Recently I visualized the problem with the environment (landfills particularly) in an entirely different way that kind of traumatizes me. I've been feeling a push lately to simplify my life and get rid of tons of junk that's just cluttering my space, but I feel guilty throwing things away because I know they'll sit in landfills for millennia. But then I realized that if they'll survive for millennia, they'll survive for millennia whether they're actually in a landfill or not. As far as the earth is concerned, our houses might as well be mini-landfills. Once stuff enters the world, it's there, and it doesn't really matter what you do with it afterward (unless it's recycled, but even that isn't entirely a pollutant-free process), it's trash. It's not like something magically happens to your junk when it enters your trash can that converts it into this mysterious "garbage" thing; it is what it is, and that thing is likely polluting the earth, or at least taking up space on it.
Once you remove the human angle of looking at things and ascribing worth to them and just try to look at it all from a purely physical point of view, it's pretty depressing. Our factories work day and night to pump stuff into our landfills with brief pauses in our houses. My mental image is of a planet (like when they show Earth on kids' TV shows with obviously too-big houses and proportionally giant people and such as a dramatization) devoid of people but with big buildings sticking up off of it filled with stuff, stuff, stuff. So really, the point isn't even what to do with all our stuff when it comes time to dispose of it, as if that's when it enters the waste stream, but whether to bring it into existence in the first place, since once it's here, it's part of the waste stream. (This is why "reduce" comes first in the "reduce, reuse, recycle" mantra, something that people too often forget.)