Homebrew PCBs

Which is safer to use and easiest to dispose of? i.e. which can I flush down the toilet ;-)

I've used the Muriatic Acid / Peroxide solution for a couple of boards, but I'm really worried because I've read how dangerous it is to use. I'm making PCBs in my basement which is not well ventilated and I'm close to a gas furnace, so I'm worried that the fumes might ignite.

I'm just looking for advice.. Thanks for your help.