from this year. So the question about whether the traditional energy sources can
cover our future energy demand is certainly not an easy one to answer. Much
of the optimism regarding new oil exploration is further complicated by the
locations and extraction methods necessary to make it protable. In recent years
the "fracking miracle" in the US has been put under scrutiny and independent
researchers claim that the future production levels from some of the new US
tight oil and shale gas sites are grossly overestimated 18. While these sites are
certainly rich in resources, the total cost of extraction is dicult to assess. From
an environmental point of view, hydraulic fracturing and horizontal drilling are
highly controversial methods, requiring large amounts of water and chemicals.
The methods may, among other eects, cause signicant contamination of water
supply as well as air pollution 19. From an economic point of view, the energy
return on (energy) invested, EROI, for tight oil and shale gas resources are far
lower than for the more traditional oil wells. EROI is a ratio of how much a unit
of input energy will return as output 20. This ratio must be above 1 for any
feasible process, regardless of market value of the product. The decreasing EROI
for oil is partly due to the "easy oil rst" approach, but also to the technical
advances over time allowing for oil to be found and extracted almost anywhere.
In gure 1.9 EROI ratios are shown for the dierent resources.
Figure 1.9: A bar plot of calculated Energy Return on (Energy) Invested, EROI,
for various energy sources. The EROI numbers are taken from 21.
These values are taken from Murphy and Hall (2010) 21 but as the authors
note, EROI ratios are complex and can vary signicantly dependent on the research
group or organization behind the calculation. However, it is clear that
the energy return for oil and gas has decreased over time and is now approaching
the values found for wind turbines. In fact, the more recently discovered