In his 1865 book, The Coal Question, William Jevons, a British economist, first raised the issue of finite coal reserves and, therefore, limited energy resources as well as the relation between economic growth and energy consumption. Today, and 150 years after Jevons' book was published, we find ourselves in the same position, questioning the availability of resources but with added environmental and ethical concerns. It is no surprise that the world's energy demand is increasing exponentially given the rapidly growing global economy. According to the World Energy Outlook report prepared by the US Energy Information Administration (EIA), the world marketed energy consumption is expected to grow by about 50% from 2007 to 2035.
The concept of sustainability has evolved over the last few decades. It has shifted from merely representing the availability, efficient use and security of resources to a more ethical notion that considers environmental impact. Although individual countries may still put energy security at the top of their agenda, they now realise the need for a collective global effort to reduce the emission of greenhouse gases, to tackle the problem of climate change.
The consumption of energy to drive the world's economy is not environmentally harmless. Apart from renewable and nuclear energy, all other energy resources contribute, in one way or another, to climate change and air pollution. The undeniable damaging effects of the use of fossil fuel to generate power on the environment have contributed to a shift towards more environmentally friendly plans, especially in Western economies. If the world's reliance on fossil fuel continues to increase, carbon dioxide emissions due to the use of fossil fuel, which comprised about 57% of the total emissions of greenhouse gases in 2004, will increase, too. On the other hand, and according to the International Panel of Climate Change (IPCC), carbon dioxide emissions should be reduced by 50-85% by 2050 to ensure that the global average temperature does not increase more than two degrees.