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Currently, in everyday life, fossil fuels are the world’s primary energy source. It is formed over millions of years from organic materials (remains of dead animals and plants) and is mostly used to power vehicles and generate electricity. Types of fossil fuels includes coal, oil, and natural gas. Although it plays a great role in our lives, fossil fuels are non-renewable resources which also harms the surrounding environment when used. Fossil fuels are burned to produce heat energy. However, burning it also releases carbon dioxide along with other greenhouse gases which traps heat in the earth’s atmosphere, causing global warming. According to the U.S. Environmental Protection Agency as shown on figure 1, the burning of fossil fuels contributes most of the U.S. greenhouse gas emissions in 2015 (77%).
The solution to this problem is by using other type of fuel which can become an alternative to fossil fuels which do not harm the surrounding environment, such as Bioethanol. This fuel can replace the use of fossil fuels in powering road transport vehicles. Bioethanol is entirely made of biological products, therefore it is a renewable source of energy. It is produced by the fermentation of plants which contains sugar and starch, such as corn, wheat, sugar cane, etc. The production process of Bioethanol is very long. Based on the picture in figure 2, Bioethanol production steps consists of milling, saccharification, fermentation, and dehydration. (In this case, corn is used).
The first step is milling, or also known as grinding. During milling, a hammermill or roller mill is used to grind (shown on figure 2). As the rotor turns, the corn is hammered against the wall, causing the larger particles to breakdown into smaller ones. In this case, Milling helps to break the tough outer coatings of the corn kernel. After it is broken down, it is mixed with heated water to form mash. When the temperature of water is above 60°C, water interacts with the starch granules to form a vicious suspension. After that, a process called liquefaction is done as a hydrolysis that lowers the viciousity. Hydrolysis is where water reacts with the sugar to breakdown sugar to form glucose. It functions to break the longer starch chains into smaller chains. The next step is saccharification. It is a process of further hydrolysis done by adding enzymes, such as glucoamylase. During this process, the optimum condition is at 4.5pH and with a temperature between 55-65°C. Then, the solution is ready to become fermented into ethanol and go through a process called fermentation. During fermentation, yeast is added to the solution, causing the sucrose sugars into fructose and glucose. Commonly, the yeast used is saccharomyces cerevisiae (unicellular fungus). The exact time required for this reaction process is 2-3 days (at 30-32°C). The chemical equation for this chemical process is C6H12O6? 2C2H6OH + 2CO2.
Lastly, the last phase of bioethanol production is distillation. Distillation is a process where components are sepearated using heat, and is possible due to the difference in boiling points between the two components. In this case, the two components are water and ethanol. Water boils at 100°C and ethanol boils at 78°C.
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