I have an old MBP battery which was replaced by Apple some time ago when there was a scare about batteries. Mine was fine at the time so I never returned the 'old' battery to Apple and continued to use it alongside the new one. It's been on a shelf for a while; it started to bulge some time ago and now the seal has been broken and the metal bit has come away from the plastic. What's the safest/most environmentally-sensitive way to dispose of the battery in its current state? Any ideas gratefully received.