Actually, you can.There is a move to "renewable resource"...

Actually, you can.

There is a move to "renewable resource" polymers or biopolymers. Bioplastics are made from plant sources such as castor beans, soy, corn, potatoes, tapioca and wood fibers.

They are usually polyester type systems, with the alcohol section of the ester being the -OH group on the sugar or starch molecule. There are also PLA plastics from corn starch via lactic acid. If I went searching I'm pretty sure I could find synthetic pathways for many plastics that don't require a petro front end source in the synthesis. Theoretically, the polyethylenes can be produced via dehydration of alcohol to ethylene and then the standard polymerisation system can be used without modification. Polystyrenes would probably be an issue, as cost effectiveness of creating the styrene precursor from a non-aromatic start-point would be problematic.

In fact, the earliest "resins" were primarily plant derived - pale boiled linseed oil, castor oil derivatives, etc. Alkyd-modified and urethane modified oils are a (relatively) recent invention - and the petro-pathway was a cheap and convenient method to produce them, but it's not the only pathway to get there.

It's all about the break-even point for the process.