Fossil Fuels & The Energy Transition

The quiet fact about fossil fuels is their energy density. A kilogram of wood holds about 16 megajoules; coal, up to 32; oil, over 40 — and oil is liquid, the most convenient energy carrier ever found. That concentration is what physically made the modern world: the steam engine needed cheap coal to beat charcoal, the internal-combustion engine needed portable liquid fuel, and twentieth-century farming runs on natural gas turned into fertilizer. What we call industrial civilization is, in large part, the practice of finding and burning ever more buried sunlight — and in 2024 roughly 80% of all human energy still comes from it.

The striking thing about earlier energy transitions is that none of them was really a transition. Coal did not replace wood — Britain burned as much wood in 1900 as in 1700, and simply added coal on top. Oil was added to coal, gas to oil; each new fuel opened new uses, grew the economy that demanded energy, and left the older fuel still doing its old job. Total consumption has risen more than fiftyfold since 1750 precisely because nothing was ever retired. The climate target now asks for something with no historical precedent: the first energy transition that is genuinely a substitution, fossil use falling toward zero rather than being diluted by something newer. That is why the problem is hard in a way cost curves alone don't capture. The same energy density that built the system now resists its unwinding — a liter of gasoline carries more than ten times the energy of a liter of battery, which is why aviation, shipping, and high-temperature industrial heat have no easy electric substitute. Oil and gas also store themselves, cheaply and indefinitely, while renewable electricity must be actively banked; the pipelines and refineries already built represent trillions in capital that wants to be used; and the industry sustains millions of jobs and trillions in annual revenue that will not vote for their own obsolescence. Vaclav Smil reads all this and concludes, in How the World Really Works (2022), that transitions of this scale have always taken fifty to eighty years. The technologists read the same facts and point to solar, wind, and battery costs that have fallen faster than anyone in 2010 dared forecast. Both are arguing honestly from real evidence, which is exactly why the outcome is still genuinely open.