Transfer the unused tile mortar into a plastic bucket and allow it to dry overnight.
Place several sheets of newspaper onto a flat surface and turn the bucket upside down over the sheets.
Gently hammer the bottom and outside edges of the bucket to dislodge the dried thinset mortar from inside.
Wrap up the dried pieces of mortar in the newspaper and transfer it to a plastic garbage bag.
Secure the top of the garbage bag and dispose of it in the trash.