The use of paper sludge as a waste stream from industrial facilities represents a significant environmental challenge due to its quantity and heterogeneous composition. The aim of the study was to evaluate the adsorption characteristics of paper sludge in neutral mine effluents and aquatic solutions of metal ions: Cu(II), Zn(II), Cd(II), and Mn(II). The main novelty of the research is a comparison of the adsorption process in synthetically prepared aquatic solutions and neutral mine drainage from field sampling. The adsorption process of the monitored metals was evaluated in terms of adsorption capacity, parameters of the Freundlich and Langmuir adsorption isotherm, and the separation factor. The adsorption capacity of paper sludge of all metals is significantly lower in neutral mine drainage (NMD) compared to adsorption in aquatic solution. The adsorption capacity of Zn(II) in aqueous solution reaches equilibrium over time, similarly to Cu(II), with values ranging from 0.2 to 1.6 mg/g. For Cd(II), a slight increasing trend in the adsorption capacity of paper sludge is observed at higher initial concentrations (3–5 mg/L) over a contact time of 90–120 min. In general, aqueous solutions of metal ions exhibited higher adsorption capacities compared to NMD, with the highest value recorded for Cu(II) at 4.742 mg/g. As the concentration values in the original solution increased, a decline in K_R (from 268% to 137% at a C0 range of 4–20 mg/L) was observed. In the mine drainage with the addition of Zn(II), K_R values were also lower compared to those in aquatic solutions. The reduction in K_R became more pronounced with increasing initial concentration, showing a decrease of 29.9% to 38.9% at C0 levels ranging from 2 to 10 mg/L. The separation factors for Cu(II), Zn(II), and Cd(II) were lower in NMD, indicating better metal separation from real mine waters. The results confirm the potential of paper sludge as a low-cost adsorbent for the treatment of heavy metal contaminated waters.

In the construction sector, there is a shift towards environmentally conscious practices that prioritize the minimization of environmental burdens. In this study, we dealt with a cradle-to-gate life cycle assessment (LCA) of a wood–aluminum window in two software tools. SimaPro (PRé Sustainability) and Sphera LCA for Experts (formerly known as GaBi) were selected. The results from both software tools were compared to assess the output uniformity of the two selected tools. The results indicate the similarities and differences in the software tools. The most similar results were achieved for impact categories Photochemical Ozone Formation (1.1% difference), Human Toxicity, cancer (total) (3.6% difference), Climate Change (3.7% difference) and for Resource Use, fossils (4.5% difference), respectively. On the other hand, the results were most different in the impact categories Ozone Depletion (84.7% difference), Resource Use, minerals and metals (75% difference), Ecotoxicity, freshwater—inorganics (35.6%) and Ecotoxicity, freshwater (total) (31.2%), respectively. The differences in the LCA results between SimaPro and GaBi were analyzed in-depth and were mainly attributable to using different databases in the transportation process and due to different system boundaries in some processes, with the Ecoinvent data containing significantly more background processes and inconsistencies in the implemented characterization factors.

The aim of our contribution is to evaluate the possibilities for the biochemical utilization of paper wastes. We tested aerobic and anaerobic degradation of paper waste sludges from a plant that processes recycled paper. Testing included the assessment of phytotoxicity. We can conclude that the concentration of paper sludges did not have toxic effects on the bacterial consortium of the anaerobic or aerobic conditions. However, the leachate of paper sludges and water from sludge dewatering had a slightly negative effect on the germination of cress (Lepidium sativum L.) and lettuce (Lepidium sativum L.) seeds where the germination ranged from 83.3% to 100% but the mass yield was higher.

The processing of paper sludge is currently an important environmental topic due to its high global production. The aim of this study is to monitor the biodegradation of paper sludge when the initial conditions change. Biodegradability tests 301F and OECD 311 were used to determine biodegradation. The data obtained from the tests were subsequently obtained for the simulation in MATLAB R2023b. The highest aerobic decomposition was approximately 80% after 28 days at an initial concentration of paper sludge leachate of 76 g/L. By simulating 3D modelling, we can predict that with a retention time of 1 day with degradation under aerobic conditions at the level of 70%, the ideal initial concentration of organic substances will be 157.55 g/L. Based on this model, it is possible to estimate that with a biogas production of 554 m³/t_VS and a decomposition time of 20 days, it is necessary to set a concentration of approximately 128 g/L. Based on biodegradability tests, paper sludge was evaluated as suitable for aerobic or anaerobic biological decomposition.

The growing demand for sustainable waste management practices has prompted interest in the land application of paper sludge as an alternative to landfilling and incineration. This study evaluates the environmental potential of paper sludge derived from recycled hygienic paper production by investigating its effects on soil respiration, seed germination, and seedling development. A comprehensive set of respirometric tests using the OxiTop^® system assessed microbial activity in soil amended with various concentrations of paper sludge (1–100%). Concurrently, bioassays using Lepidium sativum L. and Pisum sativum L. seeds examined the phytotoxicity and physiological response during germination. The results show that low to moderate sludge concentrations (1–20%) stimulated microbial activity and enhanced germination parameters, with a germination index (GI) up to 150% at 1%. However, higher concentrations (>40%) led to oxygen depletion, microbial stress, and decreased plant growth, indicating potential phytotoxicity and the need for application thresholds. For certain intermediate concentrations (e.g., 30–40%), a delay of approximately 21 days before sowing is recommended to allow microbial communities to stabilize and avoid initial stress conditions for plants. This study demonstrates that controlled application of paper sludge in soil systems can serve as a viable and sustainable disposal method, supporting circular economy principles and reducing the environmental burden of paper industry by-products.

Anaerobic digestion represents a promising technology for the recovery of biodegradable waste, including paper sludge. This study experimentally evaluates the influence of temperature and pH on biogas production and the removal efficiency of organic matter, expressed as COD elimination, during the anaerobic digestion of paper sludge from recycled paper. Using a microbial consortium derived from an operational paper mill digester, the experiments simulated realistic process conditions. Previous studies examined the possibilities of using paper sludge. In our research, we focused on the contrasting optimisation of anaerobic digestion of paper sludge (when changing pH and temperature) for energy versus COD removal. The results demonstrated a strong influence of both parameters on the course and efficiency of digestion. The highest cumulative biogas yield (115 m ³ ·t ⁻¹ VS) was obtained at 35 °C and pH 7.5, representing a more than threefold increase compared to 20 °C (28 m ³ ·t ⁻¹ VS). In contrast, the highest COD removal (75.23%) was achieved at 20 °C and pH 6.2, indicating that optimal conditions for maximum energy yield and pollutant removal differ. Low pH values (6.2–6.8), particularly at higher temperature, caused methanogenic inhibition, highlighting the microbial community’s sensitivity to acidic environments. The findings contribute to a better understanding of paper sludge behaviour as a substrate in anaerobic digestion and confirm its potential as a renewable energy source. Modelling results emphasised that maintaining mesophilic temperature and optimal pH control is essential to maximise biogas yield, while extending digestion time under balanced conditions promotes efficient COD reduction.