Efficiency Metrics

Informed by the above efforts, eco-efficiency metrics were further refined for application at the operational level through the sustainability metrics work of the American Institute of Chemical Engineers (AIChE, www.aiche.org/cwrt/... 

Basic Eco-Efficiency Metrics. The above eco-efficiency categories can be captured by a small number of metrics. For illustration, let us consider the set of basic metrics adopted by BRIDGES to Sustainability (Schwarz et al., 2000, 2002), shown in Table 6.2. Informed by the work of NRTEE (1999) and WBCSD (Verfaillie and Bidwell, 2000), the metrics were chosen as ratios. Impacts are placed in the numerators and a measure of output is in the denominator. The denominator can be mass or other unit of product, functional unit, sales revenue, monetary value-added, or a certain measure of societal benefits. Expressing the metrics as ratios allow them to be compared and used in weighing decision alternatives and comparing operational units. Defined in this manner, the lower metrics are better as they reflect lower impacts per unit of value generation. 

Land use is not shown among the basic metrics in Table 6.2 and represents a category that is less developed and may not fit into the impact-per-unit-output format of the other eco-efficiency metrics. IChemE (2002) proposes a land use metric expressed in terms of total area of land occupied and affected per annual revenue. However, heuristics and decision-rules for the land use metric, especially in relation to impacts on biodiversity and the ecosystem, require further development. 

While eco-efficiency is certainly an important element of sustainability, it is by no means a representation of the whole picture. Although not as well developed as eco-efficiency metrics, separate sets of social and economic metrics of sustainability have been developed, such as by IChemE (2002). Table 6.4 lists examples of social metrics developed by IChemE, which capture a variety of workplace... 

In the today s economic and social environment, Chemical Process Industries are asked to discover innovative solutions that are not only economically efficient, but also sustainable. Production-integrated environmental protection implies that ecological issues are included in the conceptual design methodology. Besides economic efficiency, metrics for ecological and sustainability performance must be included in assessing the quality of a design solution. 

For systems like a production machine, the minimum work required for the corresponding process can be employed to identify the efficiency of the process (Gutowski and Sekulic 2011). Comparison between this theoretical energy with the real required energy serves as energy efficiency metric of the process. 

The names, symbols, and definitions of strategy efficiency metrics used are listed in the following. 

SPECTACULAR EXAMPLES OF SYNERGY BETWEEN STRATEGY AND MATERIAL EFFICIENCY METRICS... 

Lift To Drag Ratio Ratio of the lift to drsg in cruise the aerodynamic efficiency metric for transport aircraft and gliders. 

---