If you consider it from an atom and energy perspective, you only really need to worry about the atoms that are going to cause you problems no matter what you do, like mercury and the other heavy metals. Those are generally valuable, though (the fact that they are valuable is why they are in a landfill at all in the first place, because it had value at one time), so if there was a cost-effective mechanism to remove those things from a landfill for profit, what was left over would not necessarily be a problem anymore.
Garbage getting dumped somewhere is not intrinsically a problem, if the garbage is not as intrinsically harmful as our current garbage.
(This is also why radioactive waste is so difficult to get rid of; it isn't a chemical problem, it's a problem all the way down to the atoms. Were it a mere chemical problem we'd have solved it long ago.)
A fish with a polymer of "innocuous" organic atoms in the digestive tract is likely to disagree.
Removing more harmful materials would certainly be a benefit, but it wouldn't solve the large part of the problem (which, in the case of the patch, is plastics).
"A fish with a polymer of "innocuous" organic atoms in the digestive tract is likely to disagree."
First of all, since the topic was landfills, I have some questions as to how the fish managed to get plastic from a landfill stuck in them. Yeah, it's possible, but somebody screwed up along the way.
Second, that's the exact opposite of what I meant by thinking just from an atom and energy perspective. It's a small amount of energy to turn those organic atoms into something less harmful, and probably a net gain from a strictly chemical perspective (i.e., plastics tend to burn). We are intrinsically speaking from a much higher tech than we currently have here. The process of extracting out mercury and cadmium and such can be reasonably assumed to either process waste to something safe before putting it out into the ecosystem, or that they will place the plastics somewhere where they aren't going to affect anything when done. I don't think our hypothetical future landfill miners are going to be allowed to just tear open the landfills and start shooting whatever they decide they don't want with cannons into the surrounding countryside.
Garbage getting dumped somewhere is not intrinsically a problem, if the garbage is not as intrinsically harmful as our current garbage.
(This is also why radioactive waste is so difficult to get rid of; it isn't a chemical problem, it's a problem all the way down to the atoms. Were it a mere chemical problem we'd have solved it long ago.)