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Biodegradability, sustainability, and life cycle assessment of smart textiles
... One of the parameters to take into account to evaluate the sustainability of textile products is, for instance, their biodegradability and this is true for conventional cloths, but also for advanced materials, such as smart textiles [7]. Biodegradation routes can imply anaerobic or aerobic digestion, or landfilling to pass from large or complex molecules to simple, small, and nontoxic compounds, as a consequence of various microorganisms' activity [7]. ...
... One of the parameters to take into account to evaluate the sustainability of textile products is, for instance, their biodegradability and this is true for conventional cloths, but also for advanced materials, such as smart textiles [7]. Biodegradation routes can imply anaerobic or aerobic digestion, or landfilling to pass from large or complex molecules to simple, small, and nontoxic compounds, as a consequence of various microorganisms' activity [7]. These actions involve various stages, namely (i) bio-deterioration (the combined intervention of microbial communities and abiotic factors to break the materials into fragments), (ii) depolymerization (operated by microorganisms' secreted enzymes and free radicals capable of polymer cleavage), (iii) assimilation into the plasma membrane of the biological agent and, finally, (iv) mineralization [8]. ...
This study investigated the biodegradation behavior of cotton fabrics treated with polypyrrole, a polymer with conductive and antibacterial properties. Fabric samples were buried in compost-enriched soil for 10, 30 and 90 days. The biodegradation level was initially estimated by a visual inspection of the fibers and by the determination of the fabric weight loss. Other physical–chemical changes of fibers during the biodegradation process were analyzed by microscopy, thermal analyses and infrared spectroscopy. The surface resistivity of the fabrics was also measured. The results obtained comparing the bare cotton samples and the polypyrrole-added ones suggested that, on the one hand, polypyrrole hindered/delayed the biodegradation of cotton in compost-enriched soil, probably exercising its inherent antimicrobial feature during the first period of burial. On the other hand, over time, polypyrrole seemed to represent the first compound attacked by the microorganisms, preserving the cotton substrate. Despite the absence of dedicated literature regarding polypyrrole biodegradation, the mechanism hypothesized in this paper involves the loss of conjugation, as a consequence of de-doping, oxidized functionalities up to local cycle breaking.
Reducing environmental impacts by increasing circularity is highly relevant to the textiles sector. Here, we examine results from life cycle assessment (LCA) and circularity indicators applied to renewable and non-renewable fibres to evaluate the synergies between the two approaches for improving sustainability assessment of textiles. Using LCA, impacts were quantified for sweaters made from fossil feedstock-derived and bio-based PET. These same sweaters were scored using four circularity indicators. Both sweaters showed similar fossil energy footprints, but the bio-PET raw material acquisition stage greenhouse gas, water and land occupation impacts were 1.9 to 60 times higher, leading to higher full life cycle impacts. These contrasts were principally determined by what raw material acquisition processes were considered outside the system boundary of the alternative feedstocks. Using circularity indicators, fossil-feedstock PET scored lowest (worst) because the feedstock was from a non-renewable source. These examples highlight the limitations of LCA: the renewability or non-renewability of raw materials is not fully considered, and contrasts in processes included within system boundaries can preclude equitable comparisons. For LCA to be suitable for quantifying sustainability, it should be complemented by circularity indicators capable of demonstrating the contrast between renewable and non-renewable raw materials, particularly in the case of textiles.
The serious issue of textile waste accumulation has raised attention on biodegradability as a possible route to support sustainable consumption of textile fibers. However, synthetic textile fibers that dominate the market, especially poly(ethylene terephthalate) (PET), resist biological degradation, creating environmental and waste management challenges. Because pure natural fibers, like cotton, both perform well for consumer textiles and generally meet certain standardized biodegradability criteria, inspiration from the mechanisms involved in natural biodegradability are leading to new discoveries and developments in biologically accelerated textile waste remediation for both natural and synthetic fibers. The objective of this review is to present a multidisciplinary perspective on the essential bio-chemo-physical requirements for textile materials to undergo biodegradation, taking into consideration the impact of environmental or waste management process conditions on biodegradability outcomes. Strategies and recent progress in enhancing synthetic textile fiber biodegradability are reviewed, with emphasis on performance and biodegradability behavior of poly(lactic acid) (PLA) as an alternative biobased, biodegradable apparel textile fiber, and on biological strategies for addressing PET waste, including industrial enzymatic hydrolysis to generate recyclable monomers. Notably, while pure PET fibers do not biodegrade within the timeline of any standardized conditions, recent developments with process intensification and engineered enzymes show that higher enzymatic recycling efficiency for PET polymer has been achieved compared to cellulosic materials. Furthermore, combined with alternative waste management practices, such as composting, anaerobic digestion and biocatalyzed industrial reprocessing, the development of synthetic/natural fiber blends and other strategies are creating opportunities for new biodegradable and recyclable textile fibers.
Article Highlights
Poly(lactic acid) (PLA) leads other synthetic textile fibers in meeting both performance and biodegradation criteria.
Recent research with poly(ethylene terephthalate) (PET) polymer shows potential for efficient enzyme catalyzed industrial recycling.
Synthetic/natural fiber blends and other strategies could open opportunities for new biodegradable and recyclable textile fibers.
Cotton is one of the most widely used natural fibers available. However, to overcome some of its shortcomings, manufacturers have placed various finishes on cotton fabrics to improve wrinkle recovery, flame retardancy, anti-microbial behavior, water repellency, etc. This study measures the impact of common finishes on the biodegradability of 100% cotton fabrics in a soil laboratory environment. Under a controlled laboratory environment, cotton fabrics treated with 9 different finishing chemicals or chemical combinations were tested according to the standard test method, ASTM D5988-12, for up to 154 days. Results indicate crosslinked fibers show better protection from biodegradation when compared to the control fabric and non-crosslinked fabrics. The production of carbon dioxide (CO2) as a function of time was measured to determine the degree of biodegradation. Untreated cotton samples produced 2500 mg of CO2 after 154 days, approximately 40% more than that of the crosslinked treated fabric. Weightless studies showed the untreated fabrics and non-crosslinked finished having 40–60% weight loss after 154 days, while the crosslinked fabrics had unless than 20% weight loss over the same time period. Scanning electron microscope (SEM) images were used to observe the visual degradation level for each sample showed certain treated fabrics showed a less evidence of cracking on the fiber surface along with less microorganism growth. Fourier-transform infrared spectroscopy (FTIR) analysis showed that in general, treated fabrics with higher CO2 production and higher weight loss showed greater evidence of microorganism growth when analyzing peak bands typically associated with microorganism growth irreversibly bonded to the fibers.
Graphic abstract
The plastics industry is proliferating continuously and the global plastics production in 2018 has reached around 360 million tones. This has further compounded the problem of waste plastics, which if not appropriately disposed cause serious environmental problems like land pollution, marine pollution and water source pollution. As an alternative, there has been a paradigm shift from substituting synthetic plastics i.e. fossil-based to bioplastics. However, the world of bioplastics is riddled with many problems as the current terminology used around such bioplastics is confusing and general public is not provided with reliable information about the true biodegradability/compostability of the products. As a result, "greenwashing" is on the rise, with brands even making spurious claims about the environmental benefits of their products. This review article scans the world of biodegradable/bioplastics, major players and production capacities, their current status with respect to production and application. The commercial biopolymers available in the market and their technology have been also discussed in detail. The article also reviews various technologies like enzyme-based technology and oxo-degradable technology being propagated as a tool to convert conventional plastics like PE/PP/PET etc. to a biodegradable plastic. Further, various issues with oxo-based technology and enzyme-based technology have been compiled. Besides, various standards, test methods (ASTM/ISO) related to testing, specifications of biodegradable plastics, their scope/limitations and potential misuse have been covered. Further, the review article discusses the limitation of the various standards and why changes in the standards are required. The article tries to focus on various myths & realities of biodegradable/bioplastics and the challenges and expectations of the real world.
Controversy exists regarding the scale of the impacts caused by fast fashion. This article aims to provide a robust basis for discussion about the geography, the scale and the temporal trends in the impacts of fast fashion because the globalisation of the fashion industry means original, peer-reviewed, quantitative assessments of the total impacts are relatively rare and difficult to compare. This article presents the first application of Eora, a multiregional environmentally extended input output model, to the assessment of the impacts of clothing and footwear value chain. We focus on the key environmental indicators of energy consumption, climate and water resources impacts, and social indicators of wages and employment.
The results of the analysis indicate that the climate impact of clothing and footwear consumption rose from 1.0 to 1.3 Gt carbon dioxide equivalent over the 15 years to 2015. China, India, the USA and Brazil dominate these figures. The trends identified in this and the other indicators represent small increases over the study period compared to the 75% increase in textile production, meaning that the impacts per garment have improved considerably. On the other hand, the climate and water use impacts are larger as a proportion of global figures than the benefits provided via employment and wages. Our analysis of energy consumption suggests most of the per-garment improvement in emissions is the result of increased fashion-industrial efficiency, with a lesser role being played by falling carbon intensity among energy suppliers. While both the social benefits and environmental impacts per mass of garment appear to have decreased in recent times, much greater improvements in the absolute carbon footprint of the fashion industry are attainable by eliminating fossil-fueled electricity supplies, and by eliminating fast fashion as a business model.
Although recovery of fibers from used textiles with retained material quality is desired, separation of individual components from polymer blends used in today's complex textile materials is currently not available at viable scale. Biotechnology could provide a solution to this pressing problem by enabling selective depolymerization of recyclable fibers of natural and synthetic origin, to isolate constituents or even recover monomers. We compiled experimental data for biocatalytic polymer degradation with a focus on synthetic polymers with hydrolysable links and calculated conversion rates to explore this path The analysis emphasizes that we urgently need major research efforts: beyond cellulose‐based fibers, biotechnological‐assisted depolymerization of plastics so far only works for polyethylene terephthalate, with degradation of a few other relevant synthetic polymer chains being reported. In contrast, by analyzing market data and emerging trends for synthetic fibers in the textile industry, in combination with numbers from used garment collection and sorting plants, it was shown that the use of difficult‐to‐recycle blended materials is rapidly growing. If the lack of recycling technology and production trend for fiber blends remains, a volume of more than 3400 Mt of waste will have been accumulated by 2030. This work highlights the urgent need to transform the textile industry from a biocatalytic perspective.
Increasing demand for non-biodegradable plastics undesirably leads to their accumulation and calls for an appropriate solution for this global crisis. Environmental impacts of PET waste have long been addressed; although some remedies have been proposed, their extensive use in the modern world use demands new studies and recycling techniques. It shows the inadequacy of previous solutions to eliminate this environmental problem. Therefore, researching this subject should not be considered an insignificant issue. Distinctively, this review article has a specific reliance on the use of recycled PET fibers in the production of high-consumption and value-added products that, in addition to considering environmental aspects, can also be attractive to the market. This article deals with recent studies in three product categories (concrete, nonwoven fabrics, yarns) made from recycled PET fibers and shows the high potential of PET fibers for the future industry.
Acrylic polymers (AP) are a diverse group of materials with broad applications, frequent use, and increasing demand. Some of the most used AP are polyacrylamide, polyacrylic acid, polymethyl methacrylates, and polyacrylonitrile. Although no information for the production of all AP types is published, data for the most used AP is around 9 MT/year, which gives an idea of the amount of waste that can be generated after products’ lifecycles. After its lifecycle ends, the fate of an AP product will depend on its chemical structure, the environmental setting where it was used, and the regulations for plastic waste management existing in the different countries. Even though recycling is the best fate for plastic polymer wastes, few AP can be recycled, and most of them end up in landfills. Because of the pollution crisis the planet is immersed, setting regulations and developing technological strategies for plastic waste management are urgent. In this regard, biotechnological approaches, where microbial activity is involved, could be attractive eco-friendly strategies. This mini-review describes the broad AP diversity, their properties and uses, and the factors affecting their biodegradability, underlining the importance of standardizing biodegradation quantification techniques. We also describe the enzymes and metabolic pathways that microorganisms display to attack AP chemical structure and predict some biochemical reactions that could account for quaternary carbon-containing AP biodegradation. Finally, we analyze strategies to increase AP biodegradability and stress the need for more studies on AP biodegradation and developing stricter legislation for AP use and waste control.
Key points
• Acrylic polymers (AP) are a diverse and extensively used group of compounds.
• The environmental fates and health effects of AP waste are not completely known.
• Microorganisms and enzymes involved in AP degradation have been identified.
• More biodegradation studies are needed to develop AP biotechnological treatments.
Polyhydroxyalkanoates (PHAs) are bio-polyesters of hydroxyalkanoates that accumulate intracellularly in case of prokaryotes, as cytoplasmic granules, under carbon rich and paucity of nitrogen, phosphorous, sulphur and oxygen where it can serve as carbon and energy source under nutrient limiting condition and/or environmental stress conditions. In adverse growth conditions, many bacteria have ability to store nutrients in form of PHA granules using their specific metabolic pathways during stationary growth phase, in the presence of high levels of carbon containing nutrient sources. Bacterial PHAs have generated attention as an alternative to petroleum derived synthetic plastics. It possesses the characteristic physico-chemical properties comparable to the synthetic plastics. These properties of PHAs can be improved by blending of PHAs with other natural polymer like starch, cellulose and semisynthetic polymers like poly lactic acids and polycaprolactones. Being eco-friendly, biodegradable and biocompatible; major PHAs such as, Polyhydroxybutyrate (PHB) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) have found numerous vital applications in pharmaceutical, biomedical, textile, cosmetic, agricultural, treatment of waste water and have been successfully employed for Food packaging industries. This review provides a comprehensive knowledge about the world of PHAs covering its major aspects, namely its chemical nature and structure, biosynthesis, various methods of screening of potential PHA producing bacteria along with properties, several techniques used for its recovery and further characterization.
When it comes to “bioplastics”, we currently notice an immense complexity of this topic, and, most of all, a plethora of contradictory legislations, which confuses or even misleads insufficiently informed consumers. The present article therefore showcases microbial polyhydroxyalkanoate (PHA) biopolyesters as the prime class of “bioplastics” sensu stricto. In particular, biodegradability of PHA as its central benefit in elevating the current plastic waste scenario is elaborated on the biochemical basis: this covers aspects of the enzymatic machinery involved both in intra- and extracellular PHA degradation, and environmental factors impacting biodegradability. Importantly, PHA degradability is contextualized with potential fields of application of these materials. It is further shown how the particularities of PHA in terms of feedstocks, mode of synthesis, degradability, and compostability differ from other polymeric materials sold as “bioplastics”, highlighting the unique selling points of PHA as “green” plastic products in the circular economy. Moreover, current standards, norms, and certificates applicable to PHA are presented as basis for a straight-forward, scientifically grounded classification of “bioplastics”.
Abstract
A high proportion of the total microplastic (MP) load in the marine environment has been identified as microfibers (MFs), with polyester (PET) and polyamide (PA) typically found in the highest abundance. The potential for negative environmental impacts from MPs may be dependent on their degree of degradation in the environment, which is influenced by both intrinsic properties (polymer type, density, size, additive chemicals) and extrinsic environmental parameters. Most polymer products break down slowly through a combination of environmental processes, but UV degradation can be a significant source of degradation. The current study aimed to investigate the effect of UV irradiance on the degradation of natural (wool) and synthetic (PET and PA) MFs. Degradation of MFs was conducted in seawater under environmentally relevant accelerated exposure conditions using simulated sunlight. After 56 days of UV exposure, PA primarily exhibited changes in surface morphology with no significant fragmentation observed. PET and wool fibers exhibited both changes in surface morphology and fragmentation into smaller particles. A range of molecular degradation products were identified in seawater leachates after UV exposure, with increasing abundance over the duration of the experiment. Furthermore, a variety of additive chemicals were shown to leach from the MFs into seawater. While some of these chemicals were also susceptible to UV degradation and some are expected to biodegrade rapidly, others may be persistent and contribute to the overall load of chemical pollution in the marine environment.
Poly(hydroxyalkanoate)s (PHAs) represent a promising solution to allay climate change and plastic waste pollution. Being both completely bio-based and biodegradable, PHAs can approach a carbon neutral platform whereas petroleum-based plastics cannot.
The ubiquitous presence of plastic litter and its tending fate as marine debris have given rise to a strong anti-waste global movement which implicitly endorses bioplastics as a promising substitute. With ‘corporate social responsibility’ growing ever more popular as a business promotional tool, companies and businesses are continually making claims about their products being “green”, “environmentally friendly”, “biodegradable”, or “100% compostable”. Imprudent use of these words creates a false sense of assurance at the consumer end about them being responsible towards the environment by choosing these products. The policies surrounding bioplastics regulation are neither stringent not enforceable at both national and international stage which indirectly allow these “safe words” to be used as an easy plug to validate the supposed corporate social responsibility. Similar to conventional plastics, unregulated and mismanaged bioplastics could potentially create another environmental mayhem. Therefore, it is a crucial time to harness the power of law to set applicable standards with a high threshold for the classification of “bioplastics”, which companies can aspire to, and customers can trust. In this review, we analyse the multifarious international bioplastics standards, critically assess the potential shortcomings and highlight how the intersection of law with science and technology is crucial towards the reform of bioplastics regulation.
Graphic Abstract
Continual reduction of landfill space along with rising CO2 levels and environmental pollution, are global issues that will only grow with time if not correctly addressed. The lack of proper waste management infrastructure means gloablly commodity plastics are disposed of incorrectly, leading to both an economical loss and environmental destruction. The bioaccumulation of plastics and microplastics can already be seen in marine ecosystems causing a negative impact on all organisms that live there, ultimately microplastics will bioaccumulate in humans. The opportunity exists to replace the majority of petroleum derived plastics with bioplastics (bio-based, biodegradable or both). This, in conjunction with mechanical and chemical recycling is a renewable and sustainable solution that would help mitigate climate change. This review covers the most promising biopolymers PLA, PGA, PHA and bio-versions of conventional petro-plastics bio-PET, bio-PE. The most optimal recycling routes after reuse and mechanical recycling are: alcoholysis, biodegradation, biological recycling, glycolysis and pyrolysis respectively.
Microfibers are ubiquitous contaminants of emerging concern. Traditionally ascribed to the “microplastics” family, their widespread occurrence in the natural environment is commonly reported in plastic pollution studies, based on the assumption that fibers largely derive from wear and tear of synthetic textiles. By compiling a global dataset from 916 seawater samples collected in six ocean basins, we show that although synthetic polymers currently account for two-thirds of global fiber production, oceanic fibers are mainly composed of natural polymers. µFT-IR characterization of ~2000 fibers revealed that only 8.2% of oceanic fibers are synthetic, with most being cellulosic (79.5%) or of animal origin (12.3%). The widespread occurrence of natural fibers throughout marine environments emphasizes the necessity of chemically identifying microfibers before classifying them as microplastics. Our results highlight a considerable mismatch between the global production of synthetic fibers and the current composition of marine fibers, a finding that clearly deserves further attention.
Microbial polyhydroxyalkanoates (PHAs) are biopolyesters produced by microorganisms as intracellular granules under nutrient stress. Due to non-toxic and biodegradable behavior these polyesters are a sustainable source of wide range of biomaterials such as bioplastics. As a result of excellent polymeric properties such as melting temperatures (Tm), glass transition temperature (Tg), crystallinity, Young’s modulus and stress to break ratio these polyesters are capable of replacing the synthetic plastics. Bioplastics produced using PHAs as biomass source can be used for packaging material and disposable products on the other hand biofuels can also be generated using PHAs. PHAs find countless applications in industry, agriculture, pharmaceuticals and health. A large number of bacterial, microalgal and fungal species can produce these polyesters. Bacterial species such as Bacillus megaterium, Pseudomonas aeruginosa, P. oleovorans, P. stutzeri and Cupriavidus necator are some highly studied microorganisms for PHA production. This review summarizes the most important aspects of PHAs, crystalline and granular structure of PHA biosynthesizing genes and their relevant proteins. Thermal and physical properties, sources, extraction, purification methods of PHAs are briefly discussed. Applications of PHAs, phylogenetic analysis of Pseudomonas sp. in term of its PHAs synthesizing genes, future prospects and possible outcomes are discussed.
Advanced developments in the field of enzyme technology have increased the use of enzymes in industrial applications, especially in detergents. Enzymes as detergent additives have been extensively studied and the demand is considerably increasing due to its distinct properties and potential applications. Enzymes from microorganisms colonized at various geographical locations ranging from extreme hot to cold are explored for compatibility studies as detergent additives. Especially psychrophiles growing at cold conditions have cold-active enzymes with high catalytic activity and their stability under extreme conditions makes it as an appropriate eco-friendly and cost-effective additive in detergents. Adequate number of reports are available on cold-active enzymes such as proteases, lipases, amylases, and cellulases with high efficiency and exceptional features. These enzymes with increased thermostability and alkaline stability have become the premier choice as detergent additives. Modern approaches in genomics and proteomics paved the way to understand the compatibility of cold-active enzymes as detergent additives in broader dimensions. The molecular techniques such as gene coding, amino acid sequencing, and protein engineering studies helped to solve the mysteries related to alkaline stability of these enzymes and their chemical compatibility with oxidizing agents. The present review provides an overview of cold-active enzymes used as detergent additives and molecular approaches that resulted in development of these enzymes as commercial hit in detergent industries. The scope and challenges in using cold-active enzymes as eco-friendly and sustainable detergent additive are also discussed.
In this study, waste cotton fibers were environmentally reused. First, they were milled into fine powders with particle sizes of around 30 µm and dyed for use as pigments. Dyeing properties of the cellulose powder were explored by determining the dye uptake, K/S value, and bath ratio. Among the various samples, powders with owf (on weight of fabric) of 0% dye (pristine cellulose powder), and 10% and 50% dyed powders were selected; and these powders were characterized by several methods to compare the properties of dyed and undyed cellulose. The surface morphologies of the powders were observed with a scanning electron microscope (SEM). Combining the SEM images with the Brunauer–Emmet–Teller (BET) data, it was found that the smaller the particle size, the larger is the surface area. In addition, the X-ray photoelectron spectroscopy (XPS) results revealed that with increasing dye concentration, the intensity of the C peak reduced, while those of O and S increased. Moreover, the main components of the dyed and undyed cellulose powders were found to be almost the same from the Fourier-transform infrared spectroscopy (FTIR) results. Finally, the dynamic mechanical analysis (DMA) data revealed that the loss modulus was significantly larger than the storage modulus, demonstrating that the material mainly undergoes viscous deformation.
The effect of fiber type (cotton, polyester, and rayon), temperature, and use of detergent on the number of microfibers released during laundering of knitted fabrics were studied during accelerated laboratory washing (Launder-Ometer) and home laundering experiments. Polyester and cellulose-based fabrics all shed significant amounts of microfibers and shedding levels were increased with higher water temperature and detergent use. Cellulose-based fabrics released more microfibers (0.2–4 mg/g fabric) during accelerated laundering than polyester (0.1–1 mg/g fabric). Using well-controlled aquatic biodegradation experiments it was shown that cotton and rayon microfibers are expected to degrade in natural aquatic aerobic environments whereas polyester microfibers are expected to persist in the environment for long periods of time.
Poly(l‐lactic acid) (PLLA) is a biodegradable and biocompatible thermoplastic polyester produced from renewable sources, widely used for biomedical devices, in food packaging and in agriculture. It is a semicrystalline polymer, and as such its properties are strongly affected by the developed semicrystalline morphology. As a function of the crystallization temperature, PLLA can form different crystal modifications, namely α′‐crystals below about 120 °C and α‐crystals at higher temperatures. The α′ modification is therefore of special importance as it may be the preferred polymorph developing at processing‐relevant conditions. It is a metastable modification which typically transforms into the more stable α‐crystals on annealing at elevated temperature. The structure, kinetics of formation and thermodynamics of α′‐ and α‐crystals of PLLA are reviewed in this contribution, together with the effect of α′‐/α‐crystal polymorphism on the properties of PLLA. © 2018 Society of Chemical Industry
The current system of production and consumption needs end‐of‐life disposal to function, but the linkage between upstream production‐consumption with the downstream landfill as terminus is, at best, a tenuous, one‐way relationship, suggesting a partial system failure. A starting point to fix this link is to confront, systematically, the messy “black box” that is mixed waste landfilling, interrogate its contents locally, and determine a baseline that can be used to scale up results. Here, we develop a detailed model characterizing landfilled municipal solid waste (MSW) in the United States across the dimensions of material quantity, quality, location, and time. The model triangulates measurements spanning 1,161 landfills (representing up to 95% of landfilled MSW) and 15,169 solid waste samples collected and analyzed at 222 sites across the United States. We confirm that landfilled quantities of paper (63 million Mg), food waste (35 million Mg), plastic (32 million megagrams [Mg]), textiles (10 million Mg), and electronic waste (3.5 million Mg) are far larger than computed by previous top‐down U.S. government estimates. We estimate the cost of MSW landfill disposal in 2015 (10.7 billion U.S. dollars [USD]) and gross lost commodity value of recyclable material (1.4 billion USD). Further, we estimate landfill methane emissions to be up to 14% greater (mass basis) than the 2015 U.S. inventory. By principally relying on measurements of waste quantity and type that are recorded annually, the model can inform more effective, targeted interventions to divert waste materials from landfill disposal, improve local, regional, and national emission estimates, enhance dissipative loss estimates in material flow analyses, and illuminate the dynamics linking material, energy, and economic dimensions to production, consumption, and disposal cycles.
The circular economy concept has gained momentum both among scholars and practitioners. However, critics claim that it means many different things to different people. This paper provides further evidence for these critics. The aim of this paper is to create transparency regarding the current understandings of the circular economy concept. For this purpose, we have gathered 114 circular economy definitions which were coded on 17 dimensions. Our findings indicate that the circular economy is most frequently depicted as a combination of reduce, reuse and recycle activities, whereas it is oftentimes not highlighted that CE necessitates a systemic shift. We further find that the definitions show few explicit linkages of the circular economy concept to sustainable development. The main aim of the circular economy is considered to be economic prosperity, followed by environmental quality; its impact on social equity and future generations is barely mentioned. Furthermore, neither business models nor consumers are frequently outlined as enablers of the circular economy. We critically discuss the various circular economy conceptualizations throughout this paper. Overall, we hope to contribute via this study towards the coherence of the circular economy concept; we presume that significantly varying circular economy definitions may eventually result in the collapse of the concept.
Microplastics in the environment are a subject of intense research as they pose a potential threat to marine organisms. Plastic fibers from textiles have been indicated as a major source of this type of contaminant, entering the oceans via wastewater and diverse non-point sources. Their presence is also documented in terrestrial samples. In this study, the amount of microfibers shedding from synthetic textiles was measured for three materials (acrylic, nylon, polyester), knit using different gauges and techniques. All textiles were found to shed, but polyester fleece fabrics shed the greatest amounts, averaging 7360 fibers/m⁻²/L⁻¹ in one wash, compared with polyester fabrics which shed 87 fibers/m⁻²/L⁻¹. We found that loose textile constructions shed more, as did worn fabrics, and high twist yarns are to be preferred for shed reduction. Since fiber from clothing is a potentially important source of microplastics, we suggest that smarter textile construction, prewashing and vacuum exhaustion at production sites, and use of more efficient filters in household washing machines could help mitigate this problem.
Cellulose acetate (CA)-based materials, like cigarette filters, contribute to landscape pollution challenging municipal authorities and manufacturers. This study investigates the potential of enzymes to degrade CA and to be potentially incorporated into the respective materials, enhancing biodegradation. Deacetylation studies based on Liquid Chromatography-Mass Spectrometry-Time of Flight (LC-MS-TOF), High Performance Liquid Chromatography (HPLC), and spectrophotometric analysis showed that the tested esterases were able to deacetylate the plasticizer triacetin (glycerol triacetate) and glucose pentaacetate (cellulose acetate model compound). The most effective esterases for deacetylation belong to the enzyme family 2 (AXE55, AXE 53, GAE), they deacetylated CA with a degree of acetylation of up to 1.8. A combination of esterases and cellulases showed synergistic effects, the absolute glucose recovery for CA 1.8 was increased from 15% to 28% when an enzymatic deacetylation was performed. Lytic polysaccharide monooxygenase (LPMO), and cellobiohydrolase were able to cleave cellulose acetates with a degree of acetylation of up to 1.4, whereas chitinase showed no activity. In general, the degree of substitution, chain length, and acetyl group distribution were found to affect CA degradation. This study shows that, for a successful enzyme-based deacetylation system, a cocktail of enzymes, which will randomly cleave and generate shorter CA fragments, is the most suitable.
In recent years, there have been increasing concerns in the disposal of textile waste around the globe. The growth of textile markets not only depends on population growth but also depends on economic and fashion cycles. The fast fashion cycle in the textile industry has led to a high level of consumption and waste generation. This can cause a negative environmental impact since the textile and clothing industry is one of the most polluting industries. Textile manufacturing is a chemical-intensive process and requires a high volume of water throughout its operations. Wastewater and fiber wastes are the major wastes generated during the textile production process. On the other hand, the fiber waste was mainly created from unwanted clothes in the textile supply chain. This fiber waste includes natural fiber, synthetic fiber, and natural/synthetic blends. The natural fiber is mostly comprised of cellulosic material, which can be used as a resource for producing bio-based products. The main challenge for utilization of textile waste is finding the method that is able to recover sugars as monosaccharides. This review provides an overview of valorization of textile waste to value-added products, as well as an overview of different strategies for sugar recovery from cellulosic fiber and their hindrances.
Keratin from wool fibers was extracted with different extraction methods, for example oxidation, reduction, sulfitolysis, and superheated water hydrolysis.
Different samples of extracted keratin were characterized by molecular weight determination, FT-IR and NIR spectroscopy, amino acid analysis, and thermal behavior.
While using oxidation, reduction, and sulfitolysis, only the cleavage of disulfide bonds takes place; keratin hydrolysis leads to the breaking of peptide bonds with the formation of low molecular weight proteins and peptides. In the FT-IR spectra of keratoses, the formation of cysteic acid appears, as well as the formation of Bunte salts (–S–SO 3 –) after the cleavage of disulfide bonds by sulfitolysis. The amino acid composition confirms the transformation of amino acid cystine, which is totally converted into cysteic acid following oxidative extraction and almost completely destroyed during superheated water hydrolysis. Thermal behavior shows that keratoses, which are characterized by stronger ionic interaction and higher molecular weight, are the most temperature stable keratin, while hydrolyzed wool shows a poor thermal stability.
Cotton is not the answer to meet the rapidly growing demand for textile fibers. Wood-based regenerated cellulose fibers are an attractive alternative. Since wood is a candidate to replace fossil raw materials in so many applications of the circular economy, other sources need investigation. Cotton linters work in the viscose process – can cotton waste be used to make dissolving pulp? We describe the textile qualities of lyocell fibers from (i) pure cotton waste pulp and (ii) blending with conventional dissolving pulp. The staple fibers were tensile tested, yarns spun and tensile tested and knitted, and tested for shrinkage, water and dye sorption, abrasion resistance, fuzzing and pilling, staining and fastness. TENCEL® staple fibers and off-the-shelf TENCEL® yarn were used as references. The results show that the two study fibers had tenacity and an E-modulus that exceeded the staple fiber reference. Also, the study yarns were at least as good as the spun reference yarn and the commercial off-the-shelf yarn in terms of wet tenacity. Single jerseys made from the study yarns shrunk less upon laundering, which is surprising since they could absorb at least as much water at a comparable rate as the references. Dyeability, staining and color fastness, durability and pilling tendency showed that the two study fiber tricots performed at least as good as the references. This study suggests that cotton waste is a promising candidate for special grade pulp to suit niche regenerated fiber products or to spice up conventional wood-based dissolving pulp.
Plastics have outgrown most man-made materials and have long been under environmental scrutiny. However, robust global information, particularly about their end-of-life fate, is lacking. By identifying and synthesizing dispersed data on production, use, and end-of-life management of polymer resins, synthetic fibers, and additives, we present the first global analysis of all mass-produced plastics ever manufactured. We estimate that 8300 million metric tons (Mt) as of virgin plastics have been produced to date. As of 2015, approximately 6300 Mt of plastic waste had been generated, around 9% of which had been recycled, 12% was incinerated, and 79% was accumulated in landfills or the natural environment. If current production and waste management trends continue, roughly 12,000 Mt of plastic waste will be in landfills or in the natural environment by 2050.
Poly(lactic acid) (PLA) is a compostable bioplastic manufactured by the polymerisation of lactic acid monomers derived from the fermentation of starch as a feedstock. Since its first commercialisation in the late 1990's, PLA production has grown annually and currently it estimated that worldwide production will reach at least 800,000 tons by 2020 with Japan and the USA the two major producers. PLA is used as a replacement to conventional petrochemical based plastics, principally as food packaging containers and films and more recently, in electronics and in the manufacture of synthetic fibres. Consequently, there has been a marked increase in PLA contamination in the environment as well as increasing amounts being diverted to commercial composting facilities. This review focuses on the development, production, stability and degradation of PLA in a range of differing environments and explores our current knowledge of the environmental and biological factors involved in PLA degradation.
The ecology of hydrocarbon degradation by microbial populations in the natural environment is reviewed, emphasizing the physical, chemical, and biological factors that contribute to the biodegradation of petroleum and individual hydrocarbons. Rates of biodegradation depend greatly on the composition, state, and concentration of the oil or hydrocarbons, with dispersion and emulsification enhancing rates in aquatic systems and absorption by soil particulates being the key feature of terrestrial ecosystems. Temperature and oxygen and nutrient concentrations are important variables in both types of environments. Salinity and pressure may also affect biodegradation rates in some aquatic environments, and moisture and pH may limit biodegradation in soils. Hydrocarbons are degraded primarily by bacteria and fungi. Adaptation by prior exposure of microbial communities to hydrocarbons increases hydrocarbon degradation rates. Adaptation is brought about by selective enrichment of hydrocarbon-utilizing microorganisms and amplification of the pool of hydrocarbon-catabolizing genes. The latter phenomenon can now be monitored through the use of DNA probes. Increases in plasmid frequency may also be associated with genetic adaptation. Seeding to accelerate rates of biodegradation has been shown to be effective in some cases, particularly when used under controlled conditions, such as in fermentors or chemostats.
The production of reclaimed fibers from used textiles and their processing into textile products has been an effective recycling solution for centuries and thus one of the oldest material cycles in the world. It has arisen historically from the scarcity of naturally occurring vegetable and animal fiber, the economy and the relative lack of need of people. The aim has always been to recover the fibers contained in unneeded textile structures as gently as possible as a raw material for new products.
Polyglycolic acid (PGA) is a class of semicrystalline, bioresorbable polymers that have been widely used in a number of applications. No other bioresorbable materials can fully replace PGA in tissue engineering. Understanding degradation mechanisms in PGA is important for improving the efficiency and effectiveness in various fields including implantation. This review begins with a discussion on terminology of polymer degradation and hydrolytic degradation mechanism with a delineative model. This review also focus on previous degradation studies taking advantage of its fast‐degrading behavior and the mechanism behind hexafluoroisopropanol (HFIP) being the sole solvent for PGA. Finally, the merits of PGA are discussed with many potential future applications along with their associated challenges.
A comprehensive understanding of the waste cotton supply chain and different end-of-life options is essential to promote cotton recycling and reuse. This study analyzed global and US data to understand the quantity, current sources, and destinations of waste cotton. Globally, 11.6 million metric tons of waste cotton are generated per year during cotton garment production. This study also reviewed different options for recycling both pre-consumer and post-consumer cotton waste via chemical and mechanical processes. Different applications of waste cotton were compared to their virgin counterparts from technical, environmental, and economic perspectives. Unlike most previous studies, this research included applications that are not traditional textile products (e. g., biofuels and composites), shedding light on potential new markets for waste cotton that will not compete with virgin cotton.
As the textile and garment industries aim at minimizing the impact caused by mass fabrication, fast consumption and relatively short utility span of materials and products, they focus on Circular Economy (CE) principles as a feasible solution. In order to build a new practice, lifestyle and ecology under the upcoming CE transition, in this manuscript we propose new approaches to implement concepts such as materials circularity index (CI) and clothing utility (CU), at personal and social levels and through new design and geometry guidelines. We believe these proposed strategies will be key in building a circular economy for smart textiles, smart clothing and future wearables.
This review assesses the state-of-the-art in comparative Life Cycle Assessment of fossil-based and bio-based polymers. Published assessments are critically reviewed and compared to the European Union Product Environmental Footprint (EU PEF) standards. No published articles were found to fully meet the standards, but the critical review method was used to classify the articles by their level of compliance. 25 articles partially met the PEF standards, giving 39 fossil-based and 50 bio-based polymer case results. Ultimately, it was possible to compare seven bio-based polymers and seven fossil-based polymers across seven impact categories (energy use, ecotoxicity, acidification, eutrophication, climate change, particulate matter formation and ozone depletion). Significant variation was found between polymer types and between fossil-based and bio-based polymers, meaning it was not possible to conclusively declare any polymer type as having the least environmental impact in any category. Significant variation was also seen between different studies of the same polymer, for both fossil-based and bio-based polymers. In some cases this variation was of the order of 400%. Results suggest that a large part of this variation is related to the Life Cycle Assessment methodologies applied, particularly in the end-of-life treatment, the use of credits for absorbed Carbon Dioxide, and the allocation of multifunctional process impacts. The feedstock source and processing method assumed for bio-based polymers was also a major sources of variation. The challenges of Life Cycle Assessment, particularly in a complex, geographically diverse and young industry like bio-based polymers, are recognised. It is proposed that the PEF standards should be adopted more widely in order to homogenise the methods used and allow meaningful comparison between LCA studies on fossil-based and bio-based polymers, and between studies of the same polymers.
Synthetic fibers represent one of the main forms of microplastics in marine environment and recently were related to household washings as a source. Although other types of fiber, like natural, do not rely under this classification, there is a potential for them to act as a vector of toxic substances to biota in the same way as microplastics do. Consequently all types of fiber have the potential to cause variable ecologic and socioeconomic impacts. In this scenario, the present study aimed to investigate the effects of washing parameters in the emission of fibers on textiles with different characteristics and fiber content: cotton, acrylic, polyester and polyamide. For this purpose individual garments were sequentially washed with and without detergent. Results showed that the use of a detergent reduced significantly the mass of particles emitted from synthetic garments but not from cotton, which, in relative terms, was responsible for the highest emissions. Textile characteristics such as mass availability and fiber cohesion influenced results, where shorter irregular fibers and lower tenacities dealt to higher releases. For all types of garments tested, 10 sequential cycles decreased particles' release, with peaks in three firsts washes (from 37% to 76%). Taking into account a regular washing machine filter, a considerable mass of fibers (from 40% to 75%) was not retained by this device, indicating a potential for improvement. Together, simple solutions as the use of detergents, three pre-washes and superimposed filter meshes, could diminish >53% of this type of pollution. Besides this potential reduction, globally, in one year, domestic washing machines would still contribute with around 15 thousand tonnes of cotton and synthetic fibers. A structured and sustained solution for this problem should advance in an interdisciplinary approach, fomenting responsibility from plural actors, taken in all stages of products' life cycle.
Plastics are an indispensable material but also a major environmental pollutant. In contrast, biodegradable polymers have the potential to be compostable. The biodegradation of four polymers as discs, polycaprolactone (PCL), polyhydroxybutyrate (PHB), polylactic acid (PLA) and poly(1,4 butylene) succinate (PBS) was compared in soil and compost over a period of more than 10 months at 25 °C, 37 °C and 50 °C. Degradation rates varied between the polymers and incubation temperatures but PCL showed the fastest degradation rate under all conditions and was completely degraded when buried in compost and incubated at 50 °C after 91 days. Furthermore, PCL strips showed a significant reduction in tensile strength in just 2 weeks when incubated in compost >45 °C. Various fungal strains growing on the polymer surfaces were identified by sequence analysis. Aspergillus fumigatus was most commonly found at 25 °C and 37 °C, while Thermomyces lanuginosus, which was abundant at 50 °C, was associated with PCL degradation.
Concerns about microplastics (MPs) environmental behavior and accumulation are growing at global scale and meanwhile, the attention to employ bioplastics for replacing conventional plastics is increasing. The research priority for a better understanding of the fate and potential impacts of MPs from bioplastics is of utmost importance. However, the investigations on the effects of bioplastics in terms of MPs are still limited and largely unknown. In this discussion, the current knowledge of MPs is timely highlighted to incorporate biodegradable MPs in the ongoing researches. Recent studies have identified that some biodegradable MPs exhibit same effect as conventional type MPs. Furthermore, we performed a simple degradation experiment and found that polyhydroxyalkanoate films formed MPs in water environment alike other biodegradable and conventional plastics sharing common research interests. In an effort to promote investigations, we recommend the knowledge gaps identified on bioplastics MPs: understanding the timeframe of disintegration and degradation of developing bioplastics; ensuring degradability and less persistence; promoting toxicity tests and potential effects on a wide variety of organisms; promoting attempts to assess the impacts on ecosystems; evaluating the interaction of microorganisms and MPs; working towards identifying novel disposal and collection methods from public to ease recycling and degradation processes.
Social and economic development has driven considerable scientific and engineering efforts on the discovery, development and utilization of polymers. Poly‐lactic acid (PLA) is one of the most promising biopolymers as it can be produced from non‐toxic renewable feedstock. PLA has emerged as an important polymeric material for biomedical applications on account of its properties such as biocompatibility, biodegradability, mechanical strength and process ability. Lactic acid (LA) can be obtained by fermentation of sugars derived from renewable resources such as corn, sugarcane etc. PLA is thus an eco‐friendly non‐toxic polymer with features that permit use in the human body. Although PLA has a wide spectrum of applications, there are certain limitations such as slow degradation rate, hydrophobicity and low impact toughness associated with its use. Blending PLA with other polymers offers convenient options to improve associated properties or to generate novel PLA polymers/blends for target applications. A variety of PLA blends have been explored for various biomedical applications such as drug delivery, implants, sutures, and tissue engineering. PLA and their copolymers are becoming widely used in tissue engineering for function restoration of impaired tissues due to their excellent biocompatibility and mechanical properties. The relationship between PLA material properties, manufacturing processes and development of products with desirable characteristics is described in this article. LA production, PLA synthesis and their applications in the biomedical field are also discussed.
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Any industry have significant impact on environment and textile manufacturing is one of the main contributors to greenhouse gas emissions. This paper summarizes and discusses the ecofriendly achievements within development of textile industry dealing with three main contributors: production, consumption and recycling. It shows that although significant environmental friendly technological improvements were made in primary textile production whereas, recycling and consumer awareness have low sustainability level for textile industry. The emphasis was also made on comparison of textile industry with other ones (paper, aluminium, glass) showing significantly higher recycling rate. Waste management regulation for textiles and the lack for standardization for global textile waste management are also discussed. Low recycling rate and continuously increasing demand in textile production makes it difficult to establish the balance between industrial and environmental systems necessary to increased life cycle for textile products. Importance of simultaneous involvement and development of customer awareness, sustainable manufacturing and high recycling level should, therefore, be in focus.
Poly (lactic acid) or polylactide (PLA) is a commercial biobased, biodegradable, biocompatible, compostable and non-toxic polymer that has competitive material and processing costs and desirable mechanical properties. Thereby, it can be considered favorably for biomedical applications and as the most promising substitute for petroleum-based polymers in a wide range of commodity and engineering applications. However, PLA has some significant shortcomings such as low melt strength, slow crystallization rate, poor processability, high brittleness, low toughness, and low service temperature, which limit its applications. To overcome these limitations, blending PLA with other polymers is an inexpensive approach that could also tailor the final properties of PLA-based products. During the last two decades, researchers investigated the synthesis, processing, properties, and development of various PLA-based blend systems including miscible blends of poly L-lactide (PLLA) and poly D-lactide (PDLA), which generate stereocomplex crystals, binary immiscible/miscible blends of PLA with other thermoplastics, multifunctional ternary blends using a third polymer or fillers such as nanoparticles, as well as PLA-based blend foam systems. This article reviews all these investigations and compares the syntheses/processing-morphology-properties interrelationships in PLA-based blends developed so far for various applications.
Anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW), leading to renewable energy production in the form of methane, is a preferable method for dealing with the increasing amount of waste. Food waste is separated at the source in many countries for anaerobic digestion. However, the presence of plastic bags is a major challenge for such processes. This study investigated the anaerobic degradability of different bioplastics, aiming at potential use as collecting bags for the OFMSW. The chemical composition of the bioplastics and the microbial community structure in the AD process affected the biodegradation of the bioplastics. Some biopolymers can be degraded at hydraulic retention times usually applied at the biogas plants, such as poly(hydroxyalkanoate)s, starch, cellulose and pectin, so no possible contamination would occur. In the future, updated standardization of collecting bags for the OFMSW will be required to meet the requirements of effective operation of a biogas plant.
PET depolymerization via enzymatic catalysis is one of the most promising technologies in the context of plastics circular economy. So far, hydrolysis reactions accounted for almost the totality of studies, since the glycolysis route was only recently reported. In the present work, a comparative analysis of hydrolysis and glycolysis of PET oligomers catalyzed by Humicola insolens cutinase (HiC) and Candida antarctica lipase B (CALB) showed completely distinct profiles of the reaction products and rates. Then, simultaneous hydrolysis-glycolysis reactions with varied water and ethylene glycol concentrations revealed a gradual increase of the esterified products mono(2-hydroxyethyl) terephthalate (MHET) and bis(2-hydroxyethyl) terephthalate (BHET) as the reaction medium became more organic. Erosion patterns on the PET surface during hydrolysis and glycolysis reactions were also shown to be different. The results here reported open new opportunities for the use of task-specific solvents for biotechnological PET recycling, providing versatility for the depolymerization products in different reuse technologies.
Waste jeans, containing cotton and polyester, are among the widely available sources for bioenergy production. In this study, the cotton part of waste jean was used for biogas and ethanol production. The hydrolysis of non-cellulosic part, i.e., polyester, and the pretreatment of cellulosic part was performed by sodium carbonate treatment. The effects of Na2CO3 concentration (0, 0.5, and 1 M) and temperature (50, 100, and 150 °C) on the cotton, polyester, and textile structure were investigated. The pretreated textile, with over 90% cellulose, was subjected to anaerobic digestion, enzymatic hydrolysis, and fermentation to produce biogas, sugars, and ethanol, respectively. The maximum methane yields of 328.9 and 361.1 mL/g VS were achieved from pure cotton and jeans after pretreatment with 0.5 M Na2CO3 at 150 °C for 120 min, respectively. Using the pretreatment, the highest glucose yields of enzymatic hydrolysis were 88.0% and 81.71% for cotton and textile, respectively, while the corresponding values for untreated samples were 36.9 and 28.0%. The maximum ethanol yields of 69.4% and 59.5% were obtained from cotton and textile, respectively. It was concluded that the pretreatment is promising for the hydrolysis of the synthetic polymer of textile and the improvement of the biodegradability of the cellulosic part with negligible cellulose destruction.
The aim of this research was to study what happens to polylactide (PLA) fibers when they are released to wastewater systems. Samples of PLA fibers were immersed in activated sludge and subjected to typical activated sludge treatment in mesophilic (36 °C) and thermophilic (56 °C) conditions for up to 4 weeks. The characteristics of the surface and cross-sections of PLA fibers were analyzed by scanning electron microscopy (SEM), showing the setlement of the microorganisms on the surface of PLA fibers immersed in sludge and also the erosion of the material with time. Diferential scanning calorimetry (DSC) analysis provided information on small changes in the crystalline structure of PLA fibers, and the results of tensile tests proved only partial degradation of PLA material treated in the activated sludge system during the processing time. The study confrmed that the standard processing of wastewater in the activated sludge system, in both mesophilic and thermophilic variants, is insufficient for the biodegradation of PLA. Therefore, PLA microplastics can be released from wastewater treatment plants.
Drastic climate change has enforced business organizations to manage their carbon emissions. Procurement and transportation is one of the supply chain business operations where carbon emissions are huge. This paper proposes an environmentally sustainable procurement and logistics model for a supply chain. The proposed models are of MINLP (Mixed Integer Non Linear Program) and MILP (Mixed Integer Linear Program) form requiring a variety of the real time parameters from buyer and supplier side such as costs, capacities, lead-times and emissions. Based on real time data, the models provide an optimal sustainable procurement and transportation decision. It is also shown that large sized problems possessing essential 3V's of big data, i.e., volume, variety and velocity consume non-polynomial time and cannot be solved optimally. Therefore, a heuristic (H-1) is also proposed to solve the large sized problems involving big data. T-test significance is also conducted between optimal and heuristic solutions obtained using 42 randomly generated data instances possessing essential characteristics of big data. Encouraging results in terms of solution quality and computational time are obtained.
Operations management tools are critical in the process of evaluating and implementing action towards a low carbon production. Currently, a sustainable production implies both an efficient resource use and the obligation to meet targets for reducing greenhouse gas (GHG) emissions. The carbon footprint (CF) tool allows estimating the overall amount of GHG emissions associated with a product or activity throughout its life cycle. In this paper, we propose a four-step method for a joint use of CF assessment and Data Envelopment Analysis (DEA). Following the eco-efficiency definition, which is the delivery of goods using fewer resources and with decreasing environmental impact, we use an output oriented DEA model to maximize production and reduce CF, taking into account simultaneously the economic and ecological perspectives. In another step, we stablish targets for the contributing CF factors in order to achieve CF reduction. The proposed method was applied to assess the eco-efficiency of five organic blueberry orchards throughout three growing seasons. The results show that this method is a practical tool for determining eco-efficiency and reducing GHG emissions.
The determination of the safe working life of polymer materials is important for their successful use in engineering, medicine and consumer-goods applications. An understanding of the physical and chemical changes to the structure of widely-used polymers such as the polyolefins, when exposed to aggressive environments, has provided a framework for controlling their ultimate service lifetime by either stabilizing the polymer or chemically accelerating the degradation reactions. The recent focus on biodegradable polymers as replacements for more bio-inert materials such as the polyolefins in areas as diverse as packaging and as scaffolds for tissue engineering has highlighted the need for a review of the approaches to being able to predict the lifetime of these materials. In many studies the focus has not been on the embrittlement and fracture of the material (as it would be for a polyolefin) but rather the products of degradation, their toxicity and ultimate fate when in the environment, which may be the human body. These differences are primarily due to time-scale. Different approaches to the problem have arisen in biomedicine, such as the kinetic control of drug delivery by the bio-erosion of polymers, but the similarities in mechanism provide real prospects for the prediction of the safe service lifetime of a biodegradable polymer as a structural material. Common mechanistic themes that emerge include the diffusion-controlled process of water sorption and conditions for surface versus bulk degradation, the role of hydrolysis versus oxidative degradation in controlling the rate of polymer chain scission and strength loss and the specificity of enzyme-mediated reactions.
Poly(lactic) acid (PLA) is currently a most potential and popular polymeric material, which will play a key role in building of a sustainable bioeconomy. Knowledge of biodegradation of PLA is crucial for treating plastic wastes and easing the serious energy crisis. The biodegradability of PLA based on microorganisms (actinomycetes, bacteria, fungus) and biochemical processes of degradation have been advanced in recent years, but the high efficient methods of PLA biodegradation are still inadequately addressed. With the development of the modern molecular biological techniques, some studies have detected specific groups of microorganisms involved in the biodegradation process of PLA. Nevertheless, few studies were conducted to establish the simulated system based on aerobic biodegradation of PLA due to the lack of available information on process parameters. In this review, PLA is treated according to its synthesis mechanisms, applications, biochemical processes in degradation, degrading microorganisms and enzymes. In addition, the simulated system based on aerobic microorganism is also presented for acceleration of PLA degradation.
Renewable resources are used increasingly in the production of polymers. In particular, monomers such as carbon dioxide, terpenes, vegetable oils and carbohydrates can be used as feedstocks for the manufacture of a variety of sustainable materials and products, including elastomers, plastics, hydrogels, flexible electronics, resins, engineering polymers and composites. Efficient catalysis is required to produce monomers, to facilitate selective polymerizations and to enable recycling or upcycling of waste materials. There are opportunities to use such sustainable polymers in both high-value areas and in basic applications such as packaging. Life-cycle assessment can be used to quantify the environmental benefits of sustainable polymers.