Energy return on investment (“EROI” or “EROEI”) is a measure of the surplus energy to that required to produce the energy. A high EROI provides society with abundant, low-cost energy. This in turn allows the development and sustenance of complex industrial societies. A low EROI provides a restricted amount of energy at high cost. If low enough then industrial societies will not be sustainable.

During the period 1900-1910 EROI on oil production in the US was around 100. Today, US oil EROI is in the 7-11 range, and falling. It is difficult to know the EROI of shale oil but it is conceivably negative. In addition to high cost of production, shale oil is very light and unsuitable for many US refineries. It therefore has to be blended with heavy oil, such as from Venezuela or Alberta, which adds substantially to cost.

Now the average EROI for renewables is below 10, however there is a huge range of estimates, from 50 for hydropower to 1.5 for biomass. In a detailed study of the transition to total renewable energy Capellán-Pérez et. al. (link below) estimate that EROI under 100% renewable energy would be 3 to 5. They conclude that this level would not allow for current society to be sustained. Further, there is doubt that sufficient minerals would be available to make the transition.

Agriculture is notorious for low EROI, often less than 1. It has been estimated that where fertilisers (mainly potassium phosphorus and nitrogen) are used EROI can be as low as 0.1. That is, 10 times more energy is consumed than is produced. This is only sustainable at higher EROI for energy production, at lower levels agricultural production will decline and need to become less energy intensive.

In conclusion, there is little doubt that the future cost of energy will become a major issue for society, without new low-cost sources. In the absence of substantially improved efficiency renewables do not seem to be the answer. Perhaps the answer is that society will need to become less complex and more energy efficient. Of course, in the background is the huge and growing population of the Earth.

 

Dynamic Energy Return on Energy Investment (EROI) and material requirements in scenarios of global transition to renewable energies

by

Iñigo Capellán-Péreza,b,∗, Carlos de Castroa,c, Luis Javier Miguel González

Note; This link is to abstract only, click on Download PDF at top of page for full article.

17 March 2020 Commodities, Macro