That the person is also eating food from the garbage suggests that something more than "normal" office thoughtlessness is going on.
In what capacity is the person employed? Do you have a ball park idea of what he earns? For example, if he is a low level employee who receives only a token hourly wage, the source of his behavior could be economic.
Or does he receive a decent wage, but have some unusually severe financial problems?
Or it could be something related to an emotional illness.
None of this may be information that you could readily obtain, much less figure out how to address it, and different companies are going to have different policies about all of that, so unless you are the owner of the business, "what to do about it" is not going to be your call, anyway.
About the only thing that you can do is make the management aware that the situation exists, and that it is impacting the workplace environment.
Whatever is going on, it does not sound like the kind of thing where any of the usual tricks and strategies for dealing with that "normal" office thoughtlessness would be either appropriate, effective, or something that you would feel good about participating in.
Just bat the ball into the boss's court.
In the meantime, just to be on the safe side, maybe you and the other employees can take turns bringing in something like bagels or cheese and crackers that are left out in the break room for everybody to enjoy.