Greenness score

Solvent and Process Greenness Scoring and Selection Tools... 

As an example, when determining a solvent s environmental waste score, data are obtained to first score the solvent based on its environmental performance or impacts when it is incinerated, recycled, or undergoes biotreatment. A fourth score is calculated based on the solvent s VOC emissions when handled or used in a process. Some of the data used to determine the basic impact scores include solvent physical property data, waste generation estimations, and ease of operability (in the case of treatment methods). The geometric mean of the four impact area scores yields the environmental waste score. The scores are calculated on a l-to-4 scale and subsequently normalized on a 1-to-lO scale. 10 represents the greenest score and 1 is the least green score for this method [9]. 

Table 3.7 Greenness scores for commonly used solvents at GSK (adapted from reference [9]).

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... 

Table 3.8 Solvent greenness scoring index scores and GSK SSG comparison.

Solvent Environmental impact-Solvent Greenness Scoring Index Environmental impact-CSK SSG... 

Attribution of a greenness score to each principle (scale 1/3, from minimum to the maximum value of greenness) following criteria defined from the hazard scores of substances and the reaction conditions (table score of hazards/scores of principles ). 

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