Search Results (143)

This work investigates the incorporation of sewage sludge-derived biochar (BC) into a recycled poly(ethylene terephthalate) (rPET) matrix at loadings ranging from 0.5 to 5% wt. in order to develop sustainable nanocomposite materials. The materials were comprehensively characterized using complementary structural, thermal, and morphological techniques to evaluate the effect of BC on the properties of the recycled polymer. XRD, DSC, and PLM analyses demonstrated that BC acts as a heterogeneous nucleating agent, without significantly altering the final crystalline fraction of rPET, while SEM observations confirmed the homogeneous dispersion of particles within the matrix. TGA and Py–GC/MS further indicated that BC moderates thermal degradation, reducing the relative formation of low-molecular-weight degradation products and promoting the retention of larger terephthalate-containing fragments. Accelerated UV irradiation experiments further demonstrated the protective role of BC against photo-induced degradation. Intrinsic viscosity (IV) measurements showed that BC-containing nanocomposites exhibited a smaller molecular-weight reduction after UV exposure compared to neat rPET, indicating reduced chain scission, while complementary DSC analyses confirmed improved preservation of thermal transitions after aging. Overall, sewage sludge-derived biochar is demonstrated to be a promising multifunctional additive for rPET, acting both as a nucleating agent and a UV stabilizer. This approach provides an alternative route for the valorization of two waste streams, contributing to enhanced materials in a circular economy framework. Full article

The present study investigates the presence, sources, and impacts of microplastics (MPs) in different soil types, including agricultural, urban, and forest areas, through a synthesis of results of published scientific papers. MPs originate from a variety of human activities, such as the widespread use of plastic mulch in agriculture and the application of organic fertilizers and treated sewage sludge, as well as from vehicle tire wear, industrial processes, and the gradual degradation of plastic products in the environment. In urban soils, the main sources of MPs are related to road traffic, industrial activity, and landfills, while in forest soils, concentrations are generally lower. However, MPs in forest areas are thought to be carried there by the air, by runoff, or from nearby areas with human activity. Available data show that larger MP particles tend to remain in the surface layers of the soil, while smaller particles can penetrate deeper soil layers, increasing their bioavailability and the likelihood of interaction with microorganisms and plant root systems. In terms of their chemical composition, polyethylene (PE) and polypropylene (PP) polymers dominate in agricultural soils, which is directly linked to agricultural practices, while polystyrene (PS) and polyvinyl chloride (PVC) are more frequently detected in urban soils. The morphological types of MPs include fragments, fibers, and films, while their color characteristics provide clues to possible sources of origin, such as plastic ground covers, tire wear, and packaging materials. Overall, the study’s results underscore the growing environmental significance of MP soil pollution and highlight the need for more effective management and recycling of plastic materials, as well as for further interdisciplinary research aimed at understanding the mechanisms of transport, accumulation, and long-term ecological effects of microplastics in terrestrial ecosystems. Full article

Anaerobic co-digestion (AcoD) is increasingly applied in sewage-sludge management and organic-waste treatment because it can improve methane recovery, stabilize mixed substrates, and reduce life-cycle greenhouse-gas emissions under appropriate feedstock and operating conditions. However, existing reviews still focus mainly on feedstock types or isolated enhancement measures and less often connect synergistic mechanisms with engineering implementation and carbon outcomes. The specific novelty of this review is to connect functional feedstock classification, mechanism boundaries, engineering controls, and carbon-performance evaluation within one sludge-centered AcoD framework. This review synthesizes recent progress in AcoD of sewage sludge, food waste, livestock manure, crop residues, and industrial organic streams through a chain from feedstock traits to substrate interactions, microbial responses, engineering performance, and carbon benefits. Feedstocks are reorganized by function rather than by waste name, highlighting how carbon-to-nitrogen contrast, buffering capacity, hydrolysis recalcitrance, and inhibitor profiles jointly define synergy potential. Key mechanisms, including C/N balancing, hydrolysis complementarity, inhibitor mitigation, and direct interspecies electron transfer (DIET), are discussed together with their applicability limits. Representative evidence shows methane-yield or methane-production increases of about 41–55% for selected food-waste–manure blends, approximately 45% for rice–straw–pig manure systems after cellulolytic pretreatment, and approximately 16–55% for selected additive strategies; these values are illustrative rather than directly comparable because the underlying studies differ in substrates, baselines, reactor configurations, pretreatment conditions, and operating parameters. The review then translates mechanism into practice through pretreatment, reactor-selection templates, operating windows, additive reinforcement, and artificial-intelligence-assisted monitoring. Representative cases and life-cycle evidence indicate that AcoD can improve methane productivity while lowering greenhouse-gas emissions relative to landfill or mono-digestion pathways when energy substitution and nutrient recycling are credibly counted. Remaining bottlenecks include incomplete kinetic integration, limited DIET quantification, insufficient reporting of quantitative operating ranges and additive dosages, and weak coupling of carbon, economics, and regional feedstock dynamics. The revised review therefore treats AcoD as a sludge-centered mechanism-to-engineering framework and highlights two transferability gaps that require stronger standardization: biodegradation/toxicity testing and local co-substrate logistics. Full article

In the face of the raw materials crisis and environmental concerns, sustainable waste management has become a priority for current and future generations. Recycling waste from wastewater treatment plants in a closed loop protects natural resources, reduces landfill volumes, and lowers disposal costs. This paper presents the results of tests on the physical, filtration, and mechanical properties of mixtures of washed mineral waste (WMW) from grit chambers with fly ash from the thermal treatment of municipal sewage sludge (SSA) in a fluidized bed furnace. Additionally, radiological tests of the mixture components were conducted. Based on the conducted tests, the possibility of sustainable use in civil engineering, such as soil backfills and embankment construction materials, was assessed. The possibility of safely using waste materials in the indicated construction solutions was demonstrated for mixtures with dominant WMW content (90% and 70% by total weight). The waste mixtures correspond to poorly or medium-grade sands with a small amount of silt (uniformity coefficients of 3.33, 3.50, and 8.00). They are characterized by maximum dry densities of 1.542, 1.770, and 1.780 g/cm³; optimal moisture contents of 12.54, 12.86, and 20.25%; permeability coefficients of 0.08, 0.22, and 0.39 m/d; and internal friction angles of 38.4, 39.5, and 40.1°. The values of the determined parameters of some mixtures are similar to those of natural sands used as construction aggregates. All mixtures meet the geotechnical criteria for use in road embankments, below frost depth, and in flood embankment bodies. Mixtures with a 90% mass fraction of WMW were also approved for application as backfill for installation trenches. However, none of the mixtures met the hydraulic conductivity threshold required for the upper layers of embankments nor for backfill of abutments and retaining structures without the use of an additional binder (cement or lime), which is considered a prerequisite for these applications. Full article

The valorization of agro-industrial residues and sewage sludge into value-added products through vermicomposting represents a promising strategy for nutrient recycling and waste reduction. This study evaluated the effects of aqueous extracts obtained from five vermicomposts (VC1-VC5) produced from different mixtures of vineyard and winery residues and sewage sludge on cucumber (Cucumis sativus L.) seedlings grown under in vitro conditions. The aqueous extracts (10%, w/v) were characterized in terms of pH, electrical conductivity, and total polyphenolic content, and applied to cucumber seedlings cultivated for 30 days under sterile and controlled in vitro conditions using commercially available peat pellets (Jiffy-7^®). Seedling development was monitored throughout the experiment, and morphological and biochemical parameters were assessed at the end of the 30-day assay. All extracts supported seedling development, with no evidence of phytotoxicity. The application of VC2 and VC4 extracts resulted in significant increases in fresh and dry weight, while VC2 led to higher chlorophyll and carotenoid contents. Conversely, VC3 and VC5 extracts were associated with slight reductions in growth parameters and photosynthetic pigment content. Correlation analysis suggested positive associations between biomass accumulation and chlorophyll content, and negative association between total polyphenolic content and stem growth. Overall, the results indicate that aqueous vermicompost extracts were not phytotoxic under the tested conditions, although their effects appear to depend on extract composition, highlighting the importance of feedstock selection for sustainable horticultural applications. Full article

The escalating challenge of solid waste disposal necessitates innovative recycling strategies. This study aims to constructed technosols from bulk solid wastes (fly ash, straw and sewage sludge) for the dual purpose of sustainable waste management and the rehabilitation of degraded land. Following a 150-day incubation period, six resulting technosols were systematically evaluated for aggregate stability, bacterial community structure, and biological safety to assess their viability as functional soil materials. All constructed technosols had a pH of 7.44–7.71 and were enriched in soil organic matter, nitrogen, and phosphorus. Aggregate stability (R_0.25: 46.6–64.0%) surpassed that of typical Chinese soils. Bacterial analysis revealed a stable consortium of 165 core genera, accounting for 92.93–98.11% of the total relative abundance, and were dominated by six phyla (Proteobacteria, Bacteroidota, Planctomycetota, Gemmatimonadota, Firmicutes, Actinobacteriota). The addition of straw modulated phylum structure, elevating Bacteroidota and reducing Proteobacteria. The bacterial communities exhibited clear functional hierarchy at class and order levels, with dominant groups forming a complementary carbon–nitrogen–phosphorus cycling network. Functional prediction further indicated distinct differentiation in carbon and nitrogen metabolic pathways. The technosols were non-phytotoxic and significantly enhanced the growth of Portulaca oleracea, increasing plant height (4.9–86.7%), dry weight per plant (67.3–605.4%), and SPAD values (8.1–15.9%), respectively. This study provides a sustainable strategy for repurposing solid wastes into functional technosols, aligning with circular economy principles and offering a viable solution for the ecological restoration of degraded lands such as mining areas. Full article

Increasing domestic sewage production associated with urban population growth poses environmental challenges. Biosolids from wastewater treatment can recycle nutrients in agriculture, while plant growth-promoting rhizobacteria (PGPR) enhance nutrient availability and plant performance. This study evaluated the effects of the combined application of sewage sludge–derived biosolid and Bacillus aryabhattai on sunflower growth, biomass production, physiological traits, and nutrient status during the early growth stage under greenhouse conditions. We hypothesized that this combined treatment would enhance plant performance compared with biosolid application alone. Four treatments were established: control (T1), 5 g of biosolid alone (T2), 5 g biosolid + 3.2 mL B. aryabhattai (T3), and 5 g biosolid + 6.4 mL B. aryabhattai (T4). The formulation contains B. aryabhattai strain CMAA 1363 (1 × 10⁸ CFU mL⁻¹) as the active microbial component, together with humic substances and other formulation agents (thickener, preservative, and water). The Plants were grown for 44 days. The data were analyzed using one-way ANOVA followed by mean comparison among treatments. Shoot dry mass was significantly higher in T4 compared with the T1 and T2 (p < 0.001), while no significant difference was observed between T3 and T4 (p > 0.05). Biosolid application increased the photosynthetic rate, and its combination with B. aryabhattai further enhanced photosynthetic performance, with significant difference detected between bacterial doses only at the end of growth period. Substomatal CO₂ concentration was lower in inoculated treatments, indicating greater CO₂ assimilation efficiency. Total chlorophyll increased with the addition of sludge and further increased by inoculation with 6.4 mL. Leaf N, Mn, and Zn contents were highest in T4. Overall, the combined application of biosolid and B. aryabhattai improved photosynthetic efficiency and biomass accumulation, highlighting the potential of integrating biosolids and beneficial rhizobacteria as a sustainable approach for nutrient recycling and improved crop productivity in agricultural systems. Full article

Sustainable agriculture is increasingly reliant on reducing anthropogenic inputs and recycling organic waste while protecting ecosystems. In this context, this study investigated the agro-environmental properties of biosulfate, focusing on its interaction with herbicides and its effects on soil fungi and horticultural plants. Two biosulfate samples obtained from urban sewage sludge from the Barletta (BIO-BA) and Foggia (BIO-FO) treatment plants were characterized by Fourier transform infrared–attenuated total reflectance (FTIR-ATR) spectroscopy and scanning electron microscopy (SEM). The adsorption/desorption of the herbicides metribuzin (MET), S-metolachlor (S-ME) and cycloxydim (CYC) on biosulfates was evaluated by studying adsorption kinetics and isotherms. All herbicides reached adsorption equilibrium within a few hours, according to pseudo-second-order kinetics, indicating a predominant chemical interaction between biosulfate and the molecules. Considering the organic C content of BIO-BA (~21%) and BIO-FO (~17%), which was less than half that commonly measured for other organic fertilizers, such as compost and digestate, their adsorption capacity was high, with Freundlich adsorption constants ranging from 772 µg g⁻¹ (S-ME on BIO-BA) to 1464 µg g⁻¹ (CYC on BIO-FO). A low hysteresis coefficient indicated a rather slow and incomplete release of the molecules from the biosulfate. Exposure of the fungi Pleurotus ostreatus and Pleurotus eryngii to 1, 2, 3, and 4% BIO-BA and BIO-FO stimulated mycelium growth, indicating that responses depended on fungal species and biosulfate dose. Finally, germination and early growth of lettuce and basil were generally unaffected by either biosulfate, as parameters such as germination percentage, root and shoot length, and fresh and dry biomass were not statistically different from the control. Some growth stimulation was observed in basil. Overall, biosulfate appears to be a promising soil fertilizer, as it can contribute to soil organic matter, retain xenobiotics, and exert biostimulatory effects under controlled conditions. Full article

Intensive agriculture, ecosystem degradation, and declining soil quality highlight the urgent need for sustainable land use strategies. The cultivation of short-rotation woody crops (SRC), combined with fertilization using sewage sludge digestate (SSD), offers a promising approach to recycle nutrient-rich waste and promote soil organic carbon (SOC) accumulation. This study evaluated SOC concentrations, stocks and their spatial distribution in the 0–20 cm soil layer under SRC cultivation, with and without SSD fertilization, across contrasting soil types in Eastern Lithuania. The investigated soils included mineral (Luvisols (LV), Retisols (RT), Planosols (PL), Arenosols (AR)), organo-mineral (Gleysols (GL)), and organic soils (Histosols (HS)), representing textures from sand to peat and classified according to the World Reference Base for Soil Resources (WRB). Part I assessed baseline SOC variability in unproductive areas planted with hybrid poplars (Populus spp.) and hybrid aspen (Populus tremula × P. tremuloides) up to 20 years old. Part II examined SOC changes in three SRC fields of different ages (3–10 years), including unfertilized and SSD-fertilized stands. SOC concentrations increased consistently from mineral (1.14–1.80%) to organo-mineral (2.13–3.20%) and organic soils (6.37–17.53%). Heavier-textured soils accumulated more SOC than lighter soils, showing a strong positive correlation between SOC and soil texture (r = 0.82, p ≤ 0.01). SRC cultivation increased SOC across all soil types, while SSD fertilization further enhanced accumulation, with fertilized fields showing SOC increases of 0.50–1.07 percentage points and carbon stocks by 18.8–41.7 t ha⁻¹, compared with smaller increases in unfertilized fields. Spatial visualization of SOC further highlighted long-term accumulation patterns across soil types, confirming the trends observed under SRC cultivation and SSD fertilization. Full article

Concrete waste generated from the demolition of structures constitutes a significant source of waste worldwide. Recycled concrete aggregates (RCA) obtained from this waste exhibit disadvantages such as high porosity and low mechanical strength; therefore, they are not used in pavement structures without improvement. This study investigates the feasibility of using RCA improved with waste-based stabilizers as highway subbase material. RCA was used as fine aggregate and blended with basalt aggregate (BA) at different replacement ratios. The mixtures were subjected to California Bearing Ratio (CBR) tests to determine the optimum RCA content. Subsequently, unconfined compressive strength (UCS) tests were conducted using calcium carbide slag (CCS) as an activator and sewage sludge ash (SSA) as pozzolanic material at various proportions. The experimental results indicated that the mixture containing 35% RCA exhibited the most favorable performance, while higher RCA contents resulted in significant reduction in CBR values. The highest UCS value was obtained in the mixture containing 30% waste additive by weight of RCA with a CCS:SSA ratio of 3:7. For this mixture, CBR reached 315%, and displacement measured in the cyclic plate loading test under a load of 35 kN was 2.5 mm. This mixture provides sustainable and mechanically suitable alternatives for highway subbase applications. Full article

Mining and sewage treatment wastes have been accumulating at growing rates in urban areas. Recycling these wastes can be used to generate safe products for various agro-environmental uses, including the synthesis of fertilizers with the potential to sequester carbon (C) in the soil. Therefore, this study evaluated the physicochemical characteristics and C sequestration potential of biochar obtained by co-pyrolysis (500 °C) of sewage sludge (SS) individually or combined at a 1:1 (w:w) ratio with zeolitic basalt (ZB), referred to as SS + ZB_BC. Subsequently, the raw materials and biochars were characterized by X-ray diffraction analysis, proximate analysis, elemental analysis, and FTIR spectroscopy, as well as pH and electrical conductivity (EC) determination. The results show that pyrolysis optimized material properties, especially SS biochar (SSB), which exhibited high stability with the highest fixed C content (13.6%) and thermostable fraction (TSF) of 43%. On the other hand, ZB had a higher pH and a lower EC than SS. Co-pyrolysis promoted complementary effects on the chemical and C stability properties of the SS + ZB_BC combination. The combination raised the pH to a value close to neutrality (6.5), indicating potential corrective action for acidic soils. Furthermore, after co-pyrolysis, the TSF remained high (25.2%) and was classified as a high-longevity material (>1000 years), indicating high aromaticity and C condensation. Therefore, the co-pyrolysis of SS and ZB optimized the individual characteristics of the materials, thereby providing a promising and sustainable alternative for agro-environmental use that addresses the need to reduce C emissions and promote waste recycling. Full article

Background/Objective: Sewage sludge (biosolids) is increasingly reused as a fertilizer to recycle nutrients and close material cycles; however, concerns persist regarding antibiotics and antimicrobial resistance. This study evaluated the agronomic safety and microbiological integrity of biosolid fertilization in soybean and maize systems, with particular attention to grain quality and food safety. Methods: Soybean and maize were cultivated in greenhouse microcosms under biosolid or mineral fertilization. Soil, roots, shoots, and grains were analyzed for antibiotic residues using LC–MS/MS and antibiotic-resistant bacteria (ARB) using culture-based assays. Minimum inhibitory concentrations for isolates from grains were compared with clinical breakpoints to verify phenotypic susceptibility. Multivariate analyses (PCA) integrating real-time antibiotic concentrations and updated resistance indicators were performed using centered and scaled data. Results: Fluoroquinolones were the predominant residues introduced by biosolids and exhibited consistent time-dependent declines across all treatments, although low concentrations remained detectable at 90 d in several soil–fertilizer–crop combinations. Tetracyclines, macrolides, and sulfonamides showed similar decreasing trends, with planted soils displaying faster dissipation than bulk control soils. Biosolid fertilization increased shoot biomass by 1.5–2.3-fold and nitrogen, phosphorus, and potassium uptake by 30–60% without impairing soybean nodulation or nitrogenase function. ARB was observed in all soils, including mineral and plant-free controls, indicating a natural background resistome. Ciprofloxacin-resistant isolates were detected in one simple sampling point, and MDR proportions were transient (67%), returning to their background levels by 45–90 days. PCA showed that crop presence, not fertilizer type, was the primary driver of microbial ordination, and that antibiotic concentrations and resistance indicators were only weakly aligned, indicating a limited selective pressure. No antibiotic residues or phenotypically resistant bacteria were detected in the soybean or maize grains. Conclusions: Updated residue, resistance, and multivariate data confirmed that biosolids did not induce, amplify, or transfer antibiotic resistance and maintained complete grain safety. Properly treated biosolids function as safe, agronomically beneficial fertilizers aligned with One Health goals, enhancing crop productivity without compromising food quality or increasing antimicrobial resistance. Full article

Advanced phosphorus (P) recycling from wastewater is critical for improving nutrient circularity and reducing soil pollution associated with the direct application of sewage sludge in agriculture. However, few studies evaluate the long-term environmental and economic trade-offs between recycled P products and raw sewage sludge application. This study compares struvite, vivianite, and dicalcium phosphate (CaP) as P alternatives to sludge to mitigate heavy metal accumulation in Spanish agricultural soils. Using data from 27,835 plots, heavy metal accumulation was simulated over 50- and 100-year fertilisation scenarios. The results indicate that continuous sludge application leads to widespread exceedances of zinc, copper, and cadmium, especially in alkaline soils, whereas substitution with recycled products can substantially reduce these risks. Vivianite balances P recycling and costs, CaP offers the best environmental performance but with higher investment, and struvite suits smaller regions prioritising environmental safety. Economic analysis favours advanced recycling over sludge, especially considering externalities such as soil remediation costs. Despite limitations, our findings emphasise the importance of integrating environmental externalities into economic assessments and the value of advanced P recycling for sustainable soil management. Full article

Second-, third-, and fourth-generation biofuels represent an important response to the challenges of clean energy supply and climate change. In this context, the Horizon 2020 “TO-SYN-FUEL” project aimed to produce advanced biofuels together with phosphorus from municipal wastewater sludge through a combination of technologies including a Thermo-Catalytic Reforming system, Pressure Swing Adsorption for hydrogen separation, Hydrodeoxygenation, and biochar gasification for phosphorous recovery. This article presents the environmental performance results of the demonstrator installed in Hohenberg (Germany), with a capacity of 500 kg per hour of dried sewage sludge. In addition, four alternative scenarios are assessed, differing in the source of additional thermal energy used for sludge drying: natural gas, biogas, heat pump, and a hybrid solar greenhouse. The environmental performance of these scenarios is then compared with that of conventional fuel. The comparative study of these scenarios demonstrates that the biofuel obtained through wood gasification complies with the Renewable Energy Directive, while natural gas remains the least sustainable option. Heat pumps, biogas, and greenhouse drying emerge as promising alternatives to align biofuel production with EU sustainability targets. Phosphorus recovery from sewage sludge ash proves essential for compliance, offering clear environmental benefits. Although sewage sludge is challenging due to its high water content, it represents a valuable feedstock whose sustainable management can enhance both energy recovery and nutrient recycling. Full article

Municipal sewage treatment plants generate significant amounts of polluting sludge, which demands innovative valorization approaches to support its sustainable recycling. This work aimed to evaluate the valorization potential of sludge from a municipal sewage treatment plant (STP) as an alternative raw material to traditional limestone in red wall tile formulations. For this purpose, four red wall tile formulations were performed with 0%, 5%, 10%, and 15% weight of STP sludge replacing traditional limestone. The tile formulations prepared by the dry process were characterized to determine their chemical and mineral compositions, thermal analysis, and sintering behavior. The red wall tile pieces were manufactured by pressing and firing at temperatures ranging from 1150 °C to 1180 °C. The effects of STP sludge incorporation and firing temperature on the densification behavior and technological properties were investigated. The results indicated that the STP sludge exhibited good chemical compatibility for use in red wall tile formulations. Water absorption values varied between 16.52% and 19.70%, indicating compliance with the red wall tile production (BIII group). These findings demonstrate the valorization potential of STP sludge in red wall tiles, which offers a relevant recycling option for the sanitation sector and the circular economy. Full article