Page 598 - Environment: The Science Behind the Stories

Calculating Ecological Footprints

Our three conventional energy alternatives vary tremendously 1. How many units of energy would you generate by invest-
in their energy returned on investment (EROI). Examine the ing 1 unit of energy into producing hydroelectric power?
data on EROI for each of the energy sources as provided in How many units of energy would you need to invest
the figure from The Science behind the Story on p. 591, and into producing nuclear power if you wanted to generate
enter the data in the table below. that same amount of energy? How many units of energy
would you need to invest into producing corn ethanol if
you wanted to generate that same amount of energy?

ENERGY SOURCE EROI 2. Based on EROI values, is it more efficient to get petro-
leum from conventional oil or from oil sands? Which
Coal 80
source would you guess has a larger ecological footprint,
Oil and gas (2005)
based on EROI values?
Oil sands
3. Let’s say you wanted to generate 130 units of energy from
Nuclear power
biodiesel. How many units of energy would you need to
Hydroelectric power invest?
Ethanol from corn 4. Based on EROI values alone, which energy sources
Biodiesel would you advocate that your nation further develop?
Wind power Which would you urge your nation to avoid? What other
issues, besides EROI, are worth considering when com-
paring energy sources?

STUDENTS INSTRUCTORS
Go to MasteringEnvironmentalScience for assignments, the Go to MasteringEnvironmentalScience for automatically
etext, and the Study Area with practice tests, videos, current graded activities, current events, videos, and reading questions
events, and activities. that you can assign to your students, plus Instructor Resources. CHAPTER 20 • CONVENTI ON AL ENERGY ALTERN ATIVES

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