Circular Economy and Resource Efficiency in Waste Paraffin Refining: A Process Optimization Framework for Secondary Raw Material Recovery

The transition toward circular and resource-efficient industrial systems requires effective strategies for recovering secondary raw materials, reducing resource losses, and improving the environmental and economic performance of industrial processes. This study examines waste paraffin refining as a circular resource recovery process and develops an integrated framework for improving resource efficiency, process stability, and product quality. An empirical–analytical case study was conducted in a Polish paraffin refining enterprise using process mapping, Ishikawa analysis, Failure Mode and Effects Analysis (FMEA), Critical to Quality (CTQ) analysis, Statistical Process Control (SPC), and process capability analysis. The results indicate that the heterogeneity of waste paraffin, inappropriate sorbent selection, insufficient process standardization, sampling limitations, and filtration instability are the main factors affecting process performance. Color and optical purity were identified as critical quality attributes. The historical analysis reported Cp = 1.18 and Cpk = 0.86 under the company’s operational color-score range of 24–30 points. These values are reported historical estimates whose underlying batch-level observations could not be independently re-examined; the measurement system has not been independently validated. The operational range should not be interpreted as an independently validated bilateral product specification, particularly because the upper value of 30 may represent the endpoint of the company-specific scoring scale. To improve resource utilization and reduce nonconforming production, an integrated improvement framework was developed incorporating standardized sampling, a sorbent selection matrix, in-line color monitoring, and SPC-based real-time monitoring. A deterministic illustrative scenario was used to examine the potential effect of assumed improvements in process centering and variability. Under the assumed parameters, Cp and Cpk increased from the reported current-state values of 1.18 and 0.86 to 1.67 and 1.39, respectively. These values are conditional analytical results, not empirically observed post-implementation outcomes. The assumed parameters were not estimated from production data collected after implementation, and the effectiveness of the proposed interventions remains to be verified under industrial operating conditions. The proposed framework illustrates how integrated quality management, statistical control, process monitoring, and digitalization may support more systematic management of waste-paraffin refining and secondary-resource utilization. The study indicates how process-level optimization may support circular resource flows by improving the management and control of waste paraffin as a secondary raw material. The proposed approach may contribute to reducing nonconforming production and improving resource utilization, although these effects require quantitative industrial validation.