Life Cyle Assessment Based Environmental Performance Comparison of Batch and Continuous Processing: A Case of 4- d -Erythronolactone Synthesis

Continuous processing, as a form of process intensification, is one of the keys of green engineering research and development in the pharmaceutical industry. It has the potential to reduce solvent use and cost of production as well as increase production quality and operational safety. In light of the increased research interest surrounding continuous processing, the goal of this work is to compare the environmental performances of batch (BP) and continuous (CP) processing of 4- d -erythronolactone (4-DEL) at pilot plant scale as case study. The processing systems are evaluated using green chemistry metrics and a cradle-to-gate life cycle assessment (LCA). The processing serves as the case study for this article’s goal. The LCA system boundary includes raw material extraction, transportation, synthesis of 4-DEL (as part of primary pharmaceutical manufacturing), equipment cleaning, plant utilities, and off-site waste management. In order to obtain life cycle inventories to support the LCA study of the BP and CP systems, a modular approach is taken to address their differences. As part of a modular approach, theoretical production campaigns are constructed for the production scale of 49.6 kg of 4-DEL within 5 days; the campaigns account for the time-bounded activities which affects the overall rate of production. The analysis shows that, under the assumptions used, using continuous processing for 4-DEL production has a lower environmental burden compared to batch mainly due to less equipment cleaning and a smaller plant footprint. This is reflected in a 30.1% lower cumulative mass intensity and reductions of various life cycle impacts such as global warming potential (−57.5%), human toxicity (−9.37%), and water depletion index (−41.7%). Sensitivity analysis on equipment cleaning and the consideration of various end-of-life waste treatment options illustrates the need to include them in the system boundary for a fair comparison between batch and continuous.