaceum (hardy sugar cane), Arundo donax (giant reed), Typha angustifolia (narrow-leaved cattail), and Ipomoea carnea (pink morning glory). The maximum reducing sugar release showed 185.00 ± 1.57, 213.73 ± 3.47, 187.57 ± 2.14, 294.08 ± 3.98 mg/g and fermentation efficiency of 72.60 ± 8.17%, 82.59 ± 7.42%, 77.45 ± 7.35%, and 85.04 ± 8.37% which was analyzed by estimating the percentage of bioethanol yield were achieved for Saccharum arundinaceum, Arundo donax, Typha angustifolia, and Ipomoea carnea, respectively. The chemical composition of biomass was characterized using National Renewable Energy Limited (NREL) protocol. The effect of ultrasound (US)-assisted alkaline pre-treatment on the four biomasses was characterized by different techniques. The cavitation phenomena of US-assisted alkaline pre-treatment was evident from the decreased value of lignin percentage, increased surface porosity and area, changes in crystallinity index (CrI) values and in the functional groups of biomass. The results revealed that all the four lignocellulosic biomass residues could be utilized as an effective and sustainable source for the production of bioethanol using US-assisted sodium hydroxide as a pre-treatment tool.