Maybe it takes more energy because of the diversity of materials? If we used an order of magnitude less types of plastic than we currently do, it might become more economical because it wouldnt require as much mechanical labor to sort and process. Removing shipping from the equation seems like the removal of quite a bit of carbon.
When you melt plastic down, you get lower quality material than what you fed in. It's not a closed loop. Plus, the wide variety of available properties are what makes plastic so useful in the first place.
Asian companies undercut all the domestic recyclers, putting them out of business. This is why you might not want to trust say Chinese companies with prices that are too good to be true (because they are probably cutting huge corners somewhere). The same thing happened with rare earths (very dirty to refine, but China didn’t really care about their environment giving them a huge price advantage that shut everyone in the developed world down).
Plastic and Glass recycling can be borderline and it depends on the specific local implementation. Either way, the savings are never going to be massive and it is an open question if it is worth the effort. (Glass re-use is different)
Aluminum is completely different. Prices for aluminum recycling per ton is an order of magnitude higher than other recyclables.
What's even better than putting your plastic bottle in recycle is not using plastic bottle at all. Is there any use case where plastic bottle is better or required?
Apparently manufacturing glass uses way more resources/energy and has a much bigger carbon footprint. (No source at hand, sorry.) It also weighs more so is more expensive to transport. Plastic is good for some things, no doubt about that.
Earlier this year, Arlington County, Virginia removed glass from their curbside recycling program, "A significant drop in the market value of glass recyclables means it is no longer economically or environmentally sustainable for the County to collect them via single-stream recycling."
They have two drop-of locations, where residents can drop off glass "for crushing and reuse as construction and landscaping material."
The answer, unless you want to check the price of commodities each morning, is to recycle glass and bottles anyway and let the recycler decide if it’s economically efficient to send it to the landfill or to reprocessing.
Depends on the area, or so I learned recently upon moving to Montana, where they don't recycle it. Apparently most recycled glass is crushed up and used as roadbase. In MT, gravel is dirt cheap, and so it's not economical to use glass for construction, so into the landfill it goes.
As for recycling glass into other glass, I can't say.
Making glass from scratch is incredibly energy intensive, and glass impurities can be handled (purified), so it always makes sense to recycle glass. Don't let your officials tell you any different.
I heard on a recent podcast from a Dutch recycler that recycling glas only saves ~10% of energy creating new glass. Melting the glass requires heat, and the raw material is not much more expensive than collecting used glass.
Is it aluminum? Recycle it.
Is is not aluminum? Don't recycle it.