Energy

The game world gets its energy from vegetable sources.

After various forms of slave labor (incl. domesticated animals), the inhabitants skipped petroleum to power their vehicles and went straight to biofuels, primarily vegetable oil. The diversion of farmland to production of oil crops for fuel led to resource wars for arable land. These diminished somewhat with the development of algaculture. They're like real-world Qingdao, except on purpose.