The Price of Energy Consumption - The Renaissance of Renewable Energy - page 219

6.15 The Energy Cost of Energy Production
A sweet-toothed child drinking soda through a straw will persevere until every last drop
of soda has been drawn from the bottom of the bottle. Leaving aside the impolite noises
that ensue, the child is getting a very low return on energy investment for these final drops.
In the early days of oil, when the first Texas gushers were struck, it took the energy of
one barrel of oil to extract 100 barrels more (Hall and Klitgaard 2012 ) . By stark contrast,
the ratio for deepwater drilling in the Gulf of Mexico today is approximately one in ten
(Moerschbaecher and Day 2011 ) . This ratio is known as energy return on investment
(EROI).

In the 1980s Charles Hall, an ecologist at the State University of New York, went down
to the coast of North Carolina, looking for a place where fish migration could be studied
fromanenergeticperspective.Hemeasuredtheecosystemproductivity(energyavailability
through food) of the freshwater environment and found some very clear patterns: “The
fish would migrate to capitalize on the abundance of energy for the first years of life,
and then the young fish would migrate downstream into a more stable but less productive
environment. The study found that fish populations that migrated would return at least four
calories for every calorie they invested in the process of migration” (Inman 2013b ) . With
this study, Hall was the first to describe and apply the concept of EROI, which has since
been applied to more complex energetic systems.

The EROI of a particular energy source is one of the most valuable indicators of its
viability. As we drill deeper and deeper to reach unexploited oil reserves, we become more
like the child slurping through the straw. For example, the steps involved in mining and
processing tar sands to produce oil are highly energy-intensive. First, the tar-like bitumen
must be separated from the heavy soil. The bitumen is then heated to convert it into crude
oil. Further energy is required to transport it by pipeline and tanker to refineries, to turn the
crude into gasoline or other fuels, and for the final cleanup and land reclamation. However,
the rising investment required to recover conventional crude oil (and its correspondingly
decreasing EROI) is turning unconventional sources of oil and gas into more attractive
energy sources (Dale et al. 2011 ; Inman 2013a ) .

Thereisgreatdivergencebetween theEROIofdifferentenergysourcesandforthesame
energy source over time. Because of their low EROI, some renewables are viable only with
subsidies. At the opposite end of the spectrum, hydropower delivers an EROI of as much
as 260 to 1, making it the most energy-effective of all (see Table 6.3 ) . The reason for this
is that most of the work in a hydropower plant is done by the sun through evaporation and
run-off, and the technology involved is both well established and cost effective.

Table 6.3. EROI of energy commodities from various sources