Designing a Compost System into a Greenhouse at Gustavus Adolphus College

CLIENT CHALLENGE

Gustavus Adolphus College is a small, liberal arts college in St. Peter, Minnesota that envisioned an integrated compost and green house operation on campus. This unique project uses the heat from the aerobic composting to heat a green house and extend the growing season. In turn, the green house will generate plant waste that can be made into compost.

After researching multiple technologies and consulting companies, Gustavus selected Green Mountain Technologies to design and engineering a solution that fit their needs.

GMT SOLUTION

GMT advised Gustavus that the easiest way to recover heat from a compost operation is to install the composting system directly inside the green house. In this way, any residual heat from the compost process travels into the green house. GMT worked with Gustavus to custom design this innovative system design.

There are multiple synergistic effects resulting from this combination. This design allows excess heat from composting to passively transfer into the greenhouse, thereby reducing the cost of heating the greenhouse with conventional energy from fossil fuels. Additionally, the process air from the composter moves into a biofilter that is built into the greenhouse. The process air passes through a heat storage bed in the floor of the green house, allowing more heat energy to transfer into the green house. Growing occurs directly on top of the biofilter, and the filtered air is then vented to the exterior.

The In-Vessel EF-24 has a footrprint of approximately 24’x8’ and can receive up to about 1 ton of total feedstocks per day. The feedstocks in this system include: food waste, paper waste, biodegradable cutlery, wood chip mix and landscape waste.

This system has allowed Gustavus to lower their waste management costs, provide an educational experience for their students and extend their greenhouse growing season, even in harsh Minnesota winters.

Gustavus has been very pleased with the Earth Flow’s performance,“Consistently composting 140-155 degrees F even in sub-zero Minnesota temperatures.”