Compost Heat Recovery Spawns Aquaponics Enterprise
The need to switch from windrows to aerated static piles to manage odors prompted Michigan landscape supply company to take advantage of the opportunity to recover heat.
By Nora Goldstein
Biocycle
Mar 21, 2022
Excerpt:
The ability to recover and circulate heat combined with Cherry’s ongoing interest and willingness to diversify Country Oaks’ offerings, led to the launch of an aquaponics enterprise in 2021. A 3,500 sq. ft. greenhouse was constructed, along with two 1,000-gallon fish tanks to raise tilapia. A second heat exchanger was installed in the AGT Compost Hot Box 250-8R to recover additional thermal energy from the composting process to heat the aquaponics operation. The glycol and water tubes inside insulated Badger pipe run underground from the heat exchanger to the fish tanks. The desired temperature in the fish tanks is 73°F to 78°F; the warm air also is used to provide radiant heating in the greenhouse.
The fish waste in the tanks goes through a clarifier to separate the solids from the nitrites. (The solids are removed and composted.) Microbes on a floating biofilter consume the nitrites and convert them to nitrates for the plant roots to absorb. “We are definitely on a learning curve since we started up the system last fall,” notes Cherry. “The tilapia requires specific conditions to thrive, and the plants require specific nutrients to grow, so optimizing the process for both fish and plants is critical. Everything is going well. We are growing lettuce, herbs, kale, tomatoes and other plants and selling the produce to restaurants and other customers. At this point, we do not have a market for the tilapia.”
