Conservative Tees Valley mayor Ben Houchen disputed the claims and praised the impact the new facility would have on jobs and investment in the region.
He said turning a disused site into “good quality jobs for local people” was “exactly the kind of project our area needs”.
Endolys said plastic film was one of the most challenging plastic materials to recycle in the UK, with no current large-scale recycling facilities available and limited kerbside collection.
The first phase of the development would see six units process 60,000 tonnes of shredded plastic film waste into 40,000 tonnes of pyrolysis oil each year.
All of the film waste will be sourced from municipal waste facilities.
A spokesman explained the process took place within “fully enclosed vessels and within a building”.
They added: “It does not involve combustion and, in fact, diverts materials away from incineration and landfill, delivering an estimated 170,000 tonnes of CO2 savings per year.”