The Arboretum serves as a host site for a collaborative compost demonstration project with Carver County Environmental Services and Specialized Environmental Technologies, Inc. All Arboretum brush, wood, weeds, dead plants end up at the compost site, as well as food and cafeteria waste from the Arboretum Restaurant.
University Dining Services (UDS) operates the Arboretum Restaurant and supplies it with biodegradable products and packaging materials that are corn resin-based and take approximately 45 days to break down in compost piles. Visitors sort their waste into compost, recycling and trash bins. In May 2012, the Green Restaurant Association designated the Arboretum Restaurant as a Certified Green Restaurant®. Read more at dinegreen.com.
Once collected, waste is brought to the compost site via truck, dropped in the designated area, spread out and sorted into three piles: yard waste, organics and contaminants, such as plastic bags. The Arboretum uses compostable bags to avoid incorporating plastic that can degrade the quality of the compost.
After sorting, brush and stumps are ground into mulch and may be sold or used in the composting process. Organics are mixed together, and the pile is adjusted to reach an optimal level of moisture, carbon-to-nitrogen ratio, and free air space. Read more on the requirements for efficient decomposition. The squeeze test helps gauge how much water is present.
Since piles at the demonstration site can be as high as 12 feet, piping is installed beneath each pile and attached to blowers set on timers that aerate, or push air through, the material, which provides microorganisms with the oxygen required for decomposing the waste.
Blended materials are monitored daily for temperature. Temperatures of 131°F are maintained for 7 days to kill off weed seeds, plant diseases and bacteria. Covering piles with a compost blanket or woodchips helps retain heat. Large machines called windrow turners drive through the pile, turning the material to ensure that colder edge areas move toward the center and to inject more oxygen.
Once the temperature requirement has been met, materials are screened to remove contaminants and then remain in a pile for another 60 to 90 days, being turned occasionally. With its fresh, earthy smell, the Arboretum gardens, and other operations, use the finished compost.