INCOPORATING EXTERNAL COSTS OF GREENHOUSE GAS EMISSIONS INTO LIFE CYCLE COSTING OF WASTEWATER TREATMENT

External costs of GHG emissions are incorporated into the life cycle costing of a wastewater treatment plant, specifically with regard to onsite energy production from biogas. External costs are calculated by including the wastewater treatment plant in an emissions trading scheme and attributing upstream GHG emissions from electricity purchases to the plant. The methodology developed is applied to a small wastewater treatment plant that uses microturbines for on-site electricity generation. The results show that the impact of GHG emissions credits on the costeffectiveness of electricity generation from biogas depends on the price of the GHG emissions credits, the price of electricity, and the GHG emissions rate of the energy sector in the region where the wastewater treatment plant is located. While the capital cost of electricity-generating equipment may be similar across jurisdictions, the external costs will vary and could significantly affect the true life cycle costs.