Biodegradability of PBAT/PLA coated paper and bioplastic bags under anaerobic digestion

Degradation dynamics of Mater-Bi and crystalline PLA during anaerobic co-digestion of household organic waste and wastewater sludge, and phytotoxicity assessment of digestate

The increasing use of biodegradable bioplastics, such as Mater-Bi (MB) and Crystalline Polylactic Acid (CPLA), as alternatives to traditional polymers has raised concerns about their degradation and environmental impact. This study examines the biodegradability of MB and CPLA during the anaerobic co-digestion of organic municipal solid waste (OFMSW) and thickened sewage sludge in semi-continuous lab-scale reactors operated under mesophilic conditions. Bioplastics were tested at different concentrations (0-8 %) under two operating phases with varying organic loading rates (1 or 3 gVS/L·d for MB and 1 or 2 gVS/L·d for CPLA) and retention times (14 or 21 days). Biomethane production, process stability, and degradation efficiency were monitored. Results show limited degradation, with MB degrading faster than CPLA (23 % vs. 15 % weight loss after six weeks). Most MB degradation is due to abiotic factors. Higher bioplastic concentrations destabilise the process, reducing methane yield and causing volatile fatty acid spikes. Phytotoxicity tests indicate that the digestate may be suitable for agriculture, though bioplastic concentration impacts require further study. These findings stress the need to identify more biodegradable biopolymers, improve waste management, optimise anaerobic digestion, and screen digestate for agricultural use. This study is among the first to combine semi-continuous anaerobic digestion with abiotic degradation tests and phytotoxicity assessment, providing a comprehensive evaluation of bioplastic behaviour and its implications for digestate reuse.

Comparative evaluation of biodegradable microplastic presence in edible and non-edible tissues of cage-cultured and wild fishes of Periyar River

Biodegradable plastics (BPs) are considered a promising alternative to conventional plastics; however, their biodegradation necessitates specific conditions and can persist in the environment for extended periods, posing toxicological effects on aquatic ecosystems and their organisms similar to conventional microplastics. The studies on biodegradable microplastics (BMPs) are limited and therefore, this study, aimed to evaluate the BMP presence in the gastrointestinal tract (GIT) and edible tissues of wild-caught and cage-cultured fishes of Periyar River, Kerala, India. Etroplus suratensis (n = 300) and Oreochromis mossambicus (n = 300) were collected from both sources. The study found BMPs in the GIT of all fishes sourced from cages and wild, with a higher but statistically insignificant abundance in wild fishes: 0.06 ± 0.26 items/individual (0.01 ± 0.00 items/g) in E. suratensis and 0.03 ± 0.23 items/individual (0.01 ± 0.01 items/g) in O. mossambicus. No BMPs were found in the edible tissues of cage-cultured fish, but they were detected in wild-caught fishes, i.e., 0.02 ± 0.13 items/individual (0.02± 0.01 items/g) in E. suratensis and 0.01 ± 0.11 items/individual (0.02± 0.01 items/g) in O. mossambicus. Poly (butylene adipate-co-terephthalate) (PBAT) and polylactic acid (PLA) were the only BMPs obtained in fish from both sources with the former being the dominant one. The potential annual average human exposure risk from the wild-caught fish was estimated from both fish species and the findings suggest children have a higher risk of exposure, i.e., 551 items/year followed by adults, i.e., 394 items/year and aged individuals, i.e., 239 items/year. The documented harmful impacts of BMPs on aquatic organisms, combined with the findings of this study, suggest the need for a thorough reassessment of BP production and disposal practices. Additionally, implementing robust monitoring systems is essential to food safety and public health.

Eco-friendly or eco-threat? Influence of feeding zone on biodegradable microplastic uptake in freshwater fish and its impact on environment and food safety

Biodegradable plastics (BPs) are considered a sustainable alternative to reduce the long-term plastic pollution. However, recent research indicates that the degradation time of BPs varies depending on several factors, and biodegradable microplastics (BMPs) exhibit toxicological effects comparable to those of conventional microplastics, raising concerns about their use. There is a significant lack of research on the factors affecting BMP uptake in fish, with some studies focusing on the effects of BMPs under controlled laboratory settings. This study, the first of its kind in India, aims to examine the uptake of BMPs in freshwater fish from different feeding zones-pelagic, benthopelagic, and demersal-of the Periyar River in Kerala, India. Xenentodon cancila (pelagic; n = 80), Etroplus suratensis (benthopelagic; n = 80) and Anabas testudineus (demersal; n = 80) were selected for the study. The gastrointestinal tract (GIT) and edible tissues were isolated and analysed. BMPs were observed in the following order: benthopelagic > demersal> pelagic. Highest mean BMP abundance was recorded in E. suratensis (benthopelagic) i.e. 0.24±0.05 items/individual (0.04±0.01 items/g) in GIT and 0.08±0.03 items/individual (0.002± 0.00 items/g) in edible tissues. Poly (butylene adipate-co-terephthalate) (PBAT) was the only polymer observed. Adults have a comparatively higher risk of BMP exposure from E. suratensis and A. testudineus than children and aged individuals. The presence of BMPs in freshwater fish collected from the three feeding zones indicates widespread contamination across diverse habitats. This finding suggests that BMPs, despite their biodegradable nature, persist in aquatic environments long enough to enter the food web and is a growing environmental concern that must be addressed and appropriate strategies should be made to align with the goals of reducing pollution and protecting ecosystems.

Chemical composition and mesophilic anaerobic digestion of commercial compostable food packaging: Implications for bio-waste management

This study assessed the chemical composition and mesophilic anaerobic biodegradability (BI) of 34 commercial compostable food packaging products, including sixteen bags, twelve coffee capsules, and six other products (cups, forks and straws). Thermogravimetric analysis and spectroscopy techniques allowed to determine the proportions of polymers (PLA, PBAT, PBS, PHBV, PE, cellulose, and starch) and additives (inorganic and organic). Six compositional clusters were identified: PHBV-based products (BI = 92 ± 1 %), cellulose-based products (BI = 85 ± 9 %), PLA-based products (BI = 30 ± 20 %), PBAT/starch-based bags (BI = 25 ± 8 %), PE/starch-based bags (BI = 9.5 ± 0.5 %), and PBS/PLA-based capsules (BI = 6.6 ± 3.0 %). Only select cellulose-based products (three bags, one cup, and one capsule) and the PHBV-based products (five capsules and one straw) exhibited a biodegradability over 80 %. Analyzing product composition reveals components that affect biodegradability in anaerobic digestion, thus aiding manufacturers to eco-design more sustainable food packaging.

Reliable methodology to determine biotransformation of PBAT in anaerobic conditions

Biodegradable plastics can enhance food waste utilization in anaerobic digestion (AD) units, but their fate under thermophilic conditions remains unclear. Previous studies using methane production, calorimetry, or spectroscopic analyses often report inconsistent results. This study tracks the biotransformation of polybutylene adipate co-terephthalate (PBAT) in thermophilic AD (55 °C) using 1H NMR to quantify monomers. While 1,4-butanediol degraded quickly, adipic (AA) and terephthalic acid (TPA) accumulated over time. Monomer analysis estimated PBAT biotransformation at 11.1 ± 1.9 % (TPA) and 10.1 ± 2.3 % (AA). The core microbial community remained stable, indicating intrinsic hydrolytic capacities, which were stable despite TPA and AA accumulation. This workflow provides a robust methodology to evaluate the biotransformation of plastics.

Analysis of biological treatment technologies, their present infrastructures and suitability for biodegradable food packaging - A review

Recently, there has been an increased demand for biodegradable plastics in the food packaging industry, especially for highly food soiled packaging items containing food/beverage solids that will not be recycled using a non-biological process. However, the increased usage of those materials have also raised concerns and confusion, as a major part of these biodegradable plastics are not effectively separated nor recycled. The lack of acceptance in recycling facilities, related to confusion with their conventional polymers counterparts, as well as short retention times of recycling facilities, often incompatible with the degradation kinetics of biodegradable plastics, stand as the major drawbacks for bioplastics treatment. Additionally, the presence of incompletely biodegraded bioplastics during biological treatments or in the final products i.e. compost or digestate, could lead to process failure or limit the commercialization of the compost. This work critically reviews the fundamentals of the biological treatments, anaerobic digestion and composting processes, and discusses the current strategies to improve their performance. In addition, this work summarizes the state-of-the-art knowledge and the impact of bioplastics on full-scale treatment plants. Finally, an overview of the current installed treatment capacity is given to show the areas of opportunity that can be improved and exploited to achieve a better waste management of biodegradable plastics.

Streamlining electrospun shellac coatings on paper for high moisture strength and barrier food packaging film: Tailoring the processing parameters for accelerated coating

Coated paper with bio-based components has sparked attention as a food packaging alternative to plastic. This study focusses on development of environmentally friendly packaging solution by electrospraying shellac over paper's surface. The goal of the study is to reduce the time of fabrication, by optimising the process parameters, concentration; 20, 30, and 40%w/v, flow rate; 10, 20, and 30 ml/h, and coating time; 100, 200, and 300 s (Concentration (% w/v))/ Flow rate (ml/h)/ time (sec)), in order to get better GSM (grams per square meter), COBB (grams of water absorbed per square meter), KIT (oil resistance ability), and WVTR (water vapor transmission rate). The developed material shows tensile strength >20 MPa with a 90 % drop in water absorption. Furthermore, when exposed to 100 % relative humidity for 48 h, the sample absorbs only 7-9 % moisture and showing minimal reduction in tensile strength of 3-5 %, indicating superior moisture resistance compared to paper. Cherry tomato (CT) freshness was tested and found to be maintained for up to 28 days, which was comparable to polyethylene packaging with mass loss during storage of 7, 4, and 20 %, respectively. In 28 days, the developed films decomposed similarly to paper in soil (23.67 %) and water (5.44 %), with no significant change in quality of water.

Biodegradable Thermoplastic Materials with Application in the Manufacture of Bags Without Synthetic Polymers

Non-degradable plastic bags are a major contributor to marine and soil pollution. They represent a significant percentage of the generated solid waste and can last for hundreds of years in the environment. The aim of the present study was to find alternatives to conventional non-degradable plastic bags by obtaining biodegradable and compostable bags starting from simple materials like starch, poly(lactic acid) (PLA), and glycerol. Increasing the strength and hardness of the polymer was achieved by adding a mineral (talcum). The preliminary studies indicated that two compositions are suitable for advanced testing to produce the initial granular material. These materials were tested for the determination of melt flow index (MFI), Fourier Transform Infrared Spectroscopy (FTIR), and the polymers response to heating (thermogravimetric analysis, TGA and differential scanning calorimetry, DSC). The polymer biodegradability was evaluated by burial in two types of soil. The obtained results were compared with the same set of experiments performed on conventional polyethylene bags. After three months in the soil, only the materials synthesized in this study show signs of accentuated degradation while polyethylene bags are still intact. The surface morphology was explored by scanning electron microscopy (SEM). The results indicated that the biodegradable thermoplastic material meets the requirements of the European standard EN13432/2002 regarding compostable and biodegradable packaging.

Enhanced effect of ferrous sulfate on nitrogen retention and PBAT degradation during co-composting by combing with biochar-loaded FN1 bacterial composites

The treatment of biodegradable plastics through composting has garnered increasing attention. This study aimed to investigate the effects of Biochar FN1 bacteria and ferrous sulfate on nitrogen retention, greenhouse gas emissions, and degradable plastics during composting and to elucidate their synergistic mechanisms on microbial communities. Compared with the control, applying biochar-loaded FN1 bacteria composites combined with Ferrous sulfate (SGC) markedly accelerated organic matter degradation and reduced cumulative CO2 and NH3 emissions. The synergistic interaction between the composites and Ferrous sulfate significantly enhanced NH4+-N levels in the thermophilic phase and NO3--N levels in the cooling phase, ultimately decreasing nitrogen loss by 14.9% (P < 0.05) and increasing the seed germination index (GI) by 22.5% (P < 0.05). Additionally, PBAT plastic degradation was improved by 31.6% (P < 0.05). The SGC treatment also altered the richness and diversity of the bacterial community in both the compost and the PBAT plastic sphere, particularly affecting Sphingobacterium, Pseudomonas, and Flavobacterium at the genus level. Symbiotic network analysis and Redundancy Analysis revealed that these functional degradation bacteria were significantly positively correlated with NO3--N levels and PBAT degradation. Furthermore, structural equation modelling indicated a positive relationship between PBAT degradation rate and composting temperature (r = 0.69, p < 0.05). The findings suggested that Fe2+ not only enhanced the FN1 activity but also promoted PBAT degradation by increasing ·OH content on the PBAT plastic sphere. Overall, the combined use of biochar-loaded FN1 bacteria and Ferrous sulfate effectively supports nitrogen retention and plastic degradation during composting.

Role of polylactic acid microplastics during anaerobic co-digestion of cow manure and Chinese cabbage waste enhanced by nanobubble

With the increasing use of plastic products globally, environmental pollution by plastic waste is becoming increasingly problematic. This study investigated the impacts of two types of polylactic acid microplastics, clear microplastics and aluminised film microplastics, on methane yield, microbial community, and volatile fatty acid accumulation during anaerobic co-digestion of cow manure and Chinese cabbage waste under different temperature conditions. The influence of the addition of air nanobubbles on microplastic degradation in the anaerobic digestion system we also examined. The results revealed that under thermophilic conditions, clear and aluminised film microplastics increased the methane yield, with the latter resulting in greater improvement. Conversely, under mesophilic conditions, the presence of microplastics reduced the methane yield, but the addition of air-nanobubble partially mitigated this effect. Microplastics also affected the microbial community, with specific species showing correlations with methane yield. Methanothermobacter, which is linked to lactic acid conversion, was positively correlated with methane yield, whereas Methanomassiliicoccus levels increased in the presence of microplastics, particularly in the inhibited state of the digester. These results suggest that, under thermophilic conditions, microplastics may increase the cumulative methane yield by facilitating the degradation of lactic acid monomers. Furthermore, the aluminised film on microplastics could serve as an electrically conductive material during anaerobic digestion, potentially increasing the methane yield.

Preparation of PBAT microplastics and their potential toxicity to zebrafish embryos and juveniles

The extensive use of traditional non-biodegradable plastics results in the generation of microplastics (MPs), forming a new pollutant that can pose significant environmental risks. Biodegradable plastics (BP) possess degradation properties and can partially replace conventional plastics, thereby reducing pollution. However, further investigation is needed into the toxicity of biodegradable microplastics (BMPs) on aquatic organisms. This study explores the toxic effects of PBAT microplastics (PBAT-BMPs) and microplastics produced from degradable PBAT/TPS (thermoplastic starch) composite film (PBAT/TPS-BMPs) on zebrafish embryos. Our findings indicate that the presence of microplastics on the embryo's surface increases with higher BMPs concentration. Nonetheless, PBAT-BMPs tend to aggregate and are blocked by the embryonic membrane, thus diminishing their toxic effects on the embryo. Acute toxicity experiments revealed that 30 mg/L of PBAT-BMPs significantly reduced the survival rate of zebrafish embryos, whereas PBAT/TPS-BMPs had a lesser effect on survival. Both types of BMPs influenced the hatching rate of the embryos, leading to prolonged incubation periods. Additionally, both types of BMPs impacted the locomotor behavior of zebrafish larvae, causing an increase in larval locomotor speed. However, these BMPs had little impact on larval body development and heartbeat behavior. Fluorescent microplastic tracer experiments demonstrated that PBAT-BMPs persisted in juvenile fish for at least 144 h and were difficult to metabolize and excrete. Our study aims to gain a better understanding of the potential effects of BMPs on aquatic ecosystems and biological health, as well as to propose effective strategies for reducing environmental pollution and protecting organisms.

PBAT is biodegradable but what about the toxicity of its biodegradation products?

CONTEXT

Poly(butylene adipate-co-terephthalate) (PBAT) is a biodegradable plastic. It was introduced to the plastics market in 1998 and since then has been widely used around the world. The main idea of this research is to perform quantum chemical calculations to study the potential toxicity of PBAT and its degradation products. We analyzed the electron transfer capacity to determine its potential toxicity. We found that biodegradable products formed with benzene rings are as good electron acceptors as PBAT and OOH•. Our results indicate that the biodegradation products are potentially as toxic as PBAT. This might explain why biodegradation products alter the photosynthetic system of plants and inhibit their growth. From this and other previous investigations, we can think that biodegradable plastics could represent a potential environmental risk.

METHODS

All DFT computations were performed using the Gaussian16 at M062x/6-311 + g(2d,p) level of theory without symmetry constraints. Electro-donating (ω-) and electro-accepting (ω +) powers were used as response functions.