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, 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. If the temperature of water is above 60°C, water will 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 sugar is broken down to glucose due to the reaction between water and sugar. It functions to break down long starch chains into smaller chains.
The next phase is saccharification. It is also a process of hydrolysis which is done by adding enzymes, such as glucoamylase. The optimum condition required by this process is at 4.5pH 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, sucrose sugar is separated into fructose and glucose by adding yeast to the solution.
Usually, the yeast used is saccharomyces cerevisiae. 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. The next phase of bioethanol production is distillation. For the ethanol to function properly as a fuel, most of the water must be separated from the solution. Distillation is a process where components are separated using heat due to the difference in boiling points between the two components. Since water and ethanol have different boiling points, distillation is the exact separation method to use. However, water and ethanol both have OH functional group which causes their molecules to become strongly bound together forming azeotrope.
The last phase is dehydration which functions to remove all the water completely. This process uses a molecular sieve with a material called zeolite. The zeolite will absorbs water into it, but not the ethanol. Bioethanol as the alternative fuel to fossil fuels can be very beneficial to the surrounding.
Firstly, bioethanol is easily accessible. Its energy is derived from plants like corn, grains, and etc. which can be easily obtained in most countries. Bioethanol is also classified as a renewable energy source, which means it is not limited. This is because it is produced from plants, and plants can be replenished naturally overtime. Moreover, bioethanol exhaust gases are much cleaner, as a result it produces less carbon and carbon monoxide.