Composting at Middlebury
Middlebury composts over 300 tons of food waste per year. In addition to collecting pre and post consumer waste from the college dining halls, compost is also collected from over 85 compost bins located in dorms and offices throughout campus.
Middlebury uses a hook lift truck with a specifically designed hook-lift box for food waste collections. Over the years we have fine tuned the box so now, it works like a charm. The back door of the box opens to the up rather than to the side to facilitate dumping at the compost site. A heavy duty rubber gasket is installed to ensure the box is leak proof. Our skilled trades' people fabricated user friendly features such as a hydraulically operated cover for the box and a toter dumper that allows two totes to be dumped simultaneously with little effort on the driver's part. The truck is then parked at our Recycling Center, moving any nuisance smells to the edge of campus. This box holds 2-3 days of food waste.
Pre Consumer Food Waste: Middlebury's dining staff deserves a ton of credit when it comes to diverting prep waste. We see very little contamination in the compost. They have built composting into their daily activities and it shows.
Post Consumer Food Waste: Middlebury is successful at composting nearly all of the post consumer food waste from the dining halls as students deposit their plates, food and all to the dish room. Dish room staff then scrapes the leftovers (including meat), napkins and tea bags into a pulper.
Middlebury uses 22 gallon Rubbermaid Brute containers with dollies with in the kitchens. These are small enough to fit through the dishwasher to maintain sanitary conditions in the kitchen. Food waste from these containers is then dumped into larger 60 gallon totes. We modify the totes adding eyehooks to the back. Doing so allows the totes to be dumped using our specifically designed hook-lift truck.
Middlebury's newest kitchens, Atwater and Ross were built with composting in mind. Walk in coolers were installed to keep the food waste from smelling in the summer and freezing in the winter. This has made compost collections more efficient while eliminating the complaints of odor on hot summer days.
Since the hook-lift box for food waste only holds 2-3 days worth of food waste, Middlebury utilizes a 40 yard enclosed roll-off (modified over the years) to store food waste. By doing so, we reduce the number of times mixing is required from two times per week down to once every 3-4 weeks. During the hard freeze winter months, we do not use the 40 yard box as the food waste freezes and dumping becomes impossible.
We mix our food waste (1 part) with woodchips (3 parts) and horse manure (1 part). Horse manure we acquire from the UVM's Morgan Horse farm for the purpose of composting. Our campus landscape debris is chipped for use in composting. We do end up purchasing wood chips occasionally.
Mixing and Turning
Our 344 HD John Deere loader works wonderfully to mix the ingredients and create windrows. These windrows are then turned on a routine basis to ensure good temperature, moisture and consistency throughout the windrow. This process is known as a Turned Windrow System.
Taking our Temp
Temperatures of active piles sore above 130 degrees killing weed seeds and harmful bacteria. Once the piles have fully "cooked" and the temperatures have reduced to near ambient level, piles are moved to a secondary pile awaiting screening. This can be tricky in the winter when freezing temperatures slows the "cooking" process. Piles then spend more time on the pad until the composting process is complete.
Once per year, Middlebury contracts with a local commercial composter who hauls a large compost screen to our site. The preceding year's worth of compost is then screened and piled.
Maturing and Use
Once screened, the compost is then stored until the following spring. By allowing the compost to age for this additional time, we are ensuring a high quality, nutrient rich, product which can then be used at our Organic garden, on our athletic fields and throughout campus wide landscaping projects.
The material too large to fit through the screen is allowed to decompose for an additional year and is then rescreened in an effort to capture as much "black gold" as possible. As an alternative to land filling this material, Middlebury staff pick contaminants from the tailings and then build earthen berms around the cement pad to aid in litter control and aesthetics.