Optimizing Acid Pretreatment and Spectroscopic Validation of Bioethanol Production from Gmelina arborea Lignocellulosic Biomass

Abstract

The production of bioethanol stands out as a highly promising alternative to fossil-based fuels. Nevertheless, for bioethanol to become a viable option, it is crucial to develop more cost-effective production methods. Scientists have examined diverse techniques for bioethanol production, utilizing an array of feedstocks in their research. This study investigates the efficacy of sulfuric acid pretreatment for bioethanol production from Gmelina arborea leaf and bark, coupled with Fourier-transform infrared (FTIR) spectroscopy to validate ethanol purity. Proximate analysis revealed high carbohydrate content in bark (75.4%) and leaf (71.5%). Acid hydrolysis (1–2 M H₂SO₄) and fermentation with Saccharomyces cerevisiae yielded 63 mL ethanol from 2 M H₂SO₄-pretreated bark (density: 0.972 g/cm³), while leaf hydrolysate at 1.5 M yielded the lowest (2.1 mL, 1.045 g/cm³). FTIR analysis confirmed ethanol’s functional groups (O-H, C-O) and identified residual by-products such as carbonyl compounds (C=O) and alkynes (C≡C). The results underscore bark’s superiority as a feedstock and highlight acid pretreatment’s role in enhancing fermentable sugar release. This work advances sustainable biofuel strategies by integrating process optimization with spectroscopic quality control.