Pretreatment Strategies of Lignocellulosic Biomass Towards Ethanol Yield: Case Study of Pine Needles
Today one of the most challenging and noticeable problem is how to supply the vast quantities of energy, fuels and chemicals when oil, gas and coal are depleting exponentially with increase in population. In current scenario lignocellulosic bioethanol seems promising alternative sources of energy and chemicals which is considered a cleaner/or green source also. Lignocellulose, is composed of mainly by three components namely cellulose, hemicelluloses and lignin. However cellulose and hemicellulose are protected by lignin layer, due to which they are not accessible to hydrolytic enzymes and efficiency of the bioethanol production also influenced by crystallinity of cellulose, lignin content, water content and surface area etc. Pretreatment technologies in practice show shortfalls and inefficiency in making cellulose and hemicelluloses free for hydrolysis and also to crack the crystallinity of cellulose. Basically selection of efficient pretreatment process depends on the biomass composition, process economics and environmental impact, therefore in search of an efficient and eco-friendly pretreatment technologies, in current chapter, pretreatment of Pine needles (PN) was carried out by using various methods in combination, such as surfactant assisted acid pretreatment (SAAP), surfactant assisted alkali pretreatment (SABP) and sequential dilute alkali and acid pretreatment (SDAPP) and during pretreatment sugar released (sugar loss) was found to be 0.211, 0.146 and 0.198 g/g, respectively. After pretreatment on enzymatic saccharification of SAAP, SABP and SDAPP liquor, reducing sugar yield was found to be enhanced up to 0.588, 0.477 and 0.582 g/g, respectively under optimized conditions. The PN without pretreatment had released 0.144 g/g of reducing sugar which implied that SDAAP had enhanced the saccharification up to 4 fold. On comparisons of all these pretreatment strategies, sequential acid and alkali pretreatment was found more advantageous in terms of lesser sugar loss and high ethanol yield. However inhibitors generated during pretreatment have to be removed with some potential resins such as Amberlite XAD-4.
KeywordsEthanol Production Lignocellulosic Biomass Acid Pretreatment Steam Explosion Pretreatment Process
The authors are thankful to Department of Science and Technology (DST) and Ministry of New and Renewable Energy (MNRE) Government of India New Delhi, for facilitating current work with financial support and Motilal Nehru National Institute of Technology (MNNIT), Allahabad for providing the space and basic facilities to carry out the research work.
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