Messages when attempting to empty Trash in macOS
Well, the messages are pretty straight forward I suppose, you do not have the correct permission to remove these files. 

I am however a bit confused as to the term "empty Trash". It seems that this can be accomplished using the GUI and this would be the preferred way to do it? The files you are trying to completely wipe of your system does not seem to be in the "trash"?

Anyway, running the same command as 'sudo' should solve your problem although I would be careful as it seems from your output that you are attempting to erase more than trashed files:

502/sda/: Permission denied

Unless you intentionally put an entire partition in the trash? The 'rm' command is not recoverable.