Energy and EROI
"The prosperity and stability of modern society is inextricably linked to the production and consumption of energy"
"Today, fossil fuel resources are among the most important global commodities and by their large energy surplus are essential for the production, distribution and con- sumption of the rest. Globally fossil fuels supply greater than 75 percent of the total energy consumed by society (Hall et al. 2009, Hamilton, 2009). The prosperity and stability of modern society is inextricably linked to the production and consumption of energy, especially oil (Hall and Klit- gaard, 2012). While many less developed nations still depend largely on biomass even there oil is critically important for transportation and often agriculture."
~ Lambert et al. 2013
"High EROI fuels allow a greater proportion of that fuel′s energy to be delivered to society ... Conversely, lower EROI fuels delivers substantially less useful energy to society."
Our research and that of Dale (2010) summarizes EROI estimates for the thermal energy delivered from various fossil fuels and also the electric power generated using fossil fuel and various renewable energy technologies. These initial estimates of general values for contemporary EROI provide us with a beginning on which we and others can build as additional and better data become available. We have fairly good confidence in the numbers represented here, in part because various studies tend to give broadly similar results when the boundaries are similar. Values from different regions and different times for the same fuels, however, can give quite different results. Given this, we present these values with considerable humility because there are no government-sponsored programs or much financial support to derive such numbers. Nevertheless we see a broad if not precise consistency in the analysis collectively that give us confidence in the general results.
~ Lambert et al. 2013
The “Net Energy Cliff” (figure adapted from Lambert and Lambert, in preparation and Murphy and Hall, 2010, concept courtesy of Nate Hagens and Euan Mearns). As EROI approaches 1:1 the ratio of the energy gained (dark gray) to the energy used (light gray) from various energy sources decreases exponentially (Murphy and Hall, 2010). High EROI fuels allow a greater proportion of that fuel′s energy to be delivered to society, e.g. a fuel with an EROI of 100:1 (horizontal axis) will delivers 99 percent of the useful energy (vertical axis) from that fuel to so- ciety (Murphy and Hall, 2010). Conversely, lower EROI fuels delivers substantially less useful energy to society (e.g. a fuel with an EROI of 2:1 will deliver only 50 percent of the energy from that fuel to society). Therefore, large shifts in high EROI values (e.g. from 100 to 50:1) may have little or no impact on society while small variations in low EROI values (e.g. from 5 to 2.5:1) may have a far greater and potentially more “negative” impact on society (Murphy and Hall, 2010).
Oil and gas EROI values are typically aggregated together. The reason is that since both are often extracted from the same wells, their production costs (capital and operations) are typically combined, and therefore the energy inputs for EROI calculations are very difficult to separate. Probably the EROI for gas alone would be much higher because typically gas is used to push and pull more valuable oil through formations.
Oil and Gas
The EROI for global petroleum production appears to be declining over time, but obtaining reliable data on global petroleum production can be very difficult since most production is from national oil companies, whose records tend not to be public. However, Gagnon et al. (2009) was able to generate an approximate global EROI for publicly traded oil and gas companies using the “upstream” financial database maintained and provided by John H. Herold Company. These results indicate an EROI for publicly-traded global oil and gas of approximately 23:1 in 1992, 33:1 in 1999 and 18:1 in 2005 (Hall and Klitgaard, 2012). This “dome shaped” pattern seems to occur wherever there is a long enough data set, perhaps as a result of initial technical improvements being trumped in time by depletion.
US Natural gas appears to have had two “peaks” in production. The first peak occurred in 1973 as the largest con- ventional fields peaked and declined. Sub- sequently, US “unconventional” fields de- veloped to a second peak in recent years (Sell et al. 2011). New technologies such as horizontal drilling and hydrofracturing, are currently keeping the total production levels of non-conventional plus conven- tional natural gas production at the same or similar rates achieved previously by conventional natural gas alone.
Although it is difficult to predict future production technology, environmental issues, consumption patterns and changes in EROI, it appears that coal may be abundantly available through the next century. The EROI for coal production in the US declined from 80:1 to 30:1 by the 1980s, but returned to 80:1 by about 1990 (Cleveland, 1992). This pattern reflects a shift in the quality and location of coal extracted, the technology employed in the extraction process and especially the shift from underground to surface mining.