Search Results (133)

The dramatic increase in urban construction waste poses severe environmental challenges. Utilizing waste concrete to produce recycled aggregates (RA) for manufacturing recycled concrete (RC) represents an effective strategy for resource utilization. However, inherent defects in RA, such as high porosity, microcracks, and adherent old mortar layers, lead to significant performance degradation of the resulting RC, limiting its widespread application. Traditional methods for enhancing RA often suffer from limitations, including high energy consumption, increased costs, or the introduction of new pollutants. MICP offers an innovative approach for enhancing RC performance. This technique employs the metabolic activity of specific microorganisms to induce the formation of a three-dimensionally interwoven calcium carbonate gel network within the pores and on the surface of RA. This gel network can improve the inherent defects of RA, thereby enhancing the performance of RC. Compared to conventional techniques, this approach demonstrates significant environmental benefits and enhances concrete compressive strength by 5–30%. Furthermore, embedding mineralizing microbial spores within the pores of RA enables the production of self-healing RC. This review systematically explores recent research advances in microbial mineral gel network for improving RC performance. It begins by delineating the fundamental mechanisms underlying microbial mineralization, detailing the key biochemical reactions driving the formation of calcium carbonate (CaCO₃) gel, and introducing the common types of microorganisms involved. Subsequently, it critically discusses the key environmental factors influencing the effectiveness of MICP treatment on RA and strategies for their optimization. The analysis focuses on the enhancement of critical mechanical properties of RC achieved through MICP treatment, elucidating the underlying strengthening mechanisms at the microscale. Furthermore, the review synthesizes findings on the self-healing efficiency of MICP-based RC, including such metrics as crack width healing ratio, permeability recovery, and restoration of mechanical properties. Key factors influencing self-healing effectiveness are also discussed. Finally, building upon the current research landscape, the review provides perspectives on future research directions for advancing microbial mineralization gel techniques to enhance RC performance, offering a theoretical reference for translating this technology into practical engineering applications. Full article

Fenton oxidation can contribute to meeting effluent standards for COD in actual wastewater treatment plant effluents. However, Fenton oxidation is prone to produce iron sludge waste. The application of heterogeneous Fenton-like systems based on Fenton iron mud carbon in wastewater treatment plants is essential for Fenton iron mud reduction and recycling. In this study, a Fenton iron mud carbon catalyst/Ferrate salts/H₂O₂ (FSC/Fe(VI)/H₂O₂) system was developed to remove chemical oxygen demand (COD) from secondary effluents at the pilot scale. The results showed that the FSC/Fe(VI)/H₂O₂ system exhibited excellent COD removal performance with a removal rate of 57% under slightly neutral conditions in laboratory experiments. In addition, the effluent COD was stabilized below 40 mg·L⁻¹ for 65 days at the pilot scale. Fe(IV) and ¹O₂ were confirmed to be the main active species in the degradation process through electron paramagnetic resonance (EPR) and quenching experiments. C=O, O-C=O, N sites and Fe⁰ were responsible for the generation of Fe(IV) and ¹O₂ in the FSC/Fe(VI)/H₂O₂ system. Furthermore, the cost per ton of water treated by the pilot-scale FSC/Fe(VI)/H₂O₂ system was calculated to be only 0.6209 USD/t, further confirming the application potential of the FSC/Fe(VI)/H₂O₂ system. This study promotes the engineering application of heterogeneous Fenton-like systems for water treatment. Full article

In China, the recycling system for waste tires is characterized by high output but low standardized recovery rates. This study examines the environmental and health risks caused by non-compliant treatment by individual recyclers and explores the barriers to the large-scale adoption of Pyrolysis Technology. A Tripartite Evolutionary Game Model involving pyrolysis plants, waste tire recyclers, and government regulators is developed. The model incorporates pollutants from pretreatment and pyrolysis processes into a unified metric—Carbon Dioxide Equivalent (CO₂-eq)—based on Global Warming Potential (GWP), and designs a Differential Carbon Taxation mechanism accordingly. The strategy dynamics and stability conditions for Evolutionary Stable Strategies (ESS) are analyzed. Multi-scenario numerical simulations explore how key parameter changes influence evolutionary trajectories and equilibrium outcomes. Six typical equilibrium states are identified, along with the critical conditions for achieving environmentally friendly results. Based on theoretical analysis and simulation results, targeted policy recommendations are proposed to promote standardized waste tire pyrolysis: (1) Establish a phased dynamic carbon tax with supporting subsidies; (2) Build a green market cultivation and price stabilization system; (3) Implement performance-based differential incentives; (4) Strengthen coordination between central environmental inspections and local carbon tax enforcement. Full article

A previously pyrometallurgical process, developed to obtain a Pb-Ag alloy and a slag rich in sulfur from the recycling of a mixture of industrial wastes of jarosite and lead paste, was thermodynamically assessed at 1200 °C. The industrial jarosite sourced from a Mexican zinc hydrometallurgical plant corresponded to an ammonium jarosite with a measurable silver content. The specific heat capacity (Cp) of the ammonium jarosite was obtained from TGA and DSC measurements, as well as the thermodynamic functions of enthalpy, entropy, and Gibbs free energy. The Cp was successfully modeled using polynomial regression, with a second-degree polynomial employed to describe the low-temperature behavior. The thermodynamic data generated were input into the thermodynamic software FactSage 8.2 for modeling of the lead paste–ammonium jarosite-Na₂CO₃-SiC system and represented by stability phase diagrams. The thermodynamic assessment of the pyrometallurgical process predicted compounds formed at high temperatures, showing that a Pb-Ag alloy and a slag rich in Na, S, and Fe (NaFeS₂ and NaFeO₂) were obtained. The compounds formed evidence of the effective sulfur retention in the slag, which is crucial for mitigating SO₂ emissions during high-temperature treatments. The experimental compounds, after solidification, were determined by X-ray diffraction measurements to be Na₂Fe(SO₄)₂ and Na₂(SO₄), which reasonably match the thermodynamic assessment. The heat capacity of the ammonium jarosite provides essential thermodynamic insights into the compositional complexities of industrial waste, which are particularly relevant for thermodynamic modeling and process optimization in pyrometallurgical systems aimed at metal recovery and residue valorization. Full article

To facilitate the local recycling of coal mine waste gas and investigate multi-component gas adsorption under high pressure conditions, this study develops a coal nanopore model using molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) methods and simulates the adsorption behavior of coal mine waste gas components (CO₂, H₂O, N₂) under varying pressure levels and gas molar ratios at 353.15 K. We evaluated the adsorption capacity and selectivity for both single-component and multi-component gases, quantifying adsorption interactions through adsorption heat, interaction energy, and energy distribution. The simulation results revealed that the contribution of the three gases to the total adsorption amount followed the order: H₂O > CO₂ > N₂. The selective adsorption coefficient of a gas exhibits an inverse correlation with its molar volume ratio. Isothermal heat adsorption of gases in coal was positive, decreasing sharply with increasing pressure before leveling off. Electrostatic interactions dominated CO₂ and H₂O adsorption, while van der Waals forces governed N₂ adsorption. As the gas mixture complexity increased, the overlap of energy distribution curves pronounced, highlighting competitive adsorption behavior. These findings offer a theoretical foundation for optimizing coal mine waste gas treatment and CO₂ sequestration technologies. Full article

Despite efforts to recycle, boro-alumino-silicate pharmaceutical glass (BASG) results in a significant portion of glass cullet currently landfilled. Highly contaminated fractions of BASG cullet are largely unemployed because of the presence of metals in their composition that prevents recycling. This waste glass can be eligible to produce sustainable alkali-activated materials (AAMs) reducing at the same time consumption of raw materials and CO₂ emissions. The ‘weak’ alkaline attack (NaOH < 3 M) determines the gelation of glass suspensions. Condensation reactions occur in hydrated surface layers, leading to strong bonds (Si-O-Si, Al-O-Si, etc.) between individual glass particles. Alkali are mostly expelled from the gel due to the formation of water-soluble hydrated carbonates. Microwave treatment has been implemented on samples after precuring at 40 °C, saving time and energy and achieving better mechanical properties. To improve the stability and reduce the release of glass components into solution, the consolidated monoliths were subjected to boiling/drying cycles. The chemical stability, cytotoxicity and antibacterial behavior of the final products have been investigated with the purpose of obtaining new competitive and sustainable materials. For further stabilization and for finding new applications, the activated and boiled samples can be fired at low temperature (700 °C) to obtain, respectively, a homogeneous foam or a compact material with glass-like density and microstructure. Full article

Waste wheat straw (WS) is a common agricultural waste with a low acquisition cost and a high annual yield, making it a promising feedstock for a biorefinery. In this work, efficient co-production of reducing sugars and xylo-oligosaccharides (XOSs) from WS was realized through FeCl₃-assisted p-toluene sulfonic acid (PTSA) pretreatment. The effects of reaction conditions (PTSA content, FeCl₃ loading, pretreatment duration, and temperature) on lignin and xylan elimination and enzymolysis were analyzed. The results manifested that the enzymolysis of WS substantially elevated from 22.0% to 79.3% through the treatment with FeCl₃-PTSA/water (120 °C, 60 min). The xylan removal and delignification were 79.7% and 66.6%, respectively. XOSs (4.0 g/L) were acquired in the pretreatment liquor. The linear fitting about LogR₀ with enzymolysis, delignification, xylan elimination and XOSs content was investigated to explain the reasons for the elevated enzymolysis and to clarify the comprehensive understanding of WS enzymolysis through the FeCl₃-PTSA/water treatment. In addition, the recycling test of FeCl₃-PTSA/water manifested a good recycling ability for WS treatment, which would reduce the pretreatment cost and enhance the economic benefit. To sum up, FeCl₃-assisted PTSA treatment of biomass for co-production of reducing sugars and XOSs is an alternative method of waste biomass valorization. Full article

Recycled manure solids (RMS) are increasingly adopted in dairy farming for their economic advantages and their role in improving nutrient recycling and waste management; however, concerns regarding greenhouse gas (GHG) emissions during storage persist. This study assessed the effects of biochar supplementation at 2.5% (2.5B) and 10% (10B) compared to untreated RMS (C−) and acidified RMS (C+) on GHG emissions (measured both continuously and intermittently) and RMS characteristics during a one-month storage period. The results showed that the addition of biochar increased heavy metals concentration (with the exception of molybdenum) and the electrical conductivity of the RMS. Storage of RMS generally led to an increase in its dry matter content, except in the 10B treatment. The results showed that 10% biochar significantly reduced cumulative CO₂ and N₂O emissions, resulting in a 32% GWP reduction compared to untreated RMS. In contrast, the 2.5% dose led to higher CO₂ emissions, possibly due to microbial stimulation. Adding 10% biochar mitigated GHG emissions similarly to H₂SO₄ acidification but with fewer environmental and operational risks, making it a preferable farm-scale option. Continuous monitoring captured transient emission peaks, highlighting the importance of high-resolution assessments. Despite the emissions generated during biochar production, its application in RMS bedding systems offsets these environmental costs by mitigating GHG emissions and increasing nutrient content. Biochar’s mitigation potential, especially at higher doses, presents a safer, multifunctional alternative that aligns with EU climate goals. These findings support the integration of biochar into sustainable manure management strategies, though further research is needed to optimize application rates and assess cost-effectiveness in dairy farming. However, continued assessments at a larger scale and with different biochar addition rates are necessary to fully determine the potential of biochar supplementation to RMS. Full article

Due to the increasing concern about the negative impact of the modern food system and the need to design foods to improve their healthiness and sustainability, in the current study, a fortified cheesecake was developed by using juice, peels, and pomace from prickly pears, which are fruit by-products rich in active compounds. After proper dehydration and being ground to produce a fine powder, some traditional ingredients were substituted with fruit juice and by-products. The water content loss during dehydration and the energy consumed per g of dehydrated by-product were assessed using a proper mathematical approach. A sensory evaluation was carried out using a panel test, thus verifying that the new dessert made with prickly pears was comparable to the traditional one; both recorded high scores of acceptability (sensory score ranged between 8 and 9). The centesimal composition of the two cheesecakes also demonstrated that the ingredient substitution did not affect the energetic value of the final product (290 vs. 248 kcal/100 g); on the contrary, it promoted an increase in carbohydrates (27.38 vs. 26.26 g/100 g), lipids (16.98 vs. 12.94 g/100 g), and total fibers (5.7 vs. 4.2 g/100 g). To demonstrate that the recycling of by-products from prickly pears could represent an advantage from an environmental point of view, a full Life Cycle Assessment (LCA) was carried out. In relation to this, three environmental impact categories, such as Global Warming Potential, Acidification and Eutrophication, which are associated with three different biowaste treatment options—such as composting, landfilling, and recycling—were assessed. The results from the LCA highlighted that recycling always emerged as the most sustainable biowaste management option. For all environmental impact categories analyzed, recycling resulted in an overall environmental saving (−7.63 kgCO₂eq/kg biowaste; −0.116 kgSO₂eq/kg biowaste; and −0.055 kgPO₄³⁻eq/kg biowaste). In addition, the comparison between the traditional cheesecake and the fortified one, in terms of impacts per kg of cheesecake, demonstrated that replacing food items with recycled biowaste may result in a general reduction in emissions and resources. Therefore, this case study represents a valid example of zero-waste production, offering a concrete suggestion as to how processed foods can be redesigned to make them healthier from a more sustainable perspective. Full article

The preparation of new-generation concrete from recycled coarse aggregate (RA) is an effective way to realize the resource utilization of construction waste. However, loose and porous attached mortar leads to RA showing low-density, high-water absorption, and high crushing value. However, carbonation modification treatment can effectively improve the performance of RA. This paper studied the effects of carbon dioxide (CO₂) concentration, gas pressure, and moisture content on the RA physical properties (apparent density, water absorption, crushing value, and soundness) of waste concrete. The results showed that, when the (CO₂) concentration increased from 20% to 60%, the apparent density of RA after carbonation increased by 0.23–0.31%, the water absorption decreased by 0.57–0.93%, the crushing value decreased by 0.36–0.61%, and the soundness decreased by 0.47–0.85%. When the (CO₂) concentration was further increased from 60% to 80%, the apparent density of RA after carbonation was increased by 0.04–0.05%, the water absorption was improved by 0.15–0.31%, the crushing value was reduced by 0.06–0.07%, and the soundness was reduced by 0.09–0.11%. During the carbonation modification process, the performance of RA was significantly enhanced when the moisture content was 3.4% and the dissolution of hydration products was accelerated. The diffusion rate of CO₂ and the carbonation reaction rate decreased with the high moisture content of RA. As gas pressure increases to 0.01 MPa, the physical properties of RA change significantly, because gas pressure promotes the carbonation reaction between hydration products and CO₂ in attached mortar. As the gas pressure increased to 0.5 MPa, RA’s apparent density gradually increased, while its water absorption, crushing value, and stability gradually decreased. The result improved RA’s performance. SEM images show that carbonation modification of RA under different gas pressures increases CaCO₃ in attached mortar, filling the Interfacial Transition Zone (ITZ), and decreasing crack width and number. Gas pressure accelerates CO₂ diffusion and reaction with hydration products, resulting in narrower ITZ and dense mortar. Full article

Multilayer flexible packaging wastes (MFPWs) consist of complex materials composed of multiple plastic films, which are often laminated with aluminum foil, and they constitute a large portion of packaging waste. The use of several polymeric layers is essential to achieve the desired technical and mechanical performance of the packaging; however, this makes layer separation and recycling challenging. Currently, this type of waste is predominantly incinerated or landfilled; non-industrial recycling processes have recently been developed, but they mostly rely on traditional solvent-based treatments, which can be problematic. We present a versatile process for recycling MFPWs using switchable hydrophilicity solvents (SHSs). By treating waste with SHSs through a temperature-controlled process, we efficiently recovered the polymeric layers as sorted transparent films, effectively removing all additives while preserving the original properties of the polymers. Aluminum was recovered as well. N,N-dimethylcyclohexylamine was the best solvent for the delamination of the 26 different packaging materials tested, containing polypropylene, polyethylene, polyethylene terephthalate, and aluminum. The main advantage of this method is the straightforward recovery of the different components that can be efficiently delaminated and easily removed from the solvent, even from highly variable input material. Moreover, by exploiting the CO₂-triggered switchable behavior of the solvent, its purification and recovery can be achieved, maintaining its delamination efficacy over several cycles. Full article

The contamination of soil with arsenic (As) and heavy metal is an increasing global environmental concern. The objective of this study was to rehabilitate soil contaminated with As, Pb, and Zn using fishery by-products as stabilizers to achieve both soil restoration and waste resource recycling. Cockle shells (CS) and manila clam shells (MC), selected as fishery by-product stabilizers, were processed into −#10-mesh and −#20-mesh materials. Additionally, a −#10-mesh material was calcined at a high temperature to produce calcined cockle shells (CCS) and calcined manila clam shells (CMC). Contaminated soil was treated with 2–10 wt% of these stabilizers and subjected to wet incubation for 1–4 weeks. Subsequently, the concentrations of As, Pb, and Zn eluted by 0.1 M HCl were evaluated. Additionally, lettuce was grown in stabilized soil to evaluate the reduction in contaminant mobility. The stabilization treatment results indicated that the concentrations of eluted As, Pb, and Zn were significantly reduced when treated with the −#10-mesh and −#20-mesh CS and MC, and they were rarely detected when treated with the calcined materials (CCS and CMC). The Pb concentration in lettuce grown in the contaminated soil pot exceeded the criterion for leafy vegetables (0.3 mg/kg); however, Pb was not detected in lettuce from the stabilized soil pot. An X-ray diffraction (XRD) analysis revealed that CaCO₃, the main component of CS and MC, was converted to CaO after calcination. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) and SEM elemental dot map analyses revealed that the immobilization of As was related to Ca–As precipitation and the immobilization of Pb and Zn to the pozzolanic reaction. Thus, recycling and processing CS and MC as stabilizers for contaminated soil can restore the agricultural value of the soil by immobilizing As, Pb, and Zn into safe forms, thus effectively preventing their uptake by crops. Full article

The cement industry is responsible for a significant portion of global CO₂ emissions, primarily due to the decarbonatization of limestone during clinker production. To mitigate this environmental impact, this study investigated the feasibility of using waste concrete fine powder, produced during the recycling of waste concrete, as a decarbonized raw material in cement clinker production. As a decarbonized material, waste concrete fine powder presents a valuable opportunity to reduce CO₂ emissions typically produced during the decarbonatization of limestone in clinker production. In addition, its use supports the recycling of construction waste, contributing to both emissions reduction and resource sustainability. In this study, samples were collected from 20 intermediate treatment plants in South Korea, where the chemical composition, particle size distribution, and carbonation rate of the fine powders were analyzed. The experimental results show that the properties of waste concrete fine powder vary significantly depending on the recycling process. Road construction aggregate production plants, which typically involve two to three crushing stages, produce fine powders with higher CaO content (28–31%) and consistent particle size distributions. In contrast, plants producing aggregates for concrete, which involve four to six crushing stages, produce powders with lower CaO content (around 20%) and greater variability in particle size. The average carbonation rate of 7.44% suggests that these fine powders can replace limestone in clinker production. It is estimated that substituting 5% of limestone with waste concrete fine powder could reduce CO₂ emissions from limestone decarbonatization by approximately 952,560 tons in 2023, representing a 3.34% decrease in total emissions from clinker production. However, it is important to note that the CO₂ emissions reduction calculation is not from a lifecycle perspective, without considering the energy-related emissions from recycling waste concrete fine powder. Nevertheless, this study highlights the potential for waste concrete fine powder to serve as a sustainable raw material for the cement industry, contributing to both CO₂ reduction and efficient recycling of construction waste. Full article

To achieve the required recycling rates, organic recycling via composting should be widely introduced in Poland for selectively collected biowaste. However, this process not only produces compost but also leachate (L_CB), a nitrogen- and organics-rich liquid by-product. So far there has been limited information on the application of anaerobic digestion (AD) for treating L_CB, which has fermentative potential. However, for effective methane production (MP) via AD, the ratio of chemical oxygen demand to total Kjeldahl nitrogen (COD/TKN) and pH of L_CB are too low; thus, it should be co-digested with other organics-rich waste, e.g., glycerine (G). The present study tested the effect of G content in feedstock (in the range of 3–5% (v/v)) on the effectiveness of co-digestion with L_CB, based on MP and the removal of COD. MP was accessed by using an automatic methane potential test system (AMPTS). Regardless of the feedstock composition (L_CB, or L_CB with G), the efficiency of COD removal was over 91%. Co-digestion not only increased MP by 6–15%, but also the methane content in the biogas by 4–14% compared to L_CB only (353 NL/kg COD_added, 55%). MP and COD removal proceeded in two phases. During co-digestion in the 1st phase, volatile fatty acids (VFA) accumulated up to 2800 mg/L and the pH decreased below 6.8. The presence of G altered the shares of individual VFA and promoted the accumulation of propionic acid in contrast to L_CB only, where caproic acid predominated. An initial accumulation of propionic acid and acidification in the mixtures decreased the kinetic constants of MP (from 0.79 to 0.54 d⁻¹) and the rate of COD removal (from 2193 to 1603 mg/(L·d)). In the 2nd phase, the pH recovered, VFA concentrations decreased, and MP was no longer limited by these factors. However, it should be noted that excessive amounts of G, especially in reactors with constant feeding, may cause VFA accumulation to a greater extent and create a toxic environment for methanogens, inhibiting biogas production. In contrast, digestion of L_CB only may lead to ammonium buildup if the COD/TKN ratio of the feedstock is too low. Despite these limitations, the use of AD in the treatment of L_CB as a sustainable “closed-loop nutrient” technology closes the loop in composting of biowaste. Full article

To investigate the effects of kitchen waste on the chemical properties of acidic red soil and the community structure of ammonia–oxidizing archaea (AOA) and ammonia–oxidizing bacteria (AOB), a study was conducted in the flue–cured tobacco farmland ecosystem of the Erlongtan small watershed in central Yunnan. Eight fertilization methods were applied: no fertilization control CK, single application of chemical fertilizer T1 (1 t·hm⁻²), kitchen waste combined with a chemical fertilizer (T2:12 t·hm⁻² + 1 t·hm⁻², T3:15 t·hm⁻² + 1 t·hm⁻², T4:18 t·hm⁻² + 1 t·hm⁻²), and single application of kitchen waste (T5:12 t·hm⁻², T6:15 t·hm⁻², T7:18 t·hm⁻²). The numbers twelve, fifteen, and eighteen in brackets represent the amount of food waste applied, and one represents the amount of chemical fertilizer applied. The study evaluated the effects of kitchen waste on soil chemical properties, the community structure and composition of AOA and AOB, and the relationship between soil chemical properties and these microbial communities in acidic red soil. The results showed that: (1) single application of kitchen waste (T5, T6, T7) effectively improved soil nutrient status (SOC increased by 15.79–217.24%; TN increased by 1.53–92.99%; NH₄⁺–N increased by 18.19–520.74%; NO₃⁻–N) increased by 15.54–750.61%), and alleviated acidification. (2) Temporal variations had a more significant effect on the community structure of AOA and AOB than different treatments. The dominant phyla of AOA were Thaumarchaeota, Crenarchaeot. The dominant phylum of AOB was Proteobacteria, and the dominant genera were Nitrosospira and norank_Bacteri. (3) The number of AOA co–occurrence network nodes were equivalent to that of AOB, but AOB had more connection edges, indicating a more complex interaction network. In contrast, AOA exhibited higher modularity, reflecting tighter internal connections and greater stability. The AOA co–occurrence network showed stronger performance during the maturity and fallow stages, while AOB interactions were most active during the topping stage. (4) AOA demonstrated a strong correlation with soil chemical properties during the topping and maturity stages, whereas AOB showed a stronger correlation at the rosette and fallow stages. Among soil chemical factors, pH and SOC were identified as the primary drivers influencing AOA and AOB community abundance and structural differentiation. In conclusion, kitchen waste application enhances the nutrient content of acidic red soil and influences the niche differentiation of AOA and AOB, thereby affecting nitrogen recycling. This approach represents an environmentally friendly and sustainable fertilization method. Full article