How is bioethanol made?
Bioethanol is a denatured alcohol that is produced by fermentation. Bioethanol can be made from a variety of plant-based products and this article looks at how ethanol is produced from corn. Corn is a starch-rich product, and that starches easily converted into sugar for the fermentation process.
The stages of production
The production of bioethanol from corn can be divided into two separate phases. In the first phase, the corn is prepared and goes through the fermentation process. The second phase is where the product is made ready for use as a biofuel. When the two-stage process is ended the producers are left with bioethanol fuel and useable by-products that add value to the process.
Stage 1 is made up of three separate actions; preparation, liquefaction and fermentation.
Here the corn is ground by a mill into meal. Meal is a course, rough flour.
The meal is mixed with water and enzymes to create a mash. This mash is heated to reduce the number of bacteria present in the mix, as these bacteria can interfere with the fermentation process. The entire product is liquified at this point to prepare for the fermentation process.
Gluco-amylase is added to the liquified corn to turn the liquid starch into sugar. Yeast is added to the mix to ferment the sugars. When the yeast is added in the fermenter, ethanol and carbon-dioxide are produced.
Stage 2 is also a three-step process, and involves Distillation, Dehydration and Denaturing.
The fermented mash is heated to separate the alcohol produced from the liquified mash.
The alcohol produced in the distillation stage is dehydrated to remove any traces of water. A large amount of water is removed during the distillation process; though the dehydration stage leaves the producer with anhydrous-ethanol – this is pure ethanol without any trace of water.
The ethanol is denatured and made unhealthy for humans to drink by adding a small amount of gasoline.
The process of producing bioethanol also creates carbon dioxide and a waste product known as distillers grains. The distillers grains are used as an animal feed, and the carbon dioxide is often bottled and sold to soft-drinks companies.
Is this process sustainable?
The waste products produced by creating bioethanol are both useful in other areas. The grains left over after the distillation process are valuable to farmers, and the carbon dioxide is not released into the atmosphere, so the whole process is almost carbon-neutral. The carbon dioxide produced during the distillation process can also be used to feed algae – which then can be used to create ethanol. This crates an endless recyclable process with little, if any, harmful by-products.