The provision of clean, and sustainable, energy supplies to satisfy our ever-growing needs is one of the most critical challenges facing mankind at the beginning of the twenty-first century. It is becoming increasingly clear that the traditional ways in which we have satisfied our large, and growing, appetite for energy to heat our homes, power our industries, and fuel our transportation systems, are no longer sustainable. That this is so is partly due to the increasing evidence that emissions from fossil fuel usage are resulting in global climate change, as well as being responsible for local air pollution. It is also due to the realization that we are rapidly depleting the world's stock of fossil fuels, and replacement resources are getting more and more difficult to find and produce. The problem is made even more acute by the huge and rapidly growing appetite for energy in the developing world, where many countries are experiencing extremely high economic growth rates, leading to equally high demands for new energy supplies. In China, for example, total energy demand has been growing at an annual average rate of 4% in recent years, while in India it has been growing at 6%, compared with just under 2% in the rest of the world.

Global climate change, in particular the prospect for global warming, has put the spotlight on our large appetite for fossil fuels.