Critical comparison of methods to determine the energy input for discrete manufacturing processes

High variation can be observed in energy requirement values reported for unit processes as applied in discrete manufacturing. Different methods for determining such values have been suggested, ranging from theoretic energy determination till statistically determined time averaged values based on experimental process measurements. In this paper the theoretic process energy method is compared to results as obtained from two methods suggested for systematic determination of Life Cycle Inventory (LCI) database entries for unit processes. Examples from different process categories are presented to illustrate the discrepancies observed between the approaches and to illustrate the error range linked to the method selection.