Dimitra Kaffe

The increasing generation of refinery oily sludge (ROS) poses significant environmental challenges due to its high content of hazardous heavy metals, requiring effective stabilization methods. This study investigated the leaching behavior and immobilization efficiency of 31 elements in ceramic matrices incorporating ROS, comparing the toxicity characteristic leaching procedure and European standard (EN) 12457‐2 protocols to evaluate environmental risk. Ceramic specimens were prepared with 0, 5, and 10 wt.% ROS and sintered at 950°C and 1050°C. Leachates were analyzed via inductively coupled plasma mass spectrometry to quantify elemental mobility. Results demonstrated high immobilization efficiency; Cu remained consistently below detection limits (<0.001 mg/kg) in all samples, while Zn concentrations remained stable across both firing temperatures and protocols. Firing temperature significantly influenced Cr mobility; in the EN 12457‐2 protocol, increasing the temperature to 1050°C reduced Cr leaching from 0.529 mg/kg to undetectable levels for 5% wt. ROS content. However, specific variations were observed at higher waste loadings, with Cr reaching 4.590 mg/kg in the 10% wt. ROS samples at 1050°C, suggesting complex phase transformations. Ni was consistently immobilized below detection limits, and Pb showed minimal mobility in isolated cases. These findings confirm that ceramic processing is a viable stabilization technique for ROS, generally reducing metal mobility below regulatory limits. The study concludes that while higher sintering temperatures enhance the matrix stability for most elements through vitrification, the interaction between waste loading and temperature is non‐linear, requiring precise optimization for large‐scale applications.

The increasing generation of refinery oily sludge (ROS) poses significant environmental challenges due to its high content of hazardous heavy metals, requiring effective stabilization methods. This study investigated the leaching behavior and immobilization efficiency of 31 elements in ceramic matrices incorporating ROS, comparing the TCLP and EN 12457-2 protocols to evaluate environmental risk. Ceramic specimens were prepared with 0, 5, and 10 wt.% ROS and sintered at 950°C and 1050°C. Leachates were analyzed via ICP-MS to quantify elemental mobility. Results demonstrated high immobilization efficiency; Cu remained consistently below detection limits (<0.001 mg/kg) in all samples, while Zn concentrations remained stable across both firing temperatures and protocols. Firing temperature significantly influenced Cr mobility; in the EN 12457-2 protocol, increasing the temperature to 1050°C reduced Cr leaching from 0.529 mg/kg to undetectable levels for 5% wt. ROS content. However, specific variations were observed at higher waste loadings, with Cr reaching 4.590 mg/kg in the 10% wt. ROS samples at 1050°C, suggesting complex phase transformations. Ni was consistently immobilized below detection limits, and Pb showed minimal mobility in isolated cases. These findings confirm that ceramic processing is a viable stabilization technique for ROS, generally reducing metal mobility below regulatory limits. The study concludes that while higher sintering temperatures enhance the matrix stability for most elements through vitrification, the interaction between waste loading and temperature is non-linear, requiring precise optimization for large-scale applications.

The increasing generation of refinery oily sludge (ROS) poses significant environmental challenges due to its high content of hazardous heavy metals, requiring effective stabilization methods. This study investigated the leaching behavior and immobilization efficiency of 31 elements in ceramic matrices incorporating ROS, comparing the TCLP and EN 12457-2 protocols to evaluate environmental risk. Ceramic specimens were prepared with 0, 5, and 10 wt.% ROS and sintered at 950°C and 1050°C. Leachates were analyzed via ICP-MS to quantify elemental mobility. Results demonstrated high immobilization efficiency; Cu remained consistently below detection limits (<0.001 mg/kg) in all samples, while Zn concentrations remained stable across both firing temperatures and protocols. Firing temperature significantly influenced Cr mobility; in the EN 12457-2 protocol, increasing the temperature to 1050°C reduced Cr leaching from 0.529 mg/kg to undetectable levels for 5% wt. ROS content. However, specific variations were observed at higher waste loadings, with Cr reaching 4.590 mg/kg in the 10% wt. ROS samples at 1050°C, suggesting complex phase transformations. Ni was consistently immobilized below detection limits, and Pb showed minimal mobility in isolated cases. These findings confirm that ceramic processing is a viable stabilization technique for ROS, generally reducing metal mobility below regulatory limits. The study concludes that while higher sintering temperatures enhance the matrix stability for most elements through vitrification, the interaction between waste loading and temperature is non-linear, requiring precise optimization for large-scale applications.

Agro-industrial residues such as grape marc (GM) and brewer’s spent grain (BSG) present both a waste management challenge and an opportunity for renewable heat production. This study presents a comparative Life Cycle Assessment (LCA) to evaluate the environmental impacts of Grape Marc (GM) and Brewer’s Spent Grain (BSG) combustion for thermal energy production. The functional unit was 1 GJ of useful thermal energy, and harmonized system boundaries were adopted to ensure methodological consistency. Results show that GM consistently outperforms BSG across most environmental impact categories. At the midpoint level, GM exhibits 76.3% lower global warming potential (21.7 vs. 98.5 kg CO₂-eq/GJ), along with substantially reduced terrestrial ecotoxicity, fossil resource use, and air pollutant emissions. Endpoint results confirm these findings, with GM demonstrating 81.4% lower ecosystem damage, 64.9% lower human health impacts, and 77.9% lower natural resource depletion. Key environmental hotspots include biomass moisture content, energy demand for drying, and transport distance. A Monte Carlo uncertainty analysis (1,000 iterations) was performed to assess result robustness, confirming a high probability that GM maintains lower environmental impacts than BSG across major categories. The results support GM as a more sustainable biofuel option within circular bioenergy systems and EU decarbonization strategies.

The increasing generation of refinery oily sludge (ROS) poses significant environmental challenges due to its high content of hazardous heavy metals, requiring effective stabilization methods. This study investigated the leaching behavior and immobilization efficiency of 31 elements in ceramic matrices incorporating ROS, comparing the TCLP and EN 12457-2 protocols to evaluate environmental risk. Ceramic specimens were prepared with 0, 5, and 10 wt.% ROS and sintered at 950°C and 1050°C. Leachates were analyzed via ICP-MS to quantify elemental mobility. Results demonstrated high immobilization efficiency; Cu remained consistently below detection limits (<0.001 mg/kg) in all samples, while Zn concentrations remained stable across both firing temperatures and protocols. Firing temperature significantly influenced Cr mobility; in the EN 12457-2 protocol, increasing the temperature to 1050°C reduced Cr leaching from 0.529 mg/kg to undetectable levels for 5% wt. ROS content. However, specific variations were observed at higher waste loadings, with Cr reaching 4.590 mg/kg in the 10% wt. ROS samples at 1050°C, suggesting complex phase transformations. Ni was consistently immobilized below detection limits, and Pb showed minimal mobility in isolated cases. These findings confirm that ceramic processing is a viable stabilization technique for ROS, generally reducing metal mobility below regulatory limits. The study concludes that while higher sintering temperatures enhance the matrix stability for most elements through vitrification, the interaction between waste loading and temperature is non-linear, requiring precise optimization for large-scale applications.

Conventional clay brick manufacturing is highly resource-intensive, relying on virgin clay, large volumes of process water, and high fossil-fuel-driven firing temperatures (900–1200 °C), posing significant environmental pressures. This study introduces a methodological innovation by valorizing refinery oily sludge (ROS), a hazardous petroleum byproduct, to achieve simultaneous reductions in raw material, water, and energy consumption. Clay mixtures containing 0, 5, and 10 wt % ROS were extruded and fired at 950 and 1050 °C. The optimal 5 wt % ROS substitution reduced process water demand by 25% and firing energy consumption by over 30%, while nearly doubling brick production yield from 5.6 to 9.5 units/kg of clay. Minor color changes and efflorescence were observed, but the mechanical integrity remained unaffected. These findings demonstrate a scalable pathway for the ceramic industry to transform hazardous waste into a valuable resource, achieving integrated environmental and resource savings in line with circular economy and sustainability principles.

Clay brick production is a resource and energy intensive process, relying heavily on virgin clay, process water, and high firing temperatures. This study investigates the valorization of refinery oily sludge (ROS), a hazardous by-product of petroleum refining, as a partial substitute for clay in brick manufacturing. Laboratory-scale experiments incorporated 0, 5, and 10 wt.% ROS into clay mixtures, followed by extrusion, drying, and firing at 950^oC and 1050^oC. The results demonstrated substantial improvements in resource efficiency. Brick yield rose from 5.6 to 9.5 units/kg clay, while water demand decreased by up to 25% due to the sludge’s inherent moisture. Energy consumption during firing was reduced by more than 30% at higher sludge contents, attributed to the calorific contribution of ROS. Although color changes, efflorescence, and stratification were observed, mechanical integrity remained unaffected. The optimum performance was achieved at 5 wt.% ROS, balancing energy savings with material stability. This work provides the first experimental evidence of simultaneous reductions in clay, water, and energy consumption through ROS incorporation, demonstrating its dual role as a raw material substitute and auxiliary fuel. The findings highlight the potential of ROS valorization to support circular economy strategies and enhance the sustainability of the ceramic industry.

Among the wastes produced in a refinery are solids containing water, in particular: (i) bottom sludge accumulated in storage tanks and (ii) sludge agglomerated during the processing of crude oil. Potentially useful industrial secondary resources, co-processed with clays lead to the manufacturing of novel ceramic building products. Among the expected advantages, resulting to industrial symbiosis, is the inclusion of ashes and residual metals from the wastes within the ceramic structure, leading to the inertization of inorganic ingredients, through the thermal processing of clay to building ceramic products.