Compost, dairy manure, poultry litter, and activated sludge/processed human waste are effective and efficient alternative nutrient sources for growing duckweed, an aquatic plant applied directly as feed in aquaponic systems.
Duckweed, rice bran, sorghum, and soy meal are effective alternative fish feeds for application in subsistence-level aquaponic systems. Utilizing these nutrient sources will produce biomass yields comparable to that of commercial fish feed when used in our system and will improve economic feasibility.
To answer our research question, we will be carrying out a three-phase experimental process.
Phase 0 will be an 2 week preliminary study to identify which nutrient sources are best suited to fertilize duckweed, a high-protein aquatic plant that can be administered as a feed for our aquponic system. The most successful nutrient source will then be used to grow duckweed for later phases in our research.
Phase I will consist of two 8-12 studies to determine which alternative fish feeds are the most promising and how two plants, Genovese basil and Bibb lettuce, respond to these feeds. This initial phase of research will be contained in specialized growth chambers, which provide a highly controlled environment for small-scale aquaponic systems.
Phase II will consist of three 8-12 week studies that will be much closer in scale to that of a potential subsistence-level application, allowing us to properly gauge how a realistic system will function using both traditional feed and alternative sources. In Phase II, we will choose the most promising alternative feeds and low-energy innovations from Phase I and apply these selections to a community-level aquaponic system of our own design. In addition to basil and lettuce, we will grow tomato and okra, to verify that our alternative feed is capable of sustaining a variety of plant species.
Phase I Designs
Phase I systems are pictured in a 3-D render of a growth chamber in the Environmental Science & Technology building. The fish-rearing tanks will hold 55 gallons of water and will house 9 tilapia each. The plant beds are located above the fish tanks to maximize use of space.
(Click to enlarge images)
Clockwise from left to right: Overall view of Phase I system, top view of plant beds, top view of water tanks, side view of water tanks
Phase II Designs
Phase II systems are pictured in a cut-away view of a high-tunnel greenhouse. The fish-rearing tanks will hold 200 gallons of water and will house 29 tilapia each. These plant beds will each have (3) 2 ft. x 7 ft. raceways with floating rafts of plants, giving approximately 2.5 times the surface area of fish rearing tanks. Water will be circulated with a small, low-energy pump.