Table 2. Energy returns on investment (EROI) estimates for source production.

                  Process

                           EROI

Oil and gas (domestic wellhead)

         1940s

         1970s


discoveries >100.0

production 23.0, discoveries 8.0

Coal mine (mine mouth)

         1950s

         1970s


80.0

30.0

Coal liquidification

0.5 to 8.2

Oil shale

0.7 to 13.3

Ethanol (sugar cane)

           (corn)

0.8 to 1.7

1.3

Methanol (wood)

2.6

Solar space heat (with fossil backup)

           flat-plate collector

           concentrating collector


1.9

1.6

Electrical production

           Coal

              U.S. average

              Western surface coal

              No scrubbers

              Scrubbers



9.0


6.0

2.5

           Hydropower

11.2

           Nuclear (light-water reactor)

4.0

           Solar

           Power tower

           Photovoltaics


4.2

1.7 to 10.0

         Geothermal

           Liquid dominated

            Hot dry rock


4.0

1.9 to 13.0

From: Cleveland, Cutler J., Robert Costanza, Charles A.S. Hall, Robert Kaufmann. “Energy and the U.S. economy: A biophysical perspective.” (1984) Science, 225:890-897.