BillyBB is correct, but a certain amount of energy corresponds to a minute, fixed amount of mass irrespective of how the energy is generated.
So if a spring releases the same amount of energy as burning acetylene, then the spring will lose some mass and this loss in mass will be the same as the difference in mass between the acetylene and its combustion products,
Sorry, jno, I don't understand your question. Are you comparing the present Earth with the pre-historic Earth when there were no people?