Recirculating Aquaculture Energy-Feed Balance Calculator

Make recirculating aquaculture profitable without guessing the energy bill

Recirculating aquaculture systems (RAS) promise local, year-round seafood with minimal water use. They also carry serious energy loads: pumps, drum filters, biofilters, ultraviolet sterilizers, oxygen cones, and climate controls hum around the clock. Feed remains the largest single expense, but electricity and labor compete closely for second place. This calculator links the biological and mechanical halves of a RAS so you can evaluate whether stocking density, feed conversion, and pump sizing align with your financial targets.

The input block begins with biomass. Enter the total water volume across tanks and sumps, then choose a stocking density. Intensive RAS operations often target 40 kg of fish per cubic meter, though species like tilapia tolerate higher levels. Feed conversion ratio (FCR) captures how efficiently feed becomes fish: a value of 1.25 means 1.25 kg of feed yields 1 kg of growth. Grow-out cycle length controls how long pumps and staff run before harvest; multi-batch systems can adjust the cycle length to mimic continuous harvest.

Daily feed offered ties the biology to operations. Multiplying daily feed by cycle length gives total feed input. Survival rate determines how much of that feed becomes harvestable biomass versus mortalities that require disposal. Harvest price per kilogram reflects your market: premium salmon fetches $8–10/kg, while catfish may sell for $4–5/kg. Feed cost per kilogram is sensitive to protein content; inflation has pushed high-protein diets above $2/kg in some regions.

Mechanical inputs capture electricity demand. Pumps and filtration loads include mechanical filters, degassers, and recirculation pumps. Aeration load accounts for blowers or liquid oxygen systems. Daily heating or cooling energy covers heat pumps, chillers, or immersion heaters needed to maintain optimal water temperature. Multiplying these loads by energy cost per kilowatt-hour reveals daily utility expenses.

Water exchange stays low in RAS, but any percentage of makeup water multiplies across the entire volume. For a 150 m³ system, a 1.5 percent exchange uses 2.25 m³ per day. Enter the cost of water and wastewater discharge. Labor cost per day reflects technician wages and supervisory overhead. Disposal cost per kilogram of mortalities covers rendering or composting fees along with labor for removal.

The math balances inputs and outputs. Let \(F_d\) be daily feed (kg), \(L\) the cycle length (days), \(FCR\) the feed conversion ratio, and \(S\) the survival rate. Total harvestable biomass \(B_h\) equals:

Mortalities total \(B_m = F_d \times L / FCR - B_h\). Energy consumption \(E\) combines continuous loads and daily heating energy:

Here \(P_p\) and \(P_a\) represent pump and aeration loads in kilowatts, while \(E_h\) is daily heating/cooling energy. Water use \(W\) equals system volume times exchange percentage times cycle length. Operating costs sum feed, energy, water, labor, and mortality disposal. Net revenue equals harvest biomass times price. The calculator outputs energy per kilogram \(E/B_h\), feed per kilogram \(F_d L / B_h\), operating cost per kilogram, and resulting margin.

The results panel summarizes these metrics with plain language, including total revenue, total operating cost, and EBITDA-style margin. It also notes whether daily feed input aligns with FCR-based growth; if feed exceeds what biomass can consume at the chosen density, the tool warns you about potential waste and water-quality risks.

The scenario table presents three cases. “Baseline” mirrors your inputs. “Energy squeeze” assumes utility rates jump 30 percent and heating demand rises 20 percent during winter. “Feed optimization” lowers FCR by 10 percent through diet upgrades but increases feed cost by 12 percent to reflect premium ingredients. Each scenario lists energy per kilogram, feed per kilogram, operating cost per kilogram, margin, and water use.

Consider the default numbers: 150 m³ at 40 kg/m³ targets 6,000 kg of biomass. Feeding 120 kg/day over 180 days delivers 21,600 kg of feed. With a 1.25 FCR and 92 percent survival, harvestable biomass reaches about 15,897 kg. Mortalities total roughly 1,381 kg. Pumps and aeration draw 30 kW combined, consuming 129,600 kWh across the cycle; heating adds 14,400 kWh. At $0.11/kWh, energy costs about $15,840. Feed costs $39,000, water roughly $270, labor $46,800, and mortality disposal about $829. Total operating cost is near $102,739. Selling 15,897 kg at $7.80/kg yields $124,003 in revenue, leaving $21,264 in gross margin. Energy intensity is 9.06 kWh per kilogram of harvest, and feed use is 1.36 kg per kilogram after accounting for mortalities.

The comparison table below recaps these figures:

Winter energy spikes erode margin dramatically, while better feed efficiency recovers profits even with pricier diets. The calculator also shows water use at 17 liters per kilogram—far lower than flow-through systems—reinforcing the sustainability case when pitching investors.

Limitations: the model assumes constant stocking density throughout the cycle, ignoring early-stage tanks and grading events. Adjust the daily feed input if you stagger cohorts or use split-pond systems. Energy loads are treated as steady, but actual operations may throttle pumps or oxygen at night. Incorporate duty cycles if you have telemetry data. Finally, the calculator omits capital expenses, depreciation, and financing costs.

Use the CSV export to align feed suppliers, electricians, and bankers. When feed prices climb, input new costs and share the updated margin with investors. If utility companies propose demand charges, simulate higher energy costs to justify installing variable frequency drives or waste-heat recovery. The goal is to answer “How low can we let margin fall before stocking a second species or renegotiating power rates?” With this calculator, you have data ready before the next planning meeting.