An EROEI intro from a certain Euan Mearns:
http://euanmearns.com/eroei-for-beginners/
If we lived in a society with a single global currency (the EJ) and without taxes or subsidies, then money may represent a fair proxy for ERoEI although distortions would remain from the different efficiencies with which that money (EJ) was spent. However, in the real world, different currencies, interest rates, debts, taxes and subsidies exist that allow the thermodynamic rules of the energy world to be bent, albeit temporarily. We are at risk of exchanging gold for dirt.
That's right, and many of the points raised in the guide support what I've been saying across two threads. Other sources include Charles Hall, Ugo Baldi (whose Seneca Cliff is similar to the Net Energy Cliff shared by Mearns), and more. For another interesting video intro, try Martenson, who refers to the three "E"s that essentially make up the context of this issue: the economy, the environment, and energy:
The gist is that the global economy is primarily dependent on energy: to get more energy, to make goods and services that will use that energy, and energy to be used for both basic needs and wants.
It is those basic needs and wants and meeting them that make up the economy, and to make transactions smoother, we use credit to trade energy, goods, and services. In addition, we use credit to speculate on all sorts of things to create even more credit.
The type of economy in which these take place is generally free-wheeling. That is, people lend, borrow, produce, sell, buy, and work and invest to earn as they please, and given competition, they make decisions based on what is most profitable. There are regulations that limit what they do, but because regulators are also dependent on funds from the same people, then they tend not to impose too many regulations.
Given the desire to maximize earnings coupled with competition, more credit is eventually concentrated among fewer people, who eventually control that economy and want to gain even more credit. Everyone else wants to earn more as well so that they can buy and use more.
Meanwhile, population increases due to lower infant mortality rates and more prosperity, while more prosperity leads to lower birth rates. But because there are large numbers of poor people worldwide, then population continues to increase, together with more energy and resources needed for that population and more energy and resources per capita as more people want basic needs and more.
That "more" was achieved through cheap energy, which is what the world had for some time, e.g., only a barrel of oil needed to get a hundred from the ground. But because the same planet from which resources are extracted is limited, then in time more energy is needed to get more resources, then the same amount of resources, then fewer resources.
More credit can be created to get more resources, which is what happened with shale, but in the long run, that only leads to increasing debt (which is what credit essentially is) and doesn't reverse the amount of energy needed to get more resources. Hence, diminishing returns, which affects not only resources extracted but even the energy needed to extract resources.
Meanwhile, as more resources are used, then more pollution takes place, with more carbon emissions. Couple that with chemical and air pollution, soil damage, etc., then the environment is damaged and resource availability is hampered. With that, the economy is also affected.
Thus, in order to maintain that capitalist economy, a lot of cheap energy (i.e., high energy return) will be needed to meet basic needs and wants of a growing population and growing resource demand per capita. In order to counter diminishing returns which affect energy return and extraction of resources, then additional energy is needed. To deal with environmental damage (including the effects of climate change), then energy on top of that.