Mixed Waste Research Articles

Review on solid wastes incorporated cementitious material using 3D concrete printing technology

The substitution of cement, natural sand, and synthetic fibers in concrete with solid wastes substantially reduces CO2 emissions. Incorporating solid wastes into 3D printed concrete, which reduces CO2 emissions from labor and formwork, can achieve innovative low-carbon construction materials. However, the previous studies lack a comprehensive review on the inherent characteristics of various solid wastes and their impacts on the printability, mechanical performance, and functionality of 3D printed concrete. This paper reviews the present state of research and introduces feasible methods for the sustainable use of solid wastes in 3D printed concrete. Numerous types of solid wastes are investigated comprising their benefits, shortages, and fit dose to guide in selecting the optimal solid waste to enhance the performance of printed concrete. Additionally, the printability, functionality, and mechanical strength of printed concrete with solid waste addition are quantified and summarized. The preliminary exploration to achieve a balance between multi-functionality and mechanical properties using mixed solid wastes is conducted for 3D concrete printing. Finally, machine learning, broadening raw material sources, automated monitoring systems, multi-functionalized composite, and BIM are proposed to address current challenges.

A comprehensive decision-making approach for the application of biochar in agriculture to enhance water security: A GIS-AHP based approach

In the context of climate change, biochar application is a promising approach to mitigate the adverse effects of climate change on agriculture. However, the selection of suitable biochar produced from food waste and optimization of loading rates to improve soil quality remains a significant challenge. This study explores the potential impact of biochar application using an integrated analytical hierarchy process (AHP) and geographical information system (GIS) approach. The study first aims to develop an AHP model to prioritize the appropriate biochar source and dosage for soil amendment. The different biochar sources considered are: peas pod shell, pistachio shell, and mixed vegetable waste. The AHP design evaluated the weight percentage of different types of biochar amendments ranging from 0 % to 8 % based on soil quality, nutrient analysis and water retention capacity. Furthermore, an integrated spatial analysis case study was conducted for fodder farms across Qatar using GIS mapping with seasonal variation to evaluate the impact of biochar on water management. According to the AHP decision making, 2 % mixed vegetable waste biochar achieved the goal with the highest priority score, with a value of 0.29, followed by 2 % pistachio shell biochar with a score of 0.22. This is attributed to the high water retention rate determined from the experimental study. The 2% biochar amendment retained 20 % more water compared to the 0 % biochar. Results from the GIS mapping identified priority areas for improving water retention and soil quality. The evapotranspiration maps for winter and summer generated using GIS provide valuable insights into the spatial disributio of biochar application across Qatar fodder farms. The outcomes may encourage policymakers and stakeholders to consider valorizing food waste into biochar.

Production of cycloalkane-rich fuel by vacuum pyrolysis of mixed waste plastics using combined titanium and aluminum oxide: a preliminary investigation

The mitigation of plastic pollution constitutes one of the major challenges worldwide. Innovative research approaches have been solicited to improve the properties of fuel derived from plastic pyrolysis. The present study looks at the effect on the chemical composition of pyrolysis oil of the application in situ of a mixed metal oxide of titanium and aluminum in vacuum pyrolysis of mixed waste polyethylene, polypropylene, and polyethylene terephthalate. The experiment was performed at process parameters of 250 °C temperature, 79.9 Kpa vacuum pressure, and 1:10 catalyst-to-feedstock ratio, first without the mixed metal oxide (parent reaction) and then with the mixed metal oxide (modified reaction). The results showed that the presence of combined titanium and aluminum oxides in the reaction medium accounted for the presence of alkyl-substituted cycloalkanes at an area% of 33.97% in the liquid product, and a calorific value of 11,950 cal/gm was reported for the modified reaction. The parent reaction produced higher liquid and gaseous yields of 28.3% and 43.1% respectively while the modified reaction produced a greater percentage of char (23.8%) and residual wax(36.0%). The fuel properties of the liquid products obtained were equally determined.

Optimal Machine Learning Model to Predict Demolition Waste Generation for a Circular Economy

A suitable waste-management strategy is crucial for a sustainable and efficient circular economy in the construction sector, and it requires precise data on the volume of demolition waste (DW) generated. Therefore, we developed an optimal machine learning model to forecast the quantity of recycling and landfill waste based on the characteristics of DW. We constructed a dataset comprising information on the characteristics of 150 buildings, demolition equipment utilized, and volume of five waste types generated (i.e., recyclable mineral, recyclable combustible, landfill specified, landfill mix waste, and recyclable minerals). We applied an artificial neural network, decision tree, gradient boosting machine, k-nearest neighbors, linear regression, random forest, and support vector regression. Further, we derived the optimal model through data preprocessing, input variable selection, and hyperparameter tuning. In both the validation and test phases, the “recyclable mineral waste” and “recyclable combustible waste” models achieved accuracies (R2) of 0.987 and 0.972, respectively. The “recyclable metals” and “landfill specified waste” models achieved accuracies (R2) of 0.953 and 0.858 or higher, respectively. Moreover, the “landfill mix waste” model exhibited an accuracy of 0.984 or higher. This study confirmed through Shapley Additive exPlanations analysis that the floor area is the most important input variable in the four models (i.e., recyclable mineral waste, recyclable combustible waste, recyclable metals, and landfill mix waste). Additionally, the type of equipment employed in demolition emerged as another crucial input variable impacting the volume of recycling and landfill waste generated. The results of this study can provide more detailed information on the generation of recycling and landfill waste. The developed model can provide precise data on waste management, thereby facilitating the decision-making process for industry professionals.

High-temperature corrosion mechanisms of a Ni-based alloy in simulated multi-source organic waste co-incineration environments

Due to the new trend of co-incinerating municipal solid waste (MSW) with sewage sludge, medical waste, or industrial organic waste to attain a “waste-free” status, mixing of multi-source organic wastes (MSOW) increases the complexity of solid waste, which fluctuates the composition of corrosive species in the boiler. The fluctuation of corrosive species alters the alkali metals/S/Cl ratios and increases the uncertainties of high-temperature corrosion of boiler key components. The corrosion behaviors and mechanisms in varying compositions of corrosive species are complex and remain elusive. To investigate the corrosion characteristics during the co-incineration of MSOW, this study examined the corrosion mechanisms of a nickel-based Ni59.08Cr24.31Al10.74W5.3B0.57 alloy in simulated co-incineration environments of MSOW. The environment contained either HCl, NaCl, or SO2 in wet oxygen at 600 °C. For each case experiment, the maximum possible value of each corrosive species expected in the actual incinerator and/or its absence was considered. HCl of either 0 or 1500 ppm, SO2 of 0 or 300 ppm, and NaCl of 0 or 50 mg/cm2 were systematically used in each experiment. The influence of each corrosive condition on the corrosion of the alloy was evaluated by mass gain measurements, and the corrosion mechanisms were elucidated through SEM, EDS mapping, XRD, XPS analyses, and thermodynamic equilibrium calculations. The results revealed that NaCl salt and HCl gas in wet oxygen have complementary effects, which accelerated the corrosion of alloy, reaching ∼ 65.6 mg/cm2 over one week. HCl enhanced the corrosion by affecting the chemical reactions that regenerated NaCl, which participated in prolonged corrosion processes. SO2 reduced the mass gain of the alloy to 38.4 mg/cm2. SO2 participated in the sulfation of NaCl, forming a mixed layer of Na2SO4 and (Al/Cr)2O3, reducing the mass gain by 1.71 times. In the environment without NaCl, SO2 helped in the formation of a protective oxide layer, which prevented HCl from reaching the alloy, reducing the corrosion impact by 23.5 times.

Pengaruh Penambahan Asbuton LGA 50/30 pada Campuran AC-WC dengan Inovasi Limbah Styrofoam

Indonesia’s road infrastructure requires 1.2 million tons of asphalt annually, but Pertamina can only supply 600,000 tons. This deficit compels the government and related stakeholders to seek alternatives to meet national asphalt needs and maintain road quality. This study aims to analyze the effects of adding Asbuton LGA 50/30 to Asphalt Concrete Wearing Course (AC-WC) with an innovative use of styrofoam waste. Experimental research was conducted to evaluate Marshall characteristics, including VMA (Void in Mineral Aggregate), VIM (Void in Mix), stability, VFA (Void Filled with Asphalt), and Marshall Quotient (MQ). Five styrofoam waste mix variations were tested at 2%, 4%, 6%, 8%, and 10% levels. For the 8% Asbuton mix, the highest stability was observed with 10% styrofoam, yielding a stability value of 2032.16 kg, VMA of 16.63%, VFA of 78.28%, VIM of 3.61%, flow of 2.45 mm, and MQ of 830.33 kg/mm. For the 9% Asbuton mix, the highest stability was achieved with 2% styrofoam, resulting in a stability value of 1882.35 kg, VMA of 16.21%, VFA of 80.17%, VIM of 3.24%, flow of 2.57 mm, and MQ of 735.72 kg/mm. The 10% and 2% styrofoam variations proved to be the most effective for AC-WC asphalt mixtures, as their Marshall values met the 2018 Bina Marga General Specifications, indicating that these styrofoam waste additions are optimal for AC-WC asphalt mixtures.

Comparative analysis of additive decomposition using one-dimensional and two–dimensional gas chromatography: Part II - Irgafos 168 and zinc stearate

Plastic production has experienced a significant increase in the last sixty years due to its cost-efficiency and adaptable characteristics, leading to the extensive use of additives to improve its performance and longevity. Due to the high demand for plastic, plastic waste production has increased, contaminating the environment and living beings by leaching additives, among other substances. Pyrolysis stands out among recycling techniques because it can handle mixed polymer waste feedstock. However, understanding the pyrolyzates distribution of additives is fundamental to assessing pyrolysis process of plastic waste. This study investigated the pyrolysis product distributions of two commonly used antioxidants, namely, Irgafos 168 and zinc stearate (ZnSt), using one-dimensional gas chromatography equipped with a quadruple mass spectrometer (GC–MS) and two-dimensional gas chromatography coupled to flame ionization detector and time–of–flight mass spectrometer (GC×GC–FID/TOF–MS). While GC separation technique provided limited information on product distribution, GC×GC offered enhanced resolution and identification of the decomposition products. In the pyrolysis of Irgafos 168 at 550 °C, GC identified 18 products, while GC×GC identified 198 products, representing an increase of approximately 11-fold. Similarly, for ZnSt, GC identified 67 products, while GC×GC identified 434 products, representing a 6-fold increase. GC×GC identified decomposition products from 15 different chemical classes for Irgafos 168 and 16 chemical classes for ZnSt, compared to 4 and 11 chemical classes identified by GC, respectively. Phenols and their derivatives were the major chemical class in the decomposition products of Irgafos 168 with a yield of 9.51 wt.%. In contrast, olefinic products were the dominant ones for ZnSt, with a yield of 9.73 wt.%. The major decomposition product of Irgafos 168 and ZnSt was 2‑tert‑butyl‑methylphenol (C11H16O) and C6 olefin (C6H12) with yields of 3.88 wt.%, and 1.13 wt.%, respectively. Utilizing the GC×GC separation method improved the ability to identify decomposition products, which can ultimately lead to a better understanding of antioxidant degradation that occurs during the pyrolysis process. GC×GC also provided thorough characterization of minor and co-eluted products along with major antioxidant degradation products. Additionally, the decomposition product distribution of Irgafos 168 and ZnSt was also compared with the primary antioxidants, Irganox 1010, Irganox 1076, and BHT, studied in part 1. The analysis indicated that the olefinic chemical class was the predominant one in Irganox 1010, Irganox 1076, and ZnSt, while ketones were the major chemical class in the decomposition of BHT and phenolics had the highest yield in Irgafos 168.

Catalytic Approaches to Tackle Mixed Plastic Waste Challenges: A Review.

Plastics are widely used materials in our daily lives and various industries due to their affordability and versatility. The massive production of plastic waste, however, has recently emerged as a pressing environmental concern across all media. To address this, emerging technologies are being explored for the sustainable valorization of postconsumer plastic wastes including thermochemical, physical, and catalytic processes aimed at transforming them into higher value-added products. However, the chemical recycling of mixed plastic wastes poses a formidable challenge due to the diverse array of monomers and catalyst systems involved, each employing distinct mechanisms. Complicating matters further is that contaminants reduce catalytic efficacy, requiring rigorous and labor-intensive separation and purification processes to extract individual plastic streams from practical plastic waste mixtures. Consequently, the majority of such mixtures often end up in incineration and landfills, perpetuating environmental and societal challenges, such as leachate, carbon dioxide emissions, and other air pollutants. This review will introduce current technical developments available for recycling practical plastic waste mixtures through catalytic processes. The current challenges in process performance, low selectivity of the desired products, and catalyst deactivation from the catalysis of plastic waste mixtures are also discussed. Promising approaches to overcome the problems are suggested in future research directions.

KOMPETENSI DALAM PENGOLAHAN LIMBAH RUMAH TANGGA MENJADI PUPUK ORAGNIK DI KOTA KENDARI

The quantity of waste generated by households is on the rise, yet the capacity of Kendari City to manage existing waste is diminishing. In order to facilitate the implementation of suitable measures for the processing of waste, it is essential to ensure that the community possesses the requisite competence. The objective of this study is to evaluate the competence of the processing of household waste into organic fertilizer in Kendari City. This study employs a qualitative research methodology. The research informants were selected using the purposive sampling technique, resulting in a total of one informant. Data were collected through observation, interviews, and document analysis with the assistance of interview guides created for this purpose. The data were analyzed qualitatively using the theory proposed by Miles & Huberman, namely data reduction, data presentation, and conclusion drawing. The findings indicate that competence in processing household waste into organic fertilizer in Kendari City is evident in the knowledge, attitudes, and skills possessed by the community in managing household waste into a useful and beneficial product such as organic fertilizer (search and solid). Effective waste management can facilitate a comprehensive and efficient approach that can positively impact the community in terms of health and the environment. Furthermore, it has the potential to serve as a source of income for the community. The processing of organic waste into organic fertilizer comprises six stages: collection and chopping of organic waste, mixing of organic waste into a composter, addition of MOL, closure of the composter, addition of organic waste and a second MOL, and sitting/fermentation of organic waste for 7 to 12 days.

Unveiling the abundance and potential impacts of microplastic contamination in commercial organic fertilizers/compost produced from different solid waste.

This study comprehensively investigated the abundance, morphologies, and polymer types of plastics, larger (1-5mm) and smaller (< 1mm) microplastics (MPs), in organic fertilizers using spectroscopic and microscopic methods. MPs abundance varied depending on the type of waste employed. MPs were detected in 80% of the investigated compost samples, while macro/meso plastics were found in only four samples. Compost from mixed municipal solid waste exhibited the highest MPs contamination (23100 ± 3615 items/kg dry weight), whereas compost produced from canteen waste had the lowest contamination (100 ± 65 items/kg dry weight). Smaller MPs were dominant in all samples. The estimated loads of MPs introduced into agricultural soil exceeded the previous studies. Common morphologies observed were sheet, film, fragment, and fiber, while dominant polymer types were polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polystyrene (PS). Heavy metals, including Cr, Cu, Ni, and Pb, were identified in association with MPs. Results indicate that the utilization of appropriate waste for composting and upgrading fertilizer regulations is crucial to protect the environment and human health from smaller MPs.

Revolutionizing waste from household plastics to eco-friendly diesel alternatives through catalytic degradation with biogas utilization

The study tackled the pressing environmental issue of managing both biodegradable and non-biodegradable household plastic waste, aiming to convert this waste into valuable hydrocarbons, thus addressing critical concerns over plastic pollution and the quest for renewable energy sources. In the context of escalating environmental degradation and the urgent need for sustainable alternatives to fossil fuels, the ability to transform various forms of waste into energy presents a significant stride towards ecological and energy sustainability. Utilizing an innovative methodology, the research employed catalytic degradation of mixed plastic waste, leveraging fly ash as a catalyst and biogas produced from a combination of cow dung and kitchen waste as a renewable and sustainable heat source. This process was fine-tuned across several catalyst-to-polymer (cat/pol) ratios, specifically 0.10, 0.15, and 0.20, with detailed documentation of the degradation temperatures and yields of liquid and gaseous hydrocarbons for each 1 kg batch of plastic waste. Notably, at a cat/pol ratio of 0.20, a remarkable 100% conversion rate was achieved, highlighting the efficiency of this method. Following this, the resultant oil was segmented based on boiling points for further analysis and evaluation of its utility as a diesel fuel substitute. Significant findings include the highest liquid hydrocarbon yield of 65.1% at 378 °C, achieved with the 0.20 cat/pol ratio. Moreover, fractions boiling above 100 °C were identified to possess superior heating values and cetane numbers compared to conventional diesel, particularly the fraction boiling at 100 °C–150 °C (C2), which demonstrated optimal performance and combustion qualities. This fraction achieved a maximum brake thermal efficiency of 32.92%, exhibited low smoke density and hydrocarbon emissions of 48 HSU and 32ppm, but it also resulted in a significant increase in NOx emission. Among all the fractions, diesel C2 was observed to be the best in terms of performance & combustion and was lower in emission. The conclusions drawn underscore the method’s potential to mitigate plastic pollution and reduce fossil fuel reliance by converting both biodegradable and non-biodegradable waste into useful energy. This study’s novelty lies in its comprehensive approach to waste management and energy recovery, significantly advancing over previous literature by achieving a 100% conversion rate at a specific cat/pol ratio and optimizing the output for use as a diesel alternative. It stands out by producing a fraction with both high efficiency and lower emissions, offering a scalable, sustainable solution to waste management challenges and paving the way for future innovations in sustainable energy production.

Comparative assessment of biochar produced from waste biomass in laboratory furnace and industrial screw reactor systems

Biochar is rapidly gaining traction as a commercially viable carbon dioxide removal (CDR) technology that can be applied globally at various scales. However, the vast majority of published research studies have involved laboratory experiments conducted in an inert environment under well-controlled conditions of heating rate, maximum temperature and residence time. To expand the biochar industry within the next decade as a CDR platform, there is a need to understand differences between biochar produced under “ideal” laboratory conditions versus those generated using the same feedstocks in continuous, industrial scale systems. In the present work, biochar was produced from widely available organic waste feedstocks, including mixed cafeteria food waste, blended coffee grounds and chaff, grape pomace and wood pellets, using both a laboratory furnace operated in a nitrogen environment, and a continuously operated commercial system capable of processing up to ∼1 t/day of dry feedstock. High quality biochar (H:C < 0.7) was obtained for all feedstocks converted by both systems, however high variability in volatiles and decomposition rates was observed in the thermogravimetric analysis (TGA) results for industrial scale biochar. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) showed similar morphologies and surface chemistries in both laboratory and industrial scale samples, in agreement with reported literature data. Based on this initial comparative assessment, we conclude that commercially available thermochemical systems have potential as localized organic waste valorization technologies to produce high quality biochar. We identified important control variables that have the greatest effect on the resulting biochar. Despite the reported differences between biochar materials derived from the same feedstock, key properties critical for soil amendment and remediation applications (i.e., H:C, surface area, %Corg, etc.) are reasonably consistent between laboratory and continuously fed equipment typical of commercial-scale systems. Thus, biochar materials obtained from well-controlled laboratory experiments conducted in a pure nitrogen atmosphere can be reasonably representative of biochar produced from the same feedstocks using industrial scale equipment.

Material Recycling of Plastics—A Challenge for Sustainability

The complexity of plastic polymers and even more so of additives has increased enormously in recent years. This makes the material recycling of plastic waste considerably more difficult, especially in the case of mixed plastic waste. Some additives have now been strictly regulated or even completely banned for good reasons (‘legacy additives’). Material or mechanical recycling generally uses old plastics that still contain these substances. Consequently, products that are manufactured using such recyclates are contaminated with these harmful substances. This poses a major challenge for sustainability, as there is a conflict of objectives between protecting the health of consumers, especially vulnerable groups, conserving resources and recycling, keeping material cycles ‘clean’ and destroying pollutants, and transporting them to a safe final sink. With regard to the first objective, we recommend avoiding the use of contaminated recyclates for products with intensive contact with consumers (‘contact-sensitive products’) until further notice. We also show that the climate policy challenges for the plastics (and chemical) industry necessitate defossilization (‘feedstock change’). This turnaround can only succeed if solely closed-loop recycling takes place in the future; recyclates should primarily replace virgin plastics. For material or mechanical recycling, this means that this can only work if used plastics with a high degree of homogeneity and known formulation are collected separately, as is already the case today with PET bottles. The objective of this article is to illustrate the increasing complexity of plastic polymers and additives, especially legacy additives, which will force a legislative readjustment of todays’ material recycling.

Mathematical Modeling Comparison for the Temperature Distribution Results in the Three Types of Blades Agricultural Waste Mixing Agitator for Forming Materials

Mathematical Modeling Comparison for the Temperature Distribution Results in the Three Types of Blades Agricultural Waste Mixing Agitator for Forming Materials

Isolation And Identification of Bacteria Associated With Bioelectricity Generation From Fruit Wastes And Gutter Sludge Using Microbial Fuel Cells (MFC) In Kano Metropolis, Kano State, Nigeria

Bioelectricity generation is another environmentally friendly mean of waste management, commonly carried out using microbial fuel cell (MFC) technology. The present work aims to generate bioelectricity from the fruit wastes using microbial fuel cells (MFC) technology and to isolate and identify bacteria during bioelectricity production. Fruit samples from different fruit wastes of banana, lemon, orange, water melon and pawpaw were collected from Na’ibawa-Yanlemo fruit market’s dump site in Kano metropolis, Kano State Nigeria. Physicochemical parameters such as biological oxygen demand (BOD), chemical oxygen demand (COD), total carbon (TC), total nitrogen (TN), organic matter (OM), Temperature and pH of slurries of individual and mixed fruit wastes were determined. Biochemical tests such as voges-proskauer test, oxidase test, catalase test, citrate test and sugar fermentation (TSI) test was also carried out using standard procedures. Generation of bioelectricity was monitored and recorded within a constructed seven dual chambered microbial fuel cells (MFCs) with wasted fruit as readily available materials. Current, current density, power and power density produced from different waste samples for twenty days was also recorded as bioelectricity generated from microbial fuel cells. Bacterial counts at the beginning and end of bioelectricity generation was also recorded from different fruits waste samples for microbial fuel cells (MFCs). The result of pH mean value of slurries of individual fruits is recorded to be all acidic with lemon having the highest acidity recorded as 3.45±0.62. The pH mean value of the mixed fruit was recorded as7.1±0.23. Waste pawpaw fruit had 6±0.62 % the percentage of organic matter among all the individual waste fruits while the mixed fruit combined had 10±0.62 % mean value of percentage organic matter (OM). Two (2) bacterial genera were biochemically identified as Klebsiella pneumoniae and Esherichia coli. The highest generation of voltage (mV) from microbial fuel cells was achieved from gutter, mixed fruit and orange as 650, 400 and 390 mV respectively. The peak highest current produced was achieved from orange waste samples as 0.7mA/m2 at day fourteen. Waste lemon had the highest colony count among all the fruits at the beginning and end of the bioelectricity generation of 2.2×103 and 4.12×102 respectively. Mixed fruits had the colony count of 2.10×105 and 7.20×103 at the beginning and end respectively.

Design and Implementation of a Biogas Pilot Plant for Bioaugmentation Strategies in a rural municipality

The transition towards renewable energy sources is imperative for achieving sustainability and mitigating climate change impacts. Among various renewable energies, biogas stands out for its dual role in waste management and energy production. This study introduces the design and implementation of a biogas pilot plant aimed at exploring bioaugmentation strategies to enhance biogas yield and quality. The pilot plant, located at Aras de los Olmos, features two independent 3.4m3 digesters, allowing for parallel comparison between standard anaerobic digestion and digestion with microbial enhancements. The plant is equipped with monitoring and control systems for precise regulation of environmental conditions, such as temperature, and for real-time measurement of biogas composition. Some initial experiments using a mix of agricultural wastes demonstrated the plant's capability to adapt to varied feedstock. Despite suboptimal temperature conditions, preliminary results indicated a high methane content, suggesting significant potential for bioaugmentation to improve biogas production efficiency. The study highlights the importance of controlled environmental conditions and introduces a novel bioaugmented digestion approach using selected microbial consortia. This research contributes to the broader goal of enhancing biogas technology's efficiency and sustainability, offering insights into the practical application of bioaugmentation in biogas production.

Closed-Loop Recycling of Mixed Plastics of Polyester and CO2-Based Polycarbonate to a Single Monomer.

Physical blending is an effective strategy for tailoring polymeric materials to specific application requirements. However, physically blended mixed plastics waste adds additional barriers in mechanical or chemical recycling. This difficulty arises from the intricate requirement for meticulous sorting and separation of the various polymers in the inherent incompatibility of mixed polymers during recycling. To overcome this impediment, this work furthers the emerging single-monomer - multiple-materials approach through the design of a bifunctional monomer that can not only orthogonally polymerize into two different types of polymers - specifically lactone-based polyester and CO2-based polycarbonate - but the resultant polymers and their mixture can also be depolymerized back to the single, original monomer when facilitated by catalysis. Specifically, the lactone/epoxide hybrid bifunctional monomer (BiLO) undergoes ring-opening polymerization through the lactone manifold to produce polyester, PE(BiLO), and is also applied to ring-opening copolymerization with CO2, via the epoxide manifold, to yield polycarbonate, PC(BiLO). Remarkably, a one-pot recycling process of a BiLO-derived PE/PC blend back to the constituent monomer BiLO in >99 % selectivity was achieved with a superbase catalyst at 150 °C, thereby effectively obviating the requirement for sorting and separation typically required for recycling of mixed polymers.

Closed‐Loop Recycling of Mixed Plastics of Polyester and CO2‐Based Polycarbonate to a Single Monomer

AbstractPhysical blending is an effective strategy for tailoring polymeric materials to specific application requirements. However, physically blended mixed plastics waste adds additional barriers in mechanical or chemical recycling. This difficulty arises from the intricate requirement for meticulous sorting and separation of the various polymers in the inherent incompatibility of mixed polymers during recycling. To overcome this impediment, this work furthers the emerging single‐monomer – multiple‐materials approach through the design of a bifunctional monomer that can not only orthogonally polymerize into two different types of polymers – specifically lactone‐based polyester and CO2‐based polycarbonate – but the resultant polymers and their mixture can also be depolymerized back to the single, original monomer when facilitated by catalysis. Specifically, the lactone/epoxide hybrid bifunctional monomer (BiLO) undergoes ring‐opening polymerization through the lactone manifold to produce polyester, PE(BiLO), and is also applied to ring‐opening copolymerization with CO2, via the epoxide manifold, to yield polycarbonate, PC(BiLO). Remarkably, a one‐pot recycling process of a BiLO‐derived PE/PC blend back to the constituent monomer BiLO in &gt;99 % selectivity was achieved with a superbase catalyst at 150 °C, thereby effectively obviating the requirement for sorting and separation typically required for recycling of mixed polymers.

Assessment of the Quantities of Non-Targeted Materials (Impurities) in Recycled Plastic Packaging Waste to Comply with EU Regulations and Sustainable Waste Management

Plastic packaging waste (PPW) can be considered as solid waste with harmful effects on the environment or as a material with recycling potential in terms of sustainable development in a circular economy. Knowing the amount of PPW generated is very important as it is related to the availability of this material for recycling and determines the actual recycling rate (denominator of a fraction). PPW is very heterogeneous and contains a certain number of impurities (e.g., product residues, direct printing, glue, labels, plastic sleeves, cap, etc.). According to EU law, an annual report (for the data in 2021) on the masses of both the PPW actually recycled (PPWR) (“targeted materials”) and impurities (“non-targeted materials”) must be prepared and submitted to the European Commission. The PPWR is used for the calculation of the recycling rate (the numerator in a fraction). The impurities should be considered for the calculation of own resources (national contributions to the general EU budget based on the uniform call rate of 0.80/kg of non-recycled PPW). To date, the Council of the EU has not proposed a method for calculating these amounts, so they have only been estimated. The present study (the first of its kind in Poland) aimed to estimate the number of impurities in PPW and the actual amount of PPWR at the calculation point using a method accepted by the EU. In the installations, PPW (plastic packaging (15 01 02), multi-material packaging (15 01 05) and mixed packaging waste (15 01 06)) is recycled together with other plastic waste (plastic (16 01 19), plastic (17 02 03), plastic and rubber (19 12 04), and plastics (20 01 39)). It was assumed that the proportions of the mass of individual types of PPW in the total mass of plastic waste processed in the installation were proportional to the mass of impurities in these individual types of PPW. It was found that the average percentage of impurities in PPW was 4.40–6.90%, which seems to be relatively low. However, this means that, when calculating the PPWR, the mass of impurities should be subtracted from the mass of PPW entering the recycling process. As a result, the mass of PPWR at the calculation point in 2021 in Poland was almost 30,000 tonnes lower than the original mass entering the installation. Thus, applying the uniform call rate to the weight of impurities in the PPW increases Poland’s own resources by approx. 24 million euros.

Energy Demand for Pyrolysis of Mixed Thermoplastics and Waste Plastics in Chemical Recycling: Model Prediction and Pilot-Scale Validation

Energy Demand for Pyrolysis of Mixed Thermoplastics and Waste Plastics in Chemical Recycling: Model Prediction and Pilot-Scale Validation