Have you ever opened up an interior wall? Do you know what that space in there is called? "Shelf space"

You have lots of space for groceries inside your inner walls. Most wall studs are made of 2x4s. If you removed the wall surface and replaced it with panelling (probably on a frame or solid sheet -- I'm not a carpenter), with hinges on the inside of one edge and an invisible spring-activated latch on the other. Just push it with your palm and a panel opens, showing you the studs, which you've carefully spaced to make more shelves.

Standard 2x4s are 3.5" wide. Regular vegetable cans are almost 3" in diameter. You could stack cans from floor to ceiling and it would be easily accessible for rotating. An area covered by one sheet of panel-covered plywood would provide about 24 linear feet of storage space if your 'shelves' were 14" apart. If you stacked the cans, you'd have room for maybe three times that, or approximately 285 cans of food. That's not a bad start, is it?

What if you had two panels?

Sue