[dredmorbius]

My point wasn't that the vast, vast majority of energy available to humans on Earth isn't ultimately nuclear in origin. Just that there are energy potentials in the Universe which aren't nuclear in origin. If you trace back the formation of the Solar System itself, as a generation 3-4 system, even the gravitational potential represented in it originates from nuclear reactions.

The Big Bang (background microwave radiation) and Dark Energy would also come to mind as non-nuclear energy systems.

Not of much practical use to us on Earth, however.