Ethanol — Part 1: Physical and Chemical Aspects

This is the first installment of a three-part series about ethanol. The series focuses on physical and chemical characteristics, manufacturing processes and hazards, and firefighter response to ethanol emergencies in transportation and at fixed...


This is the first installment of a three-part series about ethanol. The series focuses on physical and chemical characteristics, manufacturing processes and hazards, and firefighter response to ethanol emergencies in transportation and at fixed facilities. Ethanol, in the context of this series...


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This is the first installment of a three-part series about ethanol. The series focuses on physical and chemical characteristics, manufacturing processes and hazards, and firefighter response to ethanol emergencies in transportation and at fixed facilities.

Ethanol, in the context of this series, is denatured ethanol manufactured and used for use as a motor fuel and motor fuel additive. To form a comparison with ethanol, we will first look at more common motor fuels.

Gasoline and diesel fuel, hydrocarbon products refined from crude oil, have been the primary motor fuels for over 100 years. Both are flammable and have physical and chemical characteristics that make them hazardous in use, storage and transportation. These fuels are classified by the U.S. Department of Transportation (DOT) as Class 3 Flammable Liquids and are marked with red placards and labels. Gasoline and diesel fuel are usually shipped in bulk quantities so they will have the United Nations four-digit identification numbers 1203 and 1993, respectively, placed in the center of the placards.

The DOT's 2008 Emergency Response Guidebook (ERG) assigns Orange Guide 128 for both gasoline and diesel fuel. Guide 128 is titled "Flammable Liquids (Non-Polar/Water-Immiscible)" and gasoline and diesel fuel have these characteristics. While ethanol is in the same hazard class as gasoline and diesel fuel, we will discover that the concepts of polarity and miscibility are among the primary differences.

Although gasoline and diesel fuel have some different physical characteristics under fire conditions, they are handled much the same. Firefighters should, however, be aware that those differences exist when dealing with emergencies involving both fuels. Generally, firefighters should know how to deal with gasoline and diesel fuel in a fire or other emergency because they are so common and have been around for so long. In fact, the most common hazardous materials response in most jurisdictions involves these fuels.

Gasoline and diesel fuel are mixtures of hydrocarbon compounds and other additives. For example, a common blend of gasoline contains benzene, n-butane, ethyl alcohol (ethanol), n-hexane, methyl-tertiary butyl ether (MTBE), tertiary-amyl methyl ether (TAME), toluene, 1, 2, 4, trimethylbenzene and xylene mixed isomers. Physical and chemical characteristics will vary depending on the mixtures, which will very likely be different from one manufacturer to another. The mixture listed above has a flash point of -45 degrees Fahrenheit, which is the same for most blends of gasoline and an auto ignition temperature greater than 540°F. Some sources list gasoline mixtures with ignition temperatures in the 800°F range.

Diesel fuel is also a mixture made up of diesel fuel and naphthalene and other additives. Diesel fuel has a flash point greater than 125°F and an auto ignition temperature of 500°F. Diesel fuel is usually harder to ignite than gasoline, but when diesel fuel does ignite, it has a greater heat output than gasoline and therefore may be harder to extinguish. Dry chemical and foam are the most common extinguishing agents, depending on the amount of fuel on fire.

Large-scale use of ethanol as a motor fuel in highway vehicles is fairly new. Hazards of ethanol may not be as well understood by responders as hazards of gasoline and diesel fuel, which are primarily transported by pipeline and with highway transportation vehicles. There is some rail transportation of gasoline and diesel fuel, but it is not nearly the volume as pipelines and highway transportation. Ethanol, on the other hand, is largely transported by rail, supplemented by highway and minimal pipeline transportation. It is classified by the DOT as a Class 3 Flammable Liquid, just like gasoline and diesel fuel, and is marked in transportation with red placards and labels.

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