Life cycle inventory improvement in the pharmaceutical sector: Assessment of the sustainability combining PMI and LCA tools

Pharmaceutical chemicals are complex, high value added products that typically impose significantly greater impacts on the environment per kilogram compared to basic chemicals. A variety of green metrics have been developed to guide the design of chemistries and processes that are more sustainable. Among these, Process Mass Intensity (PMI) was selected by the American Chemical Society Green Chemistry Institute Pharmaceutical Roundtable as the key parameter to express sustainability. However, researchers were concerned that these metrics could miss relevant factors that would be addressed by a more comprehensive Life Cycle Assessment (LCA). Lack of inventory data for many chemicals poses a significant barrier to more extensive implementation of LCA for pharmaceuticals. A cradle-to-gate LCA of Viagra™ is used to present a practical approach to construct inventories using patent and literature data. Details of the improved inventory data were presented for four chemicals to illustrate the methodology and highlight the importance of considering out-sourced processing of reagents used in pharmaceutical synthesis. A more comprehensive impact assessment was conducted using ReCiPe v1.11 at both midpoint and endpoint levels. A comparison of two synthesis routes rated them well against results from the simpler green metrics. An area for future work is to address the lack of characterization factors for toxicity and other impact categories for many chemicals.