The reason many standard kitchen refrigerator/freezers work for restoration seed banking is because if they are single-evaporator models, the freezer self-defrost cycle lowers the humidity inside the refrigerator compartment. Stand-alone refrigerators (or dual-evaporator refrigerator/freezers) maintain higher humidity in the refrigerator — good for produce, but bad for seed banking. If you want only refrigerated storage, laboratory-grade or industrial refrigerator units would be ideal. Kitchen refrigerator-freezers should be single-evaporator models in order to lower the humidity inside the refrigerator. The target temperature inside the refrigerator is 5°C and inside the freezer is −20°C, which is in the standard range of most kitchen units.
Ideal specifications for refrigerator-freezers inside a Terraformation seed bank include:
- Reliable brand, self-defrosting with single evaporator (critical for humidity control)
- Upright (standing vertical); either top/bottom (freezer above or below the fridge) or side-by-side (freezer next to the fridge) is OK (without a water/ice dispenser)
- Approximately 500–600 L capacity (18–22 cubic feet)
- Maximum dimensions: 2200 mm (90 inches) height ✕ 800 mm (30 inches) width ✕ 800 mm (30 inches) depth (including the door)
With three refrigerator/freezer units of this size in your seed bank, and when banking seeds of a diverse set of species (where you have a mix of large and small seeds), you can typically bank 8 million seeds or more at any given time.
We recommend using temperature sensors with an alarm system to alert the staff if the temperature goes far from the expected target temperature (e.g., +/− 3°C).