Comparison of external costs between dry tomb and bioreactor landfills: taking intergenerational effects seriously

Dry tomb and bioreactor landfills were analyzed with respect to their external costs in an intergenerational cost-benefit analysis in a partial framework which enabled a sounder comparison to be carried out between these two technologies from a socio-economic viewpoint. Obviously, this approach was only a first step for building a comprehensive basis of any environmental as well as fiscal policy in the field of waste management. All external costs are identified and evaluated in three different scenarios, corresponding to a worst case, a best guess and a best case. Obviously, discounting is crucial with respect to an intergenerational perspective. Generation-adjusted discounting (GAD) was applied to take into account equity as well as efficiency criteria, in order to deal with three different types of uncertainties that are decisive in waste policy decisions: a physical uncertainty is captured by introducing our three different scenarios; a macroeconomic uncertainty is taken into consideration by calculating present values using different real growth rates; and a microeconomic uncertainty is taken into account by considering individual peculiarities reflected in their subjective time preference rate. The findings show, that whenever there is a low real GDP growth of less than 1%, the bioreactor is generally superior to the dry tomb (lower present values of external costs). This statement becomes more valid as the growth rate decreases. However, whenever there are high positive growth rates, it is the dry tomb technology which is superior to the bioreactor system.