An Introduction to Middlebury College's Passively Aerated Windrow System
Why compost?
- Diverts 75% (300 tons/year) of college food waste from the landfill, protecting the environment and avoiding tipping fees;
- Turns food residuals into compost for soil amendment in campus landscaping and vegetable production;
- reduces stress on the county's water treatment plant
- Uses composting as a vehicle for education and research within the college
A History Lesson
- Middlebury College has been composting since 1993 when the college was awarded a state grant to expand its recycling program.
- A waste audit revealed that the heaviest component of the college's waste was food, while the greatest volume component was cardboard. Encouraged by the results of the audit, the college considered composting.
- Several short term solutions, such as trucking waste to other composting facilities, were implemented and then finally replaced by the on-campus passively aerated windrow system (PAWS).
- Middlebury College has been composting since 1993 when the college was awarded a state grant to expand its recycling program.
- A waste audit revealed that the heaviest component of the college's waste was food, while the greatest volume component was cardboard. Encouraged by the results of the audit, the college considered composting.
- Several short term solutions, such as trucking waste to other composting facilities, were implemented and then finally replaced by the on-campus passively aerated windrow system (PAWS).
The Composting Process
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Step One: Staff separate pre- and post-consumer food waste from garbage in the dining halls.
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Step Two: A specially-designed truck empties toters and brings the food waste to a storage container at the composting site.
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Step Three: The container is emptied onto a concrete pad. Wood chips and horse manure are added, and PVC pipes are laid through the pile.
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Step Four: Finished compost is used as soil amendment on campus grounds and at the Organic garden.
The Passively Aerated Windrow System
P.A.W.S. is unique because air is brought through a pile of compost by passive means, eliminating the need to actively turn the piles.
The compost recipe is made up of the following layers placed on top of a concrete pad:
- bed of manure and wood chips to sponge up moisture
- perforated PVC pipes laid perpendicularly to the windrow, with the ends sticking out to passively aerate the compost pile
- food waste and paper products
- six-inch top layer of dry manure to seal in odors
- Each windrow is left to sit for 12-16 weeks to complete the decomposition process.
Why the P.A.W.System?
- Low start-up costs
- Low operating costs
- Little staff time, or special skills, are required
- Minimizes odors and pests