Enhanced pretreatment, characterization and utilization of Prosopis juliflora stem for bioethanol production

Purpose - Prosopis juliflora is a raw material for long-term sustainable production of bioethanol. The purpose of this paper is to identify the best combination of pre-treatment strategy implemented on the lignocellulosic biomass Prosopis juliflora for bioethanol production. Design/methodology/approach - Pre-treatment of lignocellulosic material was carried out using acid, alkali and sonication in order to characterize the biomass for bioethanol production. Prosopis juliflora stem was subjected to steam at reduce temperature (121 degrees C) for one hour residence time initially. Further acid and alkali treatment was carried out individually followed by combinations of acid and sonication, alkali and sonication. Sodium hydroxide, potassium hydroxide, hydrochloric acid, sulphuric acid and nitric acid were used with 3 per cent (w/v) and 3 per cent (v/v) concentration under temperature range of 60-90 degrees C for 60 min incubation time. Sonication under 60 degrees C for 5min and 40 KHz frequency was carried out. Pre-treated sample were further characterised using field emission scanning electron microscope and Fourier transform infrared spectroscopy to understand the changes in surface morphology and functional characteristics. Findings - In sono assisted acid treatment-based method, nitric acid yields better cellulose content at 70 degrees C and removes lignin that even at increased temperatures no burning was observed. Originality/value - The paper adds to the scarce research available on the combination of auto hydrolysis coupled with sono assisted acid/alkali hydrolysis which is yet to be practiced.