Earth

Fossil fuels

Modern industrial society consumes high quantities of energy for heating, transport and industries. The main energy sources are natural fuels, and in particular fossil fuels. Fossil coals originate in the subsoil from plant material that come from ancient forests, subject to chemical and physical processes for millions of years. During that period plant material looses hydrogen, oxygen and nitrogen, but acquires carbon, therefore increasing its heating value. The younger coal, which still has a relevant content of water, is called peat. Anthracite, instead, has a high content of carbon and a high heating value. The process that leads to carbon enrichment continues until graphite is formed. Graphite is a mineral consisting only of carbon. These fuels are typical of lands that originated 280 – 350 million years ago (Carboniferous period), as the previous period had been characterized by the growth of large forests with wooden trunk.Hydrocarbons, instead, are a particular type of organogenic rocks and result from the decay of organisms without oxygen. These substances accumulate on porous rocks and can be present in solid (bitumen), liquid (oil) and gaseous (natural gas) state. They are very light materials that move up to the top through permeable rock layers. When a rock layer hampers their movement, they accumulate and form a deposit.