Fossil Fuels

What are fossil fuels ?

A fuel is any substance used as a source of energy, usually heat energy. Most of the world’s energy is provided by the burning of fossil fuels (化石燃料). Fossils fuels are natural combustible substances formed originally from dead plants and animals. Fossil Fuel (http://www.enviroliteracy.org/fossil_fuels.html)

The major fossil fuels are coal (煤), petroleum (石油) and natural gas (天然氣). Fossils fuels are non-renewable (非再生能源) energy sources. This is because fossil fuels take millions of years to form. Once they are used up they can never be replaced.

World Fuel Resources   Petroleum or Oil Natural Gas Coal Power reserves 130 billion tonnes 158 billion cubic metres 950 billion tonnes Total used in 1990 2.2 billion tonnes 1.5billion cubic metres From the above table, the present world's estimated oil reserves may be used up in the next 50 to 60 years.

Coal

How was coal formed? Coal is the plants that grew in swampy areas about 300 millions ago. The plant grew and died to form layers of decaying material. Heat, pressure and the action of bacteria changed the decaying plants into coal.

How is coal used? Today, about 70 % of the total coal mined is burned in power station. Coal Education (http://www.coaleducation.org/)

Petroleum

1. How was petroleum formed? Petroleum was formed from small sea animals and plants that lived millions of years ago. After they died, heat; pressure; and the action of bacteria changed the remains into oil. The oil formed was then trapped as small drops inside the pores of rocks. Petroleum (http://www.petroleum.co.uk/)

How is petroleum used? The thick crude oil that comes from the ground is a complex mixture of compounds. It is necessary to separate the compounds. (We will discuss this method which is used to separate crude oil in the section 5.2) The separated substances have two main uses: as sources of useful fuels. e.g. petrol as raw materials to make other products. e.g. plastics, detergents.

Natural Gas

Natural gas is found together with oil and sometimes with coal. The gas consists mainly of methane CH4. Natural Gas (http://www.naturalgas.org/) Source : www.naturalgas.org

In some countries, the gas is carried by pipes to homes and factories for heating and cooking.