Over the last two years, William Reid has spent just $5.50 on food. Reid is a committed dumpster diver: He dredges unsold grub from supermarket dumpsters and collects food scraps wherever he finds them. And he feasts. A graduate student in film and electronic media at American University in Washington, D.C., Reid forswore store-bought food in August 2014. Since then, he’s been munching on found meals of green vegetables, fruits, meat, eggs, milk and candy…