In the Lab
Is it biomass? Radiocarbon testing can tell the real McCoy
It is possible to distinguish biomass-derived products from products made from petroleum or coal. This is because a tiny amount of carbon-the building block of life and organic chemistry-is radioactive. Cosmic rays continually bombard Earth, and when one hits a nitrogen atom in the atmosphere, it converts the nitrogen into carbon 14 (C 14). C 14 is radioactive with a half-life of about 5,000 years. That means it will be undetectable after about 50,000 years. Because carbon 14 is constantly being manufactured by cosmic rays, all living things will contain a certain percentage of it. Fossil fuels, which were formed millions of years ago, won't contain C 14.
Beta Analytic Inc. does thousands of radiocarbon analyses every year. Much of this work is for archeological researchers, but a growing part of the company's business is the analysis of biomass-derived products, says company President Darden Hood. "The methodology for radiocarbon analysis has been around for 50 years, so there are no surprises in what we do," he says. "It's not like coming up with a new technology."
Hood says Beta Analytic started biomass analysis after the USDA approached him with a dilemma in 2004: how to implement the Biopreferred Program (www.biobased.oce.usda.gov), which gives biomass-derived products a preference in government procurement. "If you are a manufacturer of product that contains cornstarch, cellulose or recycled carbon in any form, you qualify for preferred procurement from the federal government if you meet certain commitments," Hood says. "There were manufacturers making claims of renewable content in their products, and there was no way to validate those claims by creating an enormous auditing program with people trying to trace the whole chain of custody of all the different supplies, where they came from and how much was used. It was insurmountable."
Radiometric testing was a solution. In this test, a sample is burned in a vacuum system to form carbon dioxide. The carbon dioxide is chemically reacted to produce either benzene or graphite. Benzene is used for a radiometric test in which a scintillation counter measures the amount of radioactivity in the sample. Graphite is used with an accelerator mass spectrometer (AMS), which can count the atoms in a sample and measure the amount of C 14 directly. Hood says while the AMS is more expensive, it can analyze very small samples.
By comparing the amount of C 14 in a sample with how much is known to be contained in living tissue, Beta Analytic can determine how much of a substance was derived from biomass and how much was from petroleum.
Green power is another market where radiocarbon analysis may be a standard test in the future. Hood says it is possible to sample the emissions coming from a biomass-fueled boiler or generator in order to determine what percentage of the fuel was renewable. This could be especially important for systems powered by municipal solid waste (MSW). Since MSW is a mixture of biomass and petroleum-derived plastics, the renewable content of the fuel stream can vary over time. By analyzing the C 14 content of the emissions, regulators can determine how much of the produced electricity would qualify as "green power."
Hood says his company worked hard with ASTM International to create renewable content standard ASTM D6866-05. "We were asked to join the committee to standardize the methods of radiocarbon dating to make it applicable to the regulatory environment," he says. "The method acts as a way to verify anywhere along the chain how much impact our renewable resource industry is having on our greenhouse gas emissions as a nation."