Cellulosic Ethanol

Process

Please see our animation on the Cycle of Cellulosic Ethanol to the left.

There are two different methods of production, Cellulolysis and Gasification.

• Cellulolysis uses hydrolosis on pretreated lignocellulosic materials, enzymes break down complex cellulose into simple sugars like glucose.
  
• Gasification converts biomass into gaseous carbon monoxide and hydrogen, these can be turned into ethanol through fermentation or chemical catalysis.(Absolute Astronomy)
  

Cellulolysis

• Pretreatment
  

Pretreatment is usually done through chemical or physical means, this is done to make the biomass susceptible to the enzymes that break it down or to reduce the physical size of the biomass. This biomass can be anything from wood chips to sorghum, or corn husks to rice straw. Different types of pretreatment techniques include acid hydrolysis, organosolve, steam explosion, and many more techniques. The setback of these pretreatments are that some are toxic; some more than others.(Absolute Astronomy)

• Cellulolytic Process

Cellulose is made of long sugar molecule chains, during hydrolosis these chains are broken down into simple sugars. There are two different ways of doing this, the first is through chemical reactions using acid and the other is through an enzymatic reaction.

• Chemical Hydrolysis

Hydrolysis is done by breaking down cellulose with an acid. A decrystalized cellulosic mixture of acid and sugars creates a reaction when water is present. This completes the sugar molecules, this process is hydrolysis.(Absolute Astronomy) Yeast fermentation is then used on the individual sugar molecules to create ethanol.

• Enzymatic Hydrolysis

Cellulose can be broken down into glucose by cellulase enzymes. Lignocellulosic materials can be enzymatically hydrolyzed, this enables effective cellulose breakdown without formation of byproducts. All pretreatment methods need enzymatic hydrolysis for high sugar yield for ethanol production.

Gasification

Instead of breaking cellulose into sugars the carbon in the biomass is turned into gas. The carbon monoxide, carbon dioxide, and hydrogen made will then be "fed" into a special fermenter where a microorganism will "eat" all three and produce ethanol and water (Absolute Astronomy website).