Fossil energy, as defined by Nate Hagens, refers to the concentrated, stored energy derived from ancient organic matter that has, over millions of years, transformed into coal, oil, and natural gas. This energy, encapsulated in these fossil fuels, represents a time capsule of prehistoric solar energy, originally harnessed by biological processes such as photosynthesis. Hagens emphasizes that fossil energy is not merely a convenient power source but a finite, non-renewable inheritance, the exploitation of which has driven unprecedented economic growth and development over the past two centuries. He highlights that our dependency on this form of energy has profound ecological and societal implications, as it underscores a critical transition point for humanity to find sustainable alternatives and rethink long-term resource management.

See also: fossil fuel, fossil carbon, fossil hydrocarbons, nuclear power, nuclear fuel