Carbon dating fossil fuels

This would allow you to test a fuel mixture to determine what fraction of it is biofuel.

"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.

To measure how much heavy CO2 you have in a CO2 sample, you first inject the sample into the instrument's measurement cavity (the "C" in CRDS), which is a tube with mirrors inside at either end.

You then tune a laser to the exact wavelength that only heavy CO2 absorbs and shoot a burst of it into the cavity.

This would be especially useful in parts of the world where high-quality emissions data are not readily available.

### "There is a need for this type of measurement in many industries," Fleisher said.

Such tests could also be used to verify that bioplastics, which sell for a premium, do not contain petroleum-derived compounds.

To estimate fossil fuel emissions in a geographic area, you would collect many air samples across that area and analyze the atmospheric CO2 in those samples.

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.

CRDS instruments analyze gases by detecting the wavelengths of light they absorb.