Kinds of fuel

Wood is the oldest fuel and people still use it. Fuels made from plants and other living things are called biofuels. Charcoal is made from wood. Some plants can be made into liquid fuels for engines. The energy in these fuels came from the Sun, and the supply is renewed when new plants grow. So they are renewable fuels. But they need careful management: many trees grow only a few centimetres in a year, so cutting trees faster than they grow leads to deforestation. Fossil fuels are different. Coal formed mostly from ancient plants. Oil and natural gas formed mostly from tiny sea living things. Their remains were buried under mud and rock for millions of years, and heat and pressure slowly changed them. Petrol is made from oil. Fossil fuels take so long to form that we use them far faster than they form. They are nonrenewable.