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Ethanol
Also known as: Ethyl alcohol, EtOH, bioethanol
Ethanol is a non-refinery based hydrocarbon that is widely used as a gasoline blendstock.
Ethanol is blended into gasoline for a variety of business and policy reasons. Ethanol has high octane and can be used as an octane booster. Because ethanol contains oxygen, it can be used to reduce the carbon monoxide emissions from burning gasoline. Also, as a renewable fuel, ethanol blending is mandated in some markets to reduce reliance on fossil fuels.
Fuel ethanol is typically manufactured by fermenting the sugars in agricultural products such as corn, sugar cane, and beets. When produced this way, it is able to receive biofuel credits in countries with these regulations. In the US, most ethanol is produced through fermentation of corn. In Brazil, sugar cane is the most common feed stock.
Ethanol qualities
When blended into gasoline, ethanol significantly raises the octane and vapor pressure. However, its impact on both qualities varies widely with the concentration of ethanol in the mix and the chemical properties of the other hydrocarbons in the blend. As a result, ethanol is typically blended into gasoline in fixed ratios (e.g., 10%, 15%). Ethanol-blended gasoline is kept segregated from ethanol-free gasoline.
Ethanol has an energy content that is about 70% of typical gasoline. As a result, vehicles using ethanol blended fuels will have lower fuel economy. The price of ethanol blended fuel typically reflects this.
Ethanol highly miscible with water. Consequently, ethanol and gasoline/ethanol blends must be kept clear of any water contamination. Otherwise the water (and any contaminants that collect in the water) would form a solution in the fuel and ultimately end up in vehicle engines. To avoid this, ethanol is typically kept separate from gasoline until loaded into a tank truck for final delivery. This means ethanol can not be distributed through the pipeline systems that move large volumes of gasoline in most countries. Ethanol shipments are primarily by (more expensive) truck, rail or barges.
