Environmental quotient

In Chapter 1 the concept of atom economy was discussed as a design tool. Similarly in Chapter 2 the term E-factor was introduced as a measure of the amount of by-products formed per unit weight of product. Unlike atom economy the E-factor is determined from an actual process or can be extrapolated from laboratory work. As a valuable extension to the E-factor concept Sheldon has proposed an Environmental Quotient which is the product of the E-factor and a by-product unfriendliness ... 

To express that it is not just the amount of waste but rather its environmental impact, Sheldon introduced the environmental quotient EQ as the E factor multiplied by an unfriendliness quotient, Q, which can be assigned a value to indicate how undesirable a byproduct is. For example, Q = 0 for clean water, 1 for a benign salt, NaCl, and 100-1000 for toxic compounds. Evidently, catalytic routes that avoid waste formation are highly desirable, and the more economic value that is placed on, for example, the unfriendliness quotient, the higher the motivation to work on catalytic alternatives. Waste prevention is much to be preferred over waste remediation. 

As expected from Table 5.7, this environmental quotient for conventional oxo processes (basis Co catalysts) and for the manufacture of the bulk chemical -butanal is actually about 0.6-0.9, depending on the definition of the term "target" product. The range 0.6-0.9... 

Sheldon, R. A., Consider the environmental quotient, Chemtech, 1994, 24(3), 38-47 Sheldon, R. A., The role of catalysis in waste minimization, in Precision Process... 

Figure 9.1 compares the synthesis of acetophenone by classic oxidation of 1-phenylethanol with stoichiometric amounts of chromium oxide and sulphuric acid, with an atom efficiency of 42%, with the heterogeneous catalytic oxidation with O2, with an atom efficiency of 87%, and with water as the only by-product. This is especially important if we consider the environmental unfriendliness of chromium salts the potential environmental impact of reactions can be expressed by the environmental quotient (EQ), where E is the E-factor (kg waste/kg product) and Q is the environmental unfriendliness quotient of the waste. If Q is... 

The E factor, and derived metrics, takes only the mass of waste generated into account. However, the environmental impact of waste is determined not only by its amount but also by its nature. Hence, we introduced [13] the term environmental quotient , EQ, obtained by multiplying the E factor by an arbitrarily... 

Performance Criteria for Process Schemes, Atom Economy, and Environmental Quotient... 

Examine the list of the 12 principles of green chemistry shown at the beginning of this chapter. Which of these principles relate to the concepts of atom economy, the E-factor, and the environmental quotient Q ... 

Environmental quotient (EQ), which could be considered an extension of the E-factor the environmental quotient [32, 54] assigns an environmental hazardous quotient Q to each kind of waste produced. The amount of waste produced is multiplied by its corresponding factor and the contribution of each waste is aggregated. Examples of application can be found in Heinzle et al. [55] and Roller et al. [56]. 

Environmental Assessment Tool for Organic Syntheses (EATOS), based on the environmental quotient, the computer program EATOS [57] can be used to compare and improve chemical reactions. It expands the EQ by considering the potential environmental impact (PEI) of both waste and reactants [58]. 

All the above metrics are only based on masses of waste they do not take into account the nature of the waste. The necessity of metrics that consider not just the amount of the waste but also its environmental impact was first recognized by Sheldon [9]. To put it in his words Comparing alternative routes solely on the basis of the amount of waste is to grossly oversimplify. So, he defined the environmental quotient (EQ) as the product of the E-factor (E) and an unfriendliness quotient, Q. 

To assess the environmental impact of chemical processes, EATOS can take into consideration up to ten different substances ecotoxicological and human toxicological parameters, and each parameter can be given a different weight. Such substances parameters are then normalized (each parameter is made to vary from 1 to 10) and then combined to afford an environmental quotient (El) (much the same as Sheldon s Q). Thus, each different component of the waste can be assigned a quantitative potential environmental impact PEIout (much the same of Sheldon s environmental quotient EQ), defined as the product of its mass (relative to the product unit mass) with its El. 

Several green metrics have already been proposed and published over the years with perhaps the most well known being the E-Factor described by Roger Sheldon4 as the Amount of waste produced per kg of product. Table 1 shows some typical figures for E from the Sheldon publication. A further refinement suggested in this paper is to use the Environmental Quotient which is the product of the E-Factor and Q, where Q is defined as the unfriendliness quotient (e.g. NaCl, Q=l heavy metal salts, Q=100). 

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