In the last years, different approaches to measure sustainability performance have arisen [JOUN12, SING12, JAYA10]. For example, the Process Sustainability Index (ProcSI) regards the six clusters: manufacturing costs, energy consumption, waste management, environmental impact, operator safety, and personnel health [LU127]. The methods should be simple and affordable to apply, have low assessment time, and should not rely on user experience. The indicators have to be specified in the period of tracking and calculating (e. g. fiscal year, calendar year, month, etc.), boundaries (e. g. process level, factory level, etc.), and units of measurement [KRAJ03].
It is advisable not to choose too many indicators to keep the analysis manageable [LINK13]. In addition, sustainability indicators should be independent. Indicators should be normalized, which means they do not present their value as absolute amount but show relative terms as a ratio of performance per specific unit of output [OECD12]. A wide variety of factors can be used to normalize performance, such as number, weight or units of products produced in the facility, value added, person-hours worked in the facility, or lifetime of the products produced [SING12, OECD12]. Example sustainability indicators are energy intensity, residuals intensity, non-renewable materials intensity, safety, blood lead level, product costs, etc. For grinding, a smaller set of indicators seems to be useful (Fig. 7.39) [LINK13].