I saw a story a month or two ago that addressed this issue (bowling ball disposal/recycling) directly and basically they aren't recyclable due to the differing types of materials used in construction (cover, core, filler, etc.).
Also, destruction/reclamation was net energy-positive, meaning the calculations of cost versus whatever metrics are used to score how much the balls "cost" you to dispose of in a landfill was tilted clearly toward outright disposal, not reuse.
I have a friend that was a PSO for years and just on a lark, decided to recover the core out of an old ball to display it and the amount of time, energy (and electricity, I'm sure) that it took to get the core out of the ball and into a displayable condition was significant. And he still didn't have a completely clean core at the end.