I farmed microgreens for over two years. William is right about finding the right moisture content for optimum storage. It took some trial and error to get a feel for the right amount of moisture before packing and refrigerating the microgreens for delivery. After washing and running through a salad spinner, I would dry them with a fan and constant attention. For packaging, I used clamshells made of mostly recycled plastic. Unfortunately, I could not find anything more sustainable that was suitable for preserving microgreens. The clamshells don't have holes, but they don't seal like tupperware, so it allows for micro-air flow. My customer's microgreens would last 6-8 days consistently after I mastered the moisture levels.