Structure of energy production and supply The global energy system currently relies mainly on hydrocarbons such as oil, gas and coal, which together provide nearly 80 per cent of energy resources. Traditional biomass – such as wood and dung – accounts for 11 per cent, and nuclear for 6 per cent, whilst all renewable sources combined contribute just 3 per cent. Energy resources, with the exception of nuclear, are ultimately derived from the sun. Nonrenewable resources such as coal, oil and gas are the result of a process that takes millions of years to convert sunlight into hydrocarbons. Renewable energy sources convert solar radiation, the rotation of the Earth and geothermal energy into usable energy in a far shorter time. In the International Energy Agency (IEA) Reference Scenario (OECD, 2008), world primary energy demand grows by 1.6 per cent per year on average during 2006-2030, from 472EJ (11,730Mtoe) to just over 714EJ (17,010Mtoe). Due to continuing strong economic growth, China and India account for just over half of the increase in world primary energy demand between 2006 and 2030. Middle Eastern countries strengthen their position as an important demand centre, contributing a further 11 per cent to incremental world demand. Collectively, non-OECD countries account for 87 per cent of the increase. As a result, their share of world primary energy demand rises from 51 per cent to 62 per cent. Their energy consumption overtook that of the Organisation for Economic Co-operation and Development (OECD) in 2005 (IEA, 2006a).