Ethanol or ethyl alcohol is a colorless, clear alcohol based alternative fuel that is being produced by concentrating and fermenting starch crops that were converted into simple sugars. It can be produced from corn, wheat, barley and cellulose feedstock from rice straw, corn stalks, pulpwood and several others. Enthanol can be produced as well from cellulosic biomass that includes grasses and trees.
Modern ethanol production plants are using dry mill method that use yeast as a way of converting sugar into alcohol. The major steps involved in the process of making ethanol include the following.
- Milling – The entire feedstock or corn kernel is sent through the hammer mill, grinding it into course flour called meal.
- Liquefaction – The meal is combined with water as well as alpha amylase enzyme forming a mash that passed through cookers to liquefy the starch. Cookers that have high temperature stage and lower temperature holding period. This will help reduce the levels of bacteria in the mash.
- Saccharification – The mash will be cooled down from the cookers, adding the secondary enzyme to convert the liquefied starch to fermentable sugars.
- Fermentation – Then the mash will be cooled and moved into fermenters in which is the yeast is added and the sugar fermentation to ethanol and carbon dioxide starts. This is allowed to undergo several fermenters until it totally fermented before leaving the final tank.
- Distillation – The fermented mash, referred to as beer is made up of nearly 15% alcohol with the solids that are non-fermentable from corn as well as yeast cells.
- Dehydration – At this period, the alcohol will passed through the dehydration system in which the left over of water is expelled. Molecular sieve system is commonly used and it is capable of capturing the last bit of water in ethanol.
- Denaturing – Ethanol to be used as fuel will be denatured or made unhealthy for the consumption of human, by adding small amount of gasoline.
- Co-products – Carbon dioxide and distillers grains are the main products that are formed in this process. Distillers grains in wet or dry form are used as valuable feed for animals.