Respiration Heat Load & The Heat Living Produce Gives Off

Harvested fruit and vegetables are still alive and keep respiring — burning sugars and releasing carbon dioxide, water and heat. That metabolic heat, called vital heat, is given off continuously inside the cold store, so the refrigeration must remove it on top of the field heat carried in at harvest. The respiration heat load is that ongoing heat for your stored mass.

From the respiration rate in mg CO₂ per kg per hour, converted to heat using the energy released per gram of CO₂ (about 10.7 kJ/g CO₂), then multiplied by the stored mass. The calculator returns the heat per tonne, the total heat in watts and the daily heat for your mass — so you can size or check the refrigeration.

Respiration roughly doubles or triples for every 10°C rise (a Q10 of 2–3), so warm produce gives off far more heat than cold produce. That is why fast precooling pays off twice: it both removes field heat quickly and lowers the respiration rate, cutting the ongoing vital-heat load the store has to fight for the rest of storage.

High-respiration crops — broccoli, peas, sweetcorn, asparagus, mushrooms, leafy greens, strawberries — release a lot of vital heat and a big cooling load. Low-respiration crops — apples, potatoes, onions, citrus, nuts — give off little. Enter the respiration rate for your specific commodity and temperature; rates are tabulated in post-harvest references.

No — it is one component. The full cold-store load also includes field heat removed during precooling, conduction through walls and floor, air infiltration through doors, fans, lights, people and equipment. Respiration heat is the steady metabolic part; use the Cold Room Cooling Load calculator to add the other sources for total refrigeration sizing.

Cool the produce fast and keep it at the lowest safe temperature, since respiration falls steeply with temperature. Controlled or modified atmosphere (lower oxygen, higher CO₂) further slows respiration for suited crops. Avoid mixing chilling-sensitive commodities below their safe limit, and remove field heat promptly so the store is not fighting warm, fast-respiring produce.

Enter the stored mass in kilograms or tonnes and the respiration rate in mg CO₂/kg·hr at your storage temperature; results come back as heat per tonne, total watts and daily energy. Watts measure the instantaneous load the refrigeration must match; the daily figure helps with energy and runtime estimates.

Use the Cold Storage Capacity tool to plan how much produce fits, this tool to size the steady respiration heat once it is in, and the Precooling Time tool to remove field heat fast. Together they let you specify a refrigeration system that holds temperature without overloading. The Shelf-Life tool then shows how long that temperature buys you.

They are solid planning figures. Real respiration varies with cultivar, maturity, prior stress, atmosphere and exact temperature, and the heat-per-gram-CO₂ factor is a standard approximation. Use the result to size and sanity-check refrigeration with a margin, and rely on measured store temperatures to fine-tune in practice.