A major part of being somewhat self-sufficient is the need to safely "dispose of waste". For example, how do you "get rid" of paint thinners or leftover paint? In some parts of the world towns and cities provide places where you can take these noxious chemicals to be "safely" dumped. Out in the country (or in countries - like South Africa - where the state of recycling is less advanced) there are rarely such options. And yet, I certainly would not pour such stuff into my soil or a watercourse! It can be quite a difficult problem.
Brewing uses its share of noxious chemicals for cleaning and sanitising bottles, kegs and fermentation vessels. Industrial brewers generally favour Caustic Soda as a cheap and effective cleaner, and I, too, use it for cleaning bottles and removing their labels. Disposing of it is a headache. I don't want to pour it into a dam, as I fear that the alteration in pH would, over time, be harmful to too many organisms. Generally I dilute the hell out of it, and then pour the dilute solution onto the roots of alien weedy shrubs that I would like to see killed off. It's never yet done that, but I live in hope. I also use different disposal area each time so that no concentration builds up.
I used to use diluted Chlorine Bleach for sanitising fermentation vessels, but was always bothered by two things: you have to rinse the fermenters at least 3 times to get rid of any Chlorine taint that might threaten the beer. And if you've ever tasted Chlorine-tainted beer, you'll understand perfectly! The rinsing seems to me to defeat the whole exercise unless you happen to have a lot of sterilised (i.e. High Energy) water around to rinse with. Then, too, disposing of Chlorine is a big headache.
Lately I've been using Iodophore - a concoction of Iodine and Phosphoric acid that requires no rinsing - for sanitising fermenters, and I am quite happy to just chuck this already dilute solution onto the lawn, since I don't consider either of these chemicals to represent a hazard in the low doses and small quantities involved. In fact I'm considering pouring it into the compost heaps where the Phosphorus will make its way to plants where it can do some good.
Just the other day, though, I came across the following recipe for a Home-made No-rinse Sanitiser that I will certainly think about trying. Please note that "sanitising" is not the same as "sterilising", so this stuff would not be suitable for babies bottles or anything like that. The recipe allegedly comes from one Charlie Talley (manufacturer of Five Star Chemicals, makers of Star-San, which we can't get here.)
Thoroughly mix 30ml of distilled white vinegar to 19litres of water. When the vinegar is well diluted, add 30ml unscented Chlorine Bleach.
The high dilution of the vinegar in the water before the bleach is added
prevents any out-gassing of Chlorine from the bleach that is added at
the end. The vinegar actually helps the bleach work as a better
sanitiser by acidifying the solution. The high dilution also
means it leaves no residual tastes behind of bleach or vinegar, making
it a perfect "cheap" no-rise sanitizer.
I feel quite confident that, in such low doses, no harm will come from just pouring this solution away into the lawn, as long as I spread it around enough. The price looks pretty good, too!