In his book "Small Is Beautiful" E F Schumacher made the point that energy is fungible for almost everything else, and therefore energy is the starting point of

In his book "Small Is Beautiful" E F Schumacher made the point that energy is fungible for almost everything else, and therefore energy is the starting point of the economy. It's worth keeping that in mind any time you see a headline with the words "It could feed billions." We have many, many technologies that could feed billions, given enough energy. With enough energy, we could grow food in a greenhouse, 24 hours a day, 365 days a year, which means the growing "season" would suddenly be 400% longer (an extra 6 months of the year, an extra 12 hours of the day). Therefore, all questions of growing food are really questions of acquiring energy.