3.3 Weighting
An important function of the program EATOS is to identify weak points for the improvement of the quantitative material flows by revealing the claiming of resources and the arising of waste per product unit. This is possible already by the input described already: material input and environmental factor E (waste [kg] / product [kg] are indicated in the graphic result representation.
The other important function of the program is the inclusion of the used substances‘ quality in the evaluation of a chemical synthesis. The substance specific characteristics of the materials involved determine the potential environmental relevance and its threat to the human being. For evaluating and examining chemical syntheses as well regarding these aspects, the quantitative material flows are weighted with their qualitative characteristics according to a program-internal algorithm. The more problematic a substance is the more stronger its share in the mass balance is presented. This is made by multiplication of the substance quantity with a substance specific weighting factor , shortly indicated as „Q“. This substance specific weighting factor Q can take values between 1 and 10 and, in doing so, among other things, it optionally composes of human toxicity, eco-toxicity, ozone creation potential, and so on. By clicking the toolbar WEIGHTING (see, e. g., Figure 5) (or via EDIT), the user gains access to the weighting categories (Figure 22), which mostly correspond to those from the life cycle assessment and are represented with one or more impact categories.
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Figure 22 Weighting categoriesThe user selects the register sheets of the weighting categories desired, and to the substances used at the synthesis (given: no., name, type), he inputs the corresponding substance parameters, which act as impact categories for these weighting categories. Thereby, the human toxicity, e.g., is represented by the work place threshold value (MAK, Maximale Arbeitsplatzkonzentration) and the ecotoxicology by the WGK-value (Wassergefährdungsklasse). You revert to alternative substance parameters as, e.g., the hazard sign or the LC50-value, if MAK-value, resp., WGK-value, do not exist.After clicking the toolbar FREE, you can select directly single substances and make inputs in the COMMENT field, to explain substance parameters in detail and/or to make indications of resources concerning the data. In doing so, the toolbar FREE changes into FIXED. Clicking this toolbar once again produces the previous status FREE again, so that in the comment field the specifications to the substances appear, where the cursor is situated atop . To the substances imported from the substance list with complete data set (chapter 3.6.2), the substance parameters are available already, so that they must not be input once more. Therefore, we recommend to export newly entered substances with their complete data set into the substance list (chapter 3.6.1), so that they will be available for later applications in other investigations and simply can be imported. In this way, by the set up of a data bank in form of a substance list, a convenient utilization of the program EATOS becomes possible, because the data of a substance must be input once, only!
Totally, there are 13 weighting categories: two refer to the input of the synthesis, the others refer to the output (except for the product). The material balance is represented in form of a column diagram . Therewith, the columns lean against two of the key figures defined by R. A. Sheldon (‚Consider the environmental quotient‘, CHEMTECH 1994, 3, 38 – 47) – the selectivity ‚S‘ and the environmental factor ‚E‘. The selectivity S is the weight-related ratio of product and substrates, i.e., a degree for the effectiveness in converting the substrates to the product desired. In accordance to this key figure, an inverse selectivity (S-1); also indicated as mass intensity or mass index, resp., is defined which, indeed, takes into consideration as well all additional input materials besides the substrates. The exponent S-1 indicates that, on the contrary to the selectivity S, not the relation of the product to the input materials but the reversed relation is determined:
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