Ethanol is easily made by the hydrolysis of ethylene, a major petrochemical. Two million tons of petroleum-derived ethanol are produced annually. The principal ethanol suppliers are South Africa and Saudi Arabia, but there are also large plants in the United States, Europe, and Japan. Petroleum-derived ethanol (synthetic ethanol) is a widely used industrial solvent and has a considerable variety of other applications.
Identifying the origin of ethanol serves four significant purposes:
The tax credits for ethanol in gasoline (Energy Policy Act of 2005 H.R.6) are intended for bio-ethanol and not petroleum-derived ethanol. The issuance of these tax credits will have to require a certification that the ethanol comes from renewable sources. The recognized scientific test is ASTM D6866, which unambiguously and quantitatively distinguishes between materials produced from fossil fuels such as petroleum and those produced from contemporary biomass.
ASTM D6866 protects the interests of investors and biomass producers investing in bio-ethanol production. The method is used routinely by the USDA in the identification of biobased products and is applied without modification for the identification and quantification of bio-ethanol.
The important tax credits for bio-ethanol in gasoline will provide a temptation for unscrupulous individuals to submit synthetic ethanol. It is anticipated that the most common occurrence will be the dilution of bio-ethanol with synthetic ethanol. ASTM D6866 is a quantitative technique that will be able to clearly signal any significant dilution.
ASTM D6866 will protect the bio-ethanol industry by discouraging this cheating. An ASTM D6866 certification should be the necessary condition for each batch of bio-ethanol that is being submitted for tax credits.
ASTM D6866 uses the radiocarbon dating technique. Biomass has carbon 14 whereas fossil materials no longer have any of this weakly radioactive carbon isotope left. Measuring the concentrations of carbon 14 in an ethanol sample will show whether it had been manufactured from renewable or from fossil materials. It is also anticipated that in some cases there will be a mixture of bio-ethanol and synthetic ethanol.
In samples with both types of ethanol, ASTM D6866 will quantitatively determine the percentage of bio-ethanol so that the appropriate tax credit could be given. Likewise, ASTM D6866 would be an applicable test for bulk gasoline containing varying concentrations of bio-ethanol. The test would indicate the amount of renewable material in the total liquid. However, it must be certain that the gasoline is well mixed so that the very small sample taken is representative of the entire storage tank. This is always an important concern in bulk materials testing.
The ASTM D6866 analysis not only measures the carbon 14 content of the ethanol samples but also carbon 13, the more stable carbon isotope. Carbon 13 measurement is an integral part of radiocarbon dating. It is also, in some cases, a means of verifying the source of the biomass used for ethanol production. Carbon 13, however, is not suitable for precisely determining renewable vs. fossil contents in mixtures.
Although petroleum and corn, for example, have different carbon 13 concentrations, carbon 13 from other biomass materials have values that are quite variable. Some materials suitable for bio-ethanol production like sugar beets, sweet potatoes, grapes and other fruits, have carbon 13 values that are generally indistinguishable from that of petroleum. This would result in carbon 13 analyses giving ambiguous results in the case of dilutions of bio-ethanol with ten or twenty percent synthetic ethanol. On the other hand, radiocarbon dating analysis would clearly show this dilution.
For details on the radiocarbon dating process, see ASTM D6866.