Green energy is mostly solar power.

Solar panels are made from processed silicon. Which is essentially sand heated into glass. The barrier to entry for solar power may not be high. The issue behind most major nations of the world not becoming more involved in solar power likely has to do with lack of funding, skilled labor and expertise. Much of the existing technology behind patented solar based intellectual property has its origins in the united states. With production being moved to china in an effort to leverage lower labor costs.

In terms of efficiency, I think the advantage is with green energy given its potential for growth and scaling. Electric motors can reach 80%+ efficiency. While internal combustion engines are usually rated around 15% efficiency. The difference comes from fossil fuels having on average greater energy density as a fuel source.

It could be guaranteed that oil and fossil fuels would not last forever. At some point, we could be forced to abandon them or find alternatives when supply runs out. Perhaps its better to begin the transition now, rather than wait until its too late.