Well, a plasma torch -> energy system is basically a chemical factory attached to a plasma torch and the thing about a chemical factory is that quality inputs lead to quality outputs. Poor quality inputs lead to poor quality outputs or maybe something blowing up. Any kind of "circular economy" chemical factory has the problem that it has to run on whatever inputs are available that day and that kind of thing will have Chem-E's pulling their hair out.

If you are throwing in nothing but rubber tires a thing like that will yield a lot of energy, if it is nothing but concrete rubble from buildings it will consume a lot of energy. To keep it happy it really wants every bite you feed it to have the perfect mix of ingredients and it's not easy to get that out of municipal waste.