Removing clutter from building

I’m now serving as a residence committee in my building. The public spaces in the building are cluttered with useless junk. I want the building to be neat and clean. Can I just throw out all the items that were placed in public spaces, without asking their owners, or do I first have to let them know that they have to dispose of them? And if I do have to let them know, is it enough to publish a letter for all the residents, or do I have to speak with each resident individually?

You have to let the residents know that you intend to discard these items, and give them sufficient time to find places to store them. Therefore, you should publish a letter stating that you intend to clear out all the clutter a week from the date of the letter.