There are already ways to make some of the chemicals (largely plastics) being made from petroleum derivatives using renewable sources, like vegetable oils. I do

There are already ways to make some of the chemicals (largely plastics) being made from petroleum derivatives using renewable sources, like vegetable oils. I don't pretend to know much about the details—at any level—so I don't know if it's feasible to come up with bio-based replacements for all the derivatives if the economics shift to support it, but it's at least something worth looking into.