For HVAC and aeration engineers designing gas transfer units in high-density Recirculating Aquaculture Systems (RAS), accurately sizing degassers and off-gas scrubbers is critical. This tool helps you quantify the true biological respiration loads of your system by estimating total CO2 outgassing based on daily oxygen consumption.
By applying the standard ratio of 1.375 grams of CO2 per gram of O2 consumed (a respiratory quotient of 1.0), this calculator provides a foundational metric for designing efficient gas exchange systems, helping you maintain optimal water quality and atmospheric conditions within your facility.
Formula: CO2 = O2 × 1.375
Note: This tool provides preliminary estimations only and is not a substitute for review by a qualified/licensed engineer.
Q: Why does the calculator use 1.375 g of CO2 per g of O2?
A: 1.375 is the mass ratio 44/32: it is what a respiratory quotient (moles of CO2 per mole of O2) of 1.0 gives in grams. Fish typically have an RQ of 0.7 to 1.0, so 1.375 g/g is the conservative value commonly used to size CO2 stripping.
Q: Does this account for non-respiratory CO2 sources in a RAS?
A: No. It converts the oxygen you enter into respiratory CO2: enter the oxygen used by the fish and the heterotrophic bacteria, because nitrifying bacteria use oxygen but consume CO2 rather than producing it. It does not include external alkalinity dosing reactions or CO2 injected directly for pH control, which require separate engineering assessments.
Q: How do I convert the output from kg/day to ppm in my tank volume?
A: A daily production is a rate, not a concentration. Divide the kg/day by the water flow through your degassing unit in m³/day and multiply by 1,000 to get the CO2 rise in mg/L that each pass must remove.
Q: Where should the captured CO2 off-gas go?
A: For high-density systems, off-gas should be sent through a packed bed scrubber or membrane gas exchanger before venting to maintain safe indoor air quality standards for maintenance personnel.