Biodegradable and conventional plastic packaging: Comparison of life cycle environmental impacts of poly(mandelic acid) and polystyrene

Bioplastic packaging in circular economy: A systems-based policy approach for multi-sectoral challenges

Bioplastics have long been publicized as a sustainable plastic packaging alternative; however, their widespread industrialization is still embryonic due to complex challenges spanning multiple sectors. This review critically analyses the bioplastic lifecycle and provides a holistic evaluation of both the opportunities and potential trade-offs along their value chain. Their lifecycle is divided into three sectors: 1) resources, extraction, and manufacturing, 2) product consumption which discusses availability, consumer perception, and marketing strategies, and 3) end-of-life (EoL) management which includes segregation, recycling, and disposal. In the production phase, the primary challenges include selection of suitable raw feedstocks and addressing the techno-economic constraints of manufacturing processes. To tackle these challenges, it is recommended to source sustainable feedstocks from innovative, renewable, and waste materials, adopt green synthesis mechanisms, and optimize processes for improved efficiency. The consumption phase encompasses challenges related to market availability, cost competitiveness, and consumer perception of bioplastics. Localizing feedstock sourcing and production, leveraging the economics of scale, and promoting market demand for recycled bioplastics can positively influence the market dynamics. Additionally, dispelling misconceptions about degradability through proper labeling, and employing innovative marketing strategies to enhance consumer perception of the mechanical performance and quality of bioplastics is crucial. During the EoL management phase, major challenges include inadequate awareness, inefficient segregation protocols, and bioplastics with diverse properties that are incompatible with existing waste management infrastructure. Implementing a standardized labeling system with clear representation of suitable EoL techniques and integrating sensors and machine learning-based sorting technologies will improve segregation efficiency. Further, establishing interconnected recycling streams that clearly define the EoL pathways for different bioplastics is essential to ensure circular waste management systems. Finally, designing a comprehensive systems-based policy framework that incorporates technical, economic, environmental, and social drivers is recommended to promote bioplastics as a viable circular packaging solution.

Mechanistic study on the increase of Microcystin-LR synthesis and release in Microcystis aeruginosa by amino-modified nano-plastics

Ecological risk of micro/nano-plastics (MPs/NPs) has become an important environmental issue. Microcystin-leucine-arginine (MC-LR) produced by Microcystis aeruginosa (M. aeruginosa) is the most common and toxic secondary metabolites (SM). However, the influencing mechanism of MPs and NPs exposure on MC-LR synthesis and release have still not been clearly evaluated. In this work, under both acute (4d) and long-term exposure (10d), only high-concentration (10 mg/L) exposure of amino-modified polystyrene NPs (PS-NH2-NPs) promoted MC-LR synthesis (32.94 % and 42.42 %) and release (27.35 % and 31.52 %), respectively. Mechanistically, PS-NH2-NPs inhibited algae cell density, interrupted pigment synthesis, weakened photosynthesis efficiency, and induced oxidative stress, with subsequent enhancing the MC-LR synthesis. Additionally, PS-NH2-NPs exposure up-regulated MC-LR synthesis pathway genes (mcyA, mcyB, mcyD, and mcyG) combined with significantly increased metabolomics (Leucine and Arginine), thereby enhancing MC-LR synthesis. PS-NH2-NPs exposure enhanced the MC-LR release from M. aeruginosa via up-regulated MC-LR transport pathway genes (mcyH) and the shrinkage of plasma membrane. Our results provide new insights into the long-time coexistence of NPs with algae in freshwater systems might pose a potential threat to aquatic environments and human health.

Research advances on the toxicity of biodegradable plastics derived micro/nanoplastics in the environment: A review

The detrimental effects of plastic and microplastic accumulation on ecosystems are widely recognized and indisputable. The emergence of biodegradable plastics (BPs) offers a practical solution to plastic pollution. Problematically, however, not all BPs can be fully degraded in the environment. On the contrary, the scientific community has demonstrated that BPs are more likely than conventional plastics (CPs) to degrade into micro/nanoplastics and release additives, which can have similar or even worse effects than microplastics. However, there is very limited information available on the environmental toxicity assessment of BMPs. The absence of a toxicity evaluation system and the uncertainty regarding combined toxicity with other pollutants also impede the environmental toxicity assessment of BMPs. Currently, research is focused on thoroughly exploring the toxic effects of biodegradable microplastics (BMPs). This paper reviews the pollution status of BMPs in the environment, the degradation behavior of BPs and the influencing factors. This paper comprehensively summarizes the ecotoxicological effects of BPs on ecosystems, considering animals, plants, and microorganisms in various environments such as water bodies, soil, and sediment. The focus is on distinguishing between BMPs and conventional microplastics (CMPs). In addition, the combined toxic effects of BMPs and other pollutants are also being investigated. The findings suggest that BMPs may have different or more severe impacts on ecosystems. The rougher and more intricate surface of BMPs increases the likelihood of causing mechanical damage to organisms and breaking down into smaller plastic particles, releasing additives that lead to a series of cascading negative effects on related organisms and ecosystems. In the case of knowledge gaps, future research is also proposed and anticipated to investigate the toxic effects of BMPs and their evaluation.

Depolymerization within a Circular Plastics System

The societal importance of plastics contrasts with the carelessness with which they are disposed. Their superlative properties lead to economic and environmental efficiency, but the linearity of plastics puts the climate, human health, and global ecosystems at risk. Recycling is fundamental to transitioning this linear model into a more sustainable, circular economy. Among recycling technologies, chemical depolymerization offers a route to virgin quality recycled plastics, especially when valorizing complex waste streams poorly served by mechanical methods. However, chemical depolymerization exists in a complex and interlinked system of end-of-life fates, with the complementarity of each approach key to environmental, economic, and societal sustainability. This review explores the recent progress made into the depolymerization of five commercial polymers: poly(ethylene terephthalate), polycarbonates, polyamides, aliphatic polyesters, and polyurethanes. Attention is paid not only to the catalytic technologies used to enhance depolymerization efficiencies but also to the interrelationship with other recycling technologies and to the systemic constraints imposed by a global economy. Novel polymers, designed for chemical depolymerization, are also concisely reviewed in terms of their underlying chemistry and potential for integration with current plastic systems.

Synthesis and self-assembly of dendritic-linear block copolymers containing poly(mandelic acid) with discrete molecular weights and stereochemical structures

In this work, we present the synthesis of uniform PMAs, where the number of repeat units and their stereochemical arrangement are precisely defined. Utilizing an iterative convergent approach with orthogonally protected dimandelic acid building blocks, we achieved high molecular weight PMAs with the desired number of repeat units, extending up to 144 mandelic acids. Additionally, stereochemically defined poly(l-mandelic acid)s with up to 32 repeat units were successfully synthesized. These uniform PMAs were subsequently coupled with uniform branched poly(ethylene glycol) blocks to create uniform dendritic-linear block copolymers. The self-assembly of these block copolymers in solution was systematically investigated. In solution self-assembly, the synthesized block copolymers showed multiple phases from cylinder to inverse cubic as the molecular weight of PMA increased. In the case of solvent diffusion-evaporation-mediated self-assembly, the block copolymers underwent a phase transition as the rate of water addition decreased.

Modified Polyethylene Foams for Insulation Systems

Effective insulation of buildings and other industrial objects requires the use of materials and system solutions that ensure maximum uniformity and density of insulation shells. The study focuses on the development of insulation systems based on expanded polyethylene and, in particular, on the development of modified polyethylene with reduced flammability containing a flame-retardant modified montmorillonite clay, which does not hinder gas formation, and silicate nanofillers in layered construction. Active experiments based on mathematical design methods allowed us to establish an analytical relationship between flame-retardant and modifier consumption and extruder pressure and response functions: average density of polyethylene foam and flammability criterion. The flammability criterion was taken as the oxygen index of the modified polyethylene foam. A foaming agent masterbatch was used as the flame retardant. Analytical optimization of mathematical models obtained as a result of active experiments allowed us to determine the optimal flame-retardant consumption, which was 3.7-3.8% of the polymer mass. Optimised systems for average density and oxygen index of flammability of modified polyethylene were obtained. A nomogram for predicting the material properties and selecting the composition, and an algorithm for a computer program for evaluating the properties of modified polyethylene foam as a function of the values of various factors, were developed. Taking into account the possible expansion of the scope of application of rolled polyethylene foam and seamless insulation shells based on it, possible solutions for insulation systems were studied using the program THERM, and a combined insulation system was adopted.