Leaded or Unleaded: Considering an Alternative Use of Biogas at the Columbia Boulevard Wastewater Treatment Plant

Abstract

The City of Portland Bureau of Environmental Services (BES) is planning to implement a biogas use project to fully utilize biogas produced at the Columbia Boulevard Wastewater Treatment Plant (CBWTP). Five biogas use alternatives were evaluated to determine which would provide the largest return on investment and demonstrate the sustainability benefits. The alternatives included cogeneration to provide electricity and heat, renewable natural gas (RNG) for vehicle fuel, RNG for industrial customers, and use in biosolids dryers. Using HDR's Sustainable Return on Investment (SROI) methodology, each of the alternatives was evaluated to determine the Financial Return on Investment (FROI) and the SROI. For the SROI analysis a number of environmental and social costs and benefits were monetized in order to establish a comparison of the five alternatives. Financial, social, and environmental cost and benefits were modeled using software simulation to establish risk adjusted cost profiles.