Integrating Lean Six Sigma and Life-Cycle Assessment approaches for sustainable manufacturing of fertilizers

The utilization of fertilizers in contemporary agriculture is of paramount importance, given their capacity to enhance crop productivity. However, fertilizer manufacturing is a very energy-consuming activity that also emits harmful substances, thereby impacting the environment. In this article, we propose the integration of Lean Six Sigma and Life-Cycle Assessment methodologies to guide fertilizer manufacturers toward a more sustainable fertilizer production. We applied this approach in a case study with a Spanish fertilizer producer. A comparative study of its environmental performance was undertaken to quantify the benefit of applying Lean Six Sigma principles to achieve reduced variability in product compositions, optimized raw material use, and improved process performance. We also assessed the environmental impact of four waste treatment scenarios for the wastewater and solid waste generated in the manufacturing process. Our results showed that the improvements obtained by the application of Lean Six Sigma resulted in a reduction of the environmental impact by 8.6%, mostly driven by a lower use of copper sulfate. The best waste treatment scenario was determined to be composting of the solid waste and wastewater recovery. Human carcinogenic toxicity accounted for nearly half of the total environmental impact of fertilizer production. Furthermore, the reaction process was found to contribute the most to the overall environmental impact due to the use of ethylenediaminetetraacetic acid. It is expected that this study will motivate fertilizer manufacturers, as well as the chemical industry in general, to adopt methodologies like Lean Six Sigma and Life-Cycle Assessment to make their processes more sustainable.