Colorado's National Renewable Energy Laboratory (NREL) based in Golden, is the home of the nation's only large-scale pilot plant for the production of ethanol from biomass. Engineers and scientists at NREL lead the way in research on renewable energy technologies, from photovoltaics (solar cells) to wind to renewable fuels. NREL received a surge of media attention early this year when 32 staff positions were eliminated and then hastily reinstated just in time for President Bush's visit to NREL in February. All of this followed the president's State of the Union address in which he announced that "America is addicted to oil" and pledged a 22 percent increase in investments into clean energy. NREL's Andy Aden told LIME about the promises and limitations of cellulosic ethanol.

LIME: Lately ‘cellulosic' ethanol is being touted as a potential means of energy salvation for the United States. Can you talk about the difference between producing ethanol from corn and ethanol from switch grass, cornhusks, stalks, and other forms of biomass. Does it require an entirely different technology?

Andy Aden: Production of corn ethanol here in the United States really started around the late 70s and early 80s, soon after we had the energy crunch and the Middle East energy crisis. Back then it was very inefficient and they were still developing the technology. Cellulosic ethanol research has been going on here at NREL for at least 25 years. So cellulosic ethanol is quite a bit of a departure from the current technology for corn to ethanol. With the corn kernel you've got a lot of starch packed in there and that starch turns into sugars, and those sugars are what are fermented to ethanol. It's a pretty well known process and pretty easy to do.

Cellulosic biomass to ethanol on the other hand is taking all that fibrous material - the corn stalks, the cornhusks and everything else left over after the corn's been harvested. Cellulosic biomass also includes wheat straw and other agricultural residues, such as switch grass, which is a natural growing grass out on the prairies, and even wood chips and wastes from pulp mills. All of this plant matter is considered biomass, and it's cellulosic biomass because it contains cellulose.

One of the real challenges is how much more difficult cellulose is to break down into sugars as opposed to starch. On a chemical basis starch and cellulose are very similar, but the actual work to break them down is much more difficult. It's the way that the molecules are bonded. They have the same chemical formula but the hydrogen bonding that occurs within the cellulose molecule is much tighter and much harder to break than the starch is. It's kind of analogous to graphite and diamond. Chemically they're both carbon. But graphite is very brittle and diamond is the hardest substance on earth.