58 MARCH 2026 • WORLD AQUACULTURE • WWW.WAS.ORG aquaculture systems, facilitated by fertilizers and mechanization, has ingrained economic and infrastructural challenges impeding the rapid transition to commercial-scale IAAS today (Pueppke et al., 2020). IAAS simultaneously addresses three critical challenges: 1. Seafood security — sustainably increasing farmed aquatic animal production to offset declines in capture fisheries (Naylor et al., 2000; World Bank Projects, 2025). 2. Nutrient circularity — reusing aquaculture effluents for crop irrigation, thereby reducing fertilizer requirements and improving soil health (Farrant et al., 2021; Liu et al., 2022). 3. Climate mitigation — achieving nearzero discharge, reducing nutrient pollution, and enhancing soil carbon sequestration (Ahmed et al., 2019; Lal, 2004; Bryant, 2015). Contrary to common perceptions, fish farming is a watersparing activity, particularly BFT systems (Kourie, 2017 a, b) (Figures 2 and 3) and RAS (Brown et al., 2024) (Figures 4 and 5) both of which produce reduced waste streams of highly concentrated nutrient emissions well suited for integration into crop irrigation systems. Water productivity is then amplified under IAAS which reuses water sequentially for crop irrigation, achieving zero discharge. Tilapia are an easier fish to produce under IAAS, offering significant food security potential as an affordable protein source and a substitute for many popular whitefish species (Fitzsimmons, 2000; Kumar and Engle, 2016; Kourie and Dladla, 2022). Table 1 provides useful benchmarks for discharged solid wastes (around 50% carbon on a dry matter basis), Nitrogen (N) and Phosphorus (P) emissions reported in both pounds per ton (lbs/ ton) and kilograms per tonne (kg/tonne) of tilapia produced for tilapia cage culture installed into farm reservoirs as well as RAS and BFT tilapia culture, to guide farm planning and the scaling of fish production units. Cost-Sparing Benefits of IAAS: A Quantitative Analysis of Nitrogen Fertilization Substitution The integration of IAAS into irrigated crop farms offers a compelling opportunity to reduce fertilizer costs by substituting synthetic nitrogen inputs with nutrient-rich fish culture effluents. This section presents a detailed cost-benefit analysis using tilapia RAS as a nitrogen source for citrus, apple, and vineyard operations. Case Study: Citrus Orchard Nitrogen Requirements Assume a standard nitrogen (N) fertilization rate of 178.4 lbs N/acre/year (equivalent to 200 kg N/hectare/year) applied to an orange orchard using urea (46% N). The total annual urea requirement per acre is calculated as: For a 49.4-acre (20 ha) citrus farm, the total annual urea requirement becomes: • 19171.4 lbs (8,696 kg) of urea • At a market price of US$646.20/ton (US$712.29/tonne), the annual fertilization cost is approximately US$6,194.00 IAAS Integration: Tilapia as a Nitrogen Source To substitute 50% of the nitrogen requirement using fish culture waste, the orchard would need: • 89.2 lbs N/acre/year (or 100 kg N/ha/year) from fish effluent • Total N requirement from fish: Using Table 1, which reports 94.5 lbs N/ton (39.9 kg N/tonne) of tilapia produced in RAS, the required tilapia production to meet this nitrogen load is: 46.7 tons (51.4 tonnes) of tilapia annually. This IAAS integration would reduce urea usage by half: remaining urea requirement: 193.9 lbs/acre/year (217.4 kg/ha/ year) • total urea: 9,585.6 lbs (4,348 kg) • cost of remaining urea: US$3,097.00 • thus, IAAS integration spares US$3,097.00 annually in fertilizer costs while producing 46.7 tons of marketable tilapia, using the same water volumes already allocated for irrigation. Additional Examples: Apple Orchards and Vineyards • Apple orchard (44.6 lbs N/acre/year or 50 kg N/ha/year): IAAS substitution at 50% N saves US$15.46/acre/year (US$38.21/ha/year). • Vineyard (178.4 lbs N/acre/year or 200 kg N/ha/year): IAAS substitution at 50% N saves US$62.70/acre/year (US$154.86/ha/year). These estimates assume urea (46% N) as the sole nitrogen source and demonstrate consistent cost-sparing benefits across crop types. FIGURE 4. A 10-tonne red hybrid tilapia low pumping head-loss (<100mm), low-energy, all air operated RAS in Lebanon operated at around 368m3 of water use per tonne of fish produced. FIGURE 5. A 50-tonne low pumping head-loss (<100mm), low-energy input, all air operated, marine RAS in Tartous, Syria producing Mediterranean Sea bream (Sparus aurata).
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