Role of Declining Energy Return on Investment in the Decline of Civilizations
Discussion
From the Wikipedia:
"Energy has played a crucial role throughout human history. Energy is linked to the birth, growth, and decline of each and every society. Energy surplus is required for the division of labor and the growth of cities. Massive energy surplus is needed for widespread wealth and cultural amenities. Economic prospects fluctuate in tandem with a society's access to cheap and abundant energy.
Thomas Homer-Dixon and Charles Hall proposed an economic model called energy return on investment (EROI), which measures the amount of surplus energy a society gets from using energy to obtain energy. Energy shortages drive up prices and as such provide an incentive to explore and extract previously uneconomical sources, which may still be plentiful, but more energy would be required, and the EROI is then not as high as initially thought.
There would be no surplus if EROI approaches 1:1. Hall showed that the real cutoff is well above that and estimated that 3:1 to sustain the essential overhead energy costs of a modern society. The EROI of the most preferred energy source, petroleum, has fallen in the past century from 100:1 to the range of 10:1 with clear evidence that the natural depletion curves all are downward decay curves. An EROI of more than ~3 then is what appears necessary to provide the energy for socially important tasks, such as maintaining government, legal and financial institutions, a transportation infrastructure, manufacturing, building construction and maintenance, and the lifestyles of all members of a given society.
The social scientist Luke Kemp indicated that alternative sources of energy, such as solar panels, have a low EROI because they have low energy density, meaning they require a lot of land, and require substantial amounts of rare earth metals to produce. Charles Hall and his colleagues reached the same conclusion. There is no on-site pollution, but the EROI of renewable energy sources may be too low for them to be considered a viable alternative to fossil fuels, which continue to provide the majority of the energy consumed by humanity (79% as of 2019[91]). Moreover, renewable energy is intermittent and requires large and expensive storage facilities in order to be a base-load source for the power grid (20% or more). In that case, its EROI would be even lower. Paradoxically, therefore, expansions of renewable energy require more consumption of fossil fuels. For Hall and his colleagues, human societies in the previous few centuries could solve or at least alleviate many of their problems by making technological innovations and by consuming more energy, but contemporary society faces the difficult challenge of declining EROI for its most useful energy source, fossil fuels, and low EROI for alternatives.
The mathematician Safa Motesharrei and his collaborators showed that the use of non-renewable resources such as fossil fuels allows populations to grow to one order of magnitude larger than they would using renewable resources alone and as such is able to postpone societal collapse. However, when collapse finally comes, it is much more dramatic.[6][92] Tainter warned that in the modern world, if the supply of fossil fuels were somehow cut off, shortages of clean water and food would ensue, and millions would die in a few weeks in the worse-case scenario.
Homer-Dixon asserted that a declining EROI was one of the reasons that the Roman Empire declined and fell. The historian Joseph Tainter made the same claim about the Mayan Empire."