A student-built and operated composting system at St. John’s University in Queens, New York processes about 2 tons/semester of food and coffee grounds.
Molly Farrell Tucker
BioCycle November 2012, Vol. 53, No. 11, p. 32
On the main campus of St. John’s University in the borough of Queens in New York City, students are composting food scraps and wood chips in an aerated composting system that they constructed themselves. The finished compost is used on campus grounds and student vegetable gardens.
Under the direction of Thomas Goldsmith, Director of Energy and Environmental Conservation at St. John’s University, student workers first started composting food scraps in 2009 with the Rocket model A700, a small, commercial in-vessel food composter with capacity to process 6 gallons/day of food scraps. In fall 2010, St. John’s also started composting grass clippings, spent coffee grinds and fall leaves in a large outdoor windrow, which Goldsmith was turning periodically with a pay loader. In November 2011, Goldsmith and student workers went a step further and began assembling an O2 Composting System, an enclosed structure with three bunkers each with a 6-cubic yard capacity. The university was assisted by Compostwerks in Mt. Kisco, New York, which provided expert advice, equipment specifications and training on composting and compost tea brewing.
Standard arrangement of the O2 composting system is three bunkers, each measuring 7-feet wide by 8-feet deep and 4-feet high, with an aerated floor system. A single electric blower delivers air to the floor system in each of the three bunkers through PVC pipes. The direction and volume of airflow is controlled by three “push-pull” gate valves that allow air under fan pressure to pass through multiple three-eighth-inch holes drilled in the covers of air distribution boxes within the concrete floor. Four inches of wood chips help distribute the air evenly across bottom of mixture.
Collection And Composting
Out of 16,000 students enrolled at the Queens campus, a core group of 10 students collects the food waste from cafeteria kitchens on campus, as well as spent coffee grounds from on-campus Starbucks, Dunkin Donuts and Law School Cafe. In a typical week during the semester, student workers cart about 1,600 pounds of kitchen trimmings (fruits, vegetables and some starches) along with 400 pounds of coffee grounds in 30-gallon barrels to the composting facility. “Every two weeks there is enough food to load a bunker,” says Goldsmith. “My hat goes off to the good work performed by Chartwells Dining Services for separation of food trimmings for composting.”
A concrete mixing apron is adjacent to the bunkers. The food scraps and coffee grounds are combined with wood chips from tree prunings gathered by the university’s groundskeeping staff. If more wood chips are needed, Goldsmith makes a run to New York City Parks Department in Queens for a load. A pay loader is used to mix the feedstocks and load the bunkers. Student worker Nathan Holmes is in charge of screening the compost with a Royer screener/shredder. “All of the wood chips don’t get fully composted, so the larger chips are screened out and put back on the mixing apron ready for the next food mix,” Holmes explains. The organics are composted in the bunkers for five weeks, and then moved to an outdoor windrow for another five weeks.
The students produce a coarse compost, compost tea and fine-screened compost. These products are spread on campus lawns, mulched into planting and tree beds, as well as the 50 organic vegetable planting beds in the Student Community Garden. “In these gardens, students grow all of the vegetables to help support St. John’s Bread and Life soup kitchen in Bedford-Stuyvesant,” says Raelynne Lee, Sustainability Coordinator.
St. John’s University is a partner in the US EPA’s Food Recovery Challenge (see “Sustainable Food Management In Action,” March 2012). To participate, partners take three primary actions: Conduct an assessment of their current practices; Set a goal for reducing the amount of food waste being thrown out; and Commit to a more sustainable approach by tracking their efforts across three food diversion actions areas: prevention, donation and composting.
Holmes, who is graduating this year, says he is proud to be a part of the composting program: “One thing that students take pride in at St. John’s is the amount of green space the campus has. I feel good about helping to create and maintain it.”
Molly Farrell Tucker is a Contributing Editor to BioCycle.