Certainly they could be at least as sustainable as any grocery store; they’d just need to create more, smaller distribution centers closer to their customers. The DCs can get their supplies locally or via bulk shipments (and sort out recycling on-site) and then assemble the meal kits and add ice for the last mile.

Transporting ingredients in bulk to the DCs is more efficient than transporting a bunch of individually packaged and individually cooked meal kits.