Energy slaves revisited

"If all the energy we currently derive from fossil fuels alone (i.e. not including nuclear or renewables) was suddenly unavailable, and we had at our disposal a few handy nearby planets populated with well-fed healthy adult human males that we could capture as our 'energy slaves', how many of them would we need to allow us to enjoy the same lifestyle currently being provided by fossil fuels?"

Jason Heppenstall ask this question in a recent blog post, where he use, among others my calculations from Garden Earth where I arrive at that we are dependent on somewhere between 120 and 600 billion energy slaves - and that most of our progress and comfort can easily be explained by this. After all, you could live like a nobleman already thousand years ago if you had hundred slaves working for you. The great ancient empires where founded on an agrarian culture where the farm labourer could only feed his/her own family and at the most an equal number of other people, after all 70-80 percent of the population were farming. 

Jason has compiled some other calculations and they differ some, but not radically. Read the rest of his post.  

The point in any case is to give an illuminating perspective of the huge importance the use of energy has for our civilization. It is not the only factor explaining how we can have all those things we have, but it is in my view the single most important factor. And therefore, it is likely that an energy scarce future will have enormous consequences. 

A recent paper in the "Journal of Cleaner Production" U. Bardi. T. El Asmar and A. Lavacchi,  discuss how energy is used in agriculture and how, in the future, we could obtain this energy from renewable sources. The results?

"As you can imagine, it will not be an easy task; but it is not an impossible one, either. As modern renewables (wind and solar) increase in efficiency and come at lower costs, it is perfectly possible to think of integrating them with the agricultural process, first reducing and then fully eliminating the need of locally using fossil fuels." says Ugo Bardi read more