Concerns of Cellulosic Ethanol

In contrast to the many disadvantages of corn-based ethanol, cellulosic ethanol has fewer, less malignant concerns. This is also because research into the biofuel is relatively young, and all the aspects of cellulosic ethanol has yet to be understood. As of now however, this alternative is a much better option than corn ethanol though there are several important drawbacks to cellulosic ethanol.

The primary issue with furthering research and development of this fuel is the high cost of using enzymes to digest the cellulose and hemicellulose to get them into the polysaccharide forms so they can then be fermented into ethanol. There is currently research going on that would use a synthesized bacterium to digest the polymers more efficiently; however this is still work in progress.
Another problem with pursuing cellulosic ethanol is the immense infrastructure needed for its production. Since it is a multistep procedure, involving a pre-treatment bath and acidic/enzymatic digestion, sufficient treatment and production facilities need to be built, as well as specialized transportation pipes and pumps.

In comparison with gasoline, cellulosic ethanol yields only about 66% of that energy; this means that 117 gallons of ethanol is needed for just 77 gallons of gas. However, whereas corn ethanol has an energy-cost benefit of 26% (more energy output than input; this is debatable, as said in previous section), cellulosic ethanol yields 80% more energy than was put in. Also, cellulosic ethanol would reduce greenhouse-gas emissions by 80% (some sources say CO₂ emission could even be neutral) compared to that of gasoline.