The content of bioplastics can be verified by the radiocarbon method

More consumer goods packagers are turning to renewable, plant-based plastic, or a combination of petroleum- and plant-based polymers, for their packaging. A time-honored test method — one linked more closely to archaeology than packaging — can help them prove that the package contains the advertised amount of bio-based plastic. That method is radiocarbon testing.

Typically used to estimate the age of fossils and other ancient organic materials, radiocarbon (aka carbon-14) testing is useful for analyzing plastic materials because of their carbon content.

Using test methods that determine the relative concentrations of carbon-14 isotopes in a packaging sample, technicians can calculate how much of the material is plant-based through the percentage of carbon-14 present — versus petroleum-based.

For example, if a packaging material is found to have 75% carbon-14, the material contains 75% renewable, plant-based plastic and 25% petroleum-based plastic.

Authenticating sustainable packaging claims with scientific proof has grown more important as greenwashing — the practice of making false claims about environmental friendliness — has become commonplace, turning consumers into skeptics.

Sustainability certifications are a way to overcome that skepticism, and some third-party certification organizations rely on the results of radiocarbon testing to authenticate the plant-based and petroleum-based content of a plastic product or package.

The US Department of Agriculture (USDA) BioPreferred Program offers the USDA Certified Biobased Product label, for example, and testing/certification company TÜV Austria provides “OK biobased” certification.

“The USDA BioPreferred Program’s voluntary product label qualification requires ASTM D6866 measurements from a ISO 9001-conformant lab,” says Jordan Turner, marketing coordinator with Beta Analytic, a lab that meets both of these criteria and is one of only two approved testing labs for bio-based-content analysis. Beta uses the accelerator mass spectrometry method to perform radiocarbon testing.