Source of non-renewable energy are found to be accumulated in nature over a very long time and cannot be quickly replaced when exhausted at their origin place. Coal, natural gas, petroleum, nuclear energy, etc. are the sample example of it.
->Fossil fuels
plants and animals, which dead millions of years ago, got buried beneath the earth. They got covered under clay and sand, which prevent oxygen of air from reaching the remnants of the dead plants and animals. due to high temperature and pressure inside the earth, those dead bodies got decomposed in the absence of oxygen. This result in the formation of coal and petroleum. They are fossil fuels.
why it is non renewable?