Bioethanol – A Important second-generation Biofuel

Bioethanol is a liquid biofuel generated through ABE fermentation of a variety of raw materials, including maize, soybeans, wheat straw, barley, potatoes, woodchips, and, more recently, algae. The majority of ethanol generated worldwide is from sugarcane, mostly in Brazil. Three stages are involved in the production of bioethanol:

1. pretreatment to remove hemicellulose and lignin from cellulose,
2. hydrolysis of cellulose to get fermentable sugars, and
3. fermentation to convert carbohydrates into ethanol, followed by distillation to separate and purify the ethanol.

Fuel Properties of Ethanol

Bioethanol may be used directly in automobiles and behaves similarly to conventional fuels. Because bioethanol has a high octane number, it allows for higher engine compression ratios, increasing engine efficiency and performance. To get a standard 87 octane, lower-octane gasoline is combined with 10% ethanol. However, as compared to regular gasoline, the fuel has a poor volumetric energy density, which means that automobiles require more bioethanol per kilometer (by up to 50%) when compared to gasoline. The flammability of ethanol in the air is also substantially lower than that of gasoline, reducing the number and intensity of car fires. Anhydrous ethanol has lower and higher heating values of 21.2 and 23.4 megajoules (MJ)/liter, whereas gasoline has values of 30.1 and 34.9 MJ/liter, respectively.

The energy value of some fuels compared with ethanol

Ethanol Biofuel in Different Countries

Brazil has nearly 4 million automobiles that operate on pure, hydrated ethanol, and all gasoline in this country is blended with anhydrous ethanol (20-26% ethanol) as a result of a plan by the government that has been in place since the 1970s to produce ethanol from sugarcane.

The United States and many other nations typically employ E10 (10% ethanol, also known as gasohol) and E85 (85% ethanol) ethanol/gasoline blends. Over time, it is expected that a significant percentage of the 150 billion gallons per year petroleum market will be replaced with fuel ethanol.

In Australia, the usage of pure ethanol from sugarcane waste in automobiles is limited to 10%. But in some vehicles, these include flexible-fuel vehicles (FFV) and V8 racing supercars, that have been specifically designed or modified to use E85.

Limitations of Bioethanol

• Ethanol fuel has a low volumetric energy density when compared to conventional gasoline, which means automobiles require more bioethanol per kilometer.
• It may damage some elastomers and corrode certain metals inside the automobile, which means requiring constant replacement.
• Bioethanol is difficult to evaporate at low temperatures when used in pure form (E100 blend), making E100-equipped vehicles more difficult to start in cold weather.

Bio-ethanol fireplace

Bio-ethanol is also used in fireplaces. It works by simply pouring bio-ethanol fuel into the burner and lighting it. It generates a highly clean, smokeless kind of heat since it does not emit any toxic gases, sparks, or soot. The fuel burn for 4-5 hour, and fuel doesn’t emit smoke or fumes, so no need for a chimney.

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