From the TED-Ed YouTube channel:
How could you dispose of your cooking oil when you’re done cooking? The easiest thing to do might be to pour it down your drain — but if you save it up and send it to a processing plant, it can gain useful new life as biodiesel, a biodegradable energy source which can run in diesel engines instead of refined petroleum. Natascia Radice describes the process of turning goop into good.
Lesson by Natascia Radice, animation by Lippy.