WWW.WAS.ORG • WORLD AQUACULTURE • MARCH 2026 57 This stark contrast highlights the superior water efficiency of BFT systems in tilapia culture (Kourie, 2017a, b, d). This also demonstrates the immense untapped potential for dualuse water resource utilization, whereby the same water supply supports both fish farming and crop irrigation under zerodischarge conditions. Soil Health and Water Productivity Water scarcity, exacerbated by climate change, necessitates improved water productivity in irrigated agriculture. The US National Resource Defense Council estimates that a 1% increase in Soil Organic Matter (SOM) can enhance soil water storage capacity by more than 25,000 gallons per acre (233,849 L/ha) (Bryant, 2015). Yet conventional irrigated crop agriculture often depletes SOM, leading to soil structural degradation, reduced microbial activity, diminished carbon storage, and decreased water and nutrient retention (Doran, 2002; Du Preez et al., 2011; Materechera, 2014; Okole et al., 2022; Derpsch et al., 2024). A metaanalysis of southern African studies found that crop production reduces SOM by an average of 46% compared to uncultivated fields (Swanepoel et al., 2016). Restoring Soil Organic Carbon (SOC), which constitutes approximately 58% of SOM (USDA, 2022), through additions of carbonaceous material such as livestock manure, green manure, and fish culture wastes, as well as, agroforestry and regenerative farming, can sequester 535 lbs/acre (0.6 t/ha) of carbon for every 0.4% increase in SOM (Minasny et al., 2017; Lal, 2004). Such practices contribute to climate mitigation, enhance soil resilience, reduce irrigation frequency and reduce reliance on synthetic fertilizers (Beillouin et al., 2023; de Blécourt et al., 2019; Khan et al., 2025; Wang et al., 2022; EU Commission, 2023). IAAS as a TripleWin Strategy Water re-use and nutrient circularity form the cornerstones of integrated aquatic production systems developed into existing crop irrigation systems. The practice of IAAS has existed for millennia in a variety of regions, such as Egypt, Vietnam, China, and Hawai’i (Costa-Pierce, 1987; Abdul-Rahman et al., 2011; Kaleem and Bio Singou Sabi, 2020; Pueppke et al., 2020). The appeal of IAAS is that it increases yields using the synergies between agriculture and aquaculture systems to improve the efficiency with which energy and nutrient inputs are converted to food (Ahmed et al., 2019; Pueppke et al., 2020) without the negative trade-offs of nutrient pollution from intensive aquaculture waste streams (Farrant et al., 2021). However, the separation and specialization of agriculture and (CONTINUED ON PAGE 58) FIGURE 2. Large-scale BFT tilapia aquaculture at Chambo Fisheries, Malawi using 766m3 tanks capable of producing 100 tonnes of tilapia with a consumptive water use of 150L/kg of fish. FIGURE 3. BFT R-ended grow-out tank field at Chambo Fisheries, one of the world’s largest BFT tilapia fish farms in Malawi with a production capacity of 800 tonnes per annum. TABLE 1. Solid wastes, nitrogen (N) and Phosphorus (P) waste discharge per short ton or metric tonne of tilapia produced in cage culture, RAS and BFT aquaculture systems in units of pounds per ton (lbs/ton) and kilograms of waste per tonne of fish producced (kg/tonne). Culture Solid wastes, Nitrogen, N Phosphorus, P Feed Ref. environment lbs/ton (kg/tonne) lbs/ton (kg/tonne) lbs/ton (kg/tonne) Conversion kg/tonne lbs/ton kg/tonne lbs/ton kg/tonne lbs/ton Ratio, FCR Cage culture, 1041.6 2531.3 45.0 109.4 14.3 34.8 1.60 Neto and Ostrensky (2013) 18% feed losses RAS*1, 5% feed losses/ 470.8 1168.4 38.9 94.5 10.7 26.0 1.33 Kourie (unpublished) inefficiencies BFT*2, 20% of DE*3 289.7 704.0 7.3 17.7 6.8 16.5 1.09 Kourie (2017 d) derived via floc grazing Notes: *1 RAS, Recirculation Aquaculture System *2 BFT, Biofloc Technology *3 DE, is Digestable Energy
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