Estimations of very long-term time series of global energy-return-on-investment (EROI) of coal, oil and gas productions
par Victor Court et FLorian Fizaine
(disponible en anglais uniquement)
In the present paper we propose a methodology to assess the global EROI of coal, oil, and gas, from the beginning of their reported production (respectively 1800, 1860 and 1890) to 2011. We first estimate on the same time periods the global time series of the energy prices of these different fossil fuels, the monetary return on investment of the energy sector, and the total energy intensity of the economy. These preliminary results allow us to estimate the historical global EROI of coal, oil and gas productions, and the historical EROI of the global primary fossil energy sector. We find that the maximum EROI of global oil and gas productions have respectively reached the values of 73:1 in 1931 and 200:1 in 1945, which is in line with previous studies that had hypothesized such results. Furthermore, we suggest that the EROI of global coal production has not yet reached its maximum value and that marginal gains are still to be expected in this sector thanks to coming technological improvement. We then present a new theoretical dynamic expression of the EROI of a given energy resource as a function of its cumulated production based on the original work of Dale et al. (2011). Modifications of the original model were needed in order to be able to perform calibrations on each of our price-based historical estimates of coal, oil, and gas global EROI. The calibrations of the theoretical models confirm that the maximum EROI of global oil and gas productions have both already been reached in the 1940’ around 60±15 and180±20 respectively. We then use the theoretical EROI models in a prospective exercise and found that they give very consistent results for oil and gas since their maximum EROI is already passed. Regarding coal, we obtain more different outputs. Even if it is impossible to give a really precise estimation, we think it can be fairly postulated that the maximum coal EROI will occur between 2020 and 2045, around a value of 110(±20).