ASTM-D6866 documents the renewable carbon content (a.k.a. biobased carbon content) of plastics, liquids, and gases. Composite carbon components of renewable and fossil origin within plastic or any of its originating components are readily identified and conveyed with a single number result (e.g. 65% biobased). Both state and federal regulators have embraced the method as a means for identifying biobased carbon within manufactured products, raw materials, and even carbon-neutral CO2 emissions from stationary emission sources. The method is the foundation for identifying the biobased carbon content of plastics and other materials listed in the USDA’s BioPreferred Program and is gaining widespread utility in marketing, public-image and product defense.