(677a) Measuring Renewability: A Mass Efficiency or E Factor Approach?

The E factor measures how much waste a process generates whereas Mass Intensity (MI) or its inverse, Mass Efficiency (ME), focus on resource utilisation. Conventionally their relationship for a single-product process is expressed as:

E = MI ? 1, and ME = 100 / MI

but the formulas are misleading because the metrics measure quite different things. We believe that ME and MI are more useful in driving forward the Green Chemistry debate as it enables chemists and engineers to identify alternative approaches that can deliver pharmaceutical products with a lower environmental footprint, as the focus is on efficiency instead of on waste. Some advantages of the ME (MI) based approach are reviewed in this presentation.

For instance, analyzing resource utilisation can help to identify opportunities to increase the proportion of renewable resources used, both as feedstock and as energy carriers, and in general to develop processes with reduced life cycle impacts.

GSK have developed a life cycle approach using the FLASCTM tool, which is based on the resources used in a process, and then incorporates the life cycle impacts from the manufacture of all the materials used. Therefore the hidden impacts from bought-in starting materials are incorporated. These impacts are often ignored in other approaches when in fact they may be significant (analogous to the visibility of an iceberg).

A life cycle approach that accounts for both mass and energy can be used to identify and quantify ?resource renewability'. This goes beyond the conventional concepts based on ?oil equivalents and it is a further enhancement of ME (MI) that will be described. Trade-off between impacts will also be reviewed

Focusing on mass efficiency enables chemists and engineers to incorporate renewability assessments that include material and energy impacts into process analyses, which is not possible when only the impacts of waste are considered.