Potential Future Directions for Achieving Low Cost Cellulosic Ethanol

The dependence of a vast majority of the global population on petroleum has led to an acute concern regarding its negative environmental impact and long-term sustainability of utilizing this finite resource. The control of its reservesby some, has left others vulnerable, and has made decision makers andintellectuals alike to mull over practical alternatives. Climate damage is tied to radiative forcing that is affected strongly by carbon dioxide in the atmosphere, a greenhouse gas that had cycled between about 170 to 280 ppm from 800,000 BCE till the start of industrial revolution in 1760, and since then has been increasing continuously to today’s level of near 400 ppm, largely due to anthropogenic activities such as transportation, power and electricity generation. 

Cost, renewability, environmental impact, and availability are some of the most important considerations in finding substitutes for gasoline. Cellulosic ethanol satisfies many of such criteria with cost being its main hurdle to commercialization. Its pursuit over other fuels comes from the learning that when produced through biological route from plant biomass, it is currently the only known liquid fuel that can be produced at the high yields and scale necessary to be able to compete with the well-established gasoline fuel and its infrastructure. While it has begun its journey to penetrate the fossil fuel supply chain, its cost needs to be lowered to a point at which profit margins appear lucrative enough to attract investment and satisfy requirements for sustainability. The current bottleneck for a high yielding biological route for ethanol involves pre-treatment, enzymatic hydrolysis, and fermentation. It is the higher in cost than economically desired due to in part to pre-treatment costs and the quantity of enzyme employed to depolymerize polysaccharides in biomass into fermentable sugars. High concentration of sugars at low cost and low inhibitor levels not only leads to lower cost cellulosic ethanol, but opens doors to industry to pursue fuel and chemical production using pathways originating from sugars.(Read more)