Although many experts have indicated that the production of ethanol from cellulosic plant biomass is the way of the future, the technology has never gone completely to full-scale commercialization. However, the recent announcement of the United States Department of Energy to invest $386M for ethanol biorefineries in the next four years may signal the start of bringing commercialized cellulosic ethanol production at the forefront of the biofuels market. Six biorefineries have been identified. According to Department of Energy Secretary Samuel W. Bodman, “these biorefineries will play a critical role in helping to bring cellulosic ethanol to market, and teaching us how we can produce it in a more cost effective manner”. Non-food biomass sources are considered for use as raw materials for the proposed plants, including (1) agricultural residues (wheat straw, corn stover), (2) industrial plant wastes (saw dust, paper) and (3) cellulosic energy crops (switch grass). Relative to corn-based ethanol, cellulosic ethanol is said to have a higher net energy with lower emissions of greenhouse gases..

In the 2007 February 20 issue of Current Biology, Stanford University Professor, Chris Somerville, outlines the prospects and problems in the recent trend toward increasing reliance on liquid biofuels. Some of his findings are summarized below:

(1) Corn and cane ethanol: the production technology is reported to be mature. Studies have shown that cane ethanol has an energy output ratio of 8 (energy units produced for every energy unit consumed for its production). Life cycle studies on corn ethanol have also shown that it produces only 25% more energy than is consumed (considered not high). As such, corn ethanol is seen only as a “transition technology” while more cost effective and energy efficient technologies (like cellulose ethanol) are in development. Corn ethanol is not seen as a long term strategy for sustainably meeting energy needs.

(2) Biodiesel: the common raw materials for biodiesel production are annual oilseeds, soybean, palm, and canola. Although studies have shown that biodiesel has a better net energy output ratio than corn ethanol, it is not seen as a “significant component of fuel in the US or elsewhere in the developed world”. Some issues involved are: small oil yield per acre (relative to amount of biomass), and competition with its use as a component in the human diet. However, in developing countries, several tropical plants have been found to be potential raw materials for biodiesel production: oil palm, Babbasu palm, Jatropha.

(3) Cellulose ethanol: the common raw materials are cellulose from plant biomass. The biological route of production involves biochemical or microbiological breakdown of cellulose to component sugars, followed by fermentation to ethanol. Presently, there are still no large scale plants for commercial cellulose ethanol production. Many process components in the technology are reportedly not yet ready for commercial production. Despite the present bottlenecks, cellulose is still expected to become a significant component in transportation fuels in the future..