Search Results (288)

Phosphorus is an essential and finite resource critical for global food production, yet its inefficient use and discharge from wastewater systems contribute to eutrophication and resource depletion. The transition from conventional wastewater treatment plants to water resource recovery facilities has intensified interest in technologies that enable phosphorus recovery within a circular economy framework. This review provides a critical and up-to-date synthesis of phosphorus recovery strategies from wastewater, with primary emphasis on struvite (MgNH₄PO₄·6H₂O) crystallization as one of the most mature and practically implemented recovery routes. The occurrence and chemical forms of phosphorus in wastewater streams are discussed alongside conventional approaches, such as enhanced biological phosphorus removal and chemical precipitation, in order to position struvite recovery within the broader phosphorus management landscape. In addition to struvite crystallization, selected competing and complementary recovery pathways, including electrochemical systems, biochar-assisted processes, and sludge ash recovery, are discussed to compare technological maturity, recovery potential, and practical applicability. Particular attention is given to reactor configurations, full-scale applications, and commercial technologies to assess operational reliability, recovery performance, and fertilizer product quality. Life-cycle assessment results and regulatory developments are also discussed to contextualize sustainability claims, technology selection, and market integration. The review identifies key technical and economic challenges, particularly regarding magnesium supply, competing ions, wastewater matrix effects, and the feasibility of mainstream application. Overall, controlled sidestream struvite crystallization appears to offer the most favorable balance between recovery efficiency, operational reliability, and fertilizer product quality under suitable plant conditions. Full article

Integrated waste management through vermicomposting combined with biochar amendments represents an innovative approach for sustainable resource recovery. This study evaluated the effects of sugarcane bagasse biochar (SBB) at 0%, 5%, and 10% application rates on Eisenia fetida performance and vermicompost quality during preincubation-vermicomposting of sewage sludge and press-mud mixtures. The 10% SBB treatment significantly (p < 0.05) enhanced earthworm biomass (72.3% increase) and cocoon production (24.8 ± 1.8 per earthworm vs. 12.3 ± 1.2 in control). Lignocellulosic degradation improved substantially, achieving 22.6%, 10.7%, and 38.8% degradation for cellulose, hemicellulose, and lignin, respectively. Macronutrient concentrations increased significantly: TN by 38.4%, TP by 15%, and TK by 21.4% compared to initial mixtures. Moreover, total heavy metal concentrations decreased significantly during vermicomposting, with reductions of 8.1–8.7% for Pb, 5.3–7.6% for Cd, and 3.0–4.8% for Cr, with reduced bioavailability factors indicating enhanced metal stabilization. The final vermicompost exhibited optimal maturity indices, including a C:N ratio of 15.4 ± 0.2 and improved electrical conductivity. Results demonstrate that 10% sugarcane bagasse biochar amendment facilitates efficient concurrent management of sewage sludge and sugarcane industrial wastes while producing high-quality organic fertilizer with enhanced nutrient content, reduced heavy metal bioavailability, and accelerated stabilization for sustainable agricultural/horticultural applications. Full article

The aim of this study was to investigate the ability of sewage sludge-derived biochar to remove PO₄-P from real biologically treated wastewater. Biochar was produced via the pyrolysis of anaerobically digested sewage sludge pretreated with nanoscale zero-valent iron (nZVI) at concentrations of 3%, 1.5%, and 0.5% (w/w, based on total solids). A sample without nZVI addition was used as a control. The properties of biochar samples were analyzed, including elemental composition, specific surface area, and pore size. PO₄-P removal was evaluated using both batch adsorption and column experiments. The highest adsorption capacity determined in the batch experiment was 2.5 mg/g. When wastewater was passed through columns packed with 0.3–0.6 mm biochar particles at a hydraulic loading rate of 1 m/h, a 3-fold-higher phosphorus retention capacity was obtained in the range of 7.26–7.82 mg/g. The column containing biochar derived from sewage sludge with 3% nZVI accumulated 7% more PO₄-P than the biochar without nZVI. All columns effectively removed phosphates from wastewater (efficiency > 80%) due to the chemical composition of biochar, which mainly contained Fe and Ca elements. In contrast to the batch experiment, the columns were subject to the biological sorption of phosphates via microorganisms, physical retention between particles, and the formation of precipitates on the surface of a column. Full article

The sustainable management of olive wastes represents an important environmental challenge. Biochars and hydrochars derived from biomass are promising adsorbents for removing emerging pollutants from water. In the present work, olive stone wastes were converted into biochar and hydrochar by using pyrolysis (500 °C for 30 min) and hydrothermal carbonization (HTC) processes (220 °C for 10 h). Then, the obtained materials were physically activated by using CO₂ gas (750 °C for 30, 60 and 180 min). Various analytical techniques were applied for the chemical, textural and structural characterization of these carbonaceous materials (i.e., ultimate and proximate analysis, scanning electron microscopy (SEM), BET surface area, Raman spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy). Afterwards, the selected activated biochar and hydrochar were applied for the removal of amoxicillin from aqueous solutions. The experimental results show that the generated hydrochar has many microspheres on its surface and inside, while the produced biochar exhibits a porous structure with irregular forms. CO₂ physical activation has induced an important improvement of the biochar and hydrochar’s structural, textural, and surface chemistry properties. For instance, the activated biochar samples show a highly porous structure, with large specific surface areas that increase with the burn-off, reaching 1349.3 m² g⁻¹ following 3 h of activation. Regarding the activated hydrochar samples, they exhibit a spherical morphological structure with an important specific surface area, which increased to 846.7 m² g⁻¹ after 3 h of activation. Moreover, both activated materials have an amorphous structure with low oxygen surface groups. The selected novel CO₂-activated biochar and hydrochar efficiently remove amoxicillin from aqueous solutions under wide experimental conditions, with adsorption capacities of 386.4 and 215.9 mg g⁻¹, respectively. These efficiencies are higher than those reported for various activated biochars derived from lignocellulosic biomass, from sewage sludge, and from animal manure. Future research works are required to assess these materials’ effectiveness in treating real pharmaceutical effluents, to optimize the regeneration of the amoxicillin-loaded materials, and to design full-scale devices for a real application. Full article

Soil health is a major environmental concern. Biochars are a promising solution to address both soil contamination and amendment. They represent a sustainable valorisation alternative for solid wastes produced in huge amounts, namely agroforestry residues and sludge from wastewater treatment plants. Biochar’s superior properties, enhanced pore structure and high specific surface area can contribute to restoring soil quality, by adsorbing several pollutants (e.g., pharmaceutical compounds, pesticides, and metals) from water and soil, enhancing water retention capacity, improving soil aggregation, regulating pH, and reducing the need for synthetic fertilisers. Multiple studies have reported removal efficiencies exceeding 70% for metals and 60% for organic compounds in soils, as well as over 40% for both organic compounds and metals in waters. These efficiencies depend on factors such as feedstock, pyrolysis conditions, modification strategies, and target contaminants. Recent advancements in the field have introduced both chemical and physical modifications that can enhance adsorption selectivity. This review provides a comprehensive analysis of the fundamentals of biochar production, modification strategies, and their environmental applications in soil remediation and water treatment. By comparing unmodified and modified biochars, this review highlights the crucial factors that influence the performance of this highly versatile and cost-effective solution. Full article

The water–energy–carbon (WEC) nexus provides a systems framework for minimizing trade-offs among water security, energy reliability, and carbon mitigation. Within this framework, waste-derived biochar catalysts offer a circular pathway that simultaneously valorizes residues, reduces process energy demand, and supports carbon management through stable carbon storage and catalytic co-benefits. This review consolidates recent advances in biochar-based catalysts engineered from agricultural, industrial, municipal, and sludge-derived wastes, highlighting how feedstock selection and thermochemical processing, namely pyrolysis, hydrothermal carbonization (HTC), and torrefaction, as well as activation and post-modification (heteroatom doping and metal/metal-oxide incorporation) govern structure–property–performance relationships. The synthesized catalysts have been widely applied in water and wastewater treatment, including adsorption–advanced oxidation process (AOP) hybrids, Fenton-like systems, peroxydisulfate/persulfate (PS) and peroxymonosulfate (PMS) activation, photocatalysis, and the removal of emerging contaminants. They have also demonstrated strong potential in energy conversion processes such as the hydrogen evolution reaction (HER), oxygen reduction and evolution reactions (ORR/OER), biomass reforming, and carbon dioxide (CO₂) conversion. In addition, these materials contribute to carbon management through sequestration pathways, avoided emissions, and life cycle assessment (LCA)-based sustainability evaluations. Finally, we propose a WEC-aligned design roadmap integrating techno-economic analysis (TEA), LCA, and scale-up considerations to guide next-generation biochar catalysts toward robust performance in real matrices and deployment-ready systems. Full article

Organic phosphorus (OP) constitutes an important and chemically diverse fraction of total phosphorus (TP) in aquatic environments, yet its removal mechanisms in substrate-based treatment systems remain insufficiently understood. In particular, the relative contributions of adsorption and microbial transformation to OP removal and their coupling effects are still unclear. To address this issue, gravel-, sludge-, and sludge biochar-based biofilters were operated under controlled phosphorus inputs with varying OP/inorganic phosphate (IP) compositions. Phosphorus removal performance, effluent phosphorus speciation, phosphatase activity, and microbial community characteristics were systematically analyzed to distinguish physicochemical and biological pathways. Results indicated that phosphorus removal was dominated by adsorption at early operational stages, with comparable performance across substrates. As the operation progressed, sludge-based substrates exhibited more stable removal than gravel, attributable to stronger Fe/Al-associated adsorption. Biologically active sludge biochar systems consistently maintained higher TP removal efficiencies (87.1–93.3%) than abiotic systems. Phosphatase-mediated OP mineralization governed phosphorus speciation transformation, while effective removal depended on subsequent immobilization of transformation products. Overall, the results demonstrate that efficient OP removal relies on a coupled bio–physicochemical mechanism, in which microbial transformation and substrate adsorption act synergistically. This insight offers guidance on optimizing phosphorus control in biofilters and constructed wetlands (CWs), especially for robust biofilters and CWs designed to treat OP-rich wastewaters. Full article

Biochar application has been proposed as a promising strategy to improve soil functioning, defined as the integrated regulation of water storage, nutrient availability, and biological activity influencing crop productivity and crop performance in water-limited environments. However, its effectiveness depends on soil properties, climatic variability, and dominant processes. This study evaluated the effects of sewage sludge biochar on soil quality, water dynamics, nutrient availability, and bean productivity in sandy soil under rainfed semiarid conditions across two contrasting cropping cycles. A soil quality index (SQI) based on a minimum data set (MDS) derived from principal component analysis (PCA) was used to identify the dominant processes controlling soil functioning under different hydrological regimes. The two cropping cycles corresponded to wetter (Cycle I) and drier (Cycle II) hydrological conditions within the same agricultural year. Biochar application increased soil organic carbon and nitrogen stocks, enhanced phosphorus availability, and improved soil water storage. Despite similar evapotranspiration among treatments, water productivity increased, indicating more efficient conversion of stored soil water into yield. Biological indicators were more responsive during the wetter cycle, whereas physicochemical indicators dominated under drier conditions, revealing a shift in the processes regulating soil functioning. The minimum data set varied between cycles, demonstrating the environmental dependency of the SQI components. Overall, biochar improved soil resilience by enhancing nutrient retention and buffering crop response to water limitation, and the integrative SQI approach effectively captured these functional changes. Full article

The undegradable characteristics of heavy metals on environmental quality have become a serious human health concern. A study was conducted in a potato field to investigate the impact of soil amended with animal manure or biochar on the transport of toxic heavy metals and nitrates to runoff and seepage water. The soil in 18 field plots was separated, and each of 3 plots was mixed with biochar, chicken manure, vermicompost, sewage sludge, or cow manure, with 3 plots used as the control. Following a natural rainfall event, the impact of soil treatments on the runoff and infiltration water volume was monitored. Runoff water from the soil amended with biochar exhibited 10.6 L plot⁻¹, whereas cow manure exhibited 4.1 L plot⁻¹, indicating about 61% reduction in runoff water volume. The vermicompost-amended soil increased the seepage water volume from 1.6 L plot⁻¹ in the control treatment to 4.4 L plot⁻¹, indicating a 175% increase in percolating water, a desirable attribute to direct rainfall water towards the plant roots. The concentrations of Pb, Cd, Ni, Mn, Cr, Mg, Cu, and K in infiltration water were greater in runoff sediments, highlighting the need for runoff sediment remediation technology. Full article

This study investigated the ability of anaerobically digested sewage sludge biochar (ADSSBC), pretreated with nanoscale zero-valent iron (nZVI) prior to anaerobic digestion (AD), to remove lead (Pb(II)) ions from aqueous solutions. Batch adsorption experiments were conducted to evaluate the effects of various parameters, including nZVI dosage, O₂-exclusion method (aluminum foil wrapping or N₂ purging), pyrolysis temperature (300–800 °C), adsorbent dosage, pH, coexisting ions, contact time, and initial Pb(II) concentration. Experimental data were fitted to adsorption kinetic and isotherm models. The characteristics of nZVI30-ADSSBC-700 before and after Pb(II) adsorption were analyzed using FTIR, SEM–EDS, XPS, and XRD to identify the adsorption mechanisms. The results showed that nZVI addition at 30 mg/g-TS prior to AD significantly enhanced Pb(II) removal efficiency compared with the control. Among the investigated pyrolysis temperatures and O₂-exclusion methods, the biochar produced at 700 °C using aluminum foil wrapping exhibited the highest Pb(II) removal efficiency (99.4%) at an initial Pb(II) concentration of 200 mg/L. The maximum Langmuir adsorption capacity obtained for this biochar was 139.3 mg/g. The pseudo-second-order kinetic model best described the Pb(II) adsorption kinetics. The investigated models and the results of physicochemical analyses indicated the involvement of both physical and chemical adsorption mechanisms, including surface precipitation, ion exchange, pore filling, and, to some extent, complexation. Full article

Nanoplastics (NPs) have emerged as pervasive aquatic pollutants due to their small size, high surface activity, and potential ecological and health risks. Although sludge-derived biochar is a sustainable adsorbent for NP removal, the relative importance of coexisting adsorption mechanisms remains poorly quantified. Here, iron-modified sludge biochar (FeBC) was synthesized and evaluated for NP removal from water. Batch experiments showed that FeBC significantly outperformed pristine biochar, achieving a maximum removal efficiency of 96.09%. Adsorption was strongly pH-dependent, with enhanced removal under acidic conditions due to surface protonation and strengthened electrostatic attraction toward negatively charged NPs. SEM, BET, FTIR, and XPS analyses indicated that electrostatic interactions, hydrogen bonding, π–π interactions, and pore adsorption jointly contributed to NP capture. Importantly, structural equation modeling quantitatively disentangled these mechanisms, revealing electrostatic interactions as the dominant driver (52.6%), followed by hydrogen bonding (23%), pore adsorption (16.6%), and π–π interactions (7.9%), and further identified synergistic and antagonistic relationships among them. These results demonstrate that surface charge regulation governs NP adsorption efficiency, providing a quantitative mechanistic basis for the rational design of biochar-based adsorbents. This study advances a multi-mechanistic framework for understanding and optimizing NP removal while promoting sludge resource valorization. Full article

The widespread use of biochar in soil remediation has heightened interest in the role of its derived dissolved organic matter (DOM) in soil nutrient dynamics. However, how pyrolysis temperature shapes the characteristics of DOM released from sludge biochar remains unclear. The study examined variations in the composition and properties of DOM extracted from sludge biochar under two different solutions—ultrapure water (UP) and artificial root exudates (ARE)—across a range of pyrolysis temperatures. Results indicate that the dissolved organic carbon (DOC) content did not differ significantly between extraction environments. In contrast, pyrolysis temperature markedly influenced both the content and composition of DOM. DOM in sludge biochar was primarily composed of humic-like (C1, C2, C3) and tyrosine-like (C4) components. Specifically, DOM from low-temperature biochar was dominated by C2, C3, and C4, whereas high-temperature biochar contained mainly C2 and C4. Full article

Sewage sludge management is a major challenge in modern wastewater treatment, as sludge contains organic matter, nutrients, pathogens, heavy metals, and emerging contaminants. Increasing wastewater volumes from urbanization and population growth have led to steadily rising global sludge production, emphasizing the need for sustainable and resource-efficient treatment strategies. Conventional methods—such as landfilling, land application, and biological treatment—face limitations due to contaminant risks, regulatory restrictions, and incomplete pollutant removal. Thermal and thermochemical processes offer substantial volume reduction, energy recovery, and resource valorization. Incineration is widely implemented and ensures complete oxidation but requires high energy input and emission control. Gasification and pyrolysis produce syngas, bio-oil, and biochar, supporting circular economy applications, while hydrothermal carbonization (HTC) efficiently converts wet sludge into hydrochar without intensive drying. This study presents a comparative life cycle assessment (LCA) and mass–energy assessment of these four thermal treatment methods, highlighting their environmental impacts, energy efficiencies, and resources’ recovery potential to support more sustainable sludge management. Full article

Strawberry (Fragaria × ananassa) is one of the most consumed berries worldwide. Despite improvements in management practices and breeding, maintaining soil health and minimizing environmental impact remain a challenge for agricultural systems. Biochar has been proposed as an effective strategy to mitigate climate change, enhance soil health, and promote plant growth. This study investigated the effects of sewage sludge biochar (SSB; 0% control, 5%, and 10% w/w) on the root-associated bacterial community of strawberry plants grown in pots under greenhouse conditions. Results obtained using 16S rRNA gene sequencing revealed a stable core bacterial community comprising 1207 amplicon sequence variants (ASVs), representing 13.2% of all detected ASVs and shared across all treatments. In contrast, biochar-amended soils harbored distinct sets of unique ASVs, with 1795 ASVs (19.7%) in the 5% SSB treatment and 2097 ASVs (23.0%) in the 10% SSB treatment, indicating treatment-specific community differentiation. Phylum-level analysis showed that Cyanobacteriota and Proteobacteria dominated the root-associated bacterial communities across all treatments, with no significant differences between biochar-amended soils and control groups. Alpha diversity did not differ significantly among treatments (p > 0.05), but beta diversity indicated subtle shifts in bacterial community composition under SSB amendment. SSB application increased community homogeneity, while overall bacterial diversity remained unchanged, indicating bacterial community restructuring rather than functional enhancement. Full article

The application of forest byproducts to cropland provides significant benefits, mitigating soil degradation, supplying essential nutrients, and increasing yields. Their impact is well known in the first years, but few studies have examined the effects several years after an application. A field study was initiated in Québec, QC, Canada, to assess the effects of wood ash (10 and 20 Mg dry wt. ha⁻¹), pine biochar (10 Mg dry wt. ha⁻¹), paper mill sludge (PS) (12 Mg dry wt. ha⁻¹), and a combination of wood ash and PS, relative to an untreated control and a mineral treatment, on crop yield and soil properties three to seven years after application in a temperate circumneutral loamy soil. The site was cropped to a maize (Zea mays L.)–soybean [Glycine max (L.) Merr.]–spring wheat (Triticum aestivum L.) rotation. Each crop received supplemental N and P from mineral fertilizers, when needed, according to local agronomic recommendations. Applying wood ash increased wheat yield by 0.25–0.44 Mg ha⁻¹ three years after the addition, but no effect was detected in other cases and for the other amendments. Wood ash also resulted in the largest increases (p < 0.05) in soil pH and Mehlich-3 P, K, Ca, Mg, Zn, and Cd, alone or in combination with PS. Pine biochar promoted soil C sequestration after seven years, but did not affect other soil properties owing to its high stability and low nutrient content. This study revealed that wood ash was more advantageous than pine biochar for improving soil quality and crop productivity. Full article