I took a workshop from a famous photographer and ardent environmentalist who told us that darkroom chemicals are chemically similar to chemical fertilizer, so collect them and spread them on your lawn. I asked about selenium being a poison and he refuted that as if there was no truth to it. I know that in our workshop a fair volume of stuff went right down the drain, presumably into the unconfined river floodplain aquifer (I'm a geologist by training).

So that's the word from a lefty tree hugger photog (the teacher, not me) who spends much of his time and money fighting land development in western Washington State.