The structure and physical properties of organic molecules are characteristics that aid them to become useful fuels for human beings. Ethanol, propane and methane are examples of organic compounds which are commonly used as fuels today. What are the structure and physical properties of these compounds that help them to act as excellent alternative fuel sources?
Figure 1 Energy-rich organic molecules (biofuels) are used to fuel cars, planes and ships (Smart Energy Initiative of Southeastern Pennsylvania, 2012)
Quantity of energy released during combustion
Other than structure and properties, the amount of energy released through the combustion of the fuels is very vital. A small amount of fuel used to undergo combustion, producing high amount of energy and this is considered as a good fuel. The comparison of energy produced when one kilogram of ethanol, propane and methane are combusted is shown below:
From the above table, methane produces the highest amount of energy as compared to propane and ethanol. Propane is the intermediate in which it produces the second most energy when it is combusted. In this case, ethanol produces the least amount of energy when it undergoes combustion.
In the case of fossil fuels, they emit pollutants, greenhouse gases and wastes to the surrounding environment. The concern of the people nowadays is the greenhouse effect and global warming that mainly caused by the greenhouse gases such as carbon dioxide, carbon monoxide, sulfur dioxide and nitrogen oxides which are produced from the combustion of fuels in the process of energy generation.
Good fuels are fuels that emit less pollutant and greenhouse gases as waste products. They do not significantly harm the mankind as well as our Mother Earth and at the same time, reducing the problem of severe global warming that the people are encountering now. As an alternative motor vehicle fuel, 85% ethanol is usually mixed with 15% unleaded gasoline. This type of fuel is commonly called as E85. Aldehyde emissions from ethanol blends are generally high. Formaldehyde, the major components in aldehyde emissions is also a suspected carcinogen. When incomplete combustion occurs, poisonous gas such as carbon monoxide is produced. Ethanol does not increase atmospheric carbon dioxide levels as the carbon dioxide formed during combustion is balanced by that absorbed during annual growth of plants used to produce ethanol.
Propane gas is considered as environmental friendly gas as propane is non-toxic, non-caustic and will not create environmental hazards if released as a liquid or vapor into water or soil. According to scientific reports, there are no long term effects of ignited propane that can be damaging to the environment. Propane is not considered a greenhouse gas. In fact, propane is listed as an approved clean fuel because propane emissions cut smog producing exhaust by as much as 70%. (Propane 101, 2011) The level of damaging emissions following Liquefied Propane Gas combustion is far below that of any readily available carbon based fuel used in vehicles and engines today.
Methane gas, also known as the natural gas, is the cleanest of all the fossil fuels. Natural gas which is consists of methane undergoes combustion to produce carbon dioxide and water vapor. When propane is combusted, it releases very small amounts of sulfur dioxide, carbon monoxide and other reactive hydrocarbon that lead to further pollution of the environment. In short, ethanol, propane and methane release small amount of pollutants and greenhouse gases as compared to fossil fuels. It is of great help to the conservation of environment as if these alternative fuels are used widely by people around the world.
The Efficiency of Fuels to the Efficiency of Octane
As to compare the efficiency of fuels to that of octane, octane rating or octane number is used. Fuels with higher octane rating have higher performance in engines. According to Wikipedia, the most common type of octane rating worldwide is the Research Octane Number (RON). Different fuels have different RON and from the values of RON, the efficiency of a fuel can be determined easily. From the table above, methane has the highest RON value as compared to ethanol and Propane. In other words, methane has the greatest and highest performance in generating energy. However, the RON values of ethanol, propane and methane have only slightly difference. Therefore, they are considered as effective fuels for engine, especially for transportations.
There is no doubt that bio-fuels such as ethanol, propane and methane have the potential to serve as alternative fuel and energy supply to substitute fossil fuel. This can be seen through the physical and chemical properties of the ethanol, propane and methane in which they can effectively produce large amount of energy and at the same time, release much less amount of harmful emission to the atmosphere. In fact, they are much eco-friendly in terms of conserving the environment, preventing the greenhouse effect and global warming because the traditional way fossil fuel supply emits large amount of greenhouse gases such as carbon dioxide, carbon monoxide, sulfur dioxide and nitrogen oxides. All in all, the organic alternative fuels should be utilized by human beings for a greater energy and power source and also better future.
1. Kessel, Hans. Section 9.4 (Unit 5). Nelson chemistry 12. Toronto: Thomson Nelson, 2003. 691. Print. 2. Document. DGUV-IFA GESTIS Stoffdatenbank. N.p., n.d. Web. 24 Apr. 2012.