From the University of California at Santa Cruz to Virginia Tech, cafeteria trays are disappearing, enabling universities and food-service companies to reduce food waste, lower energy costs and make college campuses more environmentally sustainable. The reasoning goes like this: when students are allowed to use trays, they tend to roam around the cafeteria grabbing food with abandon until space on the tray runs out. If you remove their trays, you make it impossible for them to carry a surplus of dishes, and they will make their selections more carefully and be satisfied with less food overall. That saves on food. Further, getting rid of trays means dishwashers have less to wash. That saves on water and energy.