And since it requires the same source as the main recipe as well (oil), it's kinda pointless.
Base recipe needs 12 oil to get 9 plastic.
The alternate requires 16 oil to get the same 9 plastic, two refineries and an assembler.
An alternate recipe should be a pretty solid departure from the base recipe. Maybe an alternate plastic from Limestone+Coal or something similar? (5 Limestone + 3 coal = 4 plastic @ 30/m for example.