Check to see if you city or county has a hazardous waste disposal site or some communities have special collection days.
He has and they don't. The irrational part of some of the arguments in this thread is the notion that it's okay to breathe in the fumes, and expose the skin to the fumes of chemicals that are so dangerous that, even when diluted and poured into a pit in the corner of your block where they will no doubt break down, oxidise and gradually be dispersed, is not okay.
You can't have it both ways. If the darkroom chemicals really are so dangerous that it would be irresponsible to dispose of them in the way I have recommended in this thread, bearing in mind that people who have sceptic tanks are on larger than average blocks of land, then I for one would simply refuse to work with such chemicals. I've got more respect for my health.
If you really are concerned about not contributing to the pollution of the planet, then don't produce the pollution in the first place; that is, don't buy the polluting chemicals.
So far, the only mention in this thread of possible dangerous components of these waste chemicals that won't break down, is selenium. As it so happens, selenium is an essential trace element which appears to be deficient in the soil in many areas, particularly in the UK; so much so that bakers over there are considering adding it to the bread. Most of the other elements in the waste are probably just nitrogen, oxygen, hydrogen carbon, sulphur, silver sodium etc, none of which seem particularly dangerous to me.
It's not my problem of course, but if anyone is aware of any components in darkroom waste that are particularly inert, that have a long life, which are likely to resist breaking down in the soil when exposed to air and rain, and which are particularly toxic, then speak up.