But what should/could be backing this currency? I suggest the easiest, intrinsically valuable variable, would be Energy.
Very interesting.
Using units of energy as a type of currency makes sense, I've been thinking about this for a while.
And it looks like others have considered this idea as well:
Calories: The Currency of All Economies
Most economists rely on computer printouts of numerical data for their financial planning. By comparing one series of digits with another they can find the immediate trends in the economy and take advantage of those trends. To most people that seems normal. To me it always was, and still is, artificial. I have always wanted to help both people and the environment, and I learned at an early age that knowledge of the economy could be one tool to reach that end. However, I wanted more than just the knowledge of how to generate a positive series of numbers. I was looking for something bigger. I was searching for universal truths. I wanted knowledge about the economy that was constant from year to year, from culture to culture. I wanted knowledge that would be useful to a poor person or a rich person, in our culture, or in any culture. The truths about economics that I found were not in the New York Stock Exchange, but in anthropology and nature.
http://www.sacredlands.org/calcurrency.htm