Polyhydroxybutyrate (PHB), one of the most widely used biodegradable plastics, has gained attention as an environmentally friendly material synthesized and decomposed by microorganisms. However, its biodegradation behavior under landfill conditions remains insufficiently understood. In Japan, approximately 70% of incineration ash is disposed of in landfills, where soils are often exposed to high pH environments. Despite this, limited research has been conducted on PHB degradation under such alkaline landfill conditions. This study aims to evaluate the biodegradability of PHB in operational landfill soil and to elucidate the influence of high pH and the associated microbial community on its decomposition.

Soil samples were collected from the Nishi-Iburi Regional Union Final Disposal Site in Muroran, Hokkaido. As a control, uncontaminated campus soil (pH 7.0) from the Muroran Institute of Technology was used. PHB films were buried in each soil, and weight loss was measured over 28 days. On day 28, PHB in the control soil showed a 26.8% weight loss, compared to only 13.2% in the landfill soil. Microbial community structures were analyzed, and PHB-degrading bacteria were isolated using a mineral salt agar medium with PHB as the sole carbon source. A total of 16 strains were isolated from the campus soil, while only 12 were obtained from the landfill soil. These findings indicate that the strongly alkaline conditions in landfill soil suppress both the abundance and activity of PHB-degrading bacteria. Additionally, although incineration ash is stabilized before disposal, the potential presence of residual heavy metals may further affect biodegradation processes.

This study offers new insights into the fate of biodegradable plastics after disposal and contributes to the development of improved evaluation and management strategies for landfill environments.

Biodegradable plastics have emerged as a promising solution to plastic waste pollution, with increasing efforts directed toward improving their degradation under natural environmental conditions. Among polyhydroxyalkanoates (PHAs), polyhydroxybutyrate (PHB) is the most extensively studied due to its high biodegradability. However, commercial PHB-based materials typically contain various additives to enhance their mechanical properties and processability. Some of these additives are potentially toxic and may leach into the environment, raising concerns about their impact on the microbial degradation of PHB.

This study investigated the influence of selected plastic additives on the biodegradation of PHB. Three additives—benzenesulfonamide (50, 100, and 200 μg/L), dipropylene glycol (50, 100, and 200 μg/L), and triethylene glycol (100, 200, and 500 μg/L)—were evaluated at concentrations equivalent to those commonly found in commercial PHB products. PHB was incorporated into a mineral salt (MS) medium and inoculated with Ralstonia sp. C1, a known PHB-degrading bacterium, under aerobic conditions. Biodegradation was monitored over a 96-hour period by measuring the degradation progress at 24-hour intervals, and the results were compared to those in a control group without additives.

All three additives were degraded by more than 98%, and no significant differences in PHB degradation rates were observed between the additive-treated and control groups. These results suggest that the tested additives do not adversely affect PHB biodegradation. The findings also imply that Ralstonia sp. C1 may tolerate or co-metabolize these compounds, thereby preserving the biodegradability of PHB-based materials in the presence of such additives.

Polyhydroxyalkanoates (PHAs) have attracted global attention as sustainable bioplastics. In our previous study, we demonstrated that Bacillus sp. CYR1 can produce PHA using glucose and sterilized raw sewage water as a dilution medium, replacing tap water. However, the sterilization process incurs high energy costs, posing a significant challenge for industrial-scale production.

In this study, we evaluated PHA production using non-sterilized sewage water as the dilution medium and compared the results with those obtained under sterilized conditions, aiming to assess the feasibility of non-sterilized sewage water for PHA production. Experiments were conducted in 300 mL Erlenmeyer flasks containing 100 mL of sewage water (pH = 7.0) supplemented with 20 g/L glucose. Bacillus sp. CYR1 was inoculated at 8% (v/v) and aerobically cultured at 30 ℃ with shaking at 120 rpm for 5 days (primary culture). After cultivation, cells were harvested through centrifugation, and the supernatant was reused for secondary culture under identical conditions. This reuse of the supernatant continued through to tertiary culture until all glucose had been completely consumed.

To improve the PHA yield, we further investigated the effects of increasing the initial inoculum size at the start of each culture and raising the culture temperature to 40 ℃. Under sterilized conditions, a maximum PHA content of 70% (dry cell weight) was achieved, while under non-sterilized conditions, a PHA content of 56% was obtained. Although the yield decreased with non-sterilized sewage water, the production remained at an acceptable level.

These results indicate that non-sterilized sewage water has potential as a cost-effective and sustainable dilution medium for industrial-scale PHA production.

Recent research has focused on identifying cost-effective alternatives to conventional substrates used in polyhydroxyalkanoic acid (PHA) production. Among these, lignin—a complex aromatic polymer and the second most abundant organic compound on Earth after cellulose—has gained attention. Lignin is commonly discarded as a byproduct of paper and agricultural industries, yet its recalcitrant structure makes it difficult to biodegrade. However, during industrial processing, lignin is partially broken down into phenolic compounds such as ferulic acid, which are more amenable to microbial utilization. Despite this, the potential of these phenolic degradation products as substrates for PHA production has not been thoroughly explored.

In this study, we assessed the ability of various microorganisms to utilize lignin-derived phenolic compounds, with the ultimate goal of enabling PHA production from lignin waste streams. Strains from the genera Comamonas, Sphingobium, and Pseudomonas, known for both phenolic compound degradation and PHA biosynthesis, were tested. Four representative lignin-derived compounds—ferulic acid, p-coumaric acid, vanillin, and 4-hydroxybenzoic acid—were used as sole carbon sources in minimal salts (MS) medium. Each compound was dissolved in ethanol and added at concentrations of 0.1 g/L and 0.5 g/L, reflecting levels typically found in acid hydrolysates and kraft pulp.

The experimental results showed that Sphingobium jiangsuense (NBRC 112973) was able to grow on ferulic acid and vanillin, while Sphingobium sp. (NBRC 103272) utilized only ferulic acid. Pseudomonas putida (NBRC 100988) grew on all tested compounds except ferulic acid. These results demonstrate that the tested strains can metabolize a range of lignin-derived phenolics.

Based on these findings, we aim to further evaluate PHA production using these strains with individual or mixed phenolic substrates to assess production yields and overall feasibility.

The treatment of winery wastewater (WWW) is crucial for surface water protection and/or enabling water reuse. While biological treatment offers a flexible and cost-effective approach, monitoring and process control remain quite complex. Machine learning (ML) models have gained attention as effective tools to address these challenges. However, extensive operational data from such systems is inherently limited; monitoring specific recalcitrant compounds (e.g. polyphenols) is time-consuming and costly due to complex analytical methodologies and chemical reagent disposal. This study aimed to develop and evaluate ML models to predict polyphenol concentration after biological treatment using a small and high-dimensional dataset. A Sequencing Batch Reactor (SBR), fed with WWW, was monitored for 140 days, generating a small yet comprehensive dataset (38 features and 36 observations) that captured different operational conditions. These features served as input to predict polyphenol concentration (target). Three ML algorithms were evaluated: ElasticNet (EN), Support Vector Regression (SVR) and Multi-Layer Perceptron Regressor (MLPR). To maximize training data and ensure robust evaluation given the limited dataset, Leave-One-Out Cross-Validation (LOOCV) was used for model performance assessment. Mean Absolute Error (MAE) and Mean Absolute Percentage Error (MAPE) were employed as evaluation metrics. For models with default parameters, the EN model demonstrated the best initial predictive capacity for polyphenol concentration (MAE: 1.08 ± 0.94 mg/L; MAPE: 11.7 ± 12.5%). However, after feature selection and hyperparameter tuning, the SVR model achieved superior predictive capability (MAE: 0.88 ± 0.68 mg/L; MAPE: 9.3 ± 8.3%) via LOOCV. This study established a robust SVR predictive model for polyphenol concentration in SBR winery wastewater treatment. Despite the small dataset, LOOCV, feature selection and hyperparameter tuning ensured the development of a robust model with promising performance and generalization. This predictive tool offers significant potential for real-time monitoring, SBR optimization, and enhancing polyphenol removal, contributing to environmental sustainability in winery wastewater.

Since the signing of the Paris Agreement in 2016, there has been a growing emphasis on achieving sustainability across various sectors. One of these sectors is logistics. In order for this sector to be sustainable, an area of study called Green Logistics has been established. The aim of this study is to provide a literature analysis that represents the applications of Operation Research in Green Logistics, while also seeking to pinpoint gaps in research concerning these applications and offer insights for future investigations.

Leveraging data from the Web of Science and Scopus databases since 2021, duplicate records are eliminated using R Studio. VOSViewer software is used to analyze bibliometric networks, resulting in findings that include a classification of studies based on their country relationships and prevalent research fields. Moreover, a thorough examination of articles are conducted, categorizing them according to their objective functions and solution methods.

The results are evaluated to identify research gaps and potential future studies. Through Keyword co-occurrence analysis, the top three prevalent research areas are identified. These are Electrical Vehicle, Routing, and Cold Chain Logistic. The solution methodologies frequently involve algorithms, often comprising combinations of two algorithms or improvements to existing ones. This study contributes to advancing knowledge in the field of applications of Operation Research in Green Logistics.

Introduction: Synthetic dyes are extensively used in various industries. However, their persistence, toxicity, and resistance to biodegradation make them significant environmental pollutants, particularly in wastewater. Traditional treatment methods often fall short in completely removing such contaminants. In recent years, photocatalysis using semiconductor materials has emerged as a promising approach to dye degradation under mild conditions. Among various metal oxide photocatalysts, zinc ferrite (ZnFe₂O₄) has gained attention due to its narrow band gap, good stability, low cost, and activation under visible light.

Methods: ZnFe₂O₄ nanoparticles (NPs) were synthesized using a co-precipitation process and tested for photocatalytic effectiveness in degrading synthetic dyes under visible light. UV-Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) were used to confirm the structural, optical, and morphological features of the produced ZnFe₂O₄ sample. The photocatalytic activity was tested with Fast Green FCF and Orange II Sodium Salt, two common azo dyes.

Results: The spectrophotometric monitoring of dye degradation revealed that the produced material had significant photocatalytic efficacy. Under visible light irradiation for 90 minutes, the ZnFe₂O₄ NPs achieved 54% degradation of Fast Green FCF and 73% degradation of Orange II Sodium Salt.

Conclusion: This study emphasizes the benefits of utilizing ZnFe₂O₄ NPs as a visible-light-activated, cost-effective, and environmentally friendly photocatalyst. These findings add to the growing corpus of research aimed at establishing sustainable wastewater treatment options.

The presented work was motivated by the search for a low-cost and efficient adsorbent for dye removal from wastewater [1]. Raw materials from agricultural and forestry activities, such as coconut shells, olive stones, almond shells, and cork residues, were used, as collected from the field, for dye removal from wastewater. These raw materials also served as precursors for the production of activated carbon (ACs), using KOH as an activating agent, at 973 K. The adsorbents were characterized physically and texturally. It was observed that natural adsorbents have lower carbon content, surface area, and porous volume and higher acidic surfaces than their respective ACs.

Although ACs in general have superior performance in removing pollutants (dyes, pesticides, drugs) when compared to their precursors, to improve the properties of ACs and their performance in methylene blue (MB) removal from water, these were subjected to a modification process involving the introduction of nitrogen into their matrix during the activation procedure.

Screening a diversity of low-cost, available raw materials allows for the identification of those that present a high adsorption capacity, directly or after being converted into ACs, for MB removal from water. These were proposed for use in pollutant removal from water used for human consumption, especially in developing countries, where wastewater is taken from lakes, wells, and rivers and consumed without any previous treatment. This work allows us to valorize subproducts from agricultural and forestry activities, removing them from landfills and obtaining adsorbent materials that are successfully used in the treatment of water that can even be used for consumption, thus closing the cycle of the circular economy.

[1] Cansado, I.P.P., Geraldo, P.F., Mourão, P.A.M., Castanheiro, J.E., Carreiro, E.P., and Suhas. Utilization of Biomass Waste at Water Treatment. Resources, vol. 13, no. 3, Mar. 2024, doi: 10.3390/resources13030037.

Propylene production through the CO₂-assisted oxidative dehydrogenation of propane is considered an effective route for addressing the ever-increasing demand for propylene and simultaneously utilizing CO₂. In this study, a series of alumina-supported gallium oxide catalysts with variable Ga₂O₃ loadings was synthesized, characterized, and evaluated with respect to their activity for the oxidative dehydrogenation of propane with CO₂. Surface basicity was measured through CO₂-TPD experiments using mass spectrometry (MS) and in situ FTIR spectroscopy techniques, while surface acidity was determined by employing potentiometric titration and pyridine adsorption/desorption experiments. XRD, BET, and SEM-EDS techniques were also applied for the determination of the catalysts’ physicochemical and morphological properties. The results showed that surface basicity was maximized for the sample containing 20 wt.% Ga₂O₃, whereas surface acidity monotonically increased with an increasing Ga₂O₃ loading. Catalytic activity was found to be strongly influenced by the Ga₂O₃ concentration and optimized for the 30%Ga₂O₃-Al₂O₃ catalyst, which was characterized by moderate surface acidity and basicity. This catalyst was not only able to enhance propane's conversion into propylene, which reached 59% at ~600 ^oC with a corresponding propylene yield of 39%, but also to limit the undesired reactions of propane hydrogenolysis and propane/propylene decomposition, which were responsible for the formation of C₂H₄, CH₄, C₂H₆, and coke. Time-on-stream stability tests showed that the 30%Ga₂O₃–Al₂O₃ catalyst exhibited very good stability at 550 °C for 12 h, where byproduct formation and carbon deposition were limited, whereas it was gradually deactivated with the time on stream when the reaction occurred at elevated temperatures (>600 °C). Mechanistic studies conducted using in situ FTIR and transient-MS techniques indicated that the reaction proceeded through a two-step oxidative route, with the participation of CO₂ in the abstraction of H₂, originated by propane dehydrogenation, through the RWGS reaction, shifting the thermodynamic equilibrium towards propylene generation.

Wastewater streams are a low-cost nutrient source for cultivating microalgae and cyanobacteria. However, single streams often exhibit imbalanced nutrient profiles, insufficient to support optimal microbial growth. Mixing streams with complementary physicochemical properties can balance nutrients and eliminate the need for external supplementation. Optimizing the mixing ratio is essential to achieve favorable carbon-to-nitrogen (C:N) ratios, enhance biomass and biocompound production, and improve culture conditions such as turbidity and pH. This study aimed to identify the optimal mixing ratio of two agro-industrial wastewaters, second cheese whey (SCW) and poultry wastewater (PW), for the cultivation of a Leptolyngbya-dominated consortium. SCW had higher organic and lower inorganic nutrient content than PW. Increasing the SCW proportion raised the C:N ratio and induced N and P limitations, conditions known to promote lipid accumulation. Four SCW:PW ratios (50:50%, 60:40%, 70:30% and 85:15%) were examined based on the initial dissolved chemical oxygen demand (d-COD) concentration of 3000 mg L⁻¹. The 60:40% and 70:30% SCW:PW ratios yielded the highest biomass productivities (276.6 and 268.3 mg L⁻¹ d^−1, respectively), while the 50:50% resulted in the lowest productivity (174.6 mg L⁻¹ d⁻¹), likely due to turbidity. A progressive enhancement in pollutant removal efficiency was observed with increasing SCW proportions. The 70:30% ratio achieved the highest d-COD (89.2%), total nitrogen (64%) and PO₄^3--P (60%) removal, as well as the highest lipid content (14.0% d.w.). This ratio was identified as optimal. The 85:15% ratio also demonstrated enhanced lipid content (11.9% d.w.), attributed to the reduced turbidity and consequent improved light penetration, favoring the proliferation of lipid-producing autotrophic microorganisms within the consortium.