To develop viable solutions for reducing plastic waste, spatially explicit data on the management of these materials are critical. Here we employ statistical and geospatial methods to present a ...comprehensive assessment of plastic waste in the United States by resin type at the state, county, and local levels. Of the estimated 44 Mt of plastic waste managed in 2019 domestically, approximately 86% was landfilled, 9% was combusted, and 5% was recycled. Landfilled plastics represented significant losses to the country's economy in 2019: an average of US$7.2 billion in market value, about 3.4 EJ as embodied energy (equivalent to 12% of energy consumption by the industrial sector), and 1.5 EJ as an energy source (equivalent to 5.5% and 5% of energy consumption by the industrial and transportation sectors, respectively). Lastly, we posit that substantial amount of landfilled plastic waste could be recovered through advanced sorting, existing, and emerging recycling processes.
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Focusing on the engineering aspects of producing and using plastics, this book covers both the polymer basics that are helpful to bring readers quickly up-to-speed if they are not familiar with a ...particular area of plastics processing, and the recent developments that enable practitioners to discover which options best fit their requirements. --
Summary
Petroleum‐based plastics have replaced many natural materials in their former applications. With their excellent properties, they have found widespread uses in almost every area of human ...life. However, the high recalcitrance of many synthetic plastics results in their long persistence in the environment, and the growing amount of plastic waste ending up in landfills and in the oceans has become a global concern. In recent years, a number of microbial enzymes capable of modifying or degrading recalcitrant synthetic polymers have been identified. They are emerging as candidates for the development of biocatalytic plastic recycling processes, by which valuable raw materials can be recovered in an environmentally sustainable way. This review is focused on microbial biocatalysts involved in the degradation of the synthetic plastics polyethylene, polystyrene, polyurethane and polyethylene terephthalate (PET). Recent progress in the application of polyester hydrolases for the recovery of PET building blocks and challenges for the application of these enzymes in alternative plastic waste recycling processes will be discussed.
The high recalcitrance of many synthetic plastics results in their long persistence in the environment and globally in growing amounts of plastic waste. Microbial enzymes are emerging as candidates for the development of biocatalytic plastic recycling processes.
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The dynamic expansion of the Agricultural Plastics (AP) use has allowed for improved agricultural products quality, yields, and enhanced sustainability along with multiple benefits for the Agrifood ...sector. The present work investigates the relationship of AP characteristics, use and End-of-Life (EoL) practices with degradation and potential generation of micro-, nanoparticles (MNP) in soil. The composition, functionalities, and degradation behaviour of the contemporary conventional and biodegradable AP categories are systematically analysed. Their market dynamics are briefly presented. The risk and the conditions for the AP potential role in soil pollution and possible MNP generation are analysed based on a qualitative risk assessment approach. AP are classified from high to low-risk products with respect to their probability for soil contamination by MNP based on worst-best scenarios. Proposed alternative sustainable solutions to eliminate the risks are briefly presented for each AP category. Characteristic quantitative estimations of soil pollution by MNP generated by AP are presented for selected case studies reported in the literature. The significance of various indirect sources of agricultural soil pollution by MNP is analysed allowing for appropriate risk mitigation strategies and policies to be designed and implemented.
•Agricultural Plastics degradation analysed for potential microplastics generation.•Market dynamics of major agricultural plastics categories show high rates of growth.•Risk-based classification of AP for soil contamination by microplastics•Alternative solutions to eliminate the risks proposed for each AP category.•Major contribution of other sources to agricultural soil pollution by microplastics
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Most researches on the plastisphere in coastal environments deal with plastics floating in seawater. Comparatively smaller attention has been devoted to the plastisphere of plastics buried in marine ...sediments, and very little is known on that of plastics on coastal sand dunes. Yet, limited information is available on the impact of plastics, especially biodegradable plastics, on microbial organisms in their surroundings. Nevertheless, a large amount of plastics sink on the seabed or is deposited on beach-dune systems.
We investigated the succession of plastisphere microbial community on two biodegradable composites based on poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and seagrass fibres (PHBV/PO), buried in seabed and dune sediments over a 27 months period in mesocosm. PHBV is regarded as a valuable alternative to conventional plastics and PHBV/PO has recently been designed for applications in coastal habitat restoration. We also examined the degradation rate and impact of these plastics on the microbial communities of surrounding sediments.
Microbial communities of the surface of PHBV and PHBV/PO in seabed and dune sand differ from those of surrounding sediments, displaying a lower richness. Plastics colonization occurs largely from bacteria present in surrounding sediments, although the contribution from the water column bacterial pool could be not negligible for plastics in the seabed. No significant differences were detected between the communities of the two plastics and no significant impact of plastics on microbial community of the surrounding sediments was detected. The exceptional long duration of this study allowed to gain information on the succession of a plastisphere community over a previously unexplored time scale. Succession appears highly dynamic in dune sand even after two years, while the community structure in seabed seems to reach stability after one year. These findings highlight the importance of performing long-term studies when trying to characterize composition and dynamics of plastisphere bacterial communities.
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•Microbial richness is lower on PHBVs than in sediments, both in seabed and dune sand.•Degradation rates of different PHBVs are due to intrinsic characteristics of the materials.•PHBVs have no impact on the microbial community of the surrounding sediments.•Recruitment of plastic colonizers occurs largely from the surrounding sediments.•Succession appears highly dynamic even after two years, especially in dune sand.
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Microplastics, plastics particles <5 mm in length, are a widespread pollutant of the marine environment. Oral ingestion of microplastics has been reported for a wide range of marine biota, but uptake ...into the body by other routes has received less attention. Here, we test the hypothesis that the shore crab (Carcinus maenas) can take up microplastics through inspiration across the gills as well as ingestion of pre-exposed food (common mussel Mytilus edulis). We used fluorescently labeled polystyrene microspheres (8–10 μm) to show that ingested microspheres were retained within the body tissues of the crabs for up to 14 days following ingestion and up to 21 days following inspiration across the gill, with uptake significantly higher into the posterior versus anterior gills. Multiphoton imaging suggested that most microspheres were retained in the foregut after dietary exposure due to adherence to the hairlike setae and were found on the external surface of gills following aqueous exposure. Results were used to construct a simple conceptual model of particle flow for the gills and the gut. These results identify ventilation as a route of uptake of microplastics into a common marine nonfilter feeding species.
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Present estimates suggest that of the 359 million tons of plastics produced annually worldwide
, 150-200 million tons accumulate in landfill or in the natural environment
. Poly(ethylene ...terephthalate) (PET) is the most abundant polyester plastic, with almost 70 million tons manufactured annually worldwide for use in textiles and packaging
. The main recycling process for PET, via thermomechanical means, results in a loss of mechanical properties
. Consequently, de novo synthesis is preferred and PET waste continues to accumulate. With a high ratio of aromatic terephthalate units-which reduce chain mobility-PET is a polyester that is extremely difficult to hydrolyse
. Several PET hydrolase enzymes have been reported, but show limited productivity
. Here we describe an improved PET hydrolase that ultimately achieves, over 10 hours, a minimum of 90 per cent PET depolymerization into monomers, with a productivity of 16.7 grams of terephthalate per litre per hour (200 grams per kilogram of PET suspension, with an enzyme concentration of 3 milligrams per gram of PET). This highly efficient, optimized enzyme outperforms all PET hydrolases reported so far, including an enzyme
from the bacterium Ideonella sakaiensis strain 201-F6 (even assisted by a secondary enzyme
) and related improved variants
that have attracted recent interest. We also show that biologically recycled PET exhibiting the same properties as petrochemical PET can be produced from enzymatically depolymerized PET waste, before being processed into bottles, thereby contributing towards the concept of a circular PET economy.
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The future of plastics recycling Garcia, Jeannette M.; Robertson, Megan L.
Science (American Association for the Advancement of Science),
11/2017, Volume:
358, Issue:
6365
Journal Article
Peer reviewed
Chemical advances are increasing the proportion of polymer waste that can be recycled
The environmental consequences of plastic solid waste are visible in the ever-increasing levels of global plastic ...pollution both on land and in the oceans. But although there are important economic and environmental incentives for plastics recycling, end-of-life treatment options for plastic solid waste are in practice quite limited. Presorting of plastics before recycling is costly and time-intensive, recycling requires large amounts of energy and often leads to low-quality polymers, and current technologies cannot be applied to many polymeric materials. Recent research points the way toward chemical recycling methods with lower energy requirements, compatibilization of mixed plastic wastes to avoid the need for sorting, and expanding recycling technologies to traditionally nonrecyclable polymers.
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