Fossil fuels, our starter engine

The fossil fuel deposits of our Spaceship Earth correspond to our automobile’s storage battery which must be conserved to turn over our main engine’s self-starter. Thereafter, our “main engine,” the life regenerating processes, must operate exclusively on our vast daily energy income from the powers of wind, tide, water, and the direct Sun radiation energy. – Buckminster Fuller

I reference this idea often but had forgotten the source. Buckminster Fuller, of course.