Beta Analytic - Bioethanol Testing

What is ASTM D6866?

Bioethanol and synthetic ethanol are chemically indistinguishable.

Bioethanol and synthetic ethanol are both the same compound, C₂H₅OH. The only difference between the two is the isotopic composition of the carbon atoms. Synthetic ethanol comes from fossil raw materials and bioethanol comes from contemporary materials. A common procedure for studying fossils has been applied for ASTM D6866; that is, the technique of radiocarbon dating, known for its use in archaeology and other fossil studies. Radiocarbon dating measures the content of a naturally occurring isotope, carbon 14, in the samples studied and compares this to the content in contemporary materials.

The application of ASTM D6866 to derive a "Bio-Ethanol content" is built on the same concepts as radiocarbon dating, but without use of the age equations. It is done by deriving a ratio of the amount of radiocarbon (14C) in an unknown sample to that of a modern reference standard. The ratio is reported as a percentage with the units "pMC" (percent modern carbon). If the material being analyzed is a mixture of present day radiocarbon and fossil carbon (containing no radiocarbon), then the pMC value obtained correlates directly to the amount of Bio-Ethanol material present in the sample.

The modern reference standard used in radiocarbon dating is a NIST (National Institute of Standards and Technology) standard with a known radiocarbon content equivalent approximately to the year AD 1950. AD 1950 was chosen since it represented a time prior to thermo-nuclear weapons testing which introduced large amounts of excess radiocarbon into the atmosphere with each explosion (termed "bomb carbon"). This was a logical point in time to use as a reference for archaeologists and geologists. For an archaeologist or geologist using radiocarbon dates, AD 1950 equals "zero years old". It also represents 100 pMC.

"Bomb carbon" in the atmosphere reached almost twice normal levels in 1963 at the peak of testing and prior to the treaty halting the testing. Its distribution within the atmosphere has been approximated since its appearance, showing values that are greater than 100 pMC for plants and animals living since AD 1950. It's gradually decreased over time with today's value being near 107.5 pMC. This means that a fresh BioEthanol made from corn would give a radiocarbon signature near 107.5 pMC.

Combining fossil carbon with present day carbon into a material will result in a dilution of the present day pMC content. By presuming 107.5 pMC represents present day Bio-Ethanol materials and 0 pMC represents petroleum derivatives, the measured pMC value for that material will reflect the proportions of the two component types. A material derived 100% from present day soybeans would give a radiocarbon signature near 107.5 pMC. If that material was diluted with 50% petroleum derivatives, it would give a radiocarbon signature near 54 pMC.

A Bio-Ethanol content result is derived by assigning 100% equal to 107.5 pMC and 0% equal to 0 pMC. In this regard, a sample measuring 99 pMC will give an equivalent Bio-Ethanol content result of 93%. This value is referred to as the MEAN BIO-ETHANOL RESULT and assumes all the components within the analyzed material were either present day living or fossil in origin.

The results provided involve materials provided without any source information. This situation is highly probable in a real life situation. The MEAN VALUE quoted in this report encompasses an absolute range of 6% (plus and minus 3% on either side of the MEAN BIO-ETHANOL RESULT) to account for variations in end-component radiocarbon signatures (a conservative approximation).It is presumed that all materials are present day or fossil in origin and that the desired result is the amount of Bio-Ethanol component "present" in the material, not the amount of Bio-Ethanol material "used" in the manufacturing process. The most conservative interpretation of the reported percentages is as maximum values.

The graph shows relative results from 458 biomass materials measured and reported per ASTM-D6866 by Beta Analytic Inc. since 2004. Materials analyzed include RFW, CEMS/stack CO₂ effluent from WTE plants, and manufactured products consisting of solids, liquids, foams, pastes, plastics and greases.

Although actual measurement uncertainty was 1% or less (relative standard deviation), results are graphed with the absolute uncertainty of 3% as cited in ASTM-D6866. This uncertainty is designed to include indeterminant error associated with local variations and utilization of materials of some age (respiring carbon to 1996, one decade past).