And if they knew how it was done, the Greens wouldn't like it anyway.
Guess who funds them? Hence the post to which you responded. My take on what you said here (and thank you for it as the details about coal I did not know) is that burning it is better than trying to recycle it. Nothing is perfect. BTW, are you telling me that burning it with natural gas was never attempted or that it was not as successful? From a technical perspective, I don't know why it would be, albeit it might cost more.
Burning plastic with coal is a good fit for coal but not for Gas.
Coal is pulverized to a Talcum Powder consistency and blown into the boiler. Coal plants have complex pollution control systems. Gas plants have little to no pollution controls.
The shredded plastic is mixed with the pulverized coal in the boiler for the burn.
Due to the drastically different chemical makeup of plastics I can't see burning it as boiler fuel as a real practical solution to its disposal.
Complex hydrocarbons do not burn cleanly.
crude oil is a mix of drastically different hydrocarbons.
Crude oil is sent to a complex system that distils and then 'cracks' (breaks the complex chemical down) the different hydrocarbons with heat and catalyst.
That is what it would take to burn the plastic cleanly.
Just my semi-educated opinion.