In another thread there was some discussion of how to dispose of used antifreeze. According to www.green.ca.gov: " Health and Safety Code (HSC) 25218.1 lists antifreeze as a household hazardous waste, thus it is considered a Universal Waste, a product that can not be disposed in landfills or sewage systems ".
The site goes on to mention that California alone recycles 8.5 million gallons of antifreeze per year.
There is a biodegradable antifreeze that can be used to prevent freezing of plumbing in cold climates, and can be legally put into the sewer system and is safe for septic systems. I put some in the drains and toilets at my cabin in the winter.