Most of the energy we use comes from burning fossil fuels such as coal or oil. As well as depleting non-renewable resources, it gives off carbon dioxide, which is a greenhouse gas. The alternatives include hydroelectric power, wind turbines, wave power, solar panels, growing biofuels and using geothermal energy. Nuclear power is not normally considered as a type of alternative energy, despite the fact that it doesn't release greenhouse gases.
Shale gas could solve the fuel crisis. But in parts of Europe and America it's been banned over safety fears, and it was blamed in 2011 for a couple minor earthquakes in the UK. Robert Matthews investigates.