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Comparison of Costs for a Treatment Wetland vs. a Conventional Wastewater Treatment Plant Using Emergy Analysis


Energy Input (fossil fuel Kcal/gal) Treatment Wetland Treatment Plant

Fossil fuel energy input 3.28 25.3

Natural energy input 3.30 0

Note: The inputs are expressed in equivalent units so that direct comparisons can be made between the different energy types.

Source: Adapted from Mitsch, W. J. 1977. Proceedings of the International Conference on Energy Use Management. R. Fazzolari and C. B. Smith (eds.). Pergamon Press, Oxford, UK.

to-dollar ratio (11,000 coal equivalent calories to the dollar) to calculate the value of the fish in dollars. Thus, fishes are valued at $272 through emergy analysis, while the traditional economic analysis established the value at $20. This is an example of the common result that traditional economics undervalues nature.

Table 8.7 is an example of emergy analysis applied to the wetland option of wastewater treatment. The alternative of treating wastewater in a cypress wetland is compared with conventional technology in terms of two kinds of emergy. The conventional treatment alternative requires more fossil fuel energy and uses essentially no natural energy compared with the wetland alternative. Thus, the rational choice would be to choose the wetland alternative over the conventional technology alternative for wastewater treatment.

109 Fossil Fuel Equivalents

Stress of Estuarine Cooling

109 Fossil Fuel Equivalents

'Cooling) k Water/


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