28 JUNE 2017 • WORLD AQUACULTURE • WWW.WAS.ORG emissions and solids loadings into sensitive lake ecosystems such as Lake Malawi. Four selected tilapia grow-out technologies were compared (Table 2) on the basis of the following sustainability indicators: • Feed conversion ratio (kg feed/kg edible weight), • Whole carcass protein efficiency (%), • Nitrogen emission (kg/t protein produced), • Phosphorus emission (kg/t protein produced), • Land use (t edible product/ha), and • Consumptive freshwater use (m3/t). By these measures, the SAFF-BFT system performs best, followed by the SAFF-RAS. Greenwater pond farming has poor input:output nitrogen and phosphorus efficiency ratios, likely caused by high N losses through volatilization and denitrification to the atmosphere and P losses to the sediment, despite being a lowcost production technology. Clearly, the lake cage culture model represents a relatively less sustainable form of intensive tilapia aquaculture (Table 2) where no opportunity exists to recover neither dissolved and fecal-bound nutrients or organic matter that can overload the nearby benthic environment of lake ecosystems. The Future of SAFF and Chambo Fisheries BFT promises to revolutionize tilapia and shrimp aquaculture Water Use Efficiency Another big advantage of BFT is the massively reduced water requirement compared to conventional tilapia aquaculture systems. Currently Chambo Fisheries uses around 150 L of water to produce 1 kg fish, which compares well against greenwater pond culture that requires 2500-5000 L/kg of fish. The high annual fish yields per unit tank surface area and volume and reduced water use in BFT opens up great possibilities for applications in greenhouse enclosures on the highlands of Africa and on the periphery of major cities, reducing transport logistics to urban markets. The results obtained by Chambo Fisheries clearly highlight the merits of BFT as a competitive and sustainable alternative low-cost intensive feedlot technology for tilapia aquaculture. Environmental Sustainability BFT tilapia along with RAS farms, particularly when incorporating an aquaponics component, with or without duckweed (Lemna spp.) nutrient recovery lagoons designed to achieve zero effluent status, represents exemplary Best Management Practice (BMP). Direct loading of organic solids and dissolved nitrogen and phosphorus emissions to receiving surface water bodies can be eliminated in BFT and RAS farms, thereby comparing favorably to lake-cage culture operations that are characterized by high N and P
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