In this study, the viability to utilize the residue, obtained from a sewage sludge (SS) and biomass combustion/gasification plant (GR), in cement-based materials was analysed. Two pozzolanic materials were selected to make GR more recyclable: metakaolin (MK) and spent catalyst waste (Z), received from fluidized-bed catalytic cracking process. Functional and environmental properties of standard cement pastes and mortars as well as binary and ternary combinations of GR with MK and Z were assessed. Results showed that enhanced mechanical strength, reduced water absorption and heavy metals release were obtained for compositions when GR was combined with one of the pozzolanic material MK or Z. Microstructural analysis revealed that due to addition of pozzolan the surface of GR particles was covered by a layer of hydration products. In particular, the use of MK led to the formation of more porous layer whereas application of Z tends to the formation of a dense-layered structure on the surface of GR. N₂ sorption results showed that contrary to MK the incorporation of Z into cement composition with GR reduced volume of small capillary pores, and therefore, resulted in lower water absorption and heavy metals release. The obtained results suggest that the application of Z appears to be advantageous pozzolan for the stabilization of SS-biomass gasification residue in cement-based materials.

Landfills pose global challenges, notably in terms of greenhouse gas (GHG) emissions, pollution release, and extensive land occupation. The transformative practice of landfill mining has redefined these sites as valuable resource reservoirs. The fine fraction (FF), often constituting the majority of excavated waste, is currently underutilized but holds the potential for biocover construction to mitigate methane emissions. This study comprehensively analyzes the FF from the Kuršenai landfill, collecting samples from various depths, reaching up to 10.5 m. The most suitable layers for biocover construction were determined based on basic physical and chemical parameters, along with the concentration of heavy metals and microplastics. The findings unveil significant parameter variations across different depths. Moderate–high correlations (ranging from 0.5 to 0.84) between several parameters were observed. The layer at a depth of 4.5–6 m emerged as the most suitable for biocover construction. However, this layer is characterized by elevated microplastic concentrations (30,208 ± 273 particles/kg), posing a challenge for its use in biocovers as microplastics can be released into the environment during FF extraction and biocover construction. Additionally, microplastics become finer with depth, increasing the associated risks. Therefore, a balanced approach considering material properties and pollution concentrations is vital for sustainable waste management practices.

The article reviews the literature on the potential utilization of decommissioned wind turbine blade waste (WTBW) in construction materials, including geopolymers, which are rarely discussed. The review indicates that only the mechanical processing of WTBW creates prerequisites for its possible use as fillers in construction materials; however, adjustments to the composition of binding materials are necessary. Wind turbine blades (WTBs) are usually made from strong and durable composite materials, thus posing serious recycling and environmental challenges. Thermal process methods are promising approaches for recovering glass fibers from thermosets of WTBW through pyrolysis or converting WTBW into fibers via plasma processing. Preliminary durability studies of such recovered and recycled glass fibers have demonstrated their potential application in geopolymers or cement-based materials. Implementing these technologies would expand the waste management system, completing recycling and reuse solutions. To successfully adopt more environmentally friendly solutions, further development of geopolymer production processes and sustainable fiber recovery is recommended.