"I was curious to find out how that could be done, but from what I have read so far, it cannot be done profitably (yet). What scientific basis is there for turning plastic into oil?"

I'm one of the people who believes the company is consistently defrauding investors but I will say that plastics and even organic waste, including plain old land filled waste, can be turned into an oil through pyrolysis. Pryolysis is just heating material to around 500 degrees in an oxygen-starved environment. Almost all organic/carbon-based material does break down into gasses, oils and char.

But to your first point there, you are correct. Nobody has been able to do it profitably and people have been trying for decades. The quality of the oil is generally very low unless hydrocarbon-only plastics are used...but sorting those plastics out of the waste stream or snatching them from recyclers is prohibitively expensive. The economics aren't there...at least not unless a person buys controlling interest in a penny stock and convinces unwitting investors that it can be done profitably.