Plant-Based Biofuels

The largest share of organic carbon is stored on Earth in the form of plant biomass which contains a range of carbohydrate polymers such as cellulose and hemicellulose along with lignin, to make up the lignocellulose. Crude oil-based fuels being both non-renewable and hazardous to the environment, plant-based biofuels promise hope for the ever-increasing energy demands of the future. Biofuel includes solid, liquid and gas fuels which are primarily obtained from photosynthetic organisms. Hence, the burning of biofuels is a carbon–neutral process. Plant-based biofuels can be majorly categorized as lignocellulosic bioethanol, biodiesel, biohydrogen and bio-oil. Lignocellulosic bioethanol is generated through systematic deconstruction of plant biomass which involves processes like efficient mechanical and chemical pre-treatment of selected biomass followed by its enzymatic hydrolysis during the saccharification. The biomass saccharified into simple C-6 or C-5 sugars (such as D-glucose or D-xylose, respectively) is then fermented to bioethanol followed by its collection through distillation or fractionation. Another major biofuel, Biodiesel is obtained from plant materials like seeds by extraction of plant oil followed by transesterification. This chapter reviews the different areas of plant-based biofuels, their economic viability, challenges and future prospects.