In my experience( I have been bringing in my carob crop for 3 years now) you can take last years as long as they are in good condition(still shiny) and not wet.  I take mine to the carob mill in Santa Barbara but you can take them along to some co-operativas. There is also the no questions asked of origin, cash at the weekend mill in Amposta. I am sure other people will add more info. I collect mine in the black tubs for ease of pouring into sacks and when I run otu of sacks take them to the mill. They weigh your vehicle you off load the carobs on the piles. They reweigh your vehicle and give you a ticket with the weight and that days prices(I have expereinced prices from 48 cents to 28 cents a kilo depending on the time of year and whether there is a glut that year) and when you are ready you cahs in your tickets and get your money. I have four hundred olives and 24 carob trees and I would cheerfully swap this ratio around. Carobs are easier. It cost me nothing to register at this mill all they wanted was my NIE and my escitura details. But this is the first I have heard of grants.