Cellulosic Ethanol Still Needs to Get Cheaper

Cindy Zimmerman

A cost comparison study between corn based and cellulosic ethanol has found that corn is still the cheapest way to make the alternative fuel.

The study, published in the international journal Biofuels, Bioproducts & Biorefining, concludes that “the production of ethanol from lignocellulose-rich materials such as wood residues, waste paper, used cardboard and straw cannot yet be achieved at the same efficiency and cost as from corn starch” and that it will be 2020 at the earliest before it can become competitive. The study did identify many opportunities for reducing costs and improving income within the lignocellulose-to-ethanol process, and provides insight into the priority areas that must be addressed in coming years.

Reasons for the higher cost of cellulosic ethanol include that the cost of building large scale ethanol-producing facilities will likely be higher for second generation ethanol compared to first generation technologies due to the need for significant and costly pre-treatment, according to the study’s lead author Jamie Stephen, who works in the Department of Wood Science at the University of British Columbia in Vancouver, Canada.

“Researchers and companies are going to have to concentrate on reducing the cost of pretreatment and increasing the output of the digester in order to reduce the costs of the lignocellulose-to-ethanol process,” says Stephen. Another reason costs are higher is that lignocellulose is made of multiple kinds of sugar, while corn starch consists of pure glucose. Corn starch can be reduced to glucose with low-cost amylase enzymes, while pre-treated lignocellulose requires a cocktail of cellulase enzymes. Providing these enzymes is one of the major costs of the whole process, but you currently need 12 times more cellulase than amylase protein to generate the same amount of ethanol from woody biomass.

Finally, while the input to sugarcane- and corn starch-based systems is fairly constant, the feedstocks that go into lignocellulose systems are much more variable. Different species of tree produce wood that has different properties, and waste paper and agricultural wastes will have many different types of material in them. To get maximum efficiency, each type of biomass needs to be processed under different conditions, which introduces another challenge for anyone wanting to make ethanol from these materials.

Read the study here.

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