John Michael Greer’s latest blog post has some information for you. Our energy problem and societal decline isn’t occurring only because we are losing net energy rapidly (energy returned on energy invested), global civilization is in rapid decline because all our alternatives to oil are much less energy dense. From the blog post,

What makes fossil fuels so valuable is the fact that the energy they contain was gathered over countless centuries and then concentrated by geological processes involving fantastic amounts of heat and pressure over millions of years. They define the far end of the curve of energy concentration, at least on this planet, which is why they are as scarce as they are, and why no other energy resource can compete with them – as long as they still exist, that is.

As concentrated fossil fuel supplies deplete, in turn, a civilization that depends on them for its survival will find itself in a very nasty bind. If ours is anything to go by, it will proceed to make that bind even worse by trying to make up the difference by manufacturing new energy sources at roughly the same level of concentration. That’s a losing bargain, because it maximizes the amount of exergy that gets lost: you have to disperse a lot of energy to make the concentrated energy source, remember, before you can get around to using the concentrated energy source to do anything useful. Thus trying to fill our gas tanks with some manufactured substitute for gasoline, say, drains our remaining supplies of concentrated energy at a much faster pace than the other option – that of doing as much as possible with relatively low concentrations of energy, and husbanding the highly concentrated energy sources for those necessary tasks that can’t be done without them.