In a storage room off the teaching kitchen at Madison Area Technical College in Wisconsin, the cabinet-size aerobic digester consumes up to 300 pounds of food scraps per day, turning waste into garden compost. Nicknamed Chester by students, the award-winning digester has been gobbling up scraps, leftovers, expired ingredients — just about anything generated by the college’s culinary arts program as well as its cafeteria. “It could be steaks, it could be sauces, rice, pasta, pasta salad — all that stuff,” said John Johnson, a culinary arts instructor. “Our trash cans are pretty much empty now. If it can go into Chester, it goes in.”
The process is simple: Dump the food scraps in and close the door. The digester slowly churns the material while heating it up to activate the bacteria, which do most of the work. By the next day, all that’s left is a dry, brown powder. With moisture vented out through a pipe in the ceiling, Chester produces about a pound of compost for every 10 pounds of waste. Chester especially likes scraps from the baking program, as the bacteria thrive on sugars. Large bones are one of the few things it can’t handle.
Made by the Hong Kong-based company Oklin, Chester requires only electricity, supplied by the college’s rooftop solar array. There’s no need for water; nor does it produce sewage that would need further treatment. Installed in late 2019 — shortly before COVID-19 lockdowns — Chester has digested about 25 tons of food scraps per year, turning that organic waste into nutrient-rich compost rather than sending it to the landfill, where it would take up space and produce methane, a potent greenhouse gas.