What is bioethanol?
Bioethanol refers to the ethanol produced from starch and sugar rich crops. It is used for fuel purposes.
Bioethanol Production from Corn and Sugarcane
Bioethanol Produced from starch and sugar rich crops such as Corn and Sugarcane make the first generation of biofuels. One common feature of first generation biofuel crops is the requirement of suitable arable fertile land to grow them.
Corn is the most utilized crop for fuel ethanol production although its use is mostly limited to US. Brazil’s bioethanol production is based on Sugarcane which is the second most utilized crop for bioethanol production in the world.
Wheat, whey, barley, potato wastes, and sugar beets are also qualified candidates for bioethanol production.
Bioethanol production Process
In general, simple sugars derived from feedstocks are fermented with classical or genetically modified yeast strains such as Saccharomyces cerevisiae in order to get ethanol.
(i) Bioethanol Production Process using Corn as a feedstock
Corn is a rich source of starch. In order to use corn as feedstock for bioethanol production the starch must get released from corn grains.
To release starch, corn is subjected to certain mechanical (Dry milling)/acidic processing (wet milling) and enzymatic hydrolysis. This results in starch rich corn mash. Starch rich corn mash is further subjected to enzymatic hydrolysis. α-amylase is the most used enzyme for this step. This results in hydrolysis of starch into sugars.
The free sugars can be easily converted into ethanol via fermentation.
Two routes are generally followed to produce bioethanol from corn.
Dry Milling for Production of Ethanol from Corn
(ii) Bioethanol Production Process using Sugarcane as a feedstock
Unlike corn, sugarcane provides sugar rather than starch. This reduces the steps such as cooking and the enzymatic hydrolysis from the production process. A yeast fermentation process is followed to convert sugarcane juice into ethanol.
In Brazil the cane juice is directly fermented while In India ethanol can be produced only from fermentation of sugarcane molasses. Sugarcane molasses is the viscous liquid that remains after the sugar extraction process from the sugarcane juice. It contains residual amount of sugar.