Circular Economy

Prep Biochem Biotechnol. 2025 Jul 5:1-13. doi: 10.1080/10826068.2025.2522473. Online ahead of print.

ABSTRACT

This study demonstrates a circular economy approach by utilizing glycerol pitch, biodiesel co-product as a carbon source to produce biodegradable terpolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-4-hydroxybutyrate) [P(3HB-co-3HV-co-4HB)] using Cupriavidus malaysiensis USMAA1020. Various carbon sources, including oleic acid, 1,4-butanediol, and 1-pentanol, were combined with glycerol pitch as main substrates. The experiments were conducted in a mineral salt medium (MSM) with a high concentration of carbon source and limited nitrogen, which promotes both bacterial growth and PHA accumulation. Preliminary studies indicated, the composition of the polymer was triggered by varying the concentration of 1,4-butanediol, oleic acid, and glycerol pitch while keeping the amount of 1-pentanol constant. After optimization, the PHA content in dry biomass increased from 60 ± 12 to 88 ± 5 wt%, while the residual dry cell weight (RDCW) slightly decreased from 1.77 ± 0.53 to 1.11 ± 0.41 g/L. The combination of glycerol pitch in the biosynthesis of the terpolymer proved effective for the cost-efficient and sustainable production of P(3HB-co-3HV-co-4HB). This process could drive innovation while reducing waste, by harnessing glycerol pitch's properties, sustainable co-product of biodiesel production into a valuable biodegradable polymer. The characterization of the terpolymer revealed a diverse range of properties, making it suitable for various applications.

PMID:40616795 | DOI:10.1080/10826068.2025.2522473

Environ Res. 2025 Jul 3:122208. doi: 10.1016/j.envres.2025.122208. Online ahead of print.

ABSTRACT

Anionic surfactants (ASs) represent a class of contaminants persistently released into aquatic environments, with anionic fluorinated surfactants emerging as a significant concern due to their potential to infiltrate potable water and pose a threat to human health. Therefore, the development of novel tools for their early detection is crucial. In this study, the methylene blue (MB) redox probe, previously known for its selectivity toward ASs, was electropolymerized onto the surface of carbon nanotubes -modified graphite screen-printed electrodes. The electroanalytical ability of the platform was tested by cyclic (CV) and square-wave (SWV) voltammetries upon the addition of sodium dodecyl sulfate as model analyte, due to its ubiquitous presence in the environment. A comprehensive exploration of key factors, such as scan cycles, optimal instrumental parameters, and pH effect was undertaken, revealing a stable and controlled redox response. To further enhance the sensitivity and detection capabilities of the MB-based sensor, gold nanoparticles (AuNPs) were incorporated, forming MB@AuNPs-modified electrodes. This enhanced system demonstrated excellent linearity (0.05-1 ng/mL and 5-50 ng/mL), high reproducibility, and improved detection limits (8.5 pg/mL and 0.23 ng/mL), attributed to the synergistic effect of MB and AuNPs in boosting the reduction current. The sensor was successfully applied to wastewater samples, benchmarked against the MBAS reference method, and further validated for the detection of two long-chain PFAS in drinking water. Supported by quantum mechanical calculations and optical studies, this proof-of-concept platform represents a sustainable approach for efficient water quality monitoring and management.

PMID:40617567 | DOI:10.1016/j.envres.2025.122208

Sci Total Environ. 2025 Jul 4;993:180016. doi: 10.1016/j.scitotenv.2025.180016. Online ahead of print.

ABSTRACT

Microplastic (MP) fibers are pervasive in the environment, posing significant ecological risks due to their persistence and potential toxicity. Accurate quantification of fiber volume is crucial for assessing its environmental flux and ecological impacts. Traditional methods, reliant on geometric assumptions, often miscalculate the volume of complex-shaped fibers, particularly those with curvature, due to limitations in accurately extracting length and width. This study introduces a novel framework leveraging machine learning and image recognition to estimate MP fiber volume. Our volume estimation model incorporates shape descriptors and additional two-dimensional (2D) features, such as area, allowing it to learn volumetric patterns across diverse fiber and fragment shapes. Compared to geometric models, it demonstrated superior performance, achieving 89.43 % accuracy and a mean absolute percentage error (MAPE) of 10.58 % ± 4.30 % in external testing with real-world MP samples. Error analysis indicates that our machine learning approach overcomes the limitations of geometric assumptions. Interpretability analysis highlights area as the most significant feature for volume estimation, followed by aspect ratio, circularity, and solidity for fibrous MPs. This study underscores the potential of machine learning in MP volume estimation, offering a valuable tool for environmental scientists and policymakers to better understand and manage MP pollution.

PMID:40617101 | DOI:10.1016/j.scitotenv.2025.180016

Biotechnol Bioeng. 2025 Jul 5. doi: 10.1002/bit.70015. Online ahead of print.

ABSTRACT

Phosphogypsum (PG), a byproduct of phosphate mining, contains sulfate that can be leached and converted to elemental sulfur, thus offering a sustainable opportunity to recover sulfur (S) as a step toward a circular economy. Calcium, at ~15 mM in PG leachate, creates inorganic precipitation that interferes with biological sulfate reduction, the first step of S recovery. Here, we evaluated the effectiveness of using cation-exchange to lower the calcium concentration in water-leached PG (PG water) delivered to a H₂-based membrane biofilm reactor (H₂-MBfR) employed to reduce sulfate to sulfide. A high sulfate flux (1 gS/m²-day) and 65% sulfate reduction were achieved despite a high pH (10) resulting from base production during sulfate reduction. However, soluble sulfide was only 20% of the reduced S, possibly due to precipitation of sulfide, iron, and phosphate, and alkalinity analysis revealed possible formation of polysulfides. Shallow metagenomics of the biofilm documented that Desulfomicrobium was the dominant sulfate-reducing bacterium, while Thauera, a mixotroph capable of sulfate reduction and sulfide oxidation, also was an important genus. The metagenomics also revealed the presence of methanogens and acetogens that competed for H₂ and CO₂. Although calcium removal from PG water improved sulfate reduction and reduced inorganic precipitation in the H₂-MBfR, soluble sulfide generation must be improved by supplying sufficient CO₂ to moderate pH increase due to sulfate reduction and by controlling the H₂-delivery capacity to limit methanogens and acetogens.

PMID:40616449 | DOI:10.1002/bit.70015

Water Res. 2025 Jun 27;285:124122. doi: 10.1016/j.watres.2025.124122. Online ahead of print.

ABSTRACT

Greenhouse gas emissions from wastewater treatment remain a formidable challenge in reducing global carbon footprints. Here, we present a novel Co-MoS₂/ZnO (Co-ZOM)-mediated ternary coupling system integrating piezo-photocatalytic and Fenton-like processes, achieving efficient conversion of organic pollutants into carbon monoxide (CO) with minimized greenhouse gas outputs. The Co-ZOM-2 catalyst delivers an outstanding CO yield of 114.8 µmol·g^-1·h^-1, markedly surpassing the performance of previously reported systems (∼40.7 µmol·g^-1·h^-1), and achieves 16.6 % phenol conversion efficiency within 14 hours via a unique sequential oxidation-reduction pathway, where pollutants are first oxidized and then intermediate carbonates are selectively reduced to CO. The inclusion of ZnO maintains a neutral pH environment, effectively preventing potential damage to both equipment and ecosystems associated with highly acidic conditions. Notably, the ternary system demonstrates robust performance in high-salt wastewater matrices, showcasing its practical applicability. Moreover, Life Cycle Assessment (LCA) indicates that it reduces carbon emissions and lowers cumulative environmental impact compared to conventional Fenton-like methods. These findings underscore the system's potential for wastewater valorization, aligning with circular economy principles.

PMID:40614504 | DOI:10.1016/j.watres.2025.124122

Environ Pollut. 2025 Jul 2:126761. doi: 10.1016/j.envpol.2025.126761. Online ahead of print.

ABSTRACT

The seafood processing industry produces large volumes of wastewater rich in organic matter, nutrients, and salts, often exceeding legal discharge limits and posing environmental risks. This review introduces a five-stage classification of seafood processing wastewater (SPW), based on key processing operations: initial washings (stage 1), filleting (stage 2), cooking and canning (stage 3), final washings (stage 4), and combined discharge (stage 5). Unlike previous reviews, this structured approach allows for a clearer link between processing steps and pollutant profiles. By adopting this structure, our review addresses a specific gap: the need for a standardized yet detailed framework to understand pollutant load variation across different seafood processing steps. Results show that stage 3 wastewater contain the highest concentrations of BOD, COD, TN, TAN, TP, and oils, followed by stage 2. In contrast, stage 1 and 4 wastewaters carry lower pollutant loads. This categorization enables identification of critical control points and supports the design of stage-specific treatment strategies. The findings highlight the necessity of distinct treatment approaches to improve resource efficiency and reduce environmental impact in seafood processing. This not only improves effectiveness of treatment, but also enables targeted circular economy interventions such as stage-specific recovery and valorisation strategies.

PMID:40614957 | DOI:10.1016/j.envpol.2025.126761

Sci Rep. 2025 Jul 4;15(1):23860. doi: 10.1038/s41598-025-08554-6.

ABSTRACT

The study attempts to establish a connection between circular economy practices and urban air pollution in the United States, utilizing panel data from fifty states from 2009 to 2022. Given the poor state of air quality and its ominous threat to public health and environmental sustainability, the present study aims to provide empirical evidence on the effectiveness of circular economy methods in reducing harmful air pollutants. Applying the GMM estimator to the regression analysis reveals a significant positive relationship between high recycling rates and reduced air pollution levels. An Environmental Kuznets Curve has also been depicted by this study-a postulation showing that although per capita income may be increasing to start with higher pollution levels, at high-income levels it could further lead to improving air quality. These findings demonstrate the significant impact of population density on pollution levels, highlighting some of the challenges faced by metropolitan regions. The article underscores the significance of incorporating circular economy approaches into urban policy frameworks and offers fresh perspectives on guiding sustainable urban development processes.

PMID:40615572 | PMC:PMC12227538 | DOI:10.1038/s41598-025-08554-6

Mar Pollut Bull. 2025 Jul 3;220:118378. doi: 10.1016/j.marpolbul.2025.118378. Online ahead of print.

ABSTRACT

Fiber-reinforced polymer (FRP), also known as fiberglass, is a widely used composite material in marine, transportation, and construction industries because of its high strength, lightweight properties, and corrosion resistance. While FRPs are advantageous for these applications, the disposal and recycling of FRPs, especially in boats, remain challenging. The global FRP market valued at $3.9 billion USD in 2022. An increasing number of FRP vessels are reaching the end of their lifecycle, amounting to a global total of 250,000 to 500,000 tons of end-of-life vessels each year, contributing to environmental concerns. FRP boats, which have been popular since the 1950s, are often disposed of in landfills, as recycling methods are limited. Abandoned vessels pose hazards to navigation, ecosystems, and human health, releasing pollutants and breaking down into microplastics. Countries are exploring alternatives such as pyrolysis and recycling programs, although progress varies. An extended producer responsibility (EPR) system, which funds boat recycling, is an example of a proactive policy. However, broader efforts are needed to improve the recycling infrastructure and research sustainable materials. Addressing the environmental impact of FRP vessels requires collaborative research, policy development, and innovative solutions such as eco-design and improved recycling methods, especially as the global demand for boats and FRP materials continues to grow.

PMID:40614403 | DOI:10.1016/j.marpolbul.2025.118378

Lancet Reg Health Eur. 2025 Jun 21;54:101353. doi: 10.1016/j.lanepe.2025.101353. eCollection 2025 Jul.

ABSTRACT

Work and working conditions are fundamental social determinants of health. Climate change poses an urgent and growing threat to workers' health, through both direct exposure to environmental hazards and indirect exacerbation of social and health inequalities. Occupational health, which focusses on the promotion of mental and physical health and well-being of workers, is a key but often overlooked area in this context. Research at the intersection of climate change and occupational health remains limited. At the same time, climate change mitigation and adaptation efforts are driving rapid transformations in the workplace, including shifts towards sustainability and circular economy models. These transitions are creating new occupational hazards, including in renewable energy and circular economy sectors. We argue for increased investment in occupational health research and surveillance to address the evolving impacts of both climate change and the green transition, to better promote and protect workers' health and rights.

PMID:40613104 | PMC:PMC12226071 | DOI:10.1016/j.lanepe.2025.101353

Crit Rev Food Sci Nutr. 2025 Jul 3:1-18. doi: 10.1080/10408398.2025.2527946. Online ahead of print.

ABSTRACT

Global fruit production generates approximately 0.9 billion tons annually; however, nearly one-third of this yield is lost or wasted during post-harvest handling and processing. Among the underutilized by-products are fruit seeds, which represent a low-cost and valuable source of oils rich in bioactive compounds. These oils hold promising applications in the food, cosmetic, pharmaceutical, and nutraceutical industries due to their functional and nutritional properties. To realize this potential, efficient and sustainable extraction technologies are essential. Supercritical fluid extraction, particularly with carbon dioxide (SFE-CO₂), has gained considerable attention as a green, nontoxic, and scalable method for the extraction of high-value oils from plant-based materials. This review provides a comprehensive overview of SFE-CO₂ application in the extraction of fruit seed oils, discussing their chemical profiles and the influence of operating parameters on extraction efficiency. By promoting the recovery of high-value compounds from low-cost biomass, SFE-CO₂ supports both economic and environmental objectives, aligning with circular economy principles. The review also identifies current challenges and future opportunities for optimization of this green extraction technology in industrial applications.

PMID:40611616 | DOI:10.1080/10408398.2025.2527946