atomarc, yes I agree with the majority of your answers. The point that I was trying to get across, is that there are grey areas, and we just have to do our best within reason. When it comes to disposing of hazardous waste through a licensed disposal contractor, there is a huge fee that has to be paid up front to have the waste analyzed first, they will then prepare a Hazardous Waste Manifest, which you are required to sign. Then you have to pay them to take it. After spending all that money to do things the right way, you are still responsible for that waste because you were the original generator. So if the licensed disposal contractor decides to dump it illegally, and it gets traced back to you, you can still be held at least partially liable, as it is and always will be considered as waste that you generated.
According to EPA regulations (as recently as about 5 years ago), used oil is not considered hazardous waste and must be identified (tagged or marked) "used oil". If it is tagged "waste oil" you could be fined.
You not only have to worry about EPA regulations but as you stated in California, some of the state regulations can be even tougher. Technically letting solvents evaporate would also be considered harmful to the enviroment as most solvents contain ODC's (ozone depleting chemicals).
There are lots of ways to be responsible, when disposing of these substances. And a lot of them as you stated, can be done for free.
But there are a lot of grey areas.
