SBIR Phase I: Inserting Microalgae and Oysters into RAS for Waste Management Purposes

This Small Business Innovation Research (SBIR) Phase I project will determine whether integrated multi-trophic aquaculture (IMTA) can be imported from off-shore salmon farms where the concept is being pioneered into on-land recirculating aquaculture systems (RAS). RAS Corporation, and the University of Maine's Center for Cooperative Aquaculture Research are already employing a tank of black sea bass (Centropristis striata) plumbed directly to raceways containing sand and deposit-feeding polychaetes (Nereis virens) to demonstrate that the worms will consume virtually all of the particulate fecal waste and unconsumed feed, thereby eliminating intermediate filtration equipment while generating a valuable by-product. Phase I proposes to add an algae bioreactor downstream in order to culture microalgae that will cleanse CO2, nitrates and phosphates from the flow while adding back oxygen. Excess plant cells will be extracted by flowing them through adjacent impoundments, containing filter feeding oysters (Crassostrea virginica), hence a second by-product. A computer model system will be developed to maintain the balance of the four trophic levels. Success will result in having IMTA-RAS software that projects how many kilos of baitworms, microalgae and oysters can be grown from the waste of a certain load of fish, determining the optimum carrying capacity of each trophic level. The broader impact/commercial potential of this project will make on-land and indoor fish production less costly, more profitable and organic in character, thus more sustainable. Expansion of offshore cage culture of finfish is limited by natural conditions, environmental constraints and competing uses for space while RAS technologies are poised for greater enhancements. The two most common criticisms of aquaculture are: (1) it generates waste; and, (2) the fishmeal in fish feed is derived from wild-caught forage fish. This project will demonstrate that wastes are valuable resources, which, if used internally, can yield two by-products; baitworms and oysters if grown in concert with microalgae. This is achieved by substituting biological versus mechanical methods for water treatment. While recreational and commercial fishermen represent a large market for baitworms, it has also been demonstrated that polychaetes make excellent fish feed, hence a potential substitute for fish meal and oil. After trial extraction of halibut waste to feed sandworms, CCAR concluded that 10 mt of fish harvest would yield 1.0 mt of worm harvest (Brown, 2011).