This may be politically incorrect, but just dump it down the drain. While ethylene glycol is poisonous to critters that drink it straight, it's not really that bad of stuff and will dilute away to harmless in the sewer system. And as far as I know, there's not any laws against doing that in most places for private residences. Businesses can't put anything down the drains, though. That may get some of you upset.... As the chemist I work with says, "The solution to pollution is dilution".