Some personal thoughts regarding these posts:
The use and disposal of solvents are one of "the" environmental issues of our times. If a person is using diesel, it should be properly disposed of, which for the home mechanic is often difficult. There may be waste disposal services offered by your local municipality. Generally, diesel is a poor choice for the personal health of the user, a poor choice for the local environment, and a poor choice for the world environment.
Disposal of so-called biodegradable solvents is often best done down the sink or toilet, assuming you are connected to a modern wastewater treatment facility. Never do this if you are on a septic tank. This is because the treatment facility is capable of handing this type of water, which is basically the same as wastewater from a washing machine. I have seen testing on typical cleaning in the bicycle industry. Generally, we have a fairly clean industry, with very little volatile fluids, and almost none of the heavy metals such as lead, cadmium, or mercury of other industries. Do not add diesel to an otherwise toxic free industry.
Again, it is always best to discuss disposal with your local authorities.