Plastic Accumulation Research Articles

Sugar Beet Pulp as Raw Material for the Production of Bioplastics

The production of bioplastics from renewable materials has gained interest in recent years, due to the large accumulation of non-degradable plastic produced in the environment. Here, sugar beet pulp (SBP) is evaluated as a potential raw material for the production of bioplastics such as polylactic acid (PLA) and polyhydroxyalkanoates (PHAs). SBP is a by-product obtained in the sugar industry after sugar extraction from sugar beet, and it is mainly used for animal feed. It has a varied composition consisting mainly of cellulose, hemicellulose and pectin. Thus, it has been used to produce different value-added products such as methane, hydrogen, pectin, simple sugars, ethanol, lactic acid and succinic acid. This review focuses on the different bioprocesses involved in the production of lactic acid and PHAs, both precursors of bioplastics, from sugars derived from SBP. The review, therefore, describes the pretreatments applied to SBP, the conditions most frequently used for the enzymatic hydrolysis of SBP as well as the fermentation processes to obtain LA and PHAs.

Uniaxial ratcheting behavior and microstructure evolution of 316H stainless steel under the random cyclic loads

In this study, the Computational Fluid Dynamics (CFD)-Finite Element Method (CFD-FEM) were used to simulate the transient stress response of the structure surface under thermal striping environment, and a uniaxial random cyclic loading (RCL) method was used to reveal the mechanical properties and initial microstructure evolution of 316H austenitic stainless steel (SS) under random stress induced by thermal striping. The experimental results showed that 316H exhibited a lower saturation ratcheting strain rate at 334.44 MPa, along with stronger cyclic hardening effects and resistance to plastic accumulation at loading rate of 100 Hz. Random loading tests with different cycles were performed at σpeak=334.44MPa and fRCL=100Hz, and ratcheted specimens were characterized to investigate the effect of the micro-mechanism on cyclic softening/hardening. The geometrically necessary dislocation (GND) density increases and then decreases with cyclic loading, which is mainly attributed to the deformation twin (DT) and multi-dislocation slip mechanisms. The deformation mechanism during the ratcheting cycle from 1000 to 3000 cycles is mainly dominated by the twinning reduction, where the dislocation migration accelerated the transformation from dislocation walls to subgrain boundaries; the twinning increase dominates from 3000 to 9000 cycles, where the subgrain boundary grew into boundaries with high angle misorientations.

A risk assessment of marine plastics in coastal waters of a small island: Lessons from Ambon Island, eastern Indonesia

This study provides the first implementation of environmental risk assessment (ERA) regarding marine plastic accumulation (environmental threat) in the water body of small islands in the Indonesian Coral Triangle region (a case study in Ambon Bay of Ambon Island). Ambon Bay is a tropical fjord system with outer Ambon Bay (OAB) separated from inner Ambon Bay (IAB) by a shallow sill. The emphasis of ERA was to combine coastal demography determining the probability of occurrence of the threat and flushing capacity of Ambon Bay determining the vulnerability of the system to the threat to evaluate risk during the peak rainfall season (easterly monsoon, June–August). Supplementarily, ERA considered the coral ecosystem in the bay contributing to the vulnerability parameter. This study only calculated flushing time (τ) of OAB due to available information on IAB flushing, and used three simple flushing models: 1D numerical advection–diffusion, salt-exchange and land–ocean​ interaction in coastal zone (LOICZ) models. The flushing time of the entire OAB was found to be 1–1.5 weeks. Inshore OAB was found to be flushed within 1.5–2 weeks while τ of mid OAB was 1–1.5 weeks. The flushing time of offshore OAB was ≤1 week. Regarding the ERA implementation, the probability of occurrence of marine plastics was very high in IAB and inshore OAB (linked to dense-populated areas) compared to in mid and offshore OAB (i.e. moderate-to-low, where sparsely population areas are located). It was also true for the vulnerability of Ambon Bay to marine plastic accumulation that was found to be high in IAB and inshore OAB, linked to slower flushing in these locations than in mid and offshore OAB, located close to the open ocean. Combining this, IAB and inshore OAB showed a high risk of marine plastic contamination than mid and offshore OAB. The knowledge of ERA regarding marine plastic accumulation presented here is informative for other embayments in Indonesia’s Coral Triangle region due to their similarity to Ambon Bay in shape and demographic aspects.

Increasing concentration of pure micro- and macro-LDPE and PP plastic negatively affect crop biomass, nutrient cycling, and microbial biomass

Over the last 50 years, the intense use of agricultural plastic in the form of mulch films has led to an accumulation of plastic in soil, creating a legacy of plastic in agricultural fields. Plastic often contains additives, however it is still largely unknown how these compounds affect soil properties, potentially influencing or masking effects of the plastic itself. Therefore, the aim of this study was to investigate the effects of pure plastics of varying sizes and concentrations, to improve our understanding of plastic-only interactions within soil-plant mesocosms. Maize (Zea mays L.) was grown over eight weeks following the addition of micro and macro low-density polyethylene and polypropylene at increasing concentrations (equivalent to 1, 10, 25, and 50 years mulch film use) and the effects of plastic on key soil and plant properties were measured. We found the effect of both macro and microplastic on soil and plant health is negligible in the short-term (1 to <10 years). However, ≥ 10 years of plastic application for both plastic types and sizes resulted in a clear negative effect on plant growth and microbial biomass. This study provides vital insight into the effect of both macro and microplastics on soil and plant properties.

Experimental investigation and crystal plasticity simulation for the fatigue crack initiation of the equiaxed Ti-6Al-4V alloy in the very high cycle regime

This work investigated the fatigue crack initiation mechanism of the equiaxed Ti-6Al-4V alloy in the very high cycle fatigue (VCHF) regime. Ultrasonic fatigue experiments were carried out on Ti-6Al-4V specimens and a detailed analysis of the failure mechanism was conducted by means of scanning electron microscopy (SEM). The localized cyclic plastic response of the alloy was investigated using the crystal plasticity finite element (CPFE) method to further clarify the fatigue crack initiation process in the VHCF regime, and the CPFE models with varying transformed β(βt) phase volume fractions were presented to investigate the impact of βt phase on the VHCF behavior. The simulation results indicate that the proposed CPFE model can effectively captures the microstructural plastic deformation mechanisms, such as stress concentration near the phase boundaries and plastic accumulation. And the βt phase significantly affects the VHCF behavior of the alloy.

Screening of phthalate and non-phthalate plasticizers and bisphenols in Sicilian women’s blood

The plastic accumulation and its degradation into microplastics is an environmental issue not only for their ubiquity, but also for the release of intrinsic chemicals, such as phthalates (PAEs), non-phthalate plasticizers (NPPs), and bisphenols (BPs), which may reach body organs and tissues, and act as endocrine disruptors. Monitoring plastic additives in biological matrices, such as blood, may help in deriving relationships between human exposure and health outcomes. In this work, the profile of PAEs, NPPs and BPs was determined in Sicilian women’s blood with different ages (20–60 years) and interpreted by chemometrics. PAEs (DiBP and DEPH), NPPs (DEHT and DEHA), BPA and BPS were at higher frequencies and greater levels in women’s blood and varied in relation to age. According to statistical analysis, younger females’ blood had higher contents of plasticizers than older women, probably due to a more frequent use of higher quantities of plastic products in daily life.

From source to disposal: Cracking the code for sustainable polymers

The development of synthetic polymers with high stability has transformed modern life, but it has also led to a pollution crisis. Because of the useful nature of these materials, fossil fuel resources are being depleted rapidly to meet the exponentially growing demand. This increase in demand often relates to disposable items that are discarded quickly, leading to rapid accumulation of plastics in landfills and the environment. Here, we present multidisciplinary approaches that will all be needed to improve polymer sustainability, in terms of both the source of the materials and the end of life, while maintaining our quality of life. From biomass sources for the production of new plastics to the recycling and upcycling of currently produced plastics, the vast diversity of commercial plastics with different properties will need multi-pronged strategies for improvements. We hope these discussions will encourage the community to avoid a one-size-fits-all approach to polymer pollution and instead meet a complicated problem with our entire toolbox. The development of synthetic polymers with high stability has transformed modern life, but it has also led to a pollution crisis. Because of the useful nature of these materials, fossil fuel resources are being depleted rapidly to meet the exponentially growing demand. This increase in demand often relates to disposable items that are discarded quickly, leading to rapid accumulation of plastics in landfills and the environment. Here, we present multidisciplinary approaches that will all be needed to improve polymer sustainability, in terms of both the source of the materials and the end of life, while maintaining our quality of life. From biomass sources for the production of new plastics to the recycling and upcycling of currently produced plastics, the vast diversity of commercial plastics with different properties will need multi-pronged strategies for improvements. We hope these discussions will encourage the community to avoid a one-size-fits-all approach to polymer pollution and instead meet a complicated problem with our entire toolbox.

Polyhydroxyalkanoates (PHAs) from Endophytic Bacterial Strains as Potential Biocontrol Agents against Postharvest Diseases of Apples.

Due to the increasing use and accumulation of petrochemical plastics in the environment and the rapid depletion of natural resources, microbial polyhydroxyalkanoates have great potential to replace them. This study provides new insights in the field of obtaining of polyhydroxyalkanoates (PHAs) from endophytic bacterial strains and applying them as potential biocontrol agents against postharvest diseases of apples. Two strains-Pseudomonas flavescens D5 and Bacillus aerophilus A2-accumulated PHAs in amounts ranging from 2.77 to 5.9 g L-1. The potential to use low-cost substrates such as beet molasses and soapstock for PHA accumulation was shown. The PHAs produced by the Ps. flavescens D5 strain had pronounced antagonistic activity against Penicillium expansum (antifungal property = 62.98-73.08%). The use of PHAs as biocontrol agents significantly reduced the severity of apple blue mold, especially in the preventive treatment option.

Environmental advantages and challenges of nanocellulose reinforced starch-based packaging

Abstract Sustainable packaging development with lower environmental impact is urgent due to the petroleum-based plastic accumulation. Thereby, nanocellulose arouses the interest of several industrial sectors as renewable sources material and its mechanical properties for packaging manufacture. Biopolymers such as starch have been an alternative in packaging preparation, although its low mechanical and water resistance represents a challenge for its application. An alternative to improve these starch characteristics is nanocellulose incorporation. Thus, this chapter proposes obtaining nanocellulose from renewable sources, and its environmental advantage to replace plastics. Furthermore, types of nanocellulose, methods for obtaining, and the main physicochemical characteristics of nanocellulose are discussed since this polymer versatility allows its application in several industrial sectors, especially in packaging development. Finally, this review presents the incorporation nanocellulose-based nanocomposites in matrices, aiming to obtain formulations containing active agents to improve mechanical strength and water resistance and packaged product quality.

Dynamic covalent bond enabled strong Bio-based polyimide materials with Thermally-driven Adaptivity, healability and recycling

Developing new sustainable materials as plastic replacement has become an urgent task for the rapid accumulation of non-degradable petroleum-based waste plastics. Herein, we report that catalyst-free dynamic reversible exchange operated at room-temperature by Schiff base reaction between dialdehyde cellulose nanofibrils (DACNF) and plant oil-based aliphatic long-chain diamine monomers (LCD). The dynamic imine polymer films are formed using a simple method similar to wet pressing in papermaking, which exhibits excellent mechanical properties and thermally processability for the synergistic of hydrogen bond and dynamic imine bond. The tensile strength and Young's modulus reaches 83.74 MPa and 3.90 GPa, which are significantly higher than those of most traditionally commercial plastics. In addition, the number of hydrogen bonds and dynamic imine bonds from cellulose and dynamic imine polymers are evaluated by molecular dynamics (MD) simulation to gain further insights into the intermolecular interaction. By exploring the mechanism involved in the reversible exchange of dynamic imine bonds and its application in self-healing and recycling, a sustainable adaptive material is expected to be structured. More importantly, the dynamic imine polymers also exhibits excellent water barrier properties, solvent resistance and complete biodegradability, which offers a new strategy for reducing the application of non-degradable plastics.

Association of Laccase from Bacillus cereus O2-B and Pseudomonas aeruginosa O1-P with the bio-degradation of polymers: an in vitro to in silico approach.

Plastic accumulation has become a serious environmental threat. Mitigation of plastic is important to save the ecosystem of our planet. With current research being focused on microbial degradation of plastics, microbes with the potential to degrade polyethylene were isolated in this study. In vitro studies were performed to define the correlation between the degrading capability of the isolates and laccase, a common oxidase enzyme. Instrumental analyses were used to evaluate morphological and chemical modifications in polyethylene, which demonstrated a steady onset of the degradation process in case of both isolates, Pseudomonas aeruginosa O1-P and Bacillus cereus O2-B. To understand the efficiency of laccase in degrading other common polymers, in silico approach was employed, for which 3D structures of laccase in both the isolates were constructed via homology modeling and molecular docking was performed, revealing that the enzyme laccase can be exploited to degrade a wide range of polymers.

Genetic basis for the biodegradation of a polyether-polyurethane-acrylic copolymer by a landfill microbial community inferred by metagenomic deconvolution analysis

Plastic accumulation in the world amounts to approximately 8300 million tons. Polyurethanes (PU) account for 7.7 % of total plastics production worldwide, and their diverse chemical composition makes them highly recalcitrant to biodegradation. Several works have reported polyurethane-degrading microbial communities. However, it is still necessary to learn more about the chemical, biochemical, and genetic bases linked to the polyurethanolytic phenotype and the microbial taxonomic determinants responsible for metabolizing the PU polymer and its associated chemical additives. To shed light on this problem, we applied physical, chemical, biochemical, metagenomic, and bioinformatic analyses to explore the biodegradation capability and related biochemical and genetic determinants of the BP6 microbial community that can grow in PolyLack, a commercial coating containing a polyether polyurethane acrylate (PE-PU-A) copolymer and several additives, as sole carbon source. We observed complete additives (isopropanol, N-methyl-2-pyrrolidone, 2-butoxyethanol, alkyl glycol ethers) biodegradation and the appearance of released polymer components (toluene diisocyanate (TDI) and methylene diphenyl diisocyanate (MDI) derivatives), and multiple degradation products since early cultivation times. The Hi-C metagenomic analysis identified a complex microbiome with 35 deconvolved Metagenome-Assembled Genomes (MAGs) – several new species – and biodegradation markers that suggest the coexistence of hydrolytic, oxidative, and reductive metabolic strategies for degrading the additives and the PU copolymer. This work also provides evidence of the metabolic capability the BP6 community has for biodegrading polyether polyurethane foams. Based on these analyses, we propose a novel metabolic pathway for 4,4′-methylenedianiline (MDA), an initial biodegradation intermediate of MDI-based PU, encoded in the complex BP6 community metagenome and suggest that this community is a potential biotechnological tool for PU bio-recycling.

Nanotechnology in Plastic Degradation

Plastics pose a huge threat to the environment. Plastic accumulation in the land and the seas is now the world’s most terrorising problem, mainly because of its non-degrading character. Plastic degradation has always been a next to impossible concept in the field of science, but nanotechnology provides a revolutionary and modern way to solve the problem of plastic accumulation in the environment. One of the great advantages of nanoparticles is that we can increase and decrease the rate of biodegradation depending on our needs. Nanoparticles enhance the polythene degradation capacity of the microorganisms by altering their metabolic cycles. Numerous studies showed conclusively that the incorporation of nanotechnology enhances the ability of microorganisms to degrade polythene materials. Even though bio degradable plastics are nowadays produced in large quantities to substitute polythene materials, they fail to match the brittleness of plastics. Biodegradable plastics have poor thermal, mechanical and low gas barrier qualities, which are their main drawbacks. To overcome this, nanoparticles are incorporated into the biopolymers. If an appropriate balance between nanotechnology, microbiology and biotechnology is found, plastic degradation can be done economically and feasibly in all the areas.

Determining the distribution and accumulation patterns of floating litter in the Baltic Sea using modelling tools

Marine plastic floating on the sea surface is an extensive environmental problem. The present study investigated the transport patterns of marine litter and areas of its accumulation in the Baltic Sea by using a hydrodynamic model coupled with a particle-tracking model. We also studied the extent of marine litter from the main polluting rivers. Mapping of marine plastic debris distribution in 2017–2018 revealed that the largest plastic accumulation area is between latitude 59° N and 61° N, which includes the Northern Baltic Proper, Archipelago Sea, and the Gulf of Finland. The floating plastic spreads from the largest plastic pollution sites River Vistula, Oder and Neman to the waters of all the countries around the Baltic Sea.

A bionanocomposite of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/ZnO-nanoparticles intended for food packaging

Films-based bionanocomposites have gained a great importance in food plastic packaging because they are eco-friendly materials and have the potential to improve food protection, while limiting the accumulation of synthetic plastics on the planet. In this paper, biofilms were prepared using poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) reinforced with Zinc oxide nanoparticles (ZnO-NPs) to develop new bionanocomposite materials intended for food packaging. The samples were fabricated using first solvent casting method followed by melt compounding at various loading rates, i.e., 1.5, 3 and 6 wt%. The obtained results showed that the incorporation of ZnO-NPs to PHBHHx at 3 wt% leads to higher crystallinity, improved mechanical properties and antimicrobial activity, compared with neat polymer and other bionanocomposites. This was attributed to the finer and homogeneous nanofiller dispersion in the polymer matrix evidenced by scanning electron microscopy analysis. Whereas at 6 wt%, the bionanocomposite sample exhibited low mechanical properties due to the formation of ZnO-NPs aggregates. In view of the obtained results, the study highlights the potential of using the PHBHHx/ZnO-NPs bionanocomposite at 3 wt% in food packaging without any prior filler treatment.

In-situ and real-time nano/microplastic coatings and dynamics in water using nano-DIHM: A novel capability for the plastic life cycle research

A novel nano-digital inline holographic microscope (nano-DIHM) was used to advance in-situ and real-time nano/microplastic physicochemical research, such as particle coatings and dynamic processes in water. Nano-DIHM data provided evidence of distinct coating patterns on nano/microplastic particles by oleic acid, magnetite, and phytoplankton, representing organic, inorganic, and biological coatings widely present in the natural surroundings. A high-resolution scanning transmission electron microscopy confirmed nano-DIHM data, demonstrating its nano/microplastic research capabilities. The sedimentation of two plastic size categories was examined: (a) ∼10 to 700 µm, and (b) ∼ 1 to 5 mm. Particle size was the primary factor affecting the sedimentation for studied (a) microplastics and (b) pellets. Two types of silicone rubbers exhibited different sedimentation processes. We also demonstrated that inorganic ions in seawater and oleic acid organic coatings altered the sedimentation velocity of studied plastics by 9 – 13% and 5 – 9%, respectively. Semi-empirical probability functions were developed and incorporated into a numerical model (CaMPSim-3D) to simulate the transport of studied microplastics and pellets in the Saint John River estuary. Water dynamics was the driving force of plastic transport, yet the accumulation of plastics was selectively dependant on particle physicochemical properties such as size and density by ∼ 7%. The usage of nano-DIHM for targeted identification of nano/microplastic hotspots and aquatic plastic wastes remediation were discussed.

Plastics and Five Heavy Metals from Sea Beaches: A Geographical Synthesis of the Literary Information

Pollution of the oceans and seas, as well as their coastal zones, with plastics has become serious challenge, which is also related to the Anthropocene marine geology and geochemistry. Notably, plastics can bear heavy metals. The related knowledge is scattered through scientific publications, and, thus, it needs generalization. The present study synthesizes the published information about the geographical distribution of cadmium, chromium, mercury, nickel, and zinc associated with plastics on sea beaches. A bibliographical survey is undertaken, and the collected literary information is organized so as to document the principal localities of beached plastics bearing these metals. About twenty localities are established in many parts of the world, and the majority of them correspond to the coasts of the Atlantic and Indian oceans and their seas. Significant attention has been paid by the previous researchers to Northwest Europe and South and East Asia. The available information is enough to postulate the global extent of the problem of heavy metals association with plastics on beaches. Real or potential risks to the environment were reported in many cases. This review also shows that the industry of tourism, hospitality, and recreation contributes to the accumulation of such plastics. The analyzed literary information demonstrates several biases: for instance, Hg-bearing plastics on beaches were reported from the smaller number of localities relatively to the other metals, and the beaches and coastal recreational areas of many regions are yet to be studied in regard to heavy metals associated with plastics.

Conversion and Management of Plastic Waste into useful Resources – A review

The objective of this review paper is to focus few of the notable research that has been carried out to tackle the problems of disposal of plastic waste and its effective utilization into useful products. Due to less weight, low cost, non-corrosiveness of plastics have led to excessive usage and thus increasing its production resulting in the accumulation of waste plastic in the environment. The previous studies report several techniques to recycle and convert unwanted plastics into alternative fuels. This would be an added advantage to solve the problem of shortage of conventional fuel and thereby promote a sustainable environment. Nevertheless, further research is necessary to report some of the issues that have not yet been addressed.

Tunable enzymatic biodegradation of poly(butylene succinate): biobased coatings and self-degradable films

Biodegradation of polyesters driven by enzymes is considered as one of the most effective way of degradation of these materials, as a way to control plastics accumulation in the environment. In this study, we present two different strategies to tune the enzymatic degradation of PBS films triggered by a lipase from Pseudomonas cepacia. Firstly, the kinetics of enzymatic degradation of PBS films was regulated by applying multilayer coats of polysaccharide alginate and chitosan (Alg/Chi) films. Secondly, self-degradable PBS films were prepared by embedding lipase-filled alginate particles. For comparison purposes, a detailed enzymatic degradation study of neat PBS films exposed to a lipase from P. cepacia in solution was made to determine the main experimental parameters influencing their degradation in solution. The results showed that an increase in enzyme concentration increased the degradation extent and rate of neat PBS films. At a fixed enzyme concentration, stirring of the solution containing the enzyme and the PBS also increased the biodegradation rate. In the case of the PBS films coated with a different number of Alg/Chi layers by spray-assisted LbL and subjected to enzymatic degradation experiments in solution, the extent of degradation was found to be dependent on the number of protective coating layers. Therefore, the Alg/Chi biobased coating constitutes an effective barrier to the diffusion of the lipase, thus proving its effectiveness in modulating the enzymatic activity as a function of coating thickness. In the case of self-degradable PBS containing lipase-embedded alginate beads (employed to protect the enzyme during high-temperature processing), only limited biodegradation was observed as the amount of encapsulated enzyme employed was too small. Nonetheless, these results are promising, as the enzymatic activity –indicative of the degradation capacity of the enzyme– determined for all these samples was about 2 orders of magnitude lower than that of previous assays.

Polyethylene-Like Blends Amenable to Abiotic Hydrolytic Degradation.

Long-chain aliphatic polyester-18,18 (PE-18,18) exhibits high density polyethylene-like material properties and, as opposed to high density polyethylene (HDPE), can be recycled in a closed loop via depolymerization to monomers under mild conditions. Despite the in-chain ester groups, its high crystallinity and hydrophobicity render PE-18,18 stable toward hydrolysis even under acidic conditions for one year. Hydrolytic degradability, however, can be a desirable material property as it can serve as a universal backstop to plastic accumulation in the environment. We present an approach to render PE-18,18 hydrolytically degradable by melt blending with long-chain aliphatic poly(H-phosphonate)s (PP). The blends can be processed via common injection molding and 3D printing and exhibit HDPE-like tensile properties, namely, high stiffness (E = 750-940 MPa) and ductility (εtb = 330-460%) over a wide range of blend ratios (0.5-20 wt % PP content). Likewise, the orthorhombic solid-state structure and crystallinity (χ ≈ 70%) of the blends are similar to HDPE. Under aqueous conditions in phosphate-buffered media at 25 °C, the blends' PP component is hydrolyzed completely to the underlying long-chain diol and phosphorous acid within four months, as evidenced by NMR analyses. Concomitant, the PE-18,18 major blend component is partially hydrolyzed, while neat PE-18,18 is inert under identical conditions. The hydrolysis of the blend components proceeded throughout the bulk of the specimens as confirmed by gel permeation chromatography (GPC) measurements. The significant molar mass reduction upon extended immersion in water (M n(virgin blends) ≈ 50-70 kg mol-1; M n(hydrolyzed blends) ≈ 7-11 kg mol-1) resulted in embrittlement and fragmentation of the injection molded specimens. This increases the surface area and is anticipated to promote eventual mineralization by abiotic and biotic pathways of these HDPE-like polyesters in the environment.