A multi-criteria decision framework for evaluating refinery oily sludge valorization in red ceramics

This study develops a multi-criteria decision framework for the comparative evaluation of refinery oily sludge (ROS) valorization in red ceramics. Laboratory-scale ceramic specimens containing 0, 5, and 10 wt% ROS were fired at 950°C and 1050°C. Water absorption (WA), flexural strength (FS), and thermal conductivity (TC) were integrated with study-specific indicators of clay saving (CS), water saving (WS), and theoretical ROS energy contribution (REC). ROS incorporation increased WA and reduced FS relative to the reference specimens, while the thermal response depended on formulation and firing temperature. The resource efficiency indicators increased with ROS content, but REC represents a theoretical calorific contribution and not a directly measured electricity saving. Under the baseline, equal weight, and sustainability priority scenarios, 10 wt% ROS fired at 950°C ranked first. Under the baseline, equal-weight, and sustainability priority scenarios, 10 wt% ROS fired at 950°C ranked first globally. Mechanical priority weighting instead favored the 0 wt% reference fired at 1050°C, whereas durability priority weighting favored the 0 wt% reference fired at 950°C. Thus, no alternative was universally optimal and the preferred formulation temperature combination depended on the decision priorities. Thus, no alternative was universally optimal: the preferred option depended on the decision priorities. The weighted sum model is transparent but compensatory, and the resulting CSI values are comparative decision support scores rather than evidence of compliance with a specific product class or a complete environmental sustainability assessment.