How Is Ethanol Made?

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Written by Sabrina Deparine

Saturday, 22 August 2009 12:52

Page views: 1054

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Don’t you ever wonder how ethanol is made? How a simple crop or biomass is processed and turned into an alternative fuel? For this week, BiofuelsHub is featuring an article on how ethanol is made from the feedstock.

The procedure is quite easy. Here in the Philippines, the most popular and widely-used feedstock is sugarcane. The conversion of sugarcane to ethanol is actually simpler than converting crops to ethanol. It involves only the so-called “yeast fermentation process”. Technically, the sugarcane is processed in mills usually located near the plantation. This is because sugarcanes are bulky, making it pretty much expensive to transport. They also have to be processed as soon as possible in order to minimize the deterioration of the sucrose content. The output from the mills is sugarcane juice. If the objective is to make sugar, the juice is processed and crystallized into raw sugar which can then be further refined into the table or white sugar we use everyday. In the case of ethanol, enzymes are added to the sugarcane juice to promote fermentation. The enzymes utilize sugar as their food, producing ethanol and carbon dioxide in the process. The ethanol product is then distilled to the desired concentration.

Figure 1: Production of Raw Sugar from Sugarcane

Figure 1: Production of Raw Sugar from Sugarcane

What is good about using sugarcane as feedstock for ethanol production is that the whole process of conversion utilizes renewable energy sources. From Figure 1, notice that as soon as the sugarcane is processed through the shredder to extract the sugar content, one by-product is the bagasse. Bagasse is the dry, fibrous residue remaining after the extraction of sugarcane juice from the crushed stalks of sugarcane. It is traditionally used as fuel with a heating value of 7.13 GJ per ton equivalent to that of a ton of wood. Bagasse can be used in place of fossil fuel such as bunker or coal as a source of energy for the plant or mill.