Cellulosic Ethanol: How It Works [Gasification Process]

Cellulolysis Process Gasification Process Inputs & Outputs

Gasification Process
The process can thus be broken into five steps (only the first two steps differ materially from crop-based ethanol production):

Gasification—Instead of breaking the cellulose into sugar molecules, it is converted into syngas (comprised of carbon monoxide, carbon dioxide and hydrogen) by exposing the feedstock to high temperatures or steam. (Through methods such as the Fischer-Tropsch Synthesis, syngas can be a form of diesel can be produced).
Fermentation—The syngas is moved into a fermenter where a bacteria, Clostidium, is added. The Clostidium bacteria eats the syngas and produces a mix of ethanol and water.
Distillation—Similar to the production of crop-based ethanol, the fermented liquid moves into a distillation system where the liquid is heated to take advantage of the different boiling points of ethanol and water. These differing boiling points will enable the extraction of ethanol, which is roughly 95% pure.
Dehydration—The alcohol from the top of the column will then pass through a dehydration system, usually a molecular sieve, where the remaining water will be removed. This produces 200 proof, anhydrous (waterless) ethanol.
Denaturing—Ethanol that will be used for fuel in the U.S. and Europe is then denatured with a small amount, 2-5%, of gasoline to make it unfit for human consumption. Brazil uses 100% anhydrous ethanol in its vehicles.