"Energy return on investment (EROI) is the ratio of energy returned from an energy-gathering activity compared to the energy invested in that process ... EROI studies for most energy resources show a decline, indicating that depletion has been more important than technological improvements over time ... Many observers feel that the financial crises we have been experiencing since 2008 are a direct effect of the end of oil production growth (of all liquid fuels if considered on an energy basis) and of the general decline in EROI for most energy sources ... EROI advocates believe that, in time, market prices must approximately reflect comprehensive EROIs ... Obviously to have a modern civilization one needs not just surplus energy, but lots of it—and that requires either a high EROI or a massive source of moderate-EROI fuels ... If the energy and hence economic pie is no longer getting larger—indeed, if because of geological constraints it can no longer get larger—how will we slice it? ...  The abrupt rise and subsequent decline in the proportion of the GDP spent for energy was seen during the “oil shocks” of the 1970s, in mid-2008, and again in 2011. Each of these increases in the price of oil relative to GDP had large impacts on discretionary spending ... This is why each significant increase in the price of oil (and of energy generally) has been associated with an economic recession, and it suggests that declining EROI will take an increasing economic toll in the future ... An economy without enough domestic fuels of the type it needs must import the fuels and pay for them with some kind of surplus economic activity ... [B]efore the oil price increases of the 1970s, the EROI for imported oil was about 25:1 (very favorable for the United States); but this dropped to about 9:1 after the first oil price hike in 1973 and then to about 3:1 following the second oil price hike in 1979 ... As oil prices increased again in the first decade of the twenty-first century ... that ratio declined again to roughly 10:1 ... To some degree we have managed to continue purchasing foreign oil through debt, which gives us a temporarily higher EROI."

Zum Artikel Prof. Charles Hall, erschienen beim Post Carbon Institute (22. Mai 2013) »