Green chemistry metrics and life cycle assessment for microflow continuous processing

In this chapter, major green metrics are described as they have been applied to microflow continuous processes (e.g., mass intensity (MI)/process mass intensity (PMI), E‐factor, atom economy, etc.). Thereafter, life cycle assessment (LCA) and life cycle costing (LCC) analysis are reviewed in the framework of their application to evaluate microflow continuous processes. Green metrics, LCA, and LCC allow an objective quantitative measurement and decision support tool to evaluate the ecological, environmental as well as the economic impact of a chemical synthesis and process. Within the approach of green chemistry, continuous microflow processing has become a major method to achieve process intensification and engineering support. Accordingly, the specific sustainability characteristics of microflow continuous processes will be described. A comparison of microscale continuous processes and conventional macroscale processes accompanied by green metrics and LCA will be conducted. This is done in a hierarchical manner, starting from single microflow reaction optimization (both with single and bundled innovation drivers) toward combined microflow reaction separation and microflow multistep reactions. The production volume under consideration is both small (pharma) and large (fine/bulk chemical). This scenario analysis allows one to draw some generic conclusions about the environmental opportunities of continuous microflow technology and, vice versa, on the suitability of these green assessment tools. Each case scenario is for a typical, mostly experimentally validated microreactor application and illustrates the pros and cons of microflow continuous processes in the fine chemical and pharmaceutical industry. The environmental analysis is completed by a snapshot of LCC analysis for these microreactor case scenarios.