One of the key elements of a tire is carbon black, a filler that adds durability to the rubber.  The substance isn’t very eco-friendly. It’s made from petroleum, which is why researchers are experimenting with a “greener” way to replace carbon black. Using egg shells and tomato skins obtained from food industry waste, the researchers made a substance that can be added to the rubber to make it stronger while allowing it to remain flexible. It wouldn’t be the first time wasted tomato skins have been reused. In fact, researchers from Ford and Heinz have been using the skins to manufacture interior car parts.