Promession is a way of dealing with someone's body when they've died. Instead of putting their body in a coffin and burying it in the ground, promession uses special machines to freeze the body until it's really, really cold. Then, the body is shaken really hard, which makes it break up into tiny pieces.
These tiny pieces of the body are put into a special machine that removes any metal or other non-body parts that were left over. After that, the body pieces are put into a special type of compost, which is a combination of plant materials like leaves and branches.
The compost is then used to help grow trees and plants in a special area, like a memorial garden. This way, the person who has passed away is returned to the earth in a way that helps new life grow.
It's a way of saying goodbye to someone that's better for the environment and helps create new life instead of taking up space in a cemetery.