It's extraordinary how inventive one can be with ethanol right now.

So the major obstacle to the development of new supplies is not geology but what happens above ground: international affairs, politics, investment and technology.

It's extraordinary how inventive one can be with ethanol right now.

But that's not enough: To maintain energy security, one needs a supply system that provides a buffer against shocks. It needs large, flexible markets. And it's important to acknowledge the fact that the entire energy supply chain needs to be protected.

The world has produced about 1 trillion barrels of oil since the start of the industry in the nineteenth century. Currently, it is thought that there are at least 5 trillion barrels of petroleum resources, of which 1.4 trillion is sufficiently developed and technically and economically accessible.

In a world of increasing interdependence, energy security will depend much on how countries manage their relations with one another. That is why energy security will be one of the main challenges of foreign policy in the years ahead. Oil and gas have always been political commodities.

The bulk of extra supplies that could be put into the market come from two places. One, they come from other Persian Gulf suppliers, of which Saudi Arabia is at the top of the list.