Pyrolysis of polypropylene plastic waste into carbonaceous char: Priority of plastic waste management amidst COVID-19 pandemic

Upcycling of waste disposable medical masks to high value-added gasoline fuel and surfactants products by sub/supercritical water degradation and partial oxidation

The amount of waste disposable medical masks (DMMs) and the potential environmental risk increased significantly due to the huge demand of disposable medical surgical masks. In this study, two effective and environmentally friendly processes, supercritical water degradation (SCWD) and subcritical water partial oxidation (SubCWPO), were proposed for the upcycling of DMMs. The optimal conditions for the SCWD process (conversion ratio>98 %) were 410 ℃, 15 min, and 1:5 g/mL. The oil products obtained from the SCWD process were mainly small molecule hydrocarbons (C7-C12) with a content of 86 % and could be recycled as fuel feedstock for gasoline. Alkyl radicals in the SCWD reaction formed double bonds and ring structures through hydrogen capture reactions, β-scission, and dehydrogenation reactions, and aromatic hydrocarbons were formed by olefin cyclization and cycloalkane dehydrogenation. The introduction of an oxidant (H2O2) to the reaction system could significantly reduce the reaction temperature and shorten the reaction time. At 350 ℃, 15 min, 1:20 g/mL, V(H2O2): V (H2O) of 1:1, the conversion ratio of the SubCWPO process was 88 %, which was higher than that of the SCWD process at 400 ℃ (71.49 %). Oil products produced from the SubCWPO process were rich in alcohols and esters, which could be used as raw materials for nonionic surfactant of polyol and fatty acid ester. The abundant hydroxyl radical in the SubCWPO system trapped hydrogen atoms on PP and reacted with the resulting alkyl radical to form alkanols, which was oxidized to form acids. The esterification of acids and alkanols formed high level of esters. The SCWD and SubCWPO processes proposed in this study are believed to be promising strategies for DMMs degradation and the recovery of high value-added hydrocarbons.

Conversion of char from pyrolysis of plastic wastes into alternative activated carbons for heavy metal removal

The valorization of post-consumer mixed plastics in pyrolysis processes represents an abundant reservoir of carbon that can be effectively converted into useful chars. This process not only holds appeal in terms of improving plastic waste concerns but also contributes to the reduction of greenhouse gas emissions, thus aligning with the principles of a circular economy paradigm. In this study, the char produced from the pyrolysis of post-consumer mixed plastic waste has been activated with Na2CO3, KOH, NaOH, and K2CO3 to improve the textural, structural, and composition characteristics, leading to improved adsorption capability. These characteristics were studied by N2 adsorption-desorption isotherms, scanning electron microscopy, elemental and immediate analysis, and X-ray photoelectron spectroscopy. The developed surface area (SBET) was 573, 939, 704 and 592 m2 g-1 for Na2CO3, KOH, NaOH and K2CO3 activated carbons, respectively. These activated chars (ACs) were tested for the adsorption of heavy metals in both synthetic waters containing Pb, Cd, and Cu and industrial wastewater collected at an agrochemical production plant. Na2CO3-AC was the best performing material. The metal uptake in synthetic waters using a batch set-up was 40, 13 and 12 mg g-1 for Pb, Cd and Cu. Experiments in a column set-up using Na2CO3-AC resulted in a saturation time of 290, 16, and 80 min for Pb, Cd, and Cu synthetic waters, respectively, and metal uptakes of 26.8, 4.1, and 7.9 mg g-1, respectively. The agrochemical effluents, containing mainly Cr, Cu, Mn, and Zn were tested in a plug-flow column. The metal uptake notably decreased compared to synthetic water due to a competition effect for active sites.

Identification and visualization of environmental microplastics by Raman imaging based on hyperspectral unmixing coupled machine learning

Microplastics (MPs) are ubiquitous contaminants that have become an emerging pollutant of concern, potentially threatening human health and ecosystem environments. Although current detection methods can accurately identify various types of MPs, it remains necessary to develop non-destructive and rapid methods to meet growing demands for detection. Herein, we combine a hyperspectral unmixing method and machine learning to analyse Raman imaging data of environmental MPs. Five MPs types including poly(butylene adipate-co-terephthalate) (PBAT), poly(butylene succinate) (PBS), p-polyethylene (PE), polystyrene (PS) and polypropylene (PP) were visualized and identified. Individual or mixed pure or aged MPs along with environmental samples were analysed by Raman imaging. Alternating volume maximization (AVmax) combined with unconstrained least squares (UCLS) method estimated end members and abundance maps of each of the MPs in the samples. Pearson correlation coefficients (r) were used as the evaluation index; the results showed that there is a high similarity between the raw spectra and the average spectra calculated by AVmax. This indicates that Raman imaging based on machine learning and hyperspectral unmixing is a novel imaging analysis method that can directly identify and visualize MPs in the environment.

Tandem pyrolysis-catalytic upgrading of plastic waste towards kerosene-range products using Si-pillared vermiculite with transition metal modification

The transformation of waste plastics to fuel products is an appealing strategy to address plastic-associated environmental and energy issues. In this study, a tandem pyrolysis-catalytic upgrading approach, using a series of mono-/bitransition-metal-modified Si-pillared vermiculite catalysts, was adopted to transform disposable grocery bags (i.e., a polyethylene-based material) to kerosene-range fuels. The results revealed that the silicon pillars contributed to the catalyst's excellent thermal stability to withstand temperatures of up to 1000 °C, while the transition-metallic species (e.g., Co/Ni/Fe) contributed to the fine-tuning of the catalyst's acidity and porosity. Specifically, Co-Fe/Si-pillared vermiculite (SPV) (5:5) produced the highest yield of oil products (75.7 wt%), with alkane and aromatic selectivities of 57.5% and 27.8%, respectively, resembling the composition of kerosene. The catalyst's high selectivities for the targeted products were attributed to the controllable acidity and porosity, enabling a balance to be achieved between these two properties. Pathways were proposed for the tandem pyrolysis in the presence of Co-Fe/SPV. The vermiculite-based catalysts showed satisfactory reusability following regeneration. Beyond polyethylene-based plastics, these catalysts are also applicable to the pyrolysis of other plastic feedstocks. Because vermiculite is a low-cost material, the developed catalyst has good commercialization potential for a wide spectrum of waste-to-energy conversions.

Waste to energy: Trending key challenges and current technologies in waste plastic management

Due to the 'forever' degrading nature of plastic waste, plastic waste management is often complicated. The applications of plastic are ubiquitous and inevitable in many scenarios. Current global waste plastics production is ca. 3.5 MMT per year, and with the current trend, plastic waste production will reach 25,000 MMT by 2040. However, the rapid growth in plastic manufacture and the material's inherent nature resulted in the accumulation of a vast amount of plastic garbage. The current recycling rate is <10 %, while the large volumes of discarded plastic waste cause environmental and ecological problems. Recycling rates for plastic vary widely by region and type of plastic. In some developed countries, the recycling rate for plastics is around 20-30 %, while in many developing nations, it is much lower. These statistics highlight the magnitude of the plastic waste problem and the urgent need for comprehensive strategies to manage plastic waste more effectively and reduce its impact on the environment. This review critically analyses past studies on the essential and efficient techniques for turning plastic trash into treasure. Additionally, an attempt has been made to provide a comprehensive understanding of the plastic upcycling process, the 3Rs policy, and the life-cycle assessment (LCA) of plastic conversion. The review advocates pyrolysis as one of the most promising methods of turning plastic trash into valuable chemicals. In addition, plastic waste management can be severely impacted due to uncontrollable events, such as Covid 19 pandemic. Recycling and chemical upcycling can certainly bring value to the end-of-life plastic. However, the LCA analysis indicated there is still a huge scope for innovation in chemical upcycling area compared to mechanical recycling. The formulation of policies and heightened public participation could play a pivotal role in reducing the environmental repercussions of plastic waste and facilitating a shift towards a more sustainable future.

Low-Temperature Upcycling of Polypropylene Waste into H2 Fuel via a Novel Tandem Hydrothermal Process

Plastic waste is a promising and abundant resource for H2 production. However, upcycling plastic waste into H2 fuel via conventional thermochemical routes requires relatively considerable energy input and severe reaction conditions, particularly for polyolefin waste. Here, we report a tandem strategy for the selective upcycling of polypropylene (PP) waste into H2 fuel in a mild and clean manner. PP waste was first oxidized into small-molecule organic acids using pure O2 as oxidant at 190 °C, followed by the catalytic reforming of oxidation aqueous products over ZnO-modified Ru/NiAl2 O4 catalysts to produce H2 at 300 °C. A high H2 yield of 44.5 mol/kgPP and a H2 mole fraction of 60.5 % were obtained from this tandem process. The entire process operated with almost no solid residue remaining and equipment contamination, ensuring relative stability and cleanliness of the reaction system. This strategy provides a new route for low-temperature transforming PP and improving the sustainability of plastic waste disposal processes.

Towards environmentally sustainable management: A review on the generation, degradation, and recycling of polypropylene face mask waste

There has been a considerable increase in the use of face masks in the past years. Managing face mask waste has become a global concern, as the current waste management system is insufficient to deal with such a large quantity of solid waste. The drastic increase in quantity, along with the material's inability to degrade plastic components such as polypropylene, has led to a large accumulation of plastic waste, causing a series of environmental and ecological challenges. In addition, the growing use also imposes pressure on waste management methods such as landfill and incineration, raising concerns about high energy consumption, low value-added utilization, and the release of additional pollutants during the process. This article initially reviews the impact of mask-related plastic waste generation and degradation behavior in the natural environment. It then provides an overview of various recently developed methods for recycling face mask plastic waste. The article also offers forward-looking strategies and recommendations on face mask plastic waste management. The review aims to provide guidance on harnessing the complexities of mask waste and other medical plastic pollution issues, as well as improving the current waste management system's deficiencies and inefficiencies in tackling the growing plastic waste problem.

Biodegradation of Typical Plastics: From Microbial Diversity to Metabolic Mechanisms

Plastic production has increased dramatically, leading to accumulated plastic waste in the ocean. Marine plastics can be broken down into microplastics (<5 mm) by sunlight, machinery, and pressure. The accumulation of microplastics in organisms and the release of plastic additives can adversely affect the health of marine organisms. Biodegradation is one way to address plastic pollution in an environmentally friendly manner. Marine microorganisms can be more adapted to fluctuating environmental conditions such as salinity, temperature, pH, and pressure compared with terrestrial microorganisms, providing new opportunities to address plastic pollution. Pseudomonadota (Proteobacteria), Bacteroidota (Bacteroidetes), Bacillota (Firmicutes), and Cyanobacteria were frequently found on plastic biofilms and may degrade plastics. Currently, diverse plastic-degrading bacteria are being isolated from marine environments such as offshore and deep oceanic waters, especially Pseudomonas spp. Bacillus spp. Alcanivoras spp. and Actinomycetes. Some marine fungi and algae have also been revealed as plastic degraders. In this review, we focused on the advances in plastic biodegradation by marine microorganisms and their enzymes (esterase, cutinase, laccase, etc.) involved in the process of biodegradation of polyethylene terephthalate (PET), polystyrene (PS), polyethylene (PE), polyvinyl chloride (PVC), and polypropylene (PP) and highlighted the need to study plastic biodegradation in the deep sea.

Development of reusable Ni/γ-Al2O3 catalyst for catalytic hydrolysis of waste PET bottles into terephthalic acid

In order to efficiently recycle waste polyethylene terephthalate (PET) bottles, this study aimed to enhance the hydrolysis process to convert PET bottle into valuable terephthalic acid (TPA) by developing effective and reusable Ni/γ-Al2O3 catalysts. A series of Ni/γ-Al2O3 catalyst was prepared by the impregnation method with different Ni loadings (5-15 wt%) and was characterized by various techniques including XRD, SEM-EDX, and N2 adsorption-desorption. The prepared catalysts were employed in the catalytic hydrolysis of PET under varied influencing factors, namely reaction temperature (220-280 °C), reaction time (20-60 min), and Ni loading. The response surface methodology (RSM) was used to optimize the operating condition to produce the maximum TPA yield, and the optimal values were determined as follows: reaction temperature = 267.07 °C, reaction time = 48.54 min, and Ni loading = 12.90 wt%, giving the highest TPA yield of 97.06%. The R2, F-value, and P-value of the analysis of variance (ANOVA) were 0.9982, 424.96, and <0.0001, respectively, indicating a good fit of the model. The results from XRD and FTIR measurement of the produced TPA indicated the high purity and comparable chemical structures to the TPA standard. In addition, the 12.9Ni/Al catalyst exhibited high catalytic activity in repeated cycles of hydrolysis process of PET and could be regenerated by calcination to restore its catalytic activity. This finding could be a promising alternative for an effective TPA recovery from waste plastic bottles.

Mechanistic vision on polypropylene microplastics degradation by solar radiation using TiO2 nanoparticle as photocatalyst

Microplastics are emerging contaminants owing to their occurrence and distribution in everywhere the ecosystem and leading to major environmental problems. Management methods are more suitable for larger-sized plastics. Here, the current study elucidates that, TiO2 photocatalyst under sunlight irradiation actively mitigates polypropylene microplastics (pH 3, 50 h) in an aqueous medium. End of post-photocatalytic experiments, the weight loss percentage of microplastics was 50.5 ± 0.5%. Fourier transforms infrared (FTIR) and nuclear magnetic resonance spectroscopy (1H NMR) spectroscopy results revealed the formation of peroxide and hydroperoxide ions, carbonyl, keto and ester groups at the end of the post-degradation process. Ultraviolet-Visible Diffuse Reflectance spectroscopic (UV - DRS) results showed variation in the optical absorbance of polypropylene microplastics peak values at 219 and 253 nm. Increased the weight percentage of oxygen level due to the oxidation of functional groups and decreased the weight percentage of carbon content in electron dispersive spectroscopy (EDS), probably owing to breakdown of long-chain polypropylene microplastics. In addition, scanning electron microscopy (SEM) microscopic analysis showed the surface having holes, cavities, and cracks on irritated polypropylene microplastics. The overall study and their mechanistic pathway strongly confirmed the formation of reactive oxygen species (ROS) with help of the movement of electrons by photocatalyst under solar irradiation which aids the degradation of polypropylene microplastics.

Material and mechanical characterization of recycled polypropylene reinforced with different weight percentages of short glass fiber developed by injection molding

The objective of this study was to develop short glass fiber-reinforced recycled polypropylene composites using injection molding technique with varying fiber percentages (0-50 wt%). The study aimed to evaluate the mechanical and material properties of the composites and their potential applications. To achieve this, polypropylene composite pellets were prepared using a low-cost and simple manufacturing method that involved plastic recycling using a crushing method and pelletizing with different weight percentages of short glass fiber using twin-screw extruder. The study conducted various analyses, such as melt flow index, capillary rhinometry, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. Results showed that the recycled polypropylene/short glass fiber composites exhibited improved heat resistance, crystallization rate, and thermal stability compared to the pure polymer. The best impact mechanical (about 3.65 ± 0.09 J/m) properties were obtained at 50 wt% of short glass fiber in the fabricated composites. Scanning electron microscope analysis indicated a uniform dispersion of short glass fiber in the polypropylene matrix. The potential applications of these composites were found in household appliances, industrial plastic products, and other areas. Overall, this study demonstrates the potential of short glass fiber-reinforced polypropylene composites as a cost-effective, environmentally friendly and sustainable alternative for various applications.

Sustainable Solution for Plastic Pollution: Upcycling Waste Polypropylene Masks for Effective Oil-Spill Management

The use of Polypropylene PP in disposable items such as face masks, gloves, and personal protective equipment has increased exponentially during and after the COVID-19 pandemic, contributing significantly to microplastics and nanoplastics in the environment. Upcycling of waste PP provides a useful alternative to traditional thermal and mechanical recycling techniques. It transforms waste PP into useful products, minimizing its impact on the environment. Herein, we synthesized an oil-sorbent pouch using waste PP, which comprises superposed microporous and fibrous thin films of PP using spin coating. The pouch exhibited super-fast uptake kinetics and reached its saturation in fewer than five minutes with a high oil uptake value of 85 g/g. Moreover, it displayed high reusability and was found to be effective in absorbing oil up to seven times when mechanically squeezed between each cycle, demonstrating robust oil-sorption capabilities. This approach offers a potential solution for managing plastic waste while promoting a circular economy.

Post-pandemic micro/nanoplastic pollution: Toward a sustainable management

The global health crisis caused by the COVID-19 pandemic has resulted in massive plastic pollution from the use of personal protection equipment (PPE), with polypropylene (PP) being a major component. Owing to the weathering of exposed PPEs, such contamination causes microplastic (MP) and nanoplastic (NP) pollution and is extremely likely to act as a vector for the transportation of COVID-19 from one area to another. Thus, a post-pandemic scenario can forecast with certainty that a significant amount of plastic garbage combined with MP/NP formation has an adverse effect on the ecosystem. Therefore, updating traditional waste management practices, such as landfilling and incineration, is essential for making plastic waste management sustainable to avert this looming catastrophe. This study investigates the post-pandemic scenario of MP/NP pollution and provides an outlook on an integrated approach to the recycling of PP-based plastic wastes. The recovery of crude oil, solid char, hydrocarbon gases, and construction materials by approximately 75, 33, 55, and 2 %, respectively, could be achieved in an environmentally friendly and cost-effective manner. Furthermore, the development of biodegradable and self-sanitizing smart PPEs has been identified as a promising alternative for drastically reducing plastic pollution.

Low-temperature upcycling of PET waste into high-purity H2 fuel in a one-pot hydrothermal system with in situ CO2 capture

The accumulation and improper disposal of a large amount of plastic waste have exacerbated the deterioration of the global ecosystem and environment. To simplify the complex management system and alleviate the environmental impact of plastic wastes, this study reports a novel one-pot hydrothermal conversion strategy for polyethylene terephthalate (PET), integrating three steps, namely depolymerization, subsequent in-situ aqueous phase reforming, and in-situ CO₂ capture. Here, the PET waste was converted directly into the clean high-purity H₂ fuel and the disodium terephthalate (Na₂-TPA). A high yield of H₂ at 23.7 mol/kg_PET with ca. 99 % of H₂ concentration was obtained at a temperature as low as 240 °C. The feasibility of this strategy in handling real-world PET plastic wastes was demonstrated through a series of tests on beverage bottles, food packaging, and polyester fabric waste. The Na₂-TPA crystals produced from the proposed PET conversion system exhibited purity close to that of the standard sample, and thus had the potential to be directly used as an electrode material. Overall, this strategy provides an efficient way to transform PET waste into high-value products and improves the sustainability of the PET waste disposal process.

Plastic wastes in the time of COVID-19: Their environmental hazards and implications for sustainable energy resilience and circular bio-economies

The global scope of pollution from plastic waste is a well-known phenomenon associated with trade, mass consumption, and disposal of plastic products (e.g., personal protective equipment (PPE), viral test kits, and vacuum-packaged food). Recently, the scale of the problem has been exacerbated by increases in indoor livelihood activities during lockdowns imposed in response to the coronavirus disease 2019 (COVID-19) pandemic. The present study describes the effects of increased plastic waste on environmental footprint and human health. Further, the technological/regulatory options and life cycle assessment (LCA) approach for sustainable plastic waste management are critically dealt in terms of their implications on energy resilience and circular economy. The abrupt increase in health-care waste during pandemic has been worsening environmental quality to undermine the sustainability in general. In addition, weathered plastic particles from PPE along with microplastics (MPs) and nanoplastics (NPs) can all adsorb chemical and microbial contaminants to pose a risk to ecosystems, biota, occupational safety, and human health. PPE-derived plastic pollution during the pandemic also jeopardizes sustainable development goals, energy resilience, and climate control measures. However, it is revealed that the pandemic can be regarded as an opportunity for explicit LCA to better address the problems associated with environmental footprints of plastic waste and to focus on sustainable management technologies such as circular bio-economies, biorefineries, and thermal gasification. Future researches in the energy-efficient clean technologies and circular bio-economies (or biorefineries) in concert with a "nexus" framework are expected to help reduce plastic waste into desirable directions.

Reuse of end-of-life personal protective equipment in hot asphalt mixtures: an environmental evaluation

In the present global health emergency, face masks, gowns, caps, gloves play a key role in limiting the diffusion of the COVID-19 pandemic, by acting as physical barriers to avoid droplets and filtrate exhalations coming from infected subjects. Since the most widespread devices are disposable products made of plastic or rubber materials, this means that relevant quantities of fossil resources are consumed, and huge amounts of wastes are generated. Currently the end of life of personal protective equipment (PPE) represents a problem in environmental, economic, and social terms. The market considers two possible disposal scenarios: incineration with energy recovery or landfill. In both cases, significant impacts are achieved both on the environment and on human health. This study aims to propose and validate a new scenario for PPE based on material reuse for bituminous conglomerates. The Life Cycle Assessment methodology and the experimental tests has been used to assess the environmental impacts in terms of both ReCiPe midpoints and endpoints and for demonstrate the technical feasibility of this new scenario. From an environmental point of view, relevant benefits were observed in comparison with the standard incineration for energy recovery or disposal in landfill.

Production of third generation bio-fuel through thermal cracking process by utilizing Covid-19 plastic wastes

During this pandemic, it has become customary to wear a face waste mask to guard against coronavirus illness (COVID-19). However, huge production of face waste masks, PPE kit and gloves pose environmental risks, since existing disposal methods such as incineration and reclamation which are emitting hazardous substances. In the present study covid-19 medical waste material like waste face waste masks; gloves and PPE kit (personal protective equipment) are considered as the feedstock for the thermal degradation process. Mainly nylon, polyethylene and polypropylene compounds are present in the Covid-19 medical waste compounds, further feedstock material is subjected to physical characterization process like proximate, ultimate and thermo gravimetric analysis (TGA), to determine the moisture, ash, volatile matter and decomposition temperature respectively. The waste waste mask has lower ash content of 9.7 %, whereas gloves and other PPEs has 11.8 and 11.2 % of ash respectively. Similarly volatile matter is also higher for waste waste mask than other feed stocks. Pyrolysis process is carried out between a temperature range of 100 °C to 700 °C and the products of the pyrolysis process are pyrolytic liquid, gas and residue. The maximum pyrolytic oil is produced from waste masks, gloves and other PPE kit at 300, 350 and 320 °C respectively. The calorific value of the pyrolytic oil from waste mask, gloves and other PPE kit possess 40.85,40.11,40.31 MJ/kg respectively, which indicates that all the pyrolytic oil has closer to the diesel fuel. Therefore pyroltic oil obtained from the Covid-19 medical waste can be used as an alternative fuel for CI engine.

Upcycling face mask wastes generated during COVID-19 into value-added engineering materials: A review

Billions of disposable face masks (i.e., single-use masks) are used and discarded worldwide monthly due to the COVID-19 outbreak. The immethodical disposal of these polymer-based wastes containing non-biodegradable constituents (e.g., polypropylene) has provoked marked and severe damage to the ecosystem. Meanwhile, their ever-growing usage significantly strains the present-day waste management measures such as landfilling and incineration, resulting in large quantities of used face-covering masks landing in the environment as importunate contaminants. Hence, alternative waste management strategies are crucially demanded to decrease the negative impacts of face mask contamination. In this venue, developing high-yield, effective, and green routes toward recycling or upcycling face mask wastes (FMWs) into value-added materials is of great importance. While existing recycling processes assist the traditional waste management, they typically end up in materials with downgraded physicochemical, structural, mechanical, and thermal characteristics with reduced values. Therefore, pursuing potential economic upcycling processes would be more beneficial than waste disposal and/or recycling processes. This paper reviews recent advances in the FMWs upcycling methods. In particular, we focus on producing value-added materials via various waste conversion methods, including carbonization (i.e., extreme pyrolysis), pyrolysis (i.e., rapid carbonization), catalytic conversion, chemical treatment, and mechanical reprocessing. Generally, the upcycling methods are promising, firming the vital role of managing FMWs' fate and shedding light on the road of state-of-the-art materials design and synthesis.

Plastic and Waste Tire Pyrolysis Focused on Hydrogen Production—A Review

In this review, we compare hydrogen production from waste by pyrolysis and bioprocesses. In contrast, the pyrolysis feed was limited to plastic and tire waste unlikely to be utilized by biological decomposition methods. Recent risks of pyrolysis, such as pollutant emissions during the heat decomposition of polymers, and high energy demands were described and compared to thresholds of bioprocesses such as dark fermentation. Many pyrolysis reactors have been adapted for plastic pyrolysis after successful investigation experiences involving waste tires. Pyrolysis can transform these wastes into other petroleum products for reuse or for energy carriers, such as hydrogen. Plastic and tire pyrolysis is part of an alternative synthesis method for smart polymers, including semi-conductive polymers. Pyrolysis is less expensive than gasification and requires a lower energy demand, with lower emissions of hazardous pollutants. Short-time utilization of these wastes, without the emission of metals into the environment, can be solved using pyrolysis. Plastic wastes after pyrolysis produce up to 20 times more hydrogen than dark fermentation from 1 kg of waste. The research summarizes recent achievements in plastic and tire waste pyrolysis development.

Structure-oriented conversions of plastics to carbon nanomaterials

The accumulation of waste plastics has caused serious environmental issues due to their unbiodegradable nature and hazardous additives. Converting waste plastics to different carbon nanomaterials (CNMs) is a promising approach to minimize plastic pollution and realize advanced manufacturing of CNMs. The reported plastic-derived carbons include carbon filaments (i.e. carbon nanotubes and carbon nanofibers), graphene, carbon nanosheets, carbon sphere, and porous carbon. In this review, we present the influences of different intrinsic structures of plastics on the pyrolysis intermediates. We also reveal that non-charring plastics are prone to being pyrolyzed into light hydrocarbons while charring plastics are prone to being pyrolyzed into aromatics. Subsequently, light hydrocarbons favor to form graphite while aromatics are inclined to form amorphous carbon during the carbon formation process. In addition, the conversion tendency of different plastics into various morphologies of carbon is concluded. We also discuss other impact factors during the transformation process, including catalysts, temperature, processing duration and templates, and reveal how to obtain different morphological CNMs from plastics. Finally, current technology limitations and perspectives are presented to provide future research directions in effective plastic conversion and advanced CNM synthesis.

The impact factors in transforming plastics into carbon nanomaterials are reviewed.

The carbon morphology tendency from different plastics is revealed.

Directions for future research on plastic carbonization are presented.

Waste Management and the Perspective of a Green Hospital-A Systematic Narrative Review

The concept of a "green hospital" is used in reference to a hospital that includes the environment as part of its quality services and one that pays attention to the sustainable design of buildings. Waste disposal represents a potential risk for the environment; therefore, waste collection from healthcare centers is a key environmental issue. Our study aims to systematically review the experiences acquired in worldwide nosocomial settings related to the management of healthcare waste. Nineteen studies, selected between January 2020 and April 2022 on Scopus, MEDLINE/PubMed and Web of Science databases were included in our systematic narrative review. Operating room and hemodialysis activities seem to be the procedures most associated with waste production. To deal with waste production, the 5Rs rule (reduce, reuse, recycle, rethink and research) was a common suggested strategy to derive the maximum practical benefit while generating the minimum amount of waste. In this context, the COVID-19 pandemic slowed down the greening process of nosocomial environments. Waste management requires a multifactorial approach to deal with medical waste management, even considering the climate change that the world is experiencing. Education of health personnel and managers, regulation by governmental institutions, creation of an "environmental greening team", and awareness of stakeholders and policymakers are some of the measures needed for the greening of healthcare facilities.

Process Simulation and Life Cycle Assessment of Waste Plastics: A Comparison of Pyrolysis and Hydrocracking

Pyrolysis and hydrocracking of plastic waste can produce valuable products with manageable effects on the environment as compared to landfilling and incineration. This research focused on the process simulation and life cycle assessment of the pyrolysis and hydrocracking of high-density polyethylene. Aspen Plus was used as the simulator and the Peng-Robinson thermodynamic model was employed as a fluid package. Additionally, sensitivity analysis was conducted in order to optimize product distribution. Based on the simulation, the hydrocracking process produced value-added fuels, i.e., gasoline and natural gas. In contrast, pyrolysis generated a significant quantity of pyrolysis oil with a high number of cyclo-compounds and char, which are the least important to be utilized as fuels. Moreover, in the later part of the study, life cycle assessment (LCA) was adopted in order to investigate and quantify their impact upon the environment using simulation inventory data, which facilitates finding a sustainable process. Simapro was used as a tool for LCA of the processes and materials used. The results demonstrate that hydrocracking is a better process in terms of environmental impact in 10 out of the 11 impact categories. Overall, the present study proposed a promising comparison based on energy demands, product distribution, and potential environmental impacts, which will help to improve plastic waste management.

Agro-residual biomass and disposable protective face mask: a merger for converting waste to plastic-fiber fuel via an integrative carbonization-pelletization framework

Incineration and landfilling offer possibilities for addressing high-rate management of COVID-waste streams. However, they can be costly and environmentally unsustainable. In addition, they do not allow to convert them to fuels and chemicals as waste-to-energy and waste-to-product technologies. Therefore, we analyzed whether integrating hydrothermal carbonization (HTC) and pelletization can allow converting the surgical face mask (SFM) and biomass to composite plastic-fiber fuel (CPFF). We blended the plastic material and corncob, peanut shell, or sugarcane bagasse at the proportion of 50:50 (%, dry mass basis) for HTC. We performed the thermal pretreatment of blends in an autoclaving reactor at 180 °C and 1.5 MPa. Then we pelletized the hydrochars in a presser machine at 200 MPa and 125 °C. By analyzing the evidence from our study, we recognized the viability of combining the SFM and agricultural residues for CPFF from comparable technical features of our products to standards for premium-grade wood pellets. For instance, the elemental composition of their low-meltable ash was not stoichiometrically sufficient to severely produce slagging and fouling in the equipment for thermal conversion. Although they contained synthetic polymers in their structures, such as polyethylene from filter layers and nylon from the earloop, they emitted CO and NOx below the critical limits of 200 and 500 mg m-3, respectively, for occupational safety. Therefore, we extended the knowledge on waste-to-energy pathways to transform SFM into high-quality hybrid fuel by carbonization and pelletization. Our framework can provide stakeholders opportunities to address plastic and biogenic waste in the context of a circular economy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13399-022-03285-4.

Effect of Diatomite on the Thermal Degradation Behavior of Polypropylene and Formation of Graphene Products

In this work, the thermogravimetry–Fourier transform infrared spectroscopy (TG–FTIR) and gas chromatography–mass spectrometry (GC–MS) techniques are used to investigate the thermal degradation behavior of polypropylene (PP) with 20 wt.% diatomite (DM). The initial decomposition temperature of these blends was 17 °C lower than that of pristine PP, and more olefin degradation products were formed during the pyrolysis process under Ar atmosphere. These results could be attributed to the catalytic effects of DM on the degradation of PP and the changes of PP chain scission pathways around the particles (more β scission happened via the secondary radical transfer). These olefins could be caught by DM through the Si–O–C bond formed during the heat–treatment around 400~500 °C. The formation of the cross–linked structure could facilitate the growth of graphene during a high–temperature graphitization process.

The surface groups of polystyrene nanoparticles control their interaction with the methanogenic archaeon Methanosarcina acetivorans

A better understanding of the interaction between nanoplastics and archaea is crucial to fill the knowledge gaps regarding the ecological safety of nanoplastics. As a vital source for global methane emissions, methanogenic archaea have unique cell membranes that are distinctly different from those in all other forms of life, little is known about their interaction with nanoplastics. Here, we show that polystyrene nanoparticles functionalized with sulfonic acid (PS-SO₃H) and amino (PS-NH₂) interact with this methanogenic archaeon in distinct ways. Although both of them have no significant phenotype effects on Methanosarcina acetivorans C2A, these nanoparticles could affect DNA-mediated transposition of this methanogenic archaeon, and PS-SO₃H also downregulated nitrogen fixation, nitrogen cycle metabolic process, oxidoreductase activity, etc. In addition, both nanoplastics decreased the protein contents in the extracellular polymer substances (EPS), with distinct binding sequences to the functional groups of the EPS. The single particle atomic force microscopy revealed that the force between the amino group and the M. acetivorans C2A was greater than that of sulfonic acid group. Our results exhibit that the surface groups of polystyrene nanoparticles control their risk on the methanogenic archaea, and these effects might influence their contribution on global methane emission.

Analysis of Statistically Predicted Rate Constants for Pyrolysis of High-Density Plastic Using R Software

The surge in plastic waste production has forced researchers to work on practically feasible recovery processes. Pyrolysis is a promising and intriguing option for the recycling of plastic waste. Developing a model that simulates the pyrolysis of high-density polyethylene (HDPE) as the most common polymer is important in determining the impact of operational parameters on system behavior. The type and amount of primary products of pyrolysis, such as oil, gas, and waxes, can be predicted statistically using a multiple linear regression model (MLRM) in R software. To the best of our knowledge, the statistical estimation of kinetic rate constants for pyrolysis of high-density plastic through MLRM analysis using R software has never been reported in the literature. In this study, the temperature-dependent rate constants were fixed experimentally at 420 °C. The rate constants with differences of 0.02, 0.03, and 0.04 from empirically set values were analyzed for pyrolysis of HDPE using MLRM in R software. The added variable plots, scatter plots, and 3D plots demonstrated a good correlation between the dependent and predictor variables. The possible changes in the final products were also analyzed by applying a second-order differential equation solver (SODES) in MATLAB version R2020a. The outcomes of experimentally fixed-rate constants revealed an oil yield of 73% to 74%. The oil yield increased to 78% with a difference of 0.03 from the experimentally fixed rate constants, but light wax, heavy wax, and carbon black decreased. The increased oil and gas yield with reduced byproducts verifies the high significance of the conducted statistical analysis. The statistically predicted kinetic rate constants can be used to enhance the oil yield at an industrial scale.

Nickel-iron nanoparticles encapsulated in carbon nanotubes prepared from waste plastics for low-temperature solid oxide fuel cells

Low-temperature solid oxide fuel cells (LT-SOFCs) are a promising next-generation fuel cell due to their low cost and rapid start-up, posing a significant challenge to electrode materials with high electrocatalytic activity. Herein, we reported the bimetallic nanoparticles encapsulated in carbon nanotubes (NiFe@CNTs) prepared by carefully controlling catalytic pyrolysis of waste plastics. Results showed that plenty of multi-walled CNTs with outer diameters (14.38 ± 3.84 nm) were observed due to the smallest crystalline size of Ni-Fe alloy nanoparticles. SOFCs with such NiFe@CNTs blended in anode exhibited remarkable performances, reaching a maximum power density of 885 mW cm⁻² at 500°C. This could be attributed to the well-dispersed alloy nanoparticles and high graphitization degree of NiFe@CNTs to improve HOR activity. Our strategy could upcycle waste plastics to produce nanocomposites and demonstrate a high-performance LT-SOFCs system, addressing the challenges of sustainable waste management and guaranteeing global energy safety simultaneously.

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The M@CNTs from the waste plastics were utilized as anode additive of LT-SOFCs

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The effects of active metal species on the quality of nanocomposite were studied

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Maximum power density of 885 mW cm⁻² at 500°C was obtained with NiFe@CNTs

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The excellent performances of SOFCs could be attributed to the improved HOR activity

Current Prospects for Plastic Waste Treatment

The excessive amount of global plastic produced over the past century, together with poor waste management, has raised concerns about environmental sustainability. Plastic recycling has become a practical approach for diminishing plastic waste and maintaining sustainability among plastic waste management methods. Chemical and mechanical recycling are the typical approaches to recycling plastic waste, with a simple process, low cost, environmentally friendly process, and potential profitability. Several plastic materials, such as polypropylene, polystyrene, polyvinyl chloride, high-density polyethylene, low-density polyethylene, and polyurethanes, can be recycled with chemical and mechanical recycling approaches. Nevertheless, due to plastic waste’s varying physical and chemical properties, plastic waste separation becomes a challenge. Hence, a reliable and effective plastic waste separation technology is critical for increasing plastic waste’s value and recycling rate. Integrating recycling and plastic waste separation technologies would be an efficient method for reducing the accumulation of environmental contaminants produced by plastic waste, especially in industrial uses. This review addresses recent advances in plastic waste recycling technology, mainly with chemical recycling. The article also discusses the current recycling technology for various plastic materials.

Recent Advances in Catalytic Pyrolysis of Municipal Plastic Waste for the Production of Hydrocarbon Fuels

Currently, the resources of fossil fuels, such as crude oil, natural gas, and coal, are depleting day by day due to increasing energy demands. Nowadays, plastic items have witnessed a substantial surge in manufacturing due to their wide range of applications and low cost. Therefore, the amount of plastic waste is increasing rapidly. Hence, the proper management of plastic wastes for sustainable technologies is the need of the hour. Chemical recycling technologies based on pyrolysis are emerging as the best waste management approaches due to their robustness and better economics. However, research on converting plastic waste into fuels and other value-added goods has yet to be undertaken, and more R&D is required to make waste-plastic-based fuels economically viable. In this review article, the current status of the plastic waste pyrolysis process is discussed in detail. Process-controlling parameters such as temperature, pressure, residence time, reactor type, and catalyst dose are also investigated in this review paper. In addition, the application of reaction products is also described in brief. For example, plasto-oil obtained by catalytic pyrolysis may be utilized in various sectors, e.g., transportation, industrial boilers, and power generation. On the other hand, byproducts, such as solid residue (plasto-char), could be used as a road construction material or to make activated carbon or graphenes, while the non-condensable gases have a good potential to be utilized as heating/energy source.

Natural Fiber-Reinforced Thermoplastic ENR/PVC Composites as Potential Membrane Technology in Industrial Wastewater Treatment: A Review

Membrane separation processes are prevalent in industrial wastewater treatment because they are more effective than conventional methods at addressing global water issues. Consequently, the ideal membranes with high mechanical strength, thermal characteristics, flux, permeability, porosity, and solute removal capacity must be prepared to aid in the separation process for wastewater treatment. Rubber-based membranes have shown the potential for high mechanical properties in water separation processes to date. In addition, the excellent sustainable practice of natural fibers has attracted great attention from industrial players and researchers for the exploitation of polymer composite membranes to improve the balance between the environment and social and economic concerns. The incorporation of natural fiber in thermoplastic elastomer (TPE) as filler and pore former agent enhances the mechanical properties, and high separation efficiency characteristics of membrane composites are discussed. Furthermore, recent advancements in the fabrication technique of porous membranes affected the membrane's structure, and the performance of wastewater treatment applications is reviewed.

Alternating magnetic field initiated catalytic deconstruction of medical waste to produce hydrogen-rich gases and graphite

During the coronavirus 2019 (COVID-19) pandemic, there has been a dramatic increase in the use of medical products and personal protective equipment, such as masks, gowns, and disposable syringes, to treat patients or administer vaccines. However, this may lead to generation of large quantities of biohazardous medical waste. Here, an alternating-magnetic-field-initiated catalytic strategy is proposed to convert disposable syringes into hydrogen-rich gases and high-value graphite. Specifically, in addition to selecting heavy fraction of bio-oil as initiator, disposable syringe needles are used as radio frequency electromagnetic wave receptors to initiate the deconstruction of disposable syringe plastic. The highest H₂ yield of 39.9 mmol g^-1 is achieved, and 30.1 mmol g^-1 is maintained after 10 cycles. Moreover, a high carbon yield of 286 mg g^-1 can be obtained. Beyond disposable syringes, this strategy could help to solve the emerging issue for other types of medical waste (e.g., mask and protective clothing) disposal.

Hyperelastic Properties of Bamboo Cellulosic Fibre–Reinforced Silicone Rubber Biocomposites via Compression Test

Materials that exhibit highly nonlinear behaviour are intricate to study. This is due to their physical properties, as they possess a very large deformation. Silicone rubber is among the materials that can be classified as possessing such characteristics, despite their being soft and frequently applied in medical applications. Due to their low mechanical properties, however, it is believed that a filler addition could enhance them. This study, therefore, aims to investigate the effect of the addition of bamboo cellulosic filler to silicone rubber in terms of its compressive properties in order to quantify its material constants using the hyperelastic theory, specifically the Neo-Hookean and Mooney–Rivlin models. The specimens’ compressive properties were also compared between specimens immersed in seawater and those not immersed in seawater. The findings showed that the compressive properties, stiffness, and compressive strength of the bamboo cellulosic fibre reinforced the silicone rubber biocomposites, improved with higher bamboo filler addition. Specimens immersed in seawater showed that they can withstand a compressive load of up to 83.16 kPa in comparison to specimens not immersed in seawater (up to 79.8 kPa). Using the hyperelastic constitutive models, the Mooney–Rivlin model displayed the most accurate performance curve fit with the experimental compression data with an R² of up to 0.9999. The material constant values also revealed that the specimens immersed in seawater improved in stiffness property, as the C₁ material constant values are higher than for the specimens not immersed in seawater. From these findings, this study has shown that bamboo cellulosic filler added into silicone rubber enhances the material’s compressive properties and that the rubber further improves with immersion in seawater. Thus, these findings contribute significantly towards knowledge of bamboo cellulosic fibre–reinforced silicone rubber biocomposite materials.

Closing the Carbon Loop in the Circular Plastics Economy

Today, plastics are ubiquitous in everyday life, problem solvers of modern technologies, and crucial for sustainable development. Yet the surge in global demand for plastics of the growing world population has triggered a tidal wave of plastic debris in the environment. Moving from a linear to a zero-waste and carbon-neutral circular plastic economy is vital for the future of the planet. Taming the plastic waste flood requires closing the carbon loop through plastic reuse, mechanical and molecular recycling, carbon capture, and use of the greenhouse gas carbon dioxide. In the quest for eco-friendly products, plastics do not need to be reinvented but tuned for reuse and recycling. Their full potential must be exploited regarding energy, resource, and eco efficiency, waste prevention, circular economy, climate change mitigation, and lowering environmental pollution. Biodegradation holds promise for composting and bio-feedstock recovery, but it is neither the Holy Grail of circular plastics economy nor a panacea for plastic littering. As an alternative to mechanical downcycling, molecular recycling enables both closed-loop recovery of virgin plastics and open-loop valorization, producing hydrogen, fuels, refinery feeds, lubricants, chemicals, and carbonaceous materials. Closing the carbon loop does not create a Perpetuum Mobile and requires renewable energy to achieve sustainability. This article is protected by copyright. All rights reserved.

Conversion of Plastic Waste to Carbon-Based Compounds and Application in Energy Storage Devices

At present, plastic waste accumulation has been observed as one of the most alarming environmental challenges, affecting all forms of life, economy, and natural ecosystems, worldwide. The overproduction of plastic materials is mainly due to human population explosion as well as extraordinary proliferation in the global economy accompanied by global productivity. Under this threat, the development of benign and green alternative solutions instead of traditional disposal methods such as conversion of plastic waste materials into cherished carbonaceous nanomaterials such as carbon nanotubes (CNTs), carbon quantum dots (CQDs), graphene, activated carbon, and porous carbon is of utmost importance. This critical review thoroughly summarizes the different types of daily used plastics, their types, properties, ways of accumulation and their effect on the environment and human health, treatment of waste materials, conversion of waste materials into carbon-based compounds through different synthetic schemes, and their utilization in energy storage devices particularly in supercapacitors, as well as future perspectives. The main purpose of this review is to help the targeted audience to design their futuristic study in this desired field by providing information about the work done in the past few years.

Recent Advances in the Decontamination and Upgrading of Waste Plastic Pyrolysis Products: An Overview

Extensive research on the production of energy and valuable materials from plastic waste using pyrolysis has been widely conducted during recent years. Succeeding in demonstrating the sustainability of this technology economically and technologically at an industrial scale is a great challenge. In most cases, crude pyrolysis products cannot be used directly for several reasons, including the presence of contaminants. This is confirmed by recent studies, using advanced characterization techniques such as two-dimensional gas chromatography. Thus, to overcome these limitations, post-treatment methods, such as dechlorination, distillation, catalytic upgrading and hydroprocessing, are required. Moreover, the integration of pyrolysis units into conventional refineries is only possible if the waste plastic is pre-treated, which involves sorting, washing and dehalogenation. The different studies examined in this review showed that the distillation of plastic pyrolysis oil allows the control of the carbon distribution of different fractions. The hydroprocessing of pyrolytic oil gives promising results in terms of reducing contaminants, such as chlorine, by one order of magnitude. Recent developments in plastic waste and pyrolysis product characterization methods are also reported in this review. The application of pyrolysis for energy generation or added-value material production determines the economic sustainability of the process.

Assessing face masks in the environment by means of the DPSIR framework

The use of face masks outside the health care facility dates back a century ago. However, face masks use noticeably soared due to the COVID-19 (Coronavirus disease 2019) pandemic. As a result, an unprecedented influx of discarded face masks is ending up in the environment. This review paper delves into face masks in the environment using the DPSIR (driving forces, pressures, states, impacts, and responses) framework to simplify and communicate the environmental indicators. Firstly, the historical, and briefly the economic trajectory of face masks are discussed. Secondly, the main driving forces of face masks use with an emphasis on public health are explored. Then, the pressures exerted by efforts to fulfill the human needs (driving forces) are investigated. In turn, the state of the environment due to the influx of masks along with the impacts are examined. Furthermore, the upstream, and downstream societal responses to mitigate the environmental damages of the driving forces, pressures, states, and impacts are reviewed. In summary, it has been shown from this review that the COVID-19 pandemic has been causing a surge in face mask usage, which translates to face masks pollution in both terrestrial and aquatic environments. This implies proper usage and disposal of face masks is paramount to the quality of human health and the environment, respectively. Moreover, further research on eco-friendly face masks is indispensable to mitigating the environmental damages occurring due to the mass use of surgical masks worldwide.

Pyrolysis Combined with the Dry Reforming of Waste Plastics as a Potential Method for Resource Recovery—A Review of Process Parameters and Catalysts

Emissions of greenhouse gases and growing amounts of waste plastic are serious environmental threats that need urgent attention. The current methods dedicated to waste plastic recycling are still insufficient and it is necessary to search for new technologies for waste plastic management. The pyrolysis-catalytic dry reforming (PCDR) of waste plastic is a promising pro-environmental way employed for the reduction of both CO2 and waste plastic remains. PCDR allows for resource recovery, converting carbon dioxide and waste plastics into synthetic gas. The development and optimization of this technology for the high yield of high-quality synthesis gas generation requires the full understanding of the complex influence of the process parameters on efficiency and selectivity. In this regard, this review summarizes the recent findings in the field. The effect of process parameters as well as the type of catalyst and feedstock are reviewed and discussed.

Waste surgical masks to fuels via thermochemical co-processing with waste motor oil and biomass

In this work, the co-processing of waste surgical masks, waste motor oil, and biomass was investigated to reduce the environmental impacts of the increasing medical-derived plastic pollution as well as to elucidate its effect on the production of chemicals . The results showed high yields towards an oily product with an interesting hydrocarbon content in the diesel range. Furthermore, although the initial waste motor oil had a high sulfur content, the oily products showed a low sulfur content, that was logically distributed in the solid and gas phases. In addition, all oily products presented HHVs ​​higher than 44 MJ/Kg, with cetane indices, densities, and viscosities lower than those of petroleum-derived diesel. This work could impact on the management of waste surgical masks and the joint recovery of everyday waste towards high value-added products.

Low-Temperature Thermal Degradation of Disinfected COVID-19 Non-Woven Polypropylene-Based Isolation Gown Wastes into Carbonaceous Char

Yields of carbonaceous char with a high surface area were enhanced by decreasing the temperature to improve the conversion of hazardous plastic polypropylene (PP), the major component in abundantly used isolation gowns. This study applied pyrolysis with different low pyrolytic temperatures to convert disinfected PP-based isolation gown waste (PP-IG) into an optimised amount of char yields. A batch reactor with a horizontal furnace was used to mediate the thermal decomposition of PP-IG. Enhanced surface area and porosity value of PP-IG derived char were obtained via an optimised slow pyrolysis approach. The results showed that the amount of yielded char was inversely proportional to the temperature. This process relied heavily on the process parameters, especially pyrolytic temperature. Additionally, as the heating rate decreased, as well as longer isothermal residence time, the char yields were increased. Optimised temperature for maximum char yields was recorded. The enhanced SBET values for the char and its pore volume were collected, ~24 m2 g-1 and ~0.08 cm3 g-1, respectively. The char obtained at higher temperatures display higher volatilisation and carbonisation. These findings are beneficial for the utilisation of this pyrolysis model in plastic waste management and conversion of PP-IG waste into char for further activated carbon and fuel briquettes applications, with the enhanced char yields, amidst the COVID-19 pandemic.

Development of Kenaf Biochar in Engineering and Agricultural Applications

The aim of this review is to investigate the recent development of kenaf derived biochar and its composites in various engineering and agricultural applications including nanostructure catalysts and polymer composites as kenaf biochar and activated carbon are mainly used as material adsorbents and soil amendments. A systematic review on the effect of process parameters of thermal decomposition, pyrolysis towards the production of desired biochar, therefore, is in crucial needs. Based on existing literature, the properties and production of kenaf biomass and resultant biochar are discussed in this paper. This analysis focuses on the unique characteristics of kenaf crops and the resulting biochar, which has a surprisingly large surface area and increased pore volume, to explain their prospective applications, whether in environmental utilization or engineering applications. Range of optimum surface areas for kenaf biochar are around 800–1000 m²/g where they show high adsorption properties. Whereas, the pore volume of activated carbon usually exceeds 1 cm³/g. Recent developments in engineered kenaf biochar technology and its future directions for research and development are also discussed.

Determination of the Tensile Properties and Biodegradability of Cornstarch-Based Biopolymers Plasticized with Sorbitol and Glycerol

In this study, the effects of various quantities of sorbitol and glycerol plasticizers (0%, 30%, 45%, and 60%) on cornstarch-based film were examined to develop a novel polymer for usage with biodegradable materials. The film was prepared using the casting process. According to the test findings, the application of the plasticizer concentrations affected the thickness, moisture content, and water absorption of the film. When plasticizer concentrations were increased to 60%, the tensile stress and Young’s modulus of plasticized films dropped regardless of plasticizer type. However, the thin film with addition of 30% sorbitol plasticizer demonstrated a steady value of Young’s modulus (60.17 MPa) with an increase in tensile strength (13.61 MPa) of 46%, while the lowest combination of tensile strength and Young’s modulus is the film that was plasticized with 60% glycerol, with 2.33 MPa and 16.23 MPa, respectively. In summary, the properties and performance of cornstarch-based film were greatly influenced by plasticizer types and concentrations. The finest set of features in this research appeared in the film plasticized with 30% sorbitol, which achieved the best mechanical properties for food packaging applications.

Critical Review of Natural Fiber Reinforced Hybrid Composites: Processing, Properties, Applications and Cost

Increasing scientific interest has occurred concerning the utilization of natural fiber-enhanced hybrid composites that incorporate one or more types of natural enhancement. Annual natural fiber production is estimated to be 1,783,965 × 103 tons/year. Extensive studies have been conducted in the domains of natural/synthetic as well as natural/natural hybrid composites. As synthetic fibers have better rigidity and strength than natural fibers, natural/synthetic hybrid composites have superior qualities via hybridization compared to natural composites in fibers. In general, natural fiber compounds have lower characteristics, limiting the use of natural composites reinforced by fiber. Significant effort was spent in enhancing the mechanical characteristics of this group of materials to increase their strengths and applications, especially via the hybridization process, by manipulating the characteristics of fiber-reinforced composite materials. Current studies concentrate on enhancing the understanding of natural fiber-matrix adhesion, enhancing processing methods, and natural fiber compatibility. The optimal and resilient conceptions have also been addressed due to the inherently more significant variabilities. Moreover, much research has tackled natural fiber reinforced hybrid composite costs. In addition, this review article aims to offer a review of the variables that lead to the mechanical and structural failure of natural fiber reinforced polymer composites, as well as an overview of the details and costings of the composites.

Development and Characterization of Cornstarch-Based Bioplastics Packaging Film Using a Combination of Different Plasticizers

This work aims to develop cornstarch (CS) based films using fructose (F), glycerol (G), and their combination (FG) as plasticizers with different ratios for food packaging applications. The findings showed that F-plasticized film had the lowest moisture content, highest crystallinity among all films, and exhibited the highest tensile strength and thermostability. In contrast, G-plasticized films showed the lowest density and water absorption with less crystallinity compared to the control and the other plasticized film. In addition, SEM results indicated that FG-plasticized films had a relatively smoother and more coherent surface among the tested films. The findings have also shown that varying the concentration of the plasticizers significantly affected the different properties of the plasticized films. Therefore, the selection of a suitable plasticizer at an appropriate concentration may significantly optimize film properties to promote the utilization of CS films for food packaging applications.