Clean Technologies

In recent years, industrial symbiosis (IS) has gained attention as a strategy to enhance circularity and to reduce the environmental impacts of solid waste management through resource reuse and recovery. Life Cycle Assessment (LCA) is increasingly used to evaluate the environmental performance of such inter-industry collaborations. Given the growing diversity of IS practices and LCA models, this updated review serves as a methodological reference, mapping existing approaches and identifying gaps to guide future research on the systematic assessment of circular strategies. Moreover, it investigates the environmental performance of IS approaches in the field, based on the LCA results of the analyzed case studies. We analyzed 48 peer-reviewed studies to examine how LCA has been applied to model and assess the environmental impacts and benefits of IS in the context of waste management. The literature revealed wide methodological variability, including differences in system boundaries, functional units, and impact categories, affecting comparability and consistency. Case studies confirm that IS can contribute to reducing environmental burdens, particularly with regard to climate change and resource depletion, though challenges remain in modelling the complex inter-organizational exchanges and accessing reliable data. Socio-economic aspects are increasingly considered but remain underrepresented. Future research should focus on methodological improvements, such as greater standardization and the better integration of indirect effects, to strengthen LCA in decision-making and to explore a wider range of scenarios reflecting different stakeholders, analytical perspectives, and the evolution of symbiotic systems over time.

CO₂ emissions from various anthropogenic activities have led to serious global concerns (climate change and global warming), and, therefore, CO₂ capture by sustainable methods is a priority research topic. One of the most widely used and cost-effective technologies for post-combustion CO₂ capture (PCC) is the chemical absorption method, where potassium carbonate solution is proposed as a solvent (with or without the addition of promoters, such as amines). An ecological alternative, presented in this study, is the use of amino acids instead of amines as promoters—alanine (Ala), glycine (Gly) and sarcosine (Sar)—in concentrations of 25% by weight of K₂CO₃ + 5 or 10% by weight of amino acid salt, thus resulting in the so-called green solvents, which do not show high toxicity and inertness to biodegradability. The studies had as a first objective the characterization of the proposed green solvents, in terms of density and viscosity, and then the comparative testing of their efficiency for CO₂ retention from gaseous fluxes containing high CO₂ concentrations. The experiments were performed at temperatures of 298 K, 313 K, and 333 K at atmospheric pressure. The best performance was observed with K₂CO₃ + 5% Sar salt at 313 K, reaching an absorption capacity of 2.58 mol CO₂/L solvent, which is a promising improvement over the reference solution based on K₂CO₃. Increasing the amino acid concentration to 10% generally led to a reduced performance, especially for sarcosine, probably due to an increase in solution viscosity or a possible kinetic inhibition. This study provides valuable experimental data supporting the ecological potential of amino acid-promoted potassium carbonate systems, paving the way for further development of chemisorption processes and their implementation on an industrial scale.

The reaction between polyols and diisocyanates forms polyurethane (PU) adhesives. However, these materials are derived from petroleum-based chemicals, whose availability is declining. As an environmentally friendly, renewable, and formaldehyde-free alternative, tannins offer a promising solution. This study aimed to characterize tannin-based polyurethane (TPU) adhesives modified with bio-polyol, analyze their performance, and determine optimal tannin extract formulation for use as a plywood adhesive, as the first step toward developing eco-friendly TPU adhesives. TPU adhesives were made using modified polyvinyl alcohol (PVOH) and tannins at concentration levels of 0%, 10%, 20%, 30%, 40%, and 50%. The analysis is carried out on raw materials, adhesives, and plywood. The results showed that adding tannin extracts had a significant effect on viscosity, tannin solids content, density, delamination, and dry and wet adhesion strength, but not for moisture content. Functional group analysis (FTIR) confirmed that both liquid and solid TPU adhesives contained urethane, hydroxyl, and isocyanate functional groups. The lowest DMA loss modulus was observed in TPU with tannin 20%. Additionally, the highest adhesion strength was achieved with 20% TPU, which correlated with increased wood failure. Based on these findings, PVOH/tannin 20% was considered an effective formula for TPU adhesives.