Leading Feedstocks for Cost-effective Cellulosic Ethanol Production: a Comparative Analysis

Abstract:

Gasoline, which is mainly used as an engine fuel in vehicles, has its negatives linked to global warming, rising oil prices, and Middle Eastern political instability. The search for an alternative fuel to replace gasoline is crucial. Ethanol is currently the most common biofuel used across the world. Critical arguments as economically inefficient on grain-based ethanol had been increased since large amounts of ethanol production from crops would have a conflict with food needs. Contrarily, cellulosic ethanol is more sustainable, more stable, environmentally beneficial, and has a greater production yield than grain ethanol. Cellulosic ethanol can be produced from woody biomass and agricultural residues. With supply sources having long-term potential, cellulosic ethanol could become the only cost-efficient resource for large production of transportation fuels. Nevertheless, due to the complexity of the production process, the cost of cellulosic ethanol production is still higher than the price of gasoline -- about $1.50/gallon for ethanol and $1.29/gallon for gasoline, provided by UF/IFAS researchers.[1] Thus, lowering feedstock cost is crucial to the reduction of ethanol production cost, as feedstock cost can impact total cost by 40%.[2] The purpose of this research is to provide a comprehensive review of popular feedstocks including sugar-based feedstocks like sugarcane and sorghum, and cellulosic biomass like corn stover, switchgrass, and hybrid poplar. Using data from various databases and academic papers, we evaluated feedstock based on accessibility, net energy efficiency, environmental benefits, negative impacts, and most importantly, production cost. We also examine the relationship between the amount of carbohydrate content and final production effectiveness. We have found that corn stover shows the lowest ethanol production cost with a total operating cost of $375.7 ethanol/m³, compared with $458.1 ethanol/m³ for switchgrass and $485.8 ethanol/m³ for hybrid poplar.[3] And corn stover is also the most environmentally friendly feedstock among the species studied. However, hybrid poplar presents better financial returns.