I'm a big fan of Costco, but packaging is one area where I'm not sure how well it works out from an environmental footprint perspective. Buying milk? 3 standard cartons in a big cardboard box. Tomatoes? 4 lbs in a cardboard box wrapped in plastic where you would have used the same amount of plastic minus the box at a supermarket. Many of the items they sell are in the standard packaging then packaged in one additional layer of multi-unit packaging. I understand the need for it due to requiring stacking the items in large quantities plus efficiency of checkout and I optimistically hope that supply chain efficiency offsets the additional packaging but I'm not sure what the reality is.