Fossil Fuels

Coal, oil, and natural gas all start as living matter that died, got buried before it could fully decompose, and then sat under heat and pressure for millions of years. Coal comes from swamp plants, dense forests of trees and ferns that fell into oxygen-poor water, got buried under layers of sediment, and were slowly compressed and cooked into a solid carbon-rich rock. Oil and natural gas come from a different source: dead plankton and algae that settled on ancient sea floors, got buried under mud, and were squeezed and heated over millions of years until their carbon-hydrogen bonds rearranged into liquid and gaseous hydrocarbons. In both cases, the fuel is really just a time capsule of ancient sunlight, stored in chemical bonds.

A coal plant turns that stored energy into electricity through a chain of conversions. Burning coal releases heat, the heat boils water into high-pressure steam, the steam spins a turbine, and the spinning turbine drives a generator that produces electricity. Each handoff loses some energy, mostly as waste heat escaping into the air or cooling water, which is why these plants are never close to 100 percent efficient. A typical coal plant converts only around a third of the fuel's chemical energy into usable electricity.

This efficiency math connects directly to the bigger story of Unit 6: every fossil fuel has an extraction cost, a combustion cost, and an efficiency ceiling, and comparing fuels means weighing all three. Natural gas burns more efficiently and with fewer pollutants than coal, which is why it is often sold as a bridge fuel, but it is still a finite, carbon-emitting resource, and methane lost during drilling and pipeline transport is itself a potent greenhouse gas.