The functional unit in the life cycle inventory analysis of degreasing processes in the metal-processing industry

In 1986 degreasing processes in the German metal-processing industry contributed about 70,000 t to the emission of chlorinated C-1 and C-2 hydrocarbons (trichloroethane, trichloroethene, tetrachloroethene, dichloromethane). Measures aiming at the reduction of toxic emissions and ozone depletion potential (ODP) may possibly lead to a shift of environmental impacts towards higher energy consumption, emission of waste water, and Volatile organic compounds (VOC) with photochemical oxidant creation potential (POCP). The present article concerns itself with a life cycle assessment of the three main degreasing processes in order to compare their integral environmental impacts with one another. This is supplemented by presenting the methodology of the life cycle inventory life cycle inventory analysis (LCI). Generally, the applicability of the established LCI method can be shown quite clearly. However, some difficulties arise, especially at the stage of the goal definition, as the use of the process and the functional unit cannot be pinned down as easily and neatly as for most other products. The definition of the use of the process and the functional unit is not as straightforward as for most products. Among the potential functional units identified are the mass of removed impurities, cleaning time, cleaning work, percentage of purity, throughput of parts, loads, mass or surface and virtual coefficients. The mass of removed impurities turned out to be the most suitable parameter for measuring the technical performance of degreasing processes. The article discusses background, purpose, scope, system boundaries, target group, process tree and representativeness of the present study.