Reducing the Nutrient Impacts of Aquaculture Through the Use of an Algal Photobioreactor Production System
Abstract:Algal biofuel production is a promising solution for tackling nutrient pollution and energy and climate change challenges, due to algae's ability to utilize carbon dioxide from combustion processes, uptake nutrients from waste-streams and produce energy products. Florida has been identified as a favorable location for the development of algal biofuel production systems due to the climatic conditions and number and location of nutrient waste streams and combustion sources. This study examined the integration of an algal biofuel production system into Mote Aquaculture Research Park's (MAP) recirculating aquaculture system (RAS) in Sarasota, Florida, which includes a sturgeon hatchery and grow out farm that sustains approximately 180 metric tons of fish. In the proposed system, algae produced in photobioreactors using waste nutrients from the RAS would be anaerobically digested to produce energy in the form of methane and biosolids that could be used as fertilizer. Nutrients recovered from digester centrate and carbon dioxide from the combined heat and power (CHP) unit, would be recycled back to the algal photo-bioreactor. Anticipated outcomes include electricity production, reduction of nutrient (N and P) discharges to the environment and reduced chemical and energy costs for operating existing nutrient removal processes on site. The model developed estimated that 85% total nitrogen removal could be achieved in the algae photobioreactors and between ˜2,000 and 3,000 Wh electricity per kg algae could be produced through anaerobic digestion. An alternate scenario for energy production of generating biodiesel was also considered, which could provide between ˜3,000 and 7,000 Wh per kg algae; however significant technical challenges to biodiesel production must be overcome for implementation of this strategy. The model estimates were validated using nutrient removal and algae productivity data from prior studies carried out in our laboratory with Spirulena platensism grown on synthetic media. Our current research is directed at determining algal productivity rates in MAP's RAS water under natural lighting conditions and temperature and incorporating these rates into the model.
Document Type: Research Article
Publication date: January 1, 2011
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