Several grades of ethyl alcohol are available in the marketplace today. They differ primarily in the amount of impurities present. Generally, as you move down the chain to a lower quality ethanol, higher amounts of impurities are present.
The highest level of ethanol purity is “GNS” or grain neutral spirits, beverage quality. This is only domestically produced from fermentation grain sources, typically corn or wheat. Based on the type of grain processed and the enzymes used to break starch down to sugar, different quantities and types of impurities are produced. In addition to meeting all of the quality requirements for USP and FCC grade materials, GPC beverage alcohol must pass stringent organoleptic analysis. Even in this day of modern technology and sophisticated analytical equipment and techniques, the human senses are able to detect impurity levels beyond the detection limits of the equipment. Since GNS is intended for human consumption, this test is the most important screening tool. Organoleptics are normally run at 40 proof (20% by volume).
“FCC Grade” ethanol (Food Chemical Codex) adds heavy metal specification limits to the grades below since most FCC grade materials are used in food applications. This can be either of fermentation or synthetic origin.
“Industrial Grade” ethanol can be of either fermentation or synthetic origin. It has most of the impurities removed. “USP Grade” ethanol (U.S. Pharmacopoeia) has specific tests that measure impurities present, setting limits on each type. “NF Grade” ethanol (National Formulary) lowers the amount of impurities further to the 20 to 25 ppm levels.
The highest impurity levels are found in “fuel grade” ethanol that is produced via the fermentation process. It is added to gasoline as an octane enhancer/extender and to reduce carbon monoxide and nitrous oxide pollution. Manufacturers of this grade don’t take great care in removing the impurities produced in the process because they “burn” easily in a combustion engine.