A versatile membrane system for bulk storage and shipping of produce in a modified atmosphere

Modified atmosphere packaging, MAP, employs gas permeable membranes to achieve the specific atmosphere needed to prolong the shelf-life of produce; commercial implementation of this concept is growing for small, disposable retail packages. Membrane technology can also be used to create appropriate atmospheres in reusable large-scale bulk containers for storage and shipping of produce. However, this approach would be more viable if a versatile system were available that could accommodate the requirements of different types of produce without altering the hardware, i.e., one membrane system could be used to create different compositions of oxygen and carbon dioxide, depending on what produce is being shipped or stored at a given time. A scheme is proposed here that uses a selective membrane and a non-selective membrane acting in parallel. The relative amount of gas exchange through the non-selective membrane can be adjusted by varying the volumetric air feed rate to its upstream surface; this will, in turn, adjust the steady-state composition of the gas around the produce. A quantitative model for this scheme and sample calculations are presented to illustrate the concept and how to design such a system where the atmosphere created can be set to the desired range by adjusting the air feed rate.