How to determine the source of PVA: crude or plant-based? We're a small startup company looking to make products using ingredients solely derived from plants. One of the main ingredients in one of our products is polyvinyl alcohol (PVA). We have found a company that claims that their PVA is made exclusively from plants, and that no natural gas or crude oil is used in its production.

To provide some extra clarification based on the discussion below this question: PVA is a synthetic polymer prepared by hydrolysis of polyvinyl acetate. Polyvinyl acetate is made from acetic acid and ethylene. Ethylene is often made from natural gas or petroleum. Is it possible to determine whether the original ethylene used to make our PVA is derived from petroleum or plants? If so, can this be done given just the PVA itself, and no other information?

The reason I'm asking is because I want to independently verify the manufacturer's claim that their product is indeed completely derived from plant sources.
It certainly would be possible to get an indication of some of the sources of carbon through mass spectrometry and through radiocarbon dating. For example, fossil carbon sources would have little 14C, sources predating the 20th century, e.g. older trees, would have more. Post-Atomic Age sources might have more yet, beyond that due to natural decay of 14C.

That said, it's a nice question, but are you prepared to pay for the analysis to have it answered? Perhaps your government might perform such testing to verify a claim of being "organically produced".