Search Results (227)

Sewage sludge, characterized by its high organic matter and nutrient content, as well as the presence of microbial pathogens and other contaminants, requires proper management due to its significant generation rate. The table olive sector, which is highly significant in Spain as a global leader in production and export, generates various waste streams such the Organic Solid By-Products from Table Olive Processing (OSBTOP), which are mainly derived from the olive pit after the pitting process. The main aim of this study was to enhance the methane production performance of sewage sludge through co-digestion with OSBTOP as a co-substrate. Batch assays demonstrated that employing OSBTOP as a co-substrate increased methane content by 35–41% across all tested mixtures. While the highest methane yield was produced at a 40:60 (sludge:OSBTOP) ratio, a 60:40 mixture proved to be a more advantageous option for scale-up and practical application. This is attributed to factors such as the higher availability of sludge and its inherent buffering capacity, which counteracts the accumulation of volatile fatty acids and promotes process stability, thereby contributing to the study’s objective of significantly enhancing methane production from sewage sludge through co-digestion. In semi-continuous operation, methane yields in the co-digestion scenario exceeded those of mixed sludge digestion, showing a yield of 180 versus 120 LCH₄⁻¹ · kgVS_added⁻¹, representing a 50% improvement. This study highlights the potential of anaerobic digestion as a strategy for valorizing OSBTOP, a by-product with no prior studies, while demonstrating that its co-digestion with sewage sludge enhances methane generation, offering a sustainable approach to organic waste treatment. Full article

As potable water becomes limited, alternative water sources, such as reclaimed wastewater, for crop irrigation have gained attention. However, reclaimed wastewater for irrigation may expose edible crops to compounds of emerging concern (CECs), which may include pharmaceutics, hazardous waste, and volatile substances. Of these CECs, carbamazepine (CBZ) is of particular interest because only 7% of CBZ is filtered out during traditional wastewater treatment processing methods. Two trials were designed to evaluate the uptake and partitioning of CBZ in lettuce grown in a deep-water culture system (DWC) at low and high concentrations. The first trial (0 µg L⁻¹, 12.5 µg L⁻¹, 25 µg L⁻¹, and 50 µg L⁻¹) of CBZ had few effects on lettuce (Lactuca sativa var. capitata) growth, and low concentrations of accumulated CBZ were found in lettuce tissues. As a result, increased concentrations of CBZ were used in the second trial (0 mg L⁻¹, 21 mg L⁻¹, 41 mg L⁻¹, and 83 mg L⁻¹). Greater amounts of CBZ accumulated in plant tissues and the application of higher rates of CBZ negatively affected the growth and overall health of the lettuce. Further research is needed to determine the impacts of CECs on plant uptake and growth, as well as the environmental conditions. Full article

The growing global concern over plastic waste accumulation has brought this issue to the forefront of environmental discussions. The increasing demand for plastic materials has led to the widespread production of plastic resins. However, the low cost of plastics, combined with high supply and consumption rates, has resulted in a troubling surge in post-consumer plastic waste. At the same time, the essential role plastics play in ensuring quality, convenience, and modern living has made them indispensable. In this context, the concept of circularity introduces a transformative shift in consumption habits, product design, and the management of raw materials and waste. A central strategy for promoting circularity in the plastics economy is the development of chemical recycling technologies. These processes aim to convert plastic waste into higher-value materials for the chemical industry, often generating liquid and gaseous products that can serve as feedstocks—ideally leading to the recovery of the original monomers. As polyolefins are the most widely used plastics worldwide, efficient recovery of their corresponding monomers is crucial to advancing circular strategies. This review explores current methods for the chemical depolymerization of polyolefins and critically analyzes efforts focused on the direct recovery of olefinic monomers. Full article

In view of the growing global need for sustainable protein sources, this study explores the utilization of short-chain fatty acids into single-cell protein using the non-conventional yeast Cyberlindnera jadinii. Short-chain fatty acids can be sustainably produced via anaerobic digestion of organic waste, presenting a promising fermentation substrate for a circular bioeconomy. Cyberlindnera jadinii is demonstrated to be capable of growing on acetate, propionate and butyrate as both a carbon and energy source without strong inhibition. Bioprocess development was conducted in stirred tank bioreactors, where a fed-batch pH-stat bioprocess led to improved efficiency without substrate inhibition. The highest titer of 31.3 ± 1.0 g/L, rate of 0.67 ± 0.02 g/L/h and yield of 0.36 ± 0.01 g/g was achieved with propionate. The resulting biomass contained 41.3% crude protein, and 17.3% crude lipids with 81% unsaturated fatty acids. In contrast to acetate and butyrate, propionate as a substrate led to accumulation of 37% odd-chain fatty acids with titer, rate and yield of 1.74 ± 0.06 g/L, 0.037 ± 0.001 g/L/h and 0.020 ± 0.001 g/g. These findings confirm that short-chain fatty acids are viable fermentation substrates not only for single-cell protein, but also unsaturated and odd-chain fatty acid production with Cyberlindnera jadinii. Full article

Anaerobic digestion (AD) for food waste (FW) treatment has faced many challenges, especially ammonia nitrogen, acid, and salinity inhibition at a high organic loading rate (OLR). Therefore, a systematic understanding of the issues arising during the FW AD process is a necessity under a high OLR (over 3 g-VS/L d). Primarily, in terms of ammonia nitrogen inhibition, ammonia ions inhibit methane synthesis enzymes, and free ammonia (FAN) contributes to the imbalance of microbial protons. Regulation strategies include substrate C/N ratio regulation, microbial domestication, and ammonia nitrogen removal. In addition, with regard to acid inhibition, including volatile fatty acid (VFA) and long-chain fatty acid (LCFA) accumulation, the elevated acid concentration can contribute to reactive oxygen species stress, and a solution to this includes the addition of alkaline agents and trace elements or the use of microbial electrochemical and biofortification technology and micro-aeration-based AD technology. Furthermore, in terms of salinity inhibition, high salinity can result in a rapid increase in cell osmotic pressure, which can cause cell rupture, and water washing and bio-electrochemical AD are defined as solutions. Future research directions are proposed, mainly in terms of avoiding the introduction of novel containments into these regulation strategies and applying them in large-scale AD plants under a high OLR. Full article

Plastic pollution has been recognized as an emerging risk for the aquatic environment. Shifting from the prevailing linear “take-make-dispose” model to a “circular” economy framework is essential for mitigating the environmental impact of plastics. Microplastics (MPs) in the natural environment are formed when synthetic polymers are fragmented and micronized to a size ≤ 5 mm. MPs are a global environmental problem, particularly within aquatic ecosystems, due to their persistence, accumulation, and uncertain long-term effects. This review examines the degradation pathways of polymers that result in MP formulation, their rate and distribution across ecosystems, and their potential entry into food systems. Key challenges include a lack of standardized detection methods, specifically for nanoparticles; limited evidence of long-term toxicity; and the inefficiency of current waste management frameworks. Emphasis is placed on the cradle-to-grave lifecycle of plastic materials, highlighting how poor design, excessive packaging, and inadequate post-consumer treatment contribute to MP release. The transition from Directive 94/62/EC to the new Regulation (EU) 2025/40 marks a significant policy shift towards stronger preventive measures. In line with the waste hierarchy and reduction in unnecessary packaging and plastic use, effective recycling must be supported by appropriate collection systems, improved separation processes, and citizen education to prevent waste and improve recycling rates to minimize the accumulation of MPs in the environment and reduce health impacts. This review identifies critical gaps in current knowledge and suggests crucial approaches in order to mitigate MP pollution and protect marine biodiversity and public health. Full article

This study investigates how larval density and associated temperature changes affect the development and survival of two forensically essential blow fly species, Lucilia sericata and Calliphora vicina. Larvae colonies were reared at 25 °C under controlled conditions, with adults at 23.3 °C on a 16:8 light cycle. Using a split-plot design, we tested four larval densities of 50, 200, 1000, and 2000 individuals at 25 °C and 30 °C, with temperature gradients measured via thermocouple at four mass positions three times daily, and larvae fed liver at ca. 6 g/50 larvae. Key findings revealed density-dependent developmental patterns, with 1000 larvae representing a threshold where thermoregulatory benefits balance competition costs. Temperature gradients showed edge-to-center differentials up to 5.2 °C, yet high-density masses exhibited prolonged development despite warmer microclimates due to hypoxia and waste accumulation. L. sericata demonstrated greater thermal tolerance than C. vicina, particularly at 30 °C, as C. vicina showed 58% reduced emergence. We demonstrated that maggot mass temperature might not be reliable, as they may overestimate developmental rate by 18–22% at densities over 1000 larvae. We recommend a bigger container for maggot mass-related studies, starting with 1000 larvae per container. The study provides a framework for density-adjusted ADD models and highlights climate change implications for blow fly communication dynamics in forensics contexts. Full article

This study elucidates the photocatalytic NOx abatement efficacy of eco-efficient mortars incorporating construction waste-derived aggregates functionalized with nano-TiO₂. The research findings demonstrate a positive correlation between NOx abatement efficiency and nano-TiO₂ substitution ratio, with recycled glass sand (RG)-based panels exhibiting superior performance compared to standard sand and recycled clay brick sand (RCBS)-based counterparts. The employment of ultrasonic dispersion as a nano-TiO₂ incorporation method yields enhanced abatement efficiency relative to direct mixing, attributable to improved photocatalyst dispersion and surface area accessibility. The loading capacity of nano-TiO₂ on recycled aggregates is observed to be positively influenced by the concentration of nano-TiO₂ solution, with recycled clay brick sand demonstrating the highest loading capacity. RG-RCBS panels are shown to exhibit higher NOx abatement efficiency than standard sand (SS)-RCBS panels, with an optimal substitution ratio of 40% glass sand identified for maximizing abatement efficacy in RG-RCBS systems. A decline in NOx abatement efficiency is observed with increasing NOx flow rate and concentration, attributable to reduced pollutant residence time and excess pollutant load exceeding the panels’ processing capacity. Prolonged curing time also results in diminished abatement efficiency, due to microstructural alterations within the mortar matrix and the accumulation of photocatalytic reaction byproducts. Collectively, these findings underscore the potential of recycled aggregate-based mortars, in conjunction with nano-TiO₂, as a viable eco-efficient strategy for NOx abatement, highlighting the critical influence of material selection, photocatalyst loading, and operational parameters on system performance. Full article

Plastic waste accumulation presents critical environmental challenges demanding innovative circular economy solutions. This study developed a comprehensive machine learning framework to systematically identify optimal enzyme combinations for polyester depolymerization. We integrated kinetic parameters from the BRENDA database with sequence-derived features and network topology metrics to train ensemble classifiers predicting enzyme-substrate relationships. A multi-objective optimization algorithm evaluated enzyme combinations across four criteria: prediction confidence, substrate coverage, operational compatibility, and functional diversity. The ensemble classifier achieved 86.3% accuracy across six polymer families, significantly outperforming individual models. Network analysis revealed a modular organization with hub enzymes exhibiting broad substrate specificity. Multi-objective optimization identified 156 Pareto-optimal enzyme combinations, with top-ranked pairs achieving composite scores exceeding 0.89. The Cutinase–PETase combination demonstrated exceptional complementarity (score: $0.875\pm 0.008$), combining complete substrate coverage with high catalytic efficiency. Validation against experimental benchmarks confirmed enhanced depolymerization rates for recommended enzyme cocktails. This framework provides a systematic approach for enzyme prioritization in plastic valorization, advancing biological recycling technologies through data-driven biocatalyst selection while identifying key economic barriers requiring technological innovation. Full article

Today, there is considerable interest in creating artificial microbial consortia to solve various biotechnological problems. The use of such consortia allows for the improvement of process indicators, namely, increasing the rate of accumulation of target products and enhancing the conversion efficiency of the original substrates. In this work, the prospects for creating artificial consortia based on anaerobic sludge (AS) with cells of different yeasts were confirmed to increase the efficiency of methanogenesis in glucose- and glycerol-containing media and obtain biogas with an increased methane content. Yeasts of the genera Saccharomyces, Candida, Kluyveromyces, and Pachysolen were used to create the artificial consortia. Their concentration in the biomass of consortium cells was 1.5%. Yeast cells were used in an immobilized form, which was obtained by incorporating cells into a cryogel of polyvinyl alcohol. The possibility of increasing the efficiency of methanogenesis by 1.5 times in relation to the control (AS without the addition of yeast cells) was demonstrated. Using a consortium composed of methanogenic sludge and yeast cells of the genus Pachysolen, known for their ability to convert glycerol into ethanol under aerobic conditions, the possibility of highly efficient anaerobic conversion of glycerol into biogas was shown for the first time. Analysis of the metabolic activity of the consortia not only for the main components of the gas phase (CH₄, CO₂, and H₂) and metabolites in the cell culture medium, but also for the concentration of intracellular adenosine triphosphate (ATP), controlled by the method of bioluminescent ATP-metry, showed a high level of functionality and thus, prospects for using such consortia in methanogenesis processes. The advantages and the prospect of using the developed consortia instead of individual AS for the treatment of methanogenic wastewater were confirmed during static tests conducted with several samples of real and model waste. Full article

The rising demand for lithium-ion batteries (LIBs), driven by the growing consumption of electronic devices and the expansion of electric vehicles, is leading to a concerning depletion of primary metal resources and a significant accumulation of electronic waste. This urgent challenge highlights the need for sustainable recovery methods to extract valuable metals from spent LIBs, aligning with circular economy principles. In this study, the preparation of spent batteries for the bioleaching process was achieved with minimal manipulation. This included a preliminary discharge to ensure safety in subsequent processes and a brief crushing to facilitate the access of leaching agents to valuable metals. Unlike most studies that grind batteries to obtain powders between 70 and 200 microns, our approach works with particles sized around 5 mm. Additionally, our preparation process avoids any thermal or chemical treatments. This straightforward pre-treatment process marks a significant advancement by reducing the complexity and cost of processing. A systematic study was conducted on various fractions of the large particle sizes, using Fe (III) produced through bio-oxidation by A. ferrooxidans and biogenically obtained H2SO4 from A. thiooxidans. The highest metal extraction rates were achieved using the unsorted fraction, directly obtained from the black mass after the grinding process, without additional particle separation. When treated with bio-oxidized Fe (III), this fraction achieved a 95% recovery of Cu, Ni, and Al within 20 min, and over 90% recovery of Co, Mn, and Li within approximately 30 min. These recovery rates are attributed to the combined reducing power of Al and Cu already present in the black mass and the Fe (II) generated during the oxidation reactions of metallic Cu and Al. These elements actively facilitate the reduction of transition metal oxides into their more soluble, lower-valence states, enhancing the overall metal solubilization process. The extraction was carried out at room temperature in an acidic medium with a pH no lower than 1.5. These results demonstrate significant potential for efficient metal recovery from spent batteries with minimal pre-treatment, minimizing environmental impact. Additionally, the simplified residue preparation process can be easily integrated into existing waste management facilities without the need for additional equipment. Full article

Phytoremediation strategies present promising approaches for mitigating metal contamination in soils. This study examines the effectiveness of compost and biochar amendments, applied separately or in combination, in altering the properties of sandy mining waste soils (Sw) and affecting levels of metallic trace elements (MTEs). The research evaluates changes in soil physicochemical parameters, metal concentrations in soil pore water (SPW), and metal accumulation in Phaseolus vulgaris. Compost and biochar addition significantly affected SPW pH, which remained alkaline, while increasing SPW electrical conductivity (EC). A treatment combining 20% compost and 2% biochar (SwC20B2) enhanced soil enzymatic activities, with the highest values observed for FDA and ALP activities. Metal availability in the SPW appeared higher on D(0) compared to D(12), with notable reductions in Pb and Zn concentrations observed in the SwC20B2 treatment. Despite this decline, metal accumulation in plant shoots did not significantly differ from that in plants grown in unamended Sw, although all plants exhibited substantial growth. The minor decrease in SPW pH, likely due to compost, may have enhanced metal mobility at D(0). Notably, SPW Pb and Zn concentrations increased with higher compost rates, with SwC20B2 registering the highest Pb and Zn. Although these amendments did not directly alleviate metal mobility, they show potential for use in phytostabilization strategies by using suitable plant species. Full article

The increasing accumulation of polymer waste presents a significant environmental challenge and a critical opportunity for the development of circular and sustainable membranes. The answer to this complex topic requires an integral approach covering different aspects of the problem. This paper, therefore, explores innovative approaches for the chemical recycling of polymer waste into value-added products, with a specific emphasis on the production of advanced biopolymer membranes. By converting discarded materials into functional polymers through depolymerization and chemical modification processes, new pathways are emerging for the fabrication of high-performance membranes used in filtration, biomedical applications, and energy systems. Among these, electrospinning has gained prominence as a versatile and scalable technique for producing nanostructured membranes with tailored properties. As a key case study presented, the focus was on the optimization of electrospinning parameters, including solvents, polymer concentration, voltage, and flow rate, for the investigation of membranes derived from recycled materials to achieve net-zero technology. Moreover, the environmental benefits of this approach are discussed within a zero-waste and net-zero carbon framework, emphasizing the integration of life cycle assessment to evaluate sustainability metrics. This paper underscores the potential of polymer waste as a feedstock for circular membrane technologies and provides a roadmap for future innovations in waste-to-resource strategies. The results of the demonstrated case example clearly demonstrate how the effects of processing conditions on the production of fine-tuned biodegradable membranes with controlled porosity influenced membrane properties, including mechanical strength and surface functionality, for the desired suppression of the coffee-ring effect. Full article

The feasibility of using a combination of organic fertilizer with a reduced rate of chemical nitrogen fertilizer as an alternative to conventional inorganic fertilization was tested on the growth and biomass accumulation of hemp plants and the phytochemical accumulation in their inflorescences. To achieve this goal, a field experiment was set up with the following nine treatments: F0, no fertilizer; NPK, mineral fertilizer with 100 kg ha⁻¹ nitrogen; C1, compost from solid digestate (50%) + cardoon-based spent mushroom substrate (50%); C2, compost from solid digestate (50%) + straw-based spent mushroom substrate (50%); C3, C4, C5, and C6, composts from solid digestate (50%, 67%, 75%, and 84%, respectively) and cardoon waste (50%, 33%, 25%, and 16%, respectively); SD, non-composted solid digestate. C1–C6 and SD were added to the soil, along with half the rate (50 kg ha⁻¹) of chemical nitrogen fertilizer. Taking F0 as a reference, all fertilized treatments, except C6 and SD, showed a notable increase in plant growth and biomass accumulation in the stem, inflorescence, and whole plant. Among the organic treatments, the best growth performances were detected in C1 and C5, which reached, or even exceeded, that of NPK. Compared to F0, all fertilized treatments had high phenolic acid and flavonoid yields, while high carotenoid, tocopherol, terpene, and cannabinoid (mainly CBD) yields were detected in all fertilized treatments except C6 and SD. Among the organic treatments, C1 and C5 stood out for their highest phenolic acid, flavonoid, carotenoid, and tocopherol yields, while C1, C2, and C3 stood out for their highest terpene and cannabinoid yields, which, in both cases, reached, or even exceeded, those of NPK. Overall, our findings show that 50% replacement of inorganic nitrogen fertilizer with C1 to C5 composts may represent a cost-effective and environmentally safe alternative to conventional inorganic fertilization that can sustain the growth of hemp plant and the phytochemical accumulation in its inflorescences, thus promoting the use of this crop for fiber and bioenergy production, as well as for applications in food, nutraceutical, agrochemical, and cosmetic sectors. Full article

Food waste containing meat and fish presents a considerable environmental challenge due to regulatory constraints preventing its use in industrial insect farming. Although substrates derived from meat and fish are not currently approved for industrial insect feed production due to regulatory constraints, this study explores their potential in bioconversion through Hermetia illucens larvae. In this study, five different former foodstuffs containing meat and/or fish were tested to evaluate their suitability for BSFL rearing. The substrates included pizza with salami (PIZZA), cheeseburger (CHB), pasta Bolognese with meat (PASTA), chicken salad (CHISA), and fish salad (FISA). Results showed that BSFL successfully developed on all tested substrates. The highest performance was observed for FISA, with a total larval weight of 35.21 ± 3.91 g, dry matter yield of 11.21 ± 0.45 g, survival rate of 96.63 ± 0.40%, and the most efficient feed conversion ratio (FCR, 4.11 ± 0.59). Heavy metal analysis revealed substantial bioaccumulation of lead (Pb) and cadmium (Cd) in larvae. In particular, larvae reared on PIZZA showed a Pb concentration of 4.68 μg/100 g, with a corresponding bioaccumulation factor (BAF) of approximately 1.5. Cadmium accumulation was most notable in larvae fed CHB, with a Cd concentration of 0.41 ± 0.33 μg/100 g and a BAF of about 2.1. Despite this bioaccumulation, all detected concentrations remained well below the regulatory limits set by the European Union for animal feed, indicating not only the feasibility of H. illucens larvae in sustainable waste management but also its use as a safe protein source in animal feed. This research highlights the viability of integrating such food waste into insect bioconversion systems. With appropriate risk management, this practice could significantly improve nutrient recycling, waste management, and the circular economy, urging a regulatory review to allow broader substrate utilization. These positive outcomes underscore the potential of integrating currently restricted animal-derived food waste streams into H. illucens-based bioconversion systems, unlocking additional value for the circular economy and contributing to more efficient waste management practices. Full article