The best way to dispose of fat, oil and grease (FOG) from cooking is to solidify thin oil or grease with things such as coffee grounds, kitty litter or even laundry detergent, then dispose of the solid waste. Alternatively, you can place the fat, oil and grease into a sealable container, such as an old coffee can or a plastic jar with a lid, then throw away the jar after it has cooled. The reason to go through all of this trouble is because fat, oil and grease clog up sewers and pipes, and they can sometimes even turn into soap while working their way through the sewer system.
More facts about FOG:
Though it seems like simply washing oily pans with soap would take care of the problem the oil creates in plumbing, it’s not true. The soap merely breaks down the grease into smaller parts, which can then rejoin after they’re in the pipes.
FOG blockages can become bigger than cantaloupes.
Many cities now offer FOG recycling, where people can bring old cooking oil or grease to be recycled into biofuel or even livestock feed.