Superb way to generate more microplastics

This is discussed in the article, the plastic is bound up in the bitumen so it doesn't release microplastic particles during use.

OK but can't we please try bioplastics for this?

The point is to have a useful way of getting rid of all the plastic waste we already have and will continue to generate. Plastic isn't going anywhere in the near future because it's a byproduct of natural gas production, which is needed for energy.

Well... It is more that a traditional oil refinery has a BTX section

https://en.wikipedia.org/wiki/BTX_(chemistry)

which produces an excess of chemicals in the process of improving the octane of gasoline

https://en.wikipedia.org/wiki/Catalytic_reforming

and that is where you get monomers like styrene and Terephthalic acid.

https://en.wikipedia.org/wiki/Ethylene

is another important petrochemical feedstock which can be made from natural gas or other forms of petroleum.