Ok, I'm sure (or at least, I hope) that you already know that putting grease, oil and fats of any kind in to your kitchen drain when you're on a septic system is a big No-No. But what many homeowners don't understand that it's just as big a No-No when you're on a public sewer system. Think about it. The sewer pipe between your home and the street is YOUR responsibility. Enough grease goes down your kitchen drain in to that pipe and eventually you're going to have a major clog. And guess who's going to pay to have that sewer line cleared? Not to mention the fact that your front yard is going to look like a construction site for some time.
Keep 'em away from the drain and you'll be a happier homeowner in the long run. Keep a container under your kitchen sink to deposit them and then place them in your trash can. However, you might need to label that container like I have to for my family!!! Works like a charm.