Metrics greenness’ scoring

The solvent parameter and property values used in this method were estimated from several industrial and professional sociehes and government sources. The environmental index for each of the twelve parameters is calculated and normalized on a zero-to-one scale [1]. Depending on whether high or low values for the parameters prove to be greener , Equation 3.7 or Equation 3.8 is used, respectively. In Equations 3.7 and 3.8, x in and x ax are the minimum and maximum value of a specific parameter for all solvents contained within the Solvent Greenness Scoring Index database, Xj is the value of a parameter for solvent i, and Mj is the scaled value of metric M for solvent i [1]. 

To demonstrate the ability of the Solvent Greenness Scoring Index to measure the greenness of a process, consider a hypothetical waste stream which contains 25 kg of four different solvents methanol, DMF, THF, and DGM. First the metric... 

Although the first versions of these metrics were developed from SDS that used risk phrases (R-phrases) and safety phrases (S-phrases), the metrics have been revised to adapt them to GHS, which required a new definition of the criteria to score the hazards and assess the accomplishment of the GC principles. As in GHS the systemization of the hazards in classes and categories, to which hazard statements are assigned (hazard codes or H codes), is more detailed than in the system of the R- and S-phrases, the change provided a finer evaluation of hazards and made easier the construction of the metrics. The revision included also an improvement of the graphic look of the green star to increase the facility of reading the individual scores of the principles. These new versions of the metrics are those discussed in this text. 

The strategy for construction of the metrics will be exemplified here very briefly for the case of the green star when used to evaluate a synthesis reaction. A tool for its implementation can be accessed in the net, in a specific site. The tool calculates the metric automatically upon introduction of the data, by applying the criteria defined in two tables mentioned below (table H codes/score of hazards and table score of hazards/scores of principles ), that are included in it. The site provides also an example of the use of green star that shows the results along the construction of the metric. 

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