Reference values for sustainability assessment - Incorporating monetary terms for enhanced decision-support

Abstract

Large-scale infrastructure projects involve substantial investment and have far-reaching environmental consequences. As regulatory standards grow increasingly stringent, for ex ample in the wastewater sector where treatment requirements are continuously updated, developers are often required to upgrade or construct new facilities to satisfy regulatory demands. Decision-making in such settings must account for multiple, sometimes conflict ing, criteria, and multi-criteria analysis (MCA) offers a structured means of comparing alternatives across selected criteria. However, the weighting step within MCA remains susceptible to subjectivity and a lack of transparency and objectivity. This study inves tigated whether integrating reference values, derived from governmental guidelines and accepted industry norms, could support more objective and consistent weighting. The analysis focused on the environmental sustainability criteria: climate impact, energy use as a resource, and nutrient discharge (nitrogen, phosphorus, and organic matter) to re ceiving waters. It further examined the potential of basing weights on decision-makers’ willingness to pay (WTP) for improvements in specific criteria. The conventional MCA weighting-methodology was refined for WTP input and cost weighting. Workshops were conducted to compare conventional percentage weighting with WTP-based weighting, and participants reported greater confidence when relying on reference values rather than subjective estimations. When comparing previous assessments, conventional weighting exhibited wide variations both within and between groups. Weighted score ratios calcu lated from conventional weightings were compared to collected reference values, revealing noticeable inconsistencies. These findings indicate that conventional methods risk in consistency and bias, while WTP anchored in reference data contributes to improved transparency and reliability. Incorporating such reference values into MCA thus offers valuable decision-support, enabling more robust, evidence-based choices in the planning of high-cost, environmentally significant infrastructure projects.