Tom, most towns, cities, townships, etc. have laws on disposal of paints and thinners. Our township has a recycle event once a year for stuff like that. I just put it in a small bottle in the SB until it's full then take it out to the shed and transfer it to a 1 gal. plastic milk jug marked used paint thinner. When they have the recycle event, I take it there and leave it for them to dispose of. The same goes for used oil from the car and lawn tractor.
Hope that this helps.
Jim