Thanks Chris for another excellent review of an important concept. I’ve been thinking about energy budgeting since I saw the chapter yesterday. It seems things are a bit more complicated than you could portray in 15 minutes (as they always are). All of this is conjecture, so I would love anyones feedback or hard data. Here goes:Humans have been supplementing their own energy for a long time. At first it was fire for warmth, cooking and making implements (coal burned bowls, fire hardened sticks). But open fires lost most of their heat to the air, wood took a lot of energy to gather and it could only be used for a few specific tasks. Stoves and ovens helped some, but only addressed one of the issues. Animals came later. They could be used for transportation and certain kinds of work (plowing, etc.). Once again, they required grazing or grains and one person could only manaage a few of them, so they provided limited benefits.
Later innovations included sailing ships (lots of energy available, but it could only be used to transport people and goods over water). Water power was a bit more versatile in terms of manufacturing, but it was available in limited areas.
Fossil fuels changed everything. They could be used to perform just about any kind of useful work and they allowed us to do things at larger and larger scale until a few people could direct huge amounts of labor by amplifying their power through such things as giant combines, freight trains, oil tankers, giant electrical generators, etc.
This brings me to an important point. For oil and other fossil fuels, net energy is not quite so important. Even if we only get 2 units of energy out for every unit in, we can still do huge amounts of work, as long as we can still extract our energy source from the ground quickly enough.
However, I can think of three issues that might still make low net energy a serious problem.
1. The very nature of these energy sources (tar sands, biofuels), makes it impossible to extract energy at anywhere near the rate we are currently using oil, especially considering that we would have to greatly increase our energy use so we would have plenty to invest in getting more energy.
2. So much energy is required to get the energy out that we can’t possibly contain it all in the small part of the globe where the energy is located (imagine turning the Alberta tar sands region into one giant mine/factory).
3. The environmental impacts will be huge.