Economic challenges for cellulosic ethanol

The production of ethanol biofuel from cellulosic material, a technology that seems to offer much benefit over the corn ethanol that has been added to gasoline in recent years, is facing an uphill economic struggle, according to an article published in the March 11 issue of Nature.

Although produced and marketed as a biofuel, the benefits of corn ethanol over gasoline in terms of reduced carbon dioxide emissions are fairly modest, given the use of fertilizers and fossil fuels in corn production and processing. Corn production has benefited from government subsidies, while the production of corn for the manufacture of fuel has proved controversial because of potential knock-on effects on food prices.

Cellulosic ethanol, on the other hand, offers the possibility of manufacturing fuel from agricultural waste: the cellulose-rich leaves and other materials remaining after corn has been harvested, for example.

But the relative complexity of processing cellulose into ethanol means that the production cost of cellulosic alcohol is higher than that of either gasoline or corn ethanol, the Nature article says. In addition, the U.S. market for ethanol as an additive to gasoline has hit a wall, given the limit on the percentage of ethanol in the fuel mix and a decline in U.S. gasoline demand.

In November, recognizing the constraints on U.S. cellulosic ethanol production, the Environmental Protection Agency proposed changing its renewable fuel standard by substantially reducing the volume of cellulosic ethanol mandated for use in transportation fuel. The agency has yet to publish a final ruling on this question.

—Alan Bailey