Although much of the world still relies on wood for cooking and heating, most of the energy we use comes from highly
concentrated fuels formed from organisms that lived millions of years ago. This reliance on fossil fuels is unsustainable –
cheap, easily accessible oil, coal and gas are running out and their use also releases huge amounts of into the atmosphere, driving climate change and acidifying oceans. Nuclear power, often cited as a climate-friendly alternative, is expensive, relies on exhaustible uranium supplies and poses heavy environmental, health and security risks.