StarSan is essentially a blend of two acids that are considered food. Plus some proprietary ingredient in a small quantity that I'd suspect probably isn't. When diluted it can actually feed your yeast rather than kill them. And anything that gets dumped down the drain gets diluted. It is acidic, and so acidifies whatever it gets into, but that's probably the worst it does. 5 minutes into the sewer I bet it won't kill a thing any more.
Sodium percarbonate dissolves in water to produce hydrogen peroxide and baking soda. The hydrogen peroxide is what does the oxidizing for you, breaking down into oxygen and water. So in the end this stuff is only as bad as baking soda on the environment. Cleaners based on this chemical, like OxyClean and PBW, have other cleaners in them that I can't vouch for, but sodium percarbonate is at least one of the main ingredients in them.
The point of this is that being a cleaner / sanitizer does not necessarily mean being harmful to the environment. The ones that are biodegradable in the end may not do any harm at all by the time they exit the waste processing plant. The warranty is voided, of course, if you're pouring the stuff down the drain undiluted and in large quantities -- in sufficient quantity you could end up killing the bacteria in the waste processing plant. I doubt anyone working on our scale could do that kind of damage if they tried, though, with the chemicals we use.
I follow where you're coming from, but I'm alluding to how most chems are considered in concentrate/bulk form i.e. the phosphorous in a match stick wouldn't cause any harm, but a piece of pure phosphorous the size of that match stick head, when exposed to oxygen will burn a hole in your hand, or the amount of sodium in a pound of salt is harmless (other than the usual recommended intakes from a human health point of view), that same amount of sodium, when in it's pure form, will explode when placed in contact with water, etc etc etc.
That is what I was alluding too........
There are many ways of sanitising etc, with different chems or substances, that in the dilute forms, do break down and are harmless, likewise, there are two specific substances in nature that are the biggest hazards to lots of stuff, albeit, very, very slowly. Both doing their respective damage in very different ways to many different materials.
Those "dangerous" materials ? Pure oxygen, and salt water.
My suggestion of using sulphites does work, but like with any sulphites, it needs the acid to release the sulphur, and that sulphur in turn, reduces it's efficacy with time and air/O2 exposure.
Proprietary products like Iodophor, Star San, etc etc, will only have a relatively limited lifespan, whether it's X amount of hours/days/months when diluted (if it indeed does require dilution), or in it's concentrate (as packed for sale/use) form.......
Just go with what you find works for you, and is easily available where you are.
Don't forget, the only easily identifiable things that Japan and the UK have in common, is that we both drive on the "correct" side of the road and Nissan GTR Skylines ;D
