Effect of chemical pre-treatment on bioethanol production from defoliated dried neem (Azadirachta Indica) leaves

Abstract

In recent years, ethanol derived from biomass is grabbing attention due to incessant spike in petroleum prices along with increased green house gases. In this context, ethanol production from residual lignocellulosic biomass such as dried defoliated leaves which will not pose the menace food versus fuel has been gaining significant concern in the scientific community. In current study, lignocellulosic biomass derived from defoliated dried neem leaves (Azadirachta Indica) were used as a feedstock for bioethanol production. The powdered leaves were chemically pre-treated by adopting two types pre-treatment processes; (i) Single stage acid pre-treatment using three different concentrations of H2SO4 (0.1 M, 0.5 M and 1 M) and (ii) two-stage combined alkali and acid pre-treatment using three different concentrations of NaOH (0.1 M, 0.5 M and 1 M) followed by subsequent pre-treatment with 1 M H2SO4. FTIR study was adopted to characterize the biomass (neem leaves) samples before and after pre-treatmemt as well as produced bioethanol samples. The sugar content in the biomass sample and pre-treated solutions were carried out using Munson and Walker method. The ethanol concentration in the fermented broth was determined by UV–VIS spectroscopy. The FTIR studies of the neem leaves before and after pre-treatment showed breakdown in lignocellulosic biomass structure due to pre-treatment. The FTIR pattern of the produced bioethanol showed the characteristic peaks of ethanol. The study reveals that the two-stage combined alkali pre-treatment using 1 M NaOH and 1 M H2SO4 results highest quantity of recovered sugar (21 g/L) and ethanol (18.49 % (w/v)). The two-way ANOVA analysis with p < 0.05, suggests there is a significant variation in impact of two parameters i.e. concentration of pre-treating agents and nature of pre-treatment on bioethanol production. The study explored the possibility of using a residual biomass such as defoliated dried neem leaves that are abundantly available in Indian sub-continent as a potential feedstock for bioethanol production for consequent CO2 mitigation.