I recently had an idea which would allow you to turn crab shells into gas. (Not car gas, the items bought at Panther International).
Each crab colour could represent each gas type, maybe there could be more gas types too, since there's yellow, and black crab shells to.
So I was thinking, you could have a machine, similar to those at mines. You grab the machine, it shows the crab shells goin' in, out comes gas. The machines could maybe cost 10 or so gralats that way gas isn't free, and the machines could be clearly labelled to show which colour makes which gas. Maybe you could have an amount of gas you'd like to make, but don't want to use all your crab shells. (One crab shell > one gas).
Thoughts?