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Extension > Regional Sustainable Development Partnerships > RSDP Newsletter > RSDP Happenings - Focus: Small Scale Aquaponics

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RSDP Happenings - Focus: Small Scale Aquaponics

Plant bed in a greenhouse operated by PortFish in Port Washington, Wisconsin. Source: PortFish.

March 2016

By Caryn Mohr

“Putting pieces together” is how Southwest Minnesota resident Noah Ryan described the origins of a community research project that marries aquaponics systems with Deep Winter Greenhouse design. Ryan and his friend Dylan Martin had small-scale aquaponics systems at their homes. When they learned of growing interest in passive solar greenhouses, they wondered whether there might be some magic in combining the two.

The pieces
Aquaponics is a type of agricultural system that combines aquaculture (raising fish) and hydroponics (raising plants without soil). The fish waste provides nutrients for plants, and the plants filter the water for the fish. In most cases, a third party -- microbes and worms -- first processes the fish waste into usable material for the plants (The Aquaponic Source, 2015). According to aquaponics experts at the University of Minnesota, the number of aquaponics producers in the state has grown from three in 2010 to more than 40.

“It’s a natural cycle that cleans itself, and it reduces the amount of water you need to grow plants,” Ryan said. Ryan and Martin’s hope was that water in an aquaponics system could also help retain a passive solar greenhouse’s heat by acting as a thermal mass that helps maintain the temperature inside a greenhouse. Additionally, fish can provide natural fertilizer for plants.

A Deep Winter Greenhouse (DWG) is a passive solar greenhouse designed to dramatically limit the amount of fossil fuel required to grow crops in northern latitudes during the winter months. The structure is built with a south-facing, angled glazing wall that captures heat from the sun. That heat is then stored in an underground rock bed and dissipates into the above-ground planting area at night when the sun isn’t shining. The technology holds promise as a production system for small- and mid-scale farmers who want to expand production through the winter months with minimal fossil fuel inputs.

The puzzle
Ryan and Martin wondered whether there might be innovations in combining these two systems. Could incorporation of an aquaponics system into a DWG provide a beneficial additional source of heat? Ryan and Martin were also interested in understanding whether an aquaponics system could add a valuable protein source (fish) to the greenhouse as well as a source of plant food.

According to Ryan and Martin, while a greenhouse will stay warm when the sun is up, heat can gradually dissipate through the night when temperatures drop in Minnesota. If there aren’t sufficient ways to trap the heat, outside sources may be needed to keep the greenhouse at an appropriate temperature for the plants. Their hope was that aquaponics could provide an added viable, cost-effective, and environmentally conscious way of trapping solar heat when needed.

Greenhouse design comes into play. If relied on regularly due to poor greenhouse design, use of natural gas and wood burning stoves as supplemental heat sources can become expensive. The Regional Sustainable Development Partnerships (RSDP) have built a large body of work around DWGs, and are currently supporting the development of five prototype DWGs around the state that will provide vehicles for University research on production and building performance. Staff from the University of Minnesota Center for Sustainable Building Research will oversee their design and construction to ensure the best methods to-date are used.

The possibilities
Ryan and Martin submitted a proposal to the Southwest Regional Sustainable Development Partnership (SWRSDP) to conduct community-based research into their question by visiting active aquaponics and greenhouse sites in Minnesota and Wisconsin. Because combining the two systems was a novel idea, most aquaponics systems that Ryan and Martin visited were in more traditional greenhouses.

Sustainable aquaponic greenhouse production facility at Victus Farm in Silver Bay, Minnesota.

“Right away this was interesting for the [SWRSDP] board because of our ongoing work with Deep Winter Greenhouses,” said David Fluegel, SWRSDP Executive Director.

“Passive solar greenhouses have been around for a while, but it’s only more recently that produce farmers have been working on ways to extend the growing season. During the past few years many new Deep Winter Greenhouses are showing up on the landscape to allow for year-round production,” Fluegel said.

“It’s the same way for aquaponics technology. The ideas have been around for some time and there’s all these experiments that have happened but there isn’t one place you can go to find all the best practices. That’s why the Partnership board supported this research. Here was an opportunity for a couple of people to really dedicate some time to visit a number of aquaponic systems and learn more about the potential for combining aquaponics with passive solar greenhouse design.”

While Ryan and Martin’s site visits delved into technicalities of aquaponic and DWG environments, they were inspired by a larger vision. “They had a broader goal to work toward food and community resilience through aquaponics in passive solar greenhouses,” Fluegel said.

The picture
Ryan and Martin visited small- to large-scale greenhouses in Minnesota and Wisconsin which used a variety of methods for growing fish and incorporating them into the environment. Examples of sites they visited include Victus Farm, a greenhouse integrating aquaponics in Silver Bay that received its first support from the Northeast RSDP, and PortFish, which operates a greenhouse that integrates aquaponics in Port Washington, Wisconsin. They documented pros, cons, and considerations of the various technologies, including cost and revenue, energy-utilization, and technical considerations related to bacteria, filters, water quality, heat exchange, and other issues.

The SWRSDP also provided financial support for Martin to attend the Minnesota Aquaponics Symposium at the University of Minnesota. Described as the first-ever symposium on aquaponics in Minnesota, the event brought together community members, technical experts, and industry leaders to explore the latest research on food safety and good agricultural practices.

Following the site visits, Ryan and Martin shared their findings with the SWRSDP board. Asked to encapsulate their overall takeaway, Ryan said, “Small is beautiful.”

Although more research is needed and greenhouse design is a key factor, the site visits illustrated to Ryan that adding aquaponics on a smaller scale can be beneficial. Because aquaponics systems can be touchy with regulating water temperature and bacteria for the fish, he thinks that greater success can be found with incorporating smaller systems that can more easily be contained. Based on their initial site visits, Ryan believes that successfully incorporating a smaller-scale aquaponics system can provide a beneficial additional way of maintaining heat in a year-round DWG environment.

“We believe that aquaponics could be a way to lower heating costs, but it would really depend on the scale/size of the greenhouse and system. If you could pull enough heat to keep your greenhouse at 60 degrees just one hour longer, you could begin to see some cuts in your heating bill,” Ryan said.

Nutrient film technique (NFT) at Victus Farm utilizes vertical space to maximize greenhouse growing potential.

Next steps
Although their core interest is in the potential use of aquaponics in passive solar greenhouses, in Ryan’s observations there are also a number of communities with older greenhouses that might benefit. Implementing aquaponics on a small scale could help address some of the barriers to operating a greenhouse, and increase the likelihood of reusing some of these facilities. Ryan and Martin are currently working with an older greenhouse in Willmar, Minnesota, to see if introducing an aquaponics system can help address past heating challenges.

“If we could find a way that’s simple and cost effective to introduce aquaponics and get people to learn about it, that’s kind of our main goal right now,” Ryan said.

Ryan and Martin are also bringing aquaponics lessons to schools. They designed and built small, portable aquaponics systems that can be brought to schools as educational devices. They also hope to continue exploring their question about the merits and feasibility of incorporating aquaponics into a DWG by visiting additional greenhouses and aquaponics systems, and have identified additional sites that would add to their research.

It’s the larger vision that drives their continued interest in parsing the technicalities of integrating aquaponics into DWG environments. “We need to find alternative ways to grow our food and [to] extend the growing season,” Ryan said.


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