A thermodynamic basis for evaluating environmental policy trade-offs Thomas P. Seager, Thomas L. Theis Abstract This paper introduces a novel thermodynamic measure of chemical change in the environment called pollution potential, which is defined as the change in exergy of mixing per mole of chemical species in the environment that may be attributed to pollutant releases – equivalent to the ideal exergy per mole required to remove a pollutant from the environment. Because all chemical pollutants may be measured in terms of pollution poten- tial, the methodology described may provide a scientific basis for cross-comparison of disparate environmental impacts such as global warming potential (GWP) and ozone depletion potential (ODP) in a single measure. As an illustrative example, steady-state pollution potentials are calculated for several CFC replacements and a strong correlation between pollution potential and GWP is found for hydrofluorocarbons (HFCs). Although ozone depletion is found to be a significant factor in the pollution potential of CFC-11, for hydrochlorofluorocarbons (HCFCs) the contribution of ozone effects to total pollution potential is minimal. These findings suggest that policies that favor marginal reductions in ODP without regard for other en- vironmental effects (e.g. climate change) may have unin- tended and detrimental consequences. List of symbols B(z,t) exergy of mixing in polluted environment (J/K) C(z,t) concentration (mol/mol) GWP 500 year global warming potential relative to CO 2 H atmospheric column ceiling height (km) k’(z) pseudo-first order reaction rate constant =a exp(–b/T)[OH] (1/s) K z (z) vertical eddy dispersion coefficient (km 2 /s) ODP steady-state ozone depletion potential relative to CFC-11 [OH] hydroxyl radical concentration (molecules/ cm 3 ) R ideal gas constant (J/K mol) S(z,t) configurational entropy in polluted environ- ment (J/K) T(z) absolute temperature (K) m total number of perturbed chemical species in polluted environment N(z) air molar density of the atmosphere (mol/km 3 ) n(z,t) p molar quantity of primary pollutant in envi- ronment (mol) n(z,t) i molar quantity of perturbed species i in pol- luted environment (mol) nz ðÞ 0 p molar quantity of primary pollutant reference environment (mol) nz ðÞ 0 i molar quantity of perturbed species i in ref- erence environment (mol) n(tfi¥) HCFC steady-state HCFC column abundance in pol- luted environment (mol) n total ð Þ 0 HCFC total HCFC column abundance in reference environment (mol) t time y(z,t) molar concentration in polluted environment (mol/mol) y(z) o molar concentration in reference environment (mol/mol) z column height (km) Greek symbols @Bz; t ð Þ @n exergy of mixing per mole in polluted envi- ronment (J/mol) @Bz ðÞ 0 @n exergy of mixing per mole in reference envi- ronment (J/mol) @Sz; t ð Þ @n configurational entropy per mole in polluted environment (J/K mol) Received: 23 January 2002 / Accepted: 7 June 2002 Published online: 1 August 2002 Ó Springer-Verlag 2002 T.P. Seager (&) Civil and Environmental Engineering, Box 5715, William J. Rowley Laboratories, Clarkson University, Potsdam, NY 13699-5715, USA E-mail: seagertp@clarkson.edu Tel.: +1-315-2683856 Fax: +1-315-2684291 T.L. Theis Institute for Environmental Science and Policy, University of Illinois at Chicago, 2121 West Taylor Street M/C 673, Chicago, IL 60612-7260, USA This research was supported in part by a National Science Foundation Integrative Graduate Education and Research Training grant (DGE- 9870646) and an NSF/Lucent Technologies Industrial Ecology Research Fellowship (BES-9873589). Original paper Clean Techn Environ Policy 4 (2003) 217–226 DOI 10.1007/s10098-002-0160-0 217