To undertake MCA, decision-maker or stakeholder community preferences are elicited and used to assign a relative importance or weight to each criterion. This can be done on an individual basis or through focus groups.
Typically, the weighting of each criterion is achieved by assigning a numerical value that reflects the relative importance of that criterion. For this framework, the decision maker is guided to allocate points to each criterion from a total pool of 100 points. The derivation of these weights may vary in sophistication from individual preference selection and is not within the bounds of this study. Weighting is conducted across assessment types and within the assessment for assessment criteria.
Monetary valuation of impacts is typically sought by decision makers and often in preference to scientific or other recognised units (Philpott and Partl, 2006).
Two monetary valuation approaches that have been used for CBA of Waste Management (NPCC, 2001 and DEC, 2005 by Nolan-ITU) and (ZWSA, September 2007 by BDA) adopt a similar approach to European methods (Danish Topic Centre on Waste and Resources, 2005) and conduct step wise assessment involving firstly, the quantification of pollutant and resource loads in an inventory and subsequent load valuation by benefits transfer of published valuations using established techniques in environmental economics. Application of these almost mirror image methods has delivered entirely different valuations of landfill disposal due to the range of pollutants included within the analysis. Trace contaminants have been held accountable for the major portion of the environmental cost of waste treatment options (Philpott, 2009).
The valuation of these pollutants, although conducted using an internationally acknowledged scientific assessment method for the benefits transfer, proved controversial in a recent national review of waste management (Productivity Commission, 2006). The method, developed by the Centre for Environmental Studies CML at Leiden University, the Netherlands (Simapro, 2002) was already known to produce inconsistencies for a small number of organic pollutants including Benzene (Grant pers comms, 2007). The distortion brought forward when this method was adopted for the extrapolation of economic values does not reflect on the validity of economic valuation techniques nor on the suitability of the method for other applications.