Originally Posted by Iride01

For some materials it is a perfectly acceptable method and EPA approved. I don't know specifically for mineral spirits and likely it may involve what the total quantity of mineral spirits is that is being allowed to evaporate. A question better left to those that deal with EPA policy and hazardous material disposal.

Not sure what the thread topic is that you wish to keep the thread on. However for me, when I was using mineral spirits to clean parts regularly, not bicycle parts, the mineral spirits would get pretty clean and all the solids fall to the bottom. There might be a discoloration of the mineral spirits, but as long as it is cleaning off what needs to be cleaned, I never felt a need to replace it.

But still the most environmentally friendly thing would be not to clean your chain at all. Second to that, just wipe it off.