2.2 ENERGY SOURCES 33 What kind of products does the petrochemical industry produce from refining crude oil? Russia is home to the world s largest natural gas reserves, around 19% of the world s total reserves, in Siberia. barrel: barile crude oil: petrolio grezzo drilling: trivellazione gas leak: fuoriuscita di gas mining: estrazione mineraria oil spill: sversamento di petrolio turning point: punto di svolta well: pozzo di trivellazione NON-RENEWABLE ENERGY SOURCES Energy is essential to life and all living organisms. Energy choices and decisions impact the Earth s natural systems, so it is essential that we choose between nonrenewable and renewable energy sources carefully. The true cost of energy is more than just money; there are important economic, political and social factors and consequences to consider as well. Fossil fuels Non-renewable energy sources cannot naturally replenish themselves, are limited in supply and cannot be used sustainably. There are three major types of non-renewable sources: oil, natural gas and coal, which are collectively called fossil fuels. Fossil fuels were formed within the Earth from dead plants and animals 400 million years ago, hence the name fossil fuels. They are found in underground layers of rock and sediment. Pressure and heat worked together to transform the plant and animal remains into crude oil (also known as petroleum), coal, and natural gas. Oil Crude oil is a liquid fuel which can be re ned to produce products such as petrol, diesel and various other forms of petrochemicals . The most common method of extraction is drilling and the global production is at the rate of several million barrels a day. Natural gas Natural gas consists mostly of methane and is found near oil deposits below the Earth s surface. Natural gas can be pumped out through the same wells used for extracting crude oil. It is burned to produce electricity, to cook and to heat buildings. It is also used as fuel for natural gas vehicles. Coal Coal is extracted from the Earth by mining. When burned, it releases greenhouse gases. About two-thirds of the coal mined is burned in power stations to produce electricity. Impact on the environment Burning fossil fuels results in the production of carbon dioxide and other greenhouse gases which cause global warming. The risk of oil spills and gas leaks is very high and when such accidents happen, they cause terrible damage to the environment, too. Economic and social aspects While almost every country in the world depends on oil, not all countries produce it. The top ve producing countries are: Saudi Arabia, Russia, the United States, Iran and China. At the current rate of consumption, it is estimated that worldwide oil reserves will be extinguished by the 2050s. However, this problem could also become the turning point which makes us move from oil and utilise renewable resources. 74 Ecology and forEstry