Scientists at the National Institute of Standards and Technology (NIST) have developed a laboratory instrument that can measure how much of the carbon in many carbon-containing materials was derived from fossil fuels. This will open the way for new methods in the biofuels and bioplastics industries, in scientific research, and environmental monitoring. Among other things, it will allow scientists to measure how much of the carbon dioxide (CO2) in the atmosphere came from burning fossil fuels, and to estimate fossil fuel emissions in an area as small as a city or as large as a continent.
This is possible because carbon atoms occur in heavy and light forms, or isotopes, and measuring the relative amounts of each can reveal the source of the carbon. Using carbon isotopes in this way is not a new idea, but it requires extremely precise—and expensive—measurements. The new instrument, developed by NIST chemists Adam Fleisher and David Long and based on a technology called cavity ringdown spectroscopy (CRDS), promises to dramatically reduce the cost of those measurements. They described the instrument’s performance in The Journal of Physical Chemistry Letters (link is external).
“Measuring carbon isotopes is an extremely useful technique, but until now, it has found limited use because of the cost,” said Long. “Lowering the cost will open the way for new applications, especially ones that require testing a large number of samples.”
The key to these measurements is carbon-14, a radioactive (yet harmless) isotope of carbon that is formed in the upper atmosphere. That carbon-14 finds its way into all living things. Unlike regular carbon, carbon-14 is unstable, with a half-life of 5,730 years. When living things die, they stop incorporating carbon into their bodies, and their carbon-14 starts to decay away.
Scientists can calculate how long ago something died by measuring how much carbon-14 is in its remains. That technique is called carbon dating, and scientists use it to date things like Neanderthal bones and ancient plant fibers.
Fossil fuels also are the remains of living things, mainly plants that died hundreds of millions of years ago. Virtually all their carbon-14 decayed away eons ago, so anything derived from them is marked by the absence of measurable amounts of carbon-14.
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