Plastic wastage in cell culture experiments is inevitable. However we do use the following to minimize the usage.
When working with cell lines to produce protein say - we use the same plate multiple times. Like you trypsinize the cells and seed new cells on trypsinized plate from mai3.5 cm maintenance plate.
For experiments that do not demand high sterility. Such as for storing buffers for commasie stain or silver stain we autoclave the used Falcons and reuse them. Even western blot buffers stay fine in them.
For liquid waste disposal we don't use plastic bottles and rather aspirate them in glass flasks. Which can then be emptied straight to the main disposal.
One thing that is hard to replace are pipette tips. I don't think there is a possible alternative to that .
We have taken some measures as well, but it still is a lot of plastics that we use.