The management of solid waste is currently seen as one of the most important concerns that national authorities, particularly in south Europe, must address. In recent years, emphasis has begun to be paid to Construction and Demolition Waste (CDW) being the largest waste stream in the European Union that is produced by renovation and repair work on buildings, roads, bridges, and other constructions made of bulky materials such as asphalt, bricks, wood, and plastic. Many EU countries responded quickly as a result of the large amounts of such waste and the presence of hazardous substances in their composition. This study illustrates the anticipated outcomes of several CDW management strategies other than final disposal, such as recycling, reuse, and incineration, for a public-school building in Greece. In order to assess how well the chosen schemes performed in terms of various environmental criteria, the SimaPro software suite and the Ecoinvent v.3 Life Cycle Inventory database were used. In order to enhance the quality of the outcomes, inventory data from earlier studies were also employed as input data for the Life Cycle Assessment tool.

In the current research, the valorization of olive mill solid waste as beneficial admixture into clay bodies for developing greener ceramic materials with lower thermal conductivity, thus with increased thermal insulation capacity towards energy savings, is investigated. Various clay/waste mixtures were prepared. The raw material mixtures were characterized and subjected to thermal gravimetric analysis, in order to optimize the mineral composition and maintain calcium and magnesium oxides content to a minimum. Test specimens were formed employing extrusion and then sintering procedure at different peak temperatures. Apparent density, water absorption capability, mechanical strength, porosity and thermal conductivity were determined on sintered specimens and examined in relation to the waste percentage and sintering temperature. The experimental results showed that ceramic production from clay/olive-mill solid waste mixtures is feasible. In fact, the mechanical properties are not significantly impacted with the incorporation of the waste in the ceramic body. However, the thermal conductivity decreases significantly, which can be of particular interest for thermal insulating materials development. Furthermore, the shape of the produced ceramics does not appear to change with the sintering temperature increase.

The growth kinetics and the lipid and protein content of the microalgal species Chlorella sorokiniana (CS) grown heterotrophically in growth media containing glycerol and increasing amounts of anaerobic digestate (AD) equal to 0%, 15%, 30%, and 50% was studied. The effect of the AD on the fatty acid (FA) distribution of the bio-oil extracted from the CS, as well as on the fatty acid methyl ester (FAME) properties such as the saponification number (SN), the iodine value (IV), the cetane number (CN), and the higher heating value (HHV) was also estimated. The percentage of AD in the growth medium affects the rate of carbon uptake. The maximum carbon uptake rate occurs at about 30% AD. Protein and lipid content ranged from 32.3–38.4% and 18.1–23.1%, respectively. Fatty acid distribution ranged from C10 to C26. In all AD percentages the predominant fatty acids were the medium chain FA C16 to C18 constituting up to about 89% of the total FA at 0% AD and 15% AD and up to about 54% of the total FA at 30% AD and 50% AD. With respect to unsaturation, monounsaturated FA (MUFA) were predominant, up to 56%, while significant percentages, up to about 38%, of saturated FA (SFA) were also produced. The SN, IV, CN, and HHV ranged from 198.5–208.3 mg KOH/g FA, 74.5–93.1 g I/100 g FAME, 52.7–56.1, and 39.7–40.0 MJ/kg, respectively. The results showed that with increasing AD percentage, the CN values tend to increase, while decrease in IV leads to biofuel with better ignition quality.

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.

Microalgae cultivation offers promising opportunities for wastewater bioremediation and the production of high-value bio-based products; however, the environmental sustainability of existing technologies remains under evaluation. This study presents a cradle-to-gate life cycle assessment of a lab-scale Chlorella vulgaris cultivation system in Northern Greece using food industry wastewater, operated in a 5 L photobioreactor. Primary data were assessed using the ReCiPe 2016 Midpoint (H) method across 17 impact categories, with a functional unit of 1 kg dry-weight biomass. The cultivation stage was the main environmental hotspot, contributing 63% of Global Warming Potential (135 kg CO₂ eq.), and over 50% of impacts across most of the selected categories, driven mainly by electricity demand for continues artificial lighting. Compared to a reference system using urban wastewater, cultivation in industrial wastewater showed lower impacts in 12 of 17 impacts categories, due to its nutrient-rich medium. Compared to clean-water cultivation with synthetic nutrients, the analyzed system performed better in 16 of 17 categories. A scale-up sensitivity analysis demonstrated that replacing continuous artificial lighting with industrial-scale lighting strategies reduces cultivation-stage Global Warming Potential by up to 96%, confirming that the system’s high energy intensity reflects its operational scale rather than a characteristic of the technology. The system demonstrates potential for decentralized wastewater management, supporting the EU Wastewater Treatment Directive. Its integration with industrial wastewater valorization represents a circular nutrient-reuse approach aligned with industrial symbiosis and circular bioeconomy principles. Addressing a gap in the Greek context, this work provides a benchmark for sustainable practices in the Mediterranean region.