Wanted a good subject to learn more about OpenComputer programming, this definitely worked.
CompressCobble
Uses a minimal Robot to continually compress Cobblestone, up to Octouple Compressed Cobblestone.
Uses about 83 cobblestone per second, or 7.2 million per day. (If you want more, put four Robots around a Charger, each with its own cobblegen.)
Stores over 225 Octouple Compressed Cobblestone internally before quitting. May optionally be put in chest above Robot for extend run time.
Cheap in power, up to 3 RF per tick. A couple of Solar Panel Upgrades may be enough. You can us