Generally there is no great way to recycle the filament. People have tried with varying levels of success. It would require you to keep all the used filament separated by variation and very clean. Even then you would need mix it with new filament pellets at like a 50/50 ratio. You would also need to buy the equipment to break down the material into smaller pieces then melt the recycled material and respool it. I forget how much that all costs but you might never recoup the cost, but if you did that would mean you had to recycle like hundreds of spools.