Mining Black Gold
Twice a week, every week, Middlebury College’s custom-equipped Freightliner dump truck rumbles up South Street with about 10,000 pounds of food waste. It’s destination? The College’s composting facility where the staff from facilities services turn food waste into about 1,500 cubic yards of compost a year.
Composting can be a long and complicated process, both in terms of its labor and its science, but it’s one that Middlebury has been dedicated to since 1993, not only to save money and reduce its carbon footprint, but also to maintain and improve the natural beauty of its campus.
“Compost increases soil fertility, not in a traditional ‘fertilizer’ approach, but by increasing porosity, nutrient capacity, and water-holding characteristics,” explains Tim Parsons, the College horticulturalist. “Organic matter creates a living, breathing soil, a more natural ecosystem in an artificial construct, that of our trees, shrubs, and lawns.”
Backyard composters might think that those 10,000 pounds of food waste are just about all you’ll need to make compost. Mix in some leaves and grass clippings, turn it over a few times, wait a couple of months, and voila!—you’ve got compost. But no, not so fast. It’s not compost until all the raw organic materials have decomposed—a process that takes a year or more of careful monitoring, mixing, turning, and screening.
Middlebury’s recipe for compost is no secret: three parts wood chips, one part horse manure, and one part food waste. It’s a formula that Director of Facilities Services Norm Cushman developed years ago while attending the Cornell Waste Management Institute. And all of the raw materials in Middlebury’s compost recipe are local: the wood chips are produced on campus or sourced from central Vermont. (They are the same chips delivered to the College’s biomass plant.) The manure comes from the Morgan Horse Farm in nearby Weybridge. And the food waste originates from the dining halls and the Grille, with a smattering from the Materials Recovery Center, the Bread Loaf campus and some of the College’s residential houses.
The waste consists of pre-consumer by-products like eggshells, fruit and vegetable peelings, or chicken skins; post-consumer discards from students’ dishes; and biodegradable items like paper napkins. And why is there so much of it, often 10 tons per week or more? Because the College serves meals to about 2,500 people a day, not counting special events like Commencement, Reunion, and Fall Family Weekend.
Six days a week (five in the summer) the white and blue Freightliner with its “hook-lift” box and hydraulically operated cover pulls up to the back of the dining halls to collect the food waste. Usually operated by Mike Field or Ricky Rheaume, the task of loading the food waste, hauling it to the composting facility, and depositing it at the composting site is not a job for the faint of heart. If the smell doesn’t get you, the sight of the food waste and the vermin it attracts makes it an occupation well suited for the Discovery Channel’s “Dirty Jobs” with Mike Rowe, or for the book 50 Jobs Worse Than Yours by Midd alum Justin Racz ’97.
But for Field and Rheaume, both of whom have worked at the College for 20 years, it goes with the territory.
The staff at dining services plays a key role in the collection of food waste, and Melissa Beckwith, manager of waste management at Middlebury, salutes their efforts to keep the waste out of trash bound for the landfill, and for ensuring that almost no contamination gets into the future compost.
After the food waste is delivered to the composting site, it is mixed with the woodchips and horse manure on an enormous cement pad that’s about 200 feet long by about 60 feet wide. The College employs a “turned windrow system” to make its compost. A John Deere loader periodically turns the mixture to achieve a core temperature of about 130 degrees F., a level at which bacteria and other helpful organisms in the mound will grow, thrive, oxidize, and cause the solid materials to decompose.
John Gosselin, waste management team leader, keeps a watchful eye and nose on the windrows. “You can tell a lot by the smell,” he says, meaning that the aerobic oxidation of organic materials produces almost no objectionable odor. So when there is an unpleasant smell, Gosselin knows it’s time to turn the pile to achieve more aeration or to consider adjusting the mixture.
Even so, the job isn’t quite done yet. It’s not “black gold” until the material is small enough to pass through a five-eighths of an inch screen and decompose for another six to eight months. The pieces that won’t fit the screen, the “tailings,” go back for another year in the windrow before seeing if they can pass the screen test again. Then, and only then, is the compost ready to enrich the soils at the College.
Last spring, Tim Parsons and the landscaping staff spread about 75 cubic yards of College-made compost on the quadrangle formed by Old Stone Row, Warner Hall, Davis Library, and the Axinn Center at Starr Library. “The purpose was to improve compaction problems underneath some of our older, more stressed trees,” Parsons said.
“Certainly the lawn greened up as well, but the organic matter will linger in the soil for years improving aeration, holding onto moisture better in droughts, and allowing soil nutrients to remain available to the trees instead of leaching down into the soil profile.”
Recently the College began spreading compost on its natural-grass athletic fields to transition those grounds to organic maintenance practices. So are there ever any concerns with the compost? “Only one,” Parsons laments. “There’s never enough of it, not by a long shot. If we had the resources to spread it, we could use four times the amount that we generate.”
Interested in finding out more about composting? Use these links below.