"Energy return on investment (EROI) is the ratio of the energy
extracted or delivered by a process to the energy used directly
and indirectly in that process." Aggregation and the Role of
Energy in the Economy from Ecological Economics 32 (2000)
301–317 by Cutler J. Cleveland, Robert K. Kaufmann, Center for
Energy and Environmental Studies and Department of Geography,
Boston University, 675 Commonwealth Avenue, Boston, MA 02215,
USA and David I. Stern, Centre for Resource and Environmental
Studies, Australian National Uni6ersity, Canberra ACT 0200,
Australia Methods for investigating the role of energy in the
economy involve aggregating different energy flows. A variety of
methods have been proposed, but none has received universal
acceptance. This paper shows that the method of aggregation has
crucial effects on the results of the analysis. We review the
principal assumptions and methods for aggregating energy flows:
the basic heat equivalents approach, economic approaches using
prices or marginal product fo