Table to Farm: Composting System in Pitt’s Market Central Puts Waste to Good Use

Tod Shoenberger, unit manager for Sodexo, rinses the inside of the pulper, and industrial-size blender that grinds food and other organic matter into a slurry. In October, Shoenberger used the resulting compost on his home rose garden with excellent results, he said.

In an interesting twist to the concept of farm to table, the University of Pittsburgh’s Dining Services takes an additional step with some of the food it receives from Western Pennsylvania farms—it sends it back, but in the form of clean, nitrogen-rich fertilizer processed on campus.

Since August 2010, uneaten food from Market Central, Pitt’s largest dining room, has gone into an industrial composting system constructed in the lower level of Litchfield Towers. Everything from half-eaten apples to picked-at hamburgers are ground, baked, dehydrated, and reborn as compost. On top of helping local farmers produce future lunches for Pitt students, the composting system has significantly reduced the waste that would otherwise leave the University destined for a landfill.

One assumes that anything consuming up to 900 pounds of food every day would stand out, even among the 5,000 ravenous students that gather each day in Market Central. Yet the composting system is a tucked-away collection of three machines in separate locations connected by pipes beneath Market Central’s kitchen floor.

The process begins when satiated diners leave their trays, cutlery, and scraps on a conveyor belt that transports this midday flotsam into the kitchen. Workers separate the organic waste by hand, dropping food, napkins, chopsticks, and biodegradable flatware and cutlery into a stainless-steel trough. A constant stream of water in the trough feeds the waste past a giant magnet that removes stray silverware and into the pulper, an industrial-sized blender. Even this process has a green touch. Before the composting system was installed, the trough used a constant flow of fresh water, explained Sony Rane (CBA, A&S ’10), marketing and sustainability coordinator for Dining Services. Now, fresh water is added in the morning and then filtered and recycled throughout the day, a process that saves 90,000 gallons of water each year.

The extractor removes water from the slurry before the food pulp is baked into fertilizer. The water is filtered and then recylcled through the pulper.

Once the organic material is reduced to a rather less appetizing slurry, it flows underneath the kitchen into a cramped room housing an enormous extractor that strains water from the organic pulp. The water heads back to the trough, while the pulp slides down a chute leading to the loading dock on the other side of the room’s back wall.

It is on the loading dock that two large composting ovens bake the damp food paste at 180 degrees Fahrenheit for 18 hours. What emerges is sterile biomass with the feel of sawdust. Local farmers and gardeners in the community collect the biomass and mix it with carbon-rich compost, such as leaves or grass clippings. Thus, the nutrient loop between Pitt and the farms that supply the University is closed, Rane said.

But the benefit of Pitt’s composting system extends beyond the farm, explained Susan Fukushima, resident district manager for Sodexo, which operates Market Central. The food that ends up as boxes of brown compost is not lingering in a landfill, taking weeks to rot away inside a plastic trash bag. The amount of discarded food would be substantial. Market Central used to produce approximately twenty 55-gallon barrels of trash each day, Fukushima said—the number is now down to around three barrels. Plus, Pitt now pays between 35 to 40 percent less to have trash hauled away, Rane added.

Pitt’s compost system is based on a similar system found at Dickinson College in Carlisle, Pa., said Rane, who, as a Pitt student, was involved in helping Sodexo design the composting process. The idea began around 2008, when the student group Free the Planet approached Dining Services with ideas to reduce waste in Market Central, recalled Rane, then a member of Free the Planet. It was at Dickinson during a meeting of the Pennsylvania Environmental Resource Consortium—which connects people undertaking environmental projects with universities—that Rane learned about the college’s food composter and brought the idea to Pitt.

After 18 hours of baking, the food, napkins, chopsticks, and other organic material emerge as nitrogen-rich compost with the feel of sawdust.

As expected, some adjustments have been required since the composter went into operation. At first, for instance, the shredded remains of such debris as condiment packets and fortune-cookie wrappers kept turning up in the compost. Rane remedied the situation by replacing single-serve items with bulk containers, offering, for example, crackers and cookies in baskets. The compost is now trash-free. To address the inorganic material that still rides the conveyor into the kitchen, Dining Services is looking into installing a recycling station that would further reduce Market Central’s trash output, Rane said.

Nonetheless, the Market Central composter has proven its worth both sustainably and financially, Rane said. The University is exploring whether to install the system in other campus dining areas.

“It’s not just providing an organic fertilizer for local farmers and saving the University community money,” she said. “It also is a proactive measure to keep trash out of the landfills, which are rapidly running out of room. This way food waste still goes into the ground, but to produce more food.”

Benefits of Market Central’s composting system:

• Keeps as much as 900 pounds of leftover food per day from going to a landfill.

• Reduces Market Central garbage from twenty 55-gallon barrels per day to three barrels.

• Reduces trash-hauling costs by 35 to 40 percent.

• Reuses water, saving 90,000 gallons per year.

• Closes the loop: converts locally grown food into nitrogen-rich compost for local growers.