Real Simple answers your questions.
Q. I never know what to do with the leftover oil after frying. Pouring it down the sink seems so wrong. Help!
A. Try to recycle it. Check to see if your local department of public works offers a free cooking-oil recycling program (many communities have started them). If so, store the fat in a resealable container (coffee cans work well) and add drippings to it until you’re ready to run your planet-friendly errand.
No such luck? Pour the oil into an empty milk carton or an old, unrecyclable takeout container and toss it in the trash. (When the pan is cool, wipe it with a paper towel to remove any excess grease.) Whatever you do, don’t pour the oil down the sink, where it will pass through the pipes and “solidify and cause blockage,” says Latisha Petteway of the U.S. Environmental Protection Agency.