system
Given the following post, respond as if you're commenting on Reddit:
human
Why is it not yet possible to use plant-based plastics for all of the things we currently use petroleum-based plastics for?
gpt
The shortest version is that it is possible, it just results in more costly starting materials. The entire chemical industry is oriented around the cheap carbon starting materials from petroleum, and it will take *decades* to change that. Entire plants costing hundreds of millions of dollars will become obsolete and useless. 

It is actually more promising to start by developing niche technologies based on easily available plant feedstocks. They could then compete in the markets and take up some of the slack as petroleum becomes more costly and rare. But the most recent example of that was that Sun Chip bag based on polylactic acid derivatives, and we know how that went.