Theres many things the man is probably guilty of, but he didn't invent garbage or landfills, and someone has to own/operate them.
Landfills don't create the garbage, they just give it a place to decay.
Consumer consumption on the level our culture worships creates the garbage.
The interesting angle of the story as I see it, is that Bill Gates has decided there are profits to be had in a future of consumption and destruction.