Recycling waste plastics in developing countries: Use of low-density polyethylene water sachets to form plastic bonded sand blocks

Can tourism support resource circularity in small islands? On-field analysis and intervention proposals in Madagascar

Open dumping and burning of solid waste are common practices in low-income countries. On small and touristic islands, the problem is exacerbated due to the additional volume of waste amount generated by tourists. This article presents how, using Nosy Be island in Madagascar as a case study, waste recovery and recycling can be fostered by tourism to tackle the waste challenge. About 95% of the waste of Nosy Be is openly dumped, discarded to sea or openly burned. Field analysis, interviews with local stakeholders and waste flow analysis served as methodological tools to assess the current solid waste management (SWM) system of Nosy Be. Stakeholder mapping and involvement as well as first exchange among local and international actors provided the basis to identify key practice and opportunities. Research findings highlight the importance of active participation and involvement of local partners supported by international experts, to suggest how touristic centres can serve as core of circular approaches. The article presents potential circular models to be implemented in Nosy Be, taking tourism as the entry point including the aspects of financial support, separated waste flows and the interest in 'green tourism marketing'. This case study underlines how international cooperation, touristic activities and common efforts can potentially help low-income communities improve their SWM practices.

Recycling and reusing potential of disposable low-density polyethylene plastic waste for flexible paver tile construction for outdoor application

Plastic waste disposal has escalated into a serious global concern due to the non-biodegradable nature of plastics, which are composed of high-molecular-mass organic polymers along with other ingredients. Therefore, this study focuses on reusing and recycling LDPE plastic waste as a binding agent in paver tile production. This aligns with global sustainability goals by promoting resource efficiency and reducing waste generation. The investigation aims to address the environmental impact of plastic waste by finding sustainable solutions for its management. This includes exploring the feasibility and viability of using LDPE plastic waste in paver tile production as a means of recycling and reusing locally collected waste. The LDPE waste plastic collection, identification, milling, and melting at 170 °C. Subsequently, the sampled sand, sieved to a size of ≤0.75 mm, was blended with molten plastic in a specified proportion and then molded to create paving tiles using a hydraulic press machine. The researchers utilized response surface methodology (RSM) combined with Box-Benken designs (BBD) to optimize three key experimental parameters (plastic-to-sand ratio: 10 %, 25 %, 40 %; time: 2, 5, 8 min, pressure: 1, 3, 5 MPa) influencing mechanical properties of paver tiles, including water absorption (WA), flexural strength (FS), and compressive strength (CS). The result revealed that the optimal combination of 25 % waste plastic, 5 min, and 3 MPa of pressure resulted in a maximum flexural strength (FS) of 3.689 MPa and compressive strength (CS) of 4.141 MPa, with an average water absorption (WA) of 0.322 %. Therefore, the mechanical properties of the developed tiles met the desired standard. In conclusion, the mechanical qualities of the tiles were promising, indicating that reusing waste LDPE plastic to create paver tiles presents an appealing option for plastic waste disposal. The composite paver tiles exhibited promising attributes for outdoor applications, such as park pavement and outdoor public spaces, owing to their favorable mechanical properties and low water absorption.

Assessment of the Thermal Properties of Gypsum Plaster with Plastic Waste Aggregates

Building material manufacturers must support new production models that encourage the manufacture of more efficient and sustainable products. This includes thinking about savings in the use of raw materials, a contribution to the energy efficiency of buildings during their useful life, and a reduction in the generation and deposit of waste in landfills. In this research, an analysis of the thermal properties of gypsum composites added with plastic waste is carried out using the most common methods, the steady state method and the transient plane source method, and the effect of water saturation on these composites is tested. The results show an improvement in the thermal performance of the composites (values reduced with respect to the reference by 4-7%), despite their heterogeneity, as well as a variation in the measurements carried out, depending on the method used for the measurements (variation up to 10%). It is also found that the degree of humidity negatively affects the thermal conductivity coefficient but, on the contrary, this coefficient is not altered in the composites with plastic waste, due to their lower hygroscopicity. Therefore, it is considered that the proposed eco-plasters are a good alternative to traditional plasters, with which to contribute to the achievement of the objectives of the current European directives on waste and circular economy.

Feasibility study of the use of concrete blocks produced from plastic marine garbage for use in civil construction

The pursuit of development in an economically sustainable and ecologically sound manner is a goal of modern society. It has been investing in products that minimize their environmental impact, particularly concerning the use of plastic. This material is highly detrimental to nature due to its toxicity and long decomposition period. The present study aims to analyze the feasibility of producing blocks made of concrete with different amounts of waste plastic taken from coastal and estuarine areas. After laboratory analysis, it was found that blocks containing 5% plastic exhibit good compressive strength and are lighter. Additionally, there was an increase in the acidity of the sample, a decrease in the density of the block, and reductions in both flexural and compressive strength. The prototype, composed of 5% plastic by mass, proves to be efficient for constructing single-story houses. It meets the minimum requirements for normative resistance, effectively encapsulating the plastic within the block and thereby reducing its environmental impact.

Reprocessing Possibilities of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-Hemp Fiber Composites Regarding the Material and Product Quality

An important issue addressed in research on the assessment of the quality of polymer products is the quality of the polymer material itself and, in accordance with the idea of waste-free management, the impact of its repeated processing on its properties and the quality of the products. In this work, a biocomposite, based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with short hemp fibers, was obtained and repeatedly processed, which is a continuation of the research undertaken by the team in the field of this type of biocomposites. After subsequent stages of processing, the selected mechanical, processing and functional properties of the products were assessed. For this purpose, microscopic tests were carried out, mechanical properties were tested in static tensile and impact tests, viscosity curves were determined after subsequent processing cycles and changes in plastic pressure in the mold cavity were determined directly during processing. The results of the presented research confirm only a slight decrease in the mechanical properties of the produced type of biocomposite, even after it has been reprocessed five times, which gives extra weight to arguments for its commercialization as a substitute for petrochemical-based plastics. No significant changes were found in the used parameters and processing properties with the stages of processing, which allows for a predictable and stable manufacturing process using, for example, the injection molding process.

Environmental and anthropogenic drivers of watercress (Nasturtium officinale) communities in char-lands and water channels across the Swat River Basin: implication for conservation planning

Recent anthropogenic sources and excess usage have immensely threatened the communities and habitat ecology of this region's medicinally and economically significant crops. Therefore, our study aims to evaluate the community structure and related environmental characteristics sustaining Nasturtium officinale communities along the river basin (RB) in Northwest Pakistan, using the clustering procedure (Ward's method) and Redundancy analysis (RDA). From 340 phytosociological plots (34 × 10 = 340), we identified four ecologically distinct assemblages of N. officinale governed by different environmental and anthropogenic factors for the first time. The floristic structure shows the dominance of herbaceous (100%), native (77%), and annual (58.09%) species indicating relatively stable communities; however, the existence of the invasive plants (14%) is perturbing and may cause instability in the future, resulting in the replacement of herbaceous plant species. Likewise, we noticed apparent variations in the environmental factors, i.e., clay percentage (p = 3.1 × 10-5), silt and sand percentage (p< 0.05), organic matter (p< 0.001), phosphorus and potassium (p< 0.05), and heavy metals, i.e., Pb, Zn, and Cd (p< 0.05), indicating their dynamic role in maintaining the structure and composition of these ecologically distinct communities. RDA has also demonstrated the fundamental role of these factors in species-environment correlations and explained the geospatial variability and plants' ecological amplitudes in the Swat River wetland ecosystem. We concluded from this study that N. officinale communities are relatively stable due to their rapid colonization; however, most recent high anthropogenic interventions especially overharvesting and sand mining activities, apart from natural enemies, water deficit, mega-droughts, and recent flood intensification due to climate change scenario, are robust future threats to these communities. Our research highlights the dire need for the sustainable uses and conservation of these critical communities for aesthetics, as food for aquatic macrobiota and humans, enhancing water quality, breeding habitat, fodder crop, and its most promising medicinal properties in the region.

Experimental Study on Cementless PET Mortar with Marble Powder and Iron Slag as an Aggregate

There has been an increase in plastic production during the past decades, yet the recycling of plastic remains relatively low. Incorporating plastic in concrete can mitigate environmental pollution. The use of waste polyethylene terephthalate (PET) bottles as an aggregate weakens properties of concrete. An alternative is to use PET bottles as a binder in the mortar. The PET binder mixed with sand results in weak mortar. Marble and iron slag can enhance PET mortar properties by preventing alkali reactions. This study examines the mechanical and durability properties of PET mortar with different mixes. The mixes were prepared as plastic and marble (PM); plastic and iron slag (PI); plastic, sand, and marble (PSM); plastic, iron slag, and marble (PIM); and plastic, sand, and iron slag (PSI). PM with 30-45% plastic content had increased compressive and flexural strength up to 35.73% and 20.21%, respectively. PI with 30-35% plastic content showed strength improvements up to 29.19% and 5.02%, respectively. However, at 45% plastic content, strength decreased by 8.8% and 27.90%. PSM, PIM, and PSI specimens had nearly double the strength of ordinary Portland cement (OPC) mortar. The durability of PET mortar in chemical solutions, mainly 5% HCl and 20% NaOH, indicate that mass decreased after 3, 7, and 28 days. All specimens showed good resistance to HCl and NaCl solutions compared to OPC mortar. However, its resistance to NaOH is low compared to OPC mortar. PET mortar without cement showed higher strength and durability than cement mortar, making it suitable for paver tiles, drainage systems, and roads.

Experimental study on the eco-friendly plastic-sand paver blocks by utilising plastic waste and basalt fibers

Plastic waste poses a significant hazard to the environment as a result of its high production rates, which endanger both the environment and its inhabitants. Similarly, another concern is the production of cement, which accounts for roughly 8% of global CO₂ emissions. Thus, recycling plastic waste as a replacement for cementitious materials may be a more effective strategy for waste minimisation and cement elimination. Therefore, in this study, plastic waste (low-density polyethylene) is utilised in the production of plastic sand paver blocks without the use of cement. In addition to this, basalt fibers which is a green industrial material is also added in the production of eco-friendly plastic sand paver blocks to satisfy the standard of ASTM C902-15 of 20 N/mm² for the light traffic. In order to make the paver blocks, the LDPE waste plastic was melted outside in the open air and then combined with sand. Variations were made to the ratio of LDPE to sand, the proportion of basalt fibers, and sand particle size. Paver blocks were evaluated for their compressive strength, water absorption, and at different temperatures. Including 0.5% percent basalt fiber of length 4 mm gives us the best result by enhancing compressive strength by 20.5% and decreasing water absorption by 50.5%. The best results were obtained with a ratio of 30:70 LDPE to sand, while the finest sand provides the greatest compressive strength. Moreover, the temperature effect was also studied from 0 to 60 °C, and the basalt fibers incorporated in plastic paver blocks showed only a 20% decrease in compressive strength at 60 °C. This research has produced eco-friendly paver blocks by removing cement and replacing it with plastic waste, which will benefit the environment, save money, reduce carbon dioxide emissions, and be suitable for low-traffic areas, all of which contribute to sustainable development.

Thermal and mechanical characterization of composite materials from industrial plastic wastes and recycled nylon fibers for floor paving tiles application

Industrial plastic waste is growing globally at an alarming rate and environmental pollution from traditional landfill disposal and incineration treatments are of great concern. As a strategy to reduce plastic pollution, value-added composite materials from industrial plastic wastes reinforced with recycled nylon fibers for use in floor paving tile applications were developed. This is to address the disadvantages of existing ceramic tiles which are relatively heavy, brittle, and expensive. The plastic waste composite structures were produced via compression molding technique at an optimized randomly oriented constant fiber volume fraction of 50 wt% after the initial sorting, cleaning, drying, pulverizing, and melt-mixing. The molding temperature, pressure, and time for the composite's structures were 220 ℃, 65 kg.cm^-3, and 5 min respectively. The composites' thermal, mechanical, and microstructural properties were characterized in accordance with appropriate ASTM standards. From the results obtained, the differential scanning calorimetry (DSC) of mixed plastic wastes and nylon fiber wastes showed a processing temperature range of 130-180 ℃, and 250 ℃ respectively. Thermal degradation temperature (TGA) of the plastic and nylon fiber waste composites were stable above 400 ℃ with maximum bending strength, however, the reinforced plastic waste sandwiched composite structures had outstanding mechanical properties indicating unique characteristics suitable for floor paving tiles. Hence, the current research has developed tough and lightweight tiles composites that are economically viable, and their application will contribute to the development of the building and construction sectors thereby reducing about 10-15% of annual plastic waste generation and a sustainable environment.

A scientometric analysis approach on the plastic sand

The purpose of this research was to conduct a scientometric evaluation of the literature pertaining to plastic sand in order to evaluate its many aspects. Conventional review studies have several limitations when it comes to their capacity to completely and properly link different sections of the published research. Some of the more complicated features of advanced research are co-occurrence analysis, science mapping and co-citation analysis. During the study, the most inventive authors/researchers renowned for citations, the sources with the largest number of publications, the actively involved domains, and co-occurrences of keywords in the research on plastic sand are investigated. This study is limited to scientometric analysis of the available literature data on plastic sand. The VOSviewer application (version 1.6.18) was used to perform the analysis after bibliometric data for 4512 publications were extracted from the Scopus database and utilised in the extraction process from the year 2021 to June 2022. With the support of a statistical and graphical description of researchers and nations that are contributing, this study will aid researchers in the establishment of collaborative ventures and the exchange of fresh techniques and ideas with one another.

Scaling up resource recovery of plastics in the emergent circular economy to prevent plastic pollution: Assessment of risks to health and safety in the Global South

Over the coming decades, a large additional mass of plastic waste will become available for recycling, as efforts increase to reduce plastic pollution and facilitate a circular economy. New infrastructure will need to be developed, yet the processes and systems chosen should not result in adverse effects on human health and the environment. Here, we present a rapid review and critical semi-quantitative assessment of the potential risks posed by eight approaches to recovering value during the resource recovery phase from post-consumer plastic packaging waste collected and separated with the purported intention of recycling. The focus is on the Global South, where there are more chances that high risk processes could be run below standards of safe operation. Results indicate that under non-idealised operational conditions, mechanical reprocessing is the least impactful on the environment and therefore most appropriate for implementation in developing countries. Processes known as 'chemical recycling' are hard to assess due to lack of real-world process data. Given their lack of maturity and potential for risk to human health and the environment (handling of potentially hazardous substances under pressure and heat), it is unlikely they will make a useful addition to the circular economy in the Global South in the near future. Inevitably, increasing circular economy activity will require expansion towards targeting flexible, multi-material and multilayer products, for which mechanical recycling has well-established limitations. Our comparative risk overview indicates major barriers to changing resource recovery mode from the already dominant mechanical recycling mode towards other nascent or energetic recovery approaches.

Recycling/reuse of plastic waste as construction material for sustainable development: a review

The exponential rise in the production of plastic and the consequential surge in plastic waste have led the scientists and researchers look out for innovative and sustainable means to reuse/recycle the plastic waste in order to reduce its negative impact on environment. Construction material, converting waste plastic into fuel, household goods, fabric and clothing are some of the sectors where waste plastic is emerging as a viable option. Out of these, construction material modified with plastic waste has garnered lot of attention. Modification of construction material with plastic waste serves a dual purpose. It reduces the amount of plastic waste going to landfills or litter and secondly lessens the use of mined construction materials, thereby mitigating the negative impact of construction industry on environment. This paper summarizes the developments with regard to the use of plastic waste as a constituent of construction material. Inclusion of plastic waste as a binder, aggregate, fine aggregate, modifier or substitute of cement and sand in the manufacturing of bricks, tiles, concrete and roads has been comprehensively reviewed. Also, the influence of addition of plastic waste on strength properties, water absorption, durability, etc. has been thoroughly discussed. The research studies considered for this review have been categorized based on whether they dealt with the use of plastic waste for bricks and tiles or in concrete for road construction.

Impact of Micro Silica Filler Particle Size on Mechanical Properties of Polymeric Based Composite Material

In this study, silica in the form of raw local natural sand was added to high-density-polyethylene (HDPE) in order to develop a composite material in the form of sheets that could have potential applications in thin film industries, such as packaging, or recycling industries, such as in 3D printing. The silica/HDPE composite sheets were developed using a melt extruder followed by using a hot press for compression molding. The impact of two different particle sizes (25 µm and 5 µm) of the silica particles on selected properties such as toughness, elastic modulus, ductility, and composite density were analyzed. A considerable increase in the toughness and elastic modulus was observed from 0 wt% to 20 wt% with a 25 µm filler size. However, a general decreasing trend was observed in the material's toughness and elastic modulus with decreasing particle size. A similar trend was observed for the ductility and the tensile strength of the sheets prepared from both filler particle sizes. In terms of the composite density, as the filler was increased from 20 wt% to 50 wt%, an increase in the composite densities was noticed for both particle sizes. Additionally, the sheets developed with 25 µm particle size had a slightly higher density than the 5 µm particle size, which is expected as the size can account for the higher weight. Results from this work aim to analyze the use of local sand as a filler material that can contribute towards maximizing the potential of such composite materials developed in extrusion industries.

Development and Mechano-Chemical Characterization of Polymer Composite Sheets Filled with Silica Microparticles with Potential in Printing Industry

Polymer composite sheets using a low-cost filler (local natural sand) and polymer (high-density polyethylene, HDPE) as a replacement of the traditionally used wood-fiber-based sheets for paper-based applications were developed. The sand/polymer composite sheets were prepared by melt extrusion in a melt blender followed by compression molding. The effects of varying particle size, concentration, and the use of a compatibilizer (polyethylene-grafted maleic anhydride) was studied on the mechano-chemical performance properties of the composite sheets such as morphology, thermal and mechanical properties, and wettability characteristics used in the printing industry. In terms of thermal stability, filler (sand) or compatibilizer addition did not alter the crystallization, melting, or degradation temperatures significantly, thereby promoting good thermal stability of the prepared sheets. Compatibilization improved anti-wetting property with water. Additionally, for the compatibilized sheets prepared from 25 µm sand particles, at 35 wt%, the contact angle with printing ink decreased from 44° to 38.30°, suggesting improved ink-wetting performance. A decrease in the elastic modulus was also observed with the addition of the compatibilizer, with comparable results to commercial stone paper. Results from this study will be considered as a first step towards understanding compatibility of local natural sand and polymers for paper-based application.

Manufacture and Characterization of Polypropylene (PP) and High-Density Polyethylene (HDPE) Blocks for Potential Use as Masonry Component in Civil Construction

The lack of suitable destinations for plastics materials can be a global environmental problem. The alternative use of materials for sustainable construction encourages the standardization of waste and promotes effective social, environmental and economic gains at the local level and ensures savings and income for communities. The aim of this paper is the development, manufacture, and characterization of PP and HDPE recycled polyolefin blocks as masonry components in civil construction. These blocks were manufactured by the rotational molding process. Besides this, the mechanical, physical, impact and flammability properties of the blocks were studied. In conclusion, HDPE showed better behavior than PP in tests realized.

Challenges and opportunities in sustainable management of microplastics and nanoplastics in the environment

The accumulation of microplastics (MPs) and nanoplastics (NPs) in terrestrial and aquatic ecosystems has raised concerns because of their adverse effects on ecosystem functions and human health. Plastic waste management has become a universal problem in recent years. Hence, sustainable plastic waste management techniques are vital for achieving the United Nations Sustainable Development Goals. Although many reviews have focused on the occurrence and impact of micro- and nanoplastics (MNPs), there has been limited focus on the management of MNPs. This review first summarizes the ecotoxicological impacts of plastic waste sources and issues related to the sustainable management of MNPs in the environment. This paper then critically evaluates possible approaches for incorporating plastics into the circular economy in order to cope with the problem of plastics. Pollution associated with MNPs can be tackled through source reduction, incorporation of plastics into the circular economy, and suitable waste management. Appropriate infrastructure development, waste valorization, and economically sound plastic waste management techniques and viable alternatives are essential for reducing MNPs in the environment. Policymakers must pay more attention to this critical issue and implement appropriate environmental regulations to achieve environmental sustainability.

Appropriate solid waste management system in Quelimane (Mozambique): study and design of a small-scale center for plastic sorting with wastewater treatment

Appropriate solid waste management (SWM) strategies are necessary to avoid severe environmental and sanitary impacts, especially in low-income countries. Such strategies are most likely to succeed whether implementing actors are supported by scientific research. In this paper, the results of a collaboration between local authorities and researchers are presented and discussed that are the assessment of waste generation in the city of Quelimane (Mozambique), integrating existing and field-collected data and the design of a small-scale center for plastic sorting to complement the SWM system of the city. The center is expected to receive about 0.3–0.4 t/day of plastic waste (5%–7% of the overall amount of plastic waste daily produced in Quelimane). As long-term sustainability represents a typical issue, simplicity of operation was a leading principle in the design of the center; moreover, the design included a treatment plant (WWTP) for generated wastewater, whose management is usually neglected in such interventions. Among others, natural wastewater treatment (constructed wetlands) has been chosen for its affordability. Noteworthy, the so-conceived WWTP appears as a novelty in the scientific literature associated with small-scale plastic sorting plants. The system is designed to treat an average flow of 6 m³/day and consisted of a septic tank followed by a subsurface flow constructed wetland. Overall, the COD (chemical oxygen demand) and TSS (total suspended solids) removal higher than 80% and 90% were estimated, respectively. Based on this work, both the center and the WWTP were successfully realized, which are waiting to become operational. In the authors’ opinion, the implemented procedure could become a reference for broader investigations and surveys.

Conversion of Plastic Waste into Supports for Nanostructured Heterogeneous Catalysts: Application in Environmental Remediation

Plastics are ubiquitous in our society and are used in many industries, such as packaging, electronics, the automotive industry, and medical and health sectors, and plastic waste is among the types of waste of higher environmental concern. The increase in the amount of plastic waste produced daily has increased environmental problems, such as pollution by micro-plastics, contamination of the food chain, biodiversity degradation and economic losses. The selective and efficient conversion of plastic waste for applications in environmental remediation, such as by obtaining composites, is a strategy of the scientific community for the recovery of plastic waste. The development of polymeric supports for efficient, sustainable, and low-cost heterogeneous catalysts for the treatment of organic/inorganic contaminants is highly desirable yet still a great challenge; this will be the main focus of this work. Common commercial polymers, like polystyrene, polypropylene, polyethylene therephthalate, polyethylene and polyvinyl chloride, are addressed herein, as are their main physicochemical properties, such as molecular mass, degree of crystallinity and others. Additionally, we discuss the environmental and health risks of plastic debris and the main recycling technologies as well as their issues and environmental impact. The use of nanomaterials raises concerns about toxicity and reinforces the need to apply supports; this means that the recycling of plastics in this way may tackle two issues. Finally, we dissert about the advances in turning plastic waste into support for nanocatalysts for environmental remediation, mainly metal and metal oxide nanoparticles.

Market waste composition analysis and resource recovery potential in Kumasi, Ghana

Municipal solid waste constitutes significant quantities of waste generated in markets. Markets produce substantial quantities of fruit and vegetable waste, a source of nuisance in landfills. In Ghana, market waste (MW) appears to be unexplored and has limited data available. The need for MW valorization in the face of a circular economy requires reliable knowledge of MW properties. The study determined the waste compositions of selected major markets from two different classes of settlement in Kumasi and the seasonal effect on the compositions. The chemical properties of organics were determined via proximate and ultimate analyses and the theoretical biomethane potential, with the Buswell equation. From the results, MW composition in the wet season is 59.6% organic, 11.4% plastics, 8.3% paper, 5.3% textiles, 4.7% inert, 4.1% miscellaneous, 2.1% metal, 1.8% glass and 2.8% leather. The dry season values are 45.8% organic, 14.6% plastics, 12.7% paper, 7.3% textiles, 6.4% inert, 4.3% miscellaneous, 2.3% metal, 2.6% glass and 3.9% leather. An ANOVA indicates significant differences between the two seasons and some waste components; organics, plastics, paper and cardboard, leather, and inert. The high calorific values recorded ranged from 14.8 MJ kg^-1 to 16.6 MJ kg^-1. The biogas potential and biomethane content ranged from 775.3 l/kgVS to 828.9 L/kgVS and 50% to 57% respectively.Implications: Market waste (MW) in Ghana appears to be an unchartered area and there is limited data on market generation and composition. The need for MW valorization requires reliable knowledge on MW properties. This study explores MW characteristics of six major market from two different classes of settlements in a developing country. Study findings suggest that the quantities of market organics are higher than household waste. Again, MW composition can be influenced by season and geographical location. Furthermore, the study establishes the potential of MW in considerable quantities of biogas and methane generation, in comparison with household waste.

Utilization of Plastic Wastes for Sustainable Environmental Management: A Review

The advancement and modernization of industries have provided numerous benefits to human life including diversification of manufacturing a wide range of products made from plastic materials, thereby leading to the generation of huge quantities of plastic waste. Owing to the increasing issues related with plastic waste, recycling methods have attracted much interest. Recycling not only protects the environment and resources for future generations but also reduces energy consumption and greenhouse gas emissions. A wide range of valuable products including char, oil, fuels, sorbent materials, and chemicals can be obtained through different techniques. This Review highlights various sustainable research avenues and potential routes to reduce the environmental impact of plastic waste based on both traditional and potential approaches for its utilization.

Ternary and quaternary blends as partial replacement of cement to produce hollow sandcrete blocks

Hollow sandcrete blocks constitute more than 90% of residential building construction in developing countries especially in West Africa. Over-reliance on dredged river sands and conventional ordinary Portland cement (OPC) contributes to environmental degradation and post-construction problems such as swelling and shrinkage-induced cracks prevalent in construction projects. The study investigates potential utilization of locally available materials such as laterite, calcite and calcined clay as ternary and quaternary blends to replace cement and quarry dust as 100% replacement of river sand with the aid of Taguchi-Response surface methodology approach. Optimum ternary blend of 24% calcined clay +1% calcite +75% OPC is recommended to achieve volume stability, higher compressive strength and higher flexural load capacity. Alternatively, ternary blends of 24% calcite +4% calcined clay +72% OPC can also be utilized. The improved mechanical properties were attributed to the Na- and Ca-rich aluminosilicates provided by the blended cements. Successful utilization of ternary and quaternary blended cements to produce stronger, durable and eco-friendly sandcrete blocks depends on utilization of high binder-to-aggregate ratio, optimal combination of the constituents, appropriate water-cement ratio and curing/production method. Partial and 100% replacement of river sand with granite dust is possible and contributes to reduction of environmental problems caused by river dredging as well as cleaner, ecofriendly construction. Ternary and quaternary blended cements is recommended to avert post-construction problems such as swelling and shrinkage-induced cracks prevalent in construction projects.

Potential risk of BPA and phthalates in commercial water bottles: a minireview

The global water bottling market grows annually. Today, to ensure consumer safety, it is important to verify the possible migration of compounds from bottles into the water contained in them. Potential health risks due to the prevalence of bisphenol A (BPA) and phthalates (PAEs) exposure through water bottle consumption have become an important issue. BPA, benzyl butyl phthalate (BBP), di-n-butyl phthalate (DBP) and di (2-ethylhexyl) phthalate (DEHP) can cause adverse effects on human health. Papers of literature published in English, with BPA, BBP, DBP and DEHP detections during 2017, by 2019 by liquid chromatography and gas chromatography analysis methods were searched. The highest concentrations of BPA, BBP, DBP and DEHP in all the bottled waters studied were found to be 5.7, 12.11, 82.8 and 64.0 μg/L, respectively. DBP was the most compound detected and the main contributor by bottled water consumption with 23.7% of the Tolerable Daily Intake (TDI). Based on the risk assessment, BPA, BBP, DBP and DEHP in commercial water bottles do not pose a serious concern for humans. The average estrogen equivalent level revealed that BPA, BBP, DBP and DEHP in bottled waters may induce adverse estrogenic effects on human health.

A systems thinking approach to understanding the challenges of achieving the circular economy

Circular economy (CE) is extensively discussed around the globe. Presently, discussions are mostly concerned with the importance of achieving CE and the benefits associated therewith, with the various barriers surrounding its implementation being less debated. Understanding the context in which circularity can flourish is a prerequisite in building the capabilities to deal with the multi-faceted challenges that currently hamper progress in closing the material, component and product loops. In this study, we discuss the importance of systems thinking in understanding the way resource recovery systems operate, and in promoting deep transformational change. We suggest that transformational change needs to go beyond closing materials, components and products (MCPs) loops, and promote sustainability in the way resources are exploited, used and managed throughout the system. By adopting a system of systems approach, we postulate that there are five interconnected sub-systems that need to be considered for supporting transitions to CE, namely, resource flows and provisioning service; governance, regulatory framework and political landscape; business activities and the marker; infrastructure and innovation; and user practices. This holistic approach provides a useful means to cutting through systemic complexity, and focuses on the dynamics between processes, values and actors in the value chain, and their dependence on cultural, spatial and temporal characteristics. We conclude that a systems-based approach can build up the capabilities required to identify and understand persistent linear trends and, in turn, support forward-thinking and time investment in enabling sustainable transitions. This, in turn, can help to align priorities and transform our current practices, speeding up the process of closing the MCP loops in a sustainable manner. Graphical abstract.

Environmental challenges induced by extensive use of face masks during COVID-19: A review and potential solutions

The ongoing COVID-19 disease significantly affects not only human health, it also affects the wealth of country' economy and everyday routine of human life. To control the spread of the virus, face mask is used as primary personal protective equipment (PPE). Thus, the production and usage of face masks significantly increase as the COVID-19 pandemic still escalating. Further, most of these masks contain plastics or other derivatives of plastics. Therefore, this extensive usage of face masks generates million tons of plastic wastes to the environments in a short span of time. This study aims to investigate the environmental impact induced by face mask wastes and sustainable solution to reduce this waste. An online survey was carried out to identify the types of face mask and number of masks used per week by an individual from 1033 people. Based on this survey and available literature, this study quantifies the amount of plastics waste generated by face masks. However, this survey was limited with certain ages, country and durations (July-August 2020). Thus, the prediction of plastic waste generation, only provide fundamental knowledge about the mask wastes. Results revealed that there is a huge plastic waste remained in land and marine environment in the form of mask waste, which will contribute to micro-plastic pollution. Therefore, this paper also highlights the sustainable approach to the mask production by integrating the use of natural plant fiber in the woven face mask technology to reduce the plastic waste induced by masks. Further, upcycling the mask waste and producing construction materials also discussed.

Evaluación de las propiedades mecánicas de ladrillos elaborados con residuos de vidrio y plástico. Análisis de las emisiones de dióxido de carbono

El uso de desechos no biodegradables como el vidrio y el plástico en la industria de la construcción ha recibido atención significativa para un medio ambiente más limpio. Este trabajo presenta un estudio de las propiedades mecánicas de ladrillos que contienen agregados, vidrio y pellets de tereftalato de polietileno. Los ladrillos se fundieron  a 240 °C durante 3 horas y se enfriaron por convección natural. Los resultados mostraron que un aumento en el contenido de vidrio y agregados genera un incremento en la densidad, que es superior en las muestras con mayor contenido de agregados. La misma tendencia se observó en la resistencia a la compresión: la muestra con mayor contenido de agregados mostró una mejora del 243 % comparada con la referencia (preparada solo con plástico). Los resultados indicaron que las emisiones de dióxido de carbono disminuyeron alrededor del 30 % en las muestras preparadas, en comparación con los ladrillos tradicionales. Se espera que el uso de residuos de plástico y vidrio en la producción de ladrillos se convierta en una ruta para su valorización.

Mechanical and Market Study for Sand/Recycled-Plastic Cobbles in a Medium-Size Colombian City

The need to satisfy the increasing demand for building materials and the challenge of reusing plastic to help improve the critical environmental crisis has led to the recycling of plastic waste, which is further exploited and transformed into new and creative materials for the construction industry. This study looked into the use of low-density recycled polyethylene (LDPE) to produce non-conventional plastic sand cobbles. LDPE waste was melted in order to obtain enough fluid consistency which was then mixed with sand in a 25/75 plastic-sand ratio respectively, such a mixture helped producing cobbles of 10 cm × 20 cm × 4 cm. Water absorption, weight, and density measurements were performed on both commercial and non-conventional plastic sand cobbles. Moreover, compression, bending, and wear resistance were also conducted as part of their mechanical characterization. Plastic sand cobbles showed lower water absorption and density values than commercial cobbles. The mechanical properties evaluated showed that plastic sand cobbles have a higher modulus of rupture and wear resistance than commercial cobbles. In addition, plastic sand cobbles meet the Colombian Technical Standard in lightweight traffic for pedestrians and vehicle, officially known as Norma Técnica Colombiana (NTC), with 25.5 MPa, 16.3 MPa, and 12 mm compression resistance, modulus of rupture and footprint length in wear resistance respectively. Finally, a market study was conducted to establish a factory to produce this type of cobbles in Ibague, Colombia. Not only the study showed positive financial indicators, which means that it is feasible running a factory to manufacture plastic sand cobbles in the city of Ibague, but it also concluded that nonconventional plastic sand cobbles could be explored to provide a comprehensive alternative to LDPE waste.

Innovative Use of Plastic for a Clean and Sustainable Environmental Management: Learning Cases from Ghana, Africa

Addressing the plastic problem requires rigorous attention and practical education for sustainability. Due to the common effective waste management practices in some parts of the world, the plastics’ menace is generally well recognized and controlled worldwide. However, some developing countries do not have acceptable waste management practices, resulting in significant environmental, social, and health cross-cutting issues. Plastic is a significant threat to the environment in Ghana, specifically the urban environment and oceans. The new paradigm shift of virtually using non-biodegradable plastics in all daily products sold increases plastic waste in the environment, which creates problems, such as choked drainage system and breeding places for insects. The scale of these issues requires innovative and practical ideas to help solve this problem. The paper shows how plastic waste is innovatively and creatively converted to artifacts and pavement blocks in Ghana. These innovative ideas have contributed to reduce the volume of plastic waste and enhance environmental sustainability in Africa. The community’s benefits involving friendly environmental activities are identified and represent learning cases from Ghana to the world, particularly to Africa.

Rheological and Mechanical Investigation of PET, LDPE and HDPE Wastes Blended for Re-Use in Bio-Pipes

This work focuses on the re-use of biopolymer wastes to produce the pipes and reduce the impact of these materials on the environment. The ratios of 10, 20, 30 and 40wt% of recycled polyethylene terephthalate (RPET) were added to the reference blend, which consists of recycled low-density polyethylene (RLDPE) and recycled high-density polyethylene (RHDPE). Rheological and mechanical tests were performed on these blends. The blend of RLDPE and RHDPE was already successful in the manufacturing of pipes. The capillary rheometer was used to check the shear viscosity and shear stress behaviour with the shear rate increasing for different blends. The density, tensile strength, elastic modulus and impact strength were also tested for all blends. The results showed that the shear viscosity decreases and the shear stress increases with the shear rate increasing for all blends. In general, the addition of RPET to the reference blend decreases the viscosity at each shear rate. The blends of ten wt% and 20wt% are more compatible with the reference blend, while the blends of 30wt% and 40wt% exhibit a clear deviation after a shear rate of 300. The density indicates an increase with the increase of RPET to the reference blend. The tensile strength increases and impact strength decreases with the increase of RPET up to 30%. After that, the tensile strength decreases and impact strength increases up to the 40wt% RPET. The results showed that the rheological test can be used to predict the mechanical behaviour. Additionally, there was a good agreement observed between the rheological and mechanical tests. The ten wt% and 20wt% blends were more suitable for this task.

Commercial Marine-Degradable Polymers for Flexible Packaging

Plastic pollution is entering the world's oceans at alarming rates and is expected to outweigh fish populations by 2050. This plastic waste originates from land-based applications, like consumer product packaging, and is composed of high-durability polyolefins. These conventional plastics possess desirable properties, including high chemical stability, moisture barrier, and thermoplastic characteristics. Unfortunately, if these materials reach marine environments, they fragment into microplastics that cannot be biologically assimilated. The aim of this review is to investigate commercial polymers that are biodegradable in marine environments but have comparable product stability and moisture barrier properties to polyolefins. Among commercially available biopolymers, thermoplastic starches (TPS) and polyhydroxyalkanoates (PHAs) have been shown to biodegrade in marine environments. Moreover, these biopolymers are thermoplastics and possess similar thermoforming properties to polyolefins. At present, TPS and PHAs have limitations, including chemical instability, limited moisture barrier properties, and high production costs. To replace conventional polymers with PHAs and TPS, these properties must be improved.

Study on Blending of Wall Material of the Nonel Tube by CSW/PE-g-MAH

In order to improve the strength and resistance of ordinary nonel tubes, calcium sulfate whiskers (CSW, treated with silane coupling agent) and maleic anhydride grafted polyethylene (PE-g-MAH) are used to control the wall material of the nonel tube that the blending of the low-density polyethylene was enhanced. The effects of mass fraction of CSW or PE-g-MAH on the tensile properties, interfacial structure, melting and crystallization characteristics, and thermal decomposition behavior of the composite system were studied, and the thermal decomposition kinetics were calculated. The results show that, relative to pure LDPE, the strength of LDPE/CSW (85/15) is increased by 7.58%, and the strength of LDPE/CSW/PE-g-MAH (84/15/1) is increased by 7.58%. The addition of CSW or PE-g-MAH has gradually changed the fracture mode of the LDPE matrix. Thermal analysis shows that CSW can reduce the crystallinity of LDPE. The melting and crystallization characteristics of LDPE/CSW/PE-g-MAH composites have little effect, but the thermal decomposition stability is improved. The kinetic analysis showed that the reaction order (n) was around 1, CSW could improve LDPE/CSW thermal decomposition activation energy, and PE-g-MAH increased the thermal decomposition activation energy of LDPE/CSW/PE-g-MAH.

Protective Low-Density Polyethylene Residues from Prepreg for the Development of New Nanocomposites with Montmorillonite: Recycling and Characterization

A sustainable alternative to the destination of polyethylene (PE) residue from the prepreg package was established. This work intends to develop nanocomposites for packaging containing neat low-density polyethylene (LDPE), a compatibilizer agent (maleic anhydride grafted-LDPE, LDPE-g-MA), recycled LDPE obtained from the protective films of prepreg (rLDPE) and montmorillonite (MMT). The rLDPE, from the prepreg shield, has a primary role during the transport and storage of prepreg, which can be composed of epoxy resin and carbon fiber or glass fiber. However, this rLDPE is withdrawn and discarded, besides, it is estimated that tons of this material are discarded monthly by the company Alltec Materiais Compostos Ltd. (São José dos Campos-SP, Brazil). Due to several factors, including the lack of technology for recycling, the majority of this material is incinerated. In this context, this work presents a technical and ecologically viable alternative for the use of this discarded material. Nanocomposites of LDPE/rLDPE blends and montmorillonite (MMT) with different contents (0.0, 1.0, and 3.0 wt%) and with the addition of compatibilizer agent (LDPE-g-MA) were prepared by extrusion process. Test specimens were obtained by hot pressing in a hydropneumatic press followed by die-cutting. The nanocomposites produced using rLDPE presented good mechanical, thermal, and morphological properties, being the ideal concentration of 1 wt% MMT. Thus, the results obtained confirmed the viability of recycling LDPE from the prepreg package which contributes to the reduction of waste and the use of this material in technological applications.