Leveraging technology
Without the restrictions of markets, technology can be applied more liberally to solve human problems.
Much of the technology already in existence is under-utilised due to high prices. For example, there is ample technology available to create almost completely automatic farms, yet it is rarely applied. Vertical farming and hydroponics offer unique opportunities to produce food with minimal ecological footprint, yet there are very few in existence due to prohibitive construction cost.
When the question of applying technology changes from 'how much will it cost?' to 'how much do we need it?', technology will immediately be applied in the places where it is needed most. For example, in sustainable food production, ocean cleaning, energy production, sustainable transport systems, etc.