Wooden pallets trade in for cash ?

i work as a landscapers apprentice so a lot of the time we order in slabs etc, and there all delivered on wooden pallets. I also know that if the pallets are kept in good condition and are reusable you can trade them back in for money, �15 a pallet i think it is, but anyway, my question is can anyone trade in wooden pallets or do you need like a proof of ownership or anything ? that leads me on to if you need like some sort of proof of ownership can you only return them to the company who supplied you with it in the first place ? I ask this because round the back of my house someone has dumped 5 good quality wooden pallets then and rather than just leave them there or throw them away or whatever could i ring a company and get them to come and collect them and in return get some money or something ? Thanks !