CHE.07 Ethanol Production from Cellulosic Biomass Waste

• Amaan

Everyday human existence faces an increase in the world population which results in substantial increase of energy consumption. Eventually, increasing energy demand will pose challenges to security of supply as resources are scattered around the globe. While fossil fuels have become the world’s main energy resource and are at the center of global energy demands, its reserves are limited. Since traffic is one of the largest sources of carbon emission, substituting fossil fuels with renewable alternatives is an efficient way to reduce these emissions. Use of natural resources more efficiently and increase of renewable energy such as biofuels is key to the issues that the world faces. Biofuels are mainly used in ground transportation systems as blends with conventional fuels and ethanol is by far the most popular biofuel. Currently, the most common type of bioethanol is the first-generation ethanol which is produced from feedstock which mainly includes corn. Although this technique might seem efficient, it still does contain multiple disadvantages. The objective of this project is to investigate the potential of utilizing lignocellulosic waste, specifically corn stover, as a secondary biomass source for ethanol production for fuel usage. The process includes diluted-acid pretreatment of lignocellulosic biomass followed by enzymatic hydrolysis (saccharification) of remaining cellulose, followed by fermentation of the resulting glucose and xylose to ethanol as well as recovery process. In pretreatment, corn stover is treated with ammonia and diluted sulfuric acid catalyst to liberate the hemicellulose sugars and breakdown the biomass for enzymatic hydrolysis. Enzymatic hydrolysis begins in a high-solid continuous reactor where enzymes are injected. Hydrolysis is completed in the batch reactor and the slurry is then cooled and inoculated with the co-fermenting microorganism Zymomonas mobilis. After the enzymatic hydrolysis and fermentation, most of the cellulose and xylose have been converted to ethanol and the solid waste has been removed from the process using filtration. The recovery section contains two distillation columns where ethanol is distilled to a nearly azeotropic mixture with water. The mixture is then purified to 99.5% using molecular sieve adsorption (3 bed unit). Using lignocellulosic waste as raw materials for biofuels is an excellent example of answering the needs of a circular economy. Reducing the amount of waste and making the most of valuable natural resources is crucial for world future survival. In addition, biofuels help to enhance and safeguard energy security by reducing the world’s reliance on fossil energy sources, as well as biomass is a resource that is more evenly distributed globally.