Mixed Stream Research Articles

Characterization of the Municipal Plastic and Multilayer Packaging Waste in Three Cities of the Baltic States

The composition of plastic and multilayer packaging waste was assessed in the mixed municipal solid waste (MSW) streams of the Kaunas (Lithuania), Daugavpils (Latvia) and Tallinn (Estonia) municipalities. For the analysis of samples in the mixed MSW streams, the authors used manual sorting and a visual recognition method. Composition analysis of plastic and multilayer packaging waste from separately collected waste of multi-family and single-family households was performed in the Kaunas and Tallinn municipalities. For the analysis of samples in the separately collected waste streams, the research group combined manual sorting and near-infrared (NIR) spectroscopy methods. The findings reveal that the percentage distribution of plastic and multilayer packaging waste within the municipal solid waste (MSW) stream is relatively consistent across the municipalities of Kaunas, Daugavpils and Tallinn, comprising 40.16%, 36.83% and 35.09%, respectively. However, a notable variation emerges when examining separately collected plastic and multilayer packaging waste streams. In this category, the proportion of plastic and multilayer packaging within the total separately collected packaging waste stream ranges from 62.05% to 74.7% for multi-family residential buildings and from 44.66% to 56.89% for single-family residential buildings. The authors provided further insights for the enhanced recycling potential of different plastic materials through improved sorting.

Role of Ozone Microbubbles in Decoloration of a Mixture of Rhodamine B and Methylene Blue

ABSTRACT This report examines the role of ozone gas microbubbles in the decoloration of a mixed dye stream (1:1 v/v methylene blue and rhodamine B). The use of microbubbles reduces decoloration time by approximately 2.5 times compared to traditional macrobubbles. Ozone microbubbles are generated using a high-speed homogenizer. Laboratory-scale experiments are conducted to investigate the effects of initial dye concentration, ozone dosage, and impeller speed on decoloration time. A linear increase in decoloration time is observed with increasing initial dye concentration, while ozone gas concentration (16–32 g/Nm3) shows no significant effect. Increasing the impeller speed up to 12,000 RPM reduces decoloration time, but beyond this point, no further reduction is observed. Kinetics of decoloration is reported for both constituent dyes. Second-order rate constants of 0.0164 and 0.079 L/mg·s are found to fit the experimental data for rhodamine B and methylene blue, respectively.

Classification of Automotive Aluminum Scrap into Cast and Wrought Alloys via Particle Size Analysis

AbstractThe Aluminum (Al) industry is currently faced with the challenge of significantly reducing the environmental impact of Al production. Secondary Al or Al produced from Al scrap offers a beneficial pathway to lowering the production carbon footprint and energy consumption while transitioning to a circular economy business model. However, mixing of Al scrap streams and introduction of impurity elements at end of life lead to “downcycling” of Al alloys. Downcycling of Al alloys has been the norm in the automotive recycling industry. Automotive Al scrap from auto shredders dubbed “Twitch,” is an amalgamation of different Al alloys, cast as well as wrought alloys. Twitch is traditionally downcycled to low-value Al alloys due to the complexities in separating the Twitch into various alloy families as well as difficulties in blending and producing high-value Al alloys from scrap. This paper provides a framework and an approach that uses size gating, mass, and image analysis to separate the wrought and cast alloys within the Twitch feedstock and provides a simpler and a cost-effective means of separation of the scrap stream. Graphical Abstract

Burning of municipal waste in household furnaces and the health of their owners

The aim of the study was to determine the scale of emission and airborne dispersion of selected pollutants (PM2.5, PM10, TVOC, HCHO) associated with the combustion of various types of municipal waste (MW), its mixed stream and separate fractions, in a household furnace, as compared to conventional (CF) and alternative (AF) fuels. We demonstrated that each type of fuel (AF, CF, AFw) combusted in a household furnace is a significant source of air pollutants, especially fine PM2.5 particles, whose concentrations exceeded the limit values (3.1–17.2 times for PM2.5 and 0.5–7.4 times for PM10). The combustion of MW in household furnaces generated higher levels of PM2.5 (up to 345 µg/m3) and PM10 (up to 369 µg/m3) than AF or CF, at the same time being a significant source of TVOC (up to 0.3 mg/m3) and HCHO (0.4 mg/m3). The analysis showed that according to the Polish and European classification, air quality (AQI) during the combustion of all the materials analyzed is very poor (n = 12) or extremely poor (n = 19). The combustion of such materials as polystyrene, rubber and upholstery foam in household furnaces generates drastically high health risk to local inhabitants. We found that the combustion of polystyrene generated the highest Cancer Risk (CR) values of 1.04E-01 (children) and 2.60E-02 (adults), exceeding the acceptable level multiple times (CR > 10–6). Inhalation exposure to very poor air quality can lead to health problems, such as disorders of the respiratory, cardiovascular and immune systems. Additional risk is posed by solid fuel combustion in rural areas, which may be a significant factor deteriorating the chemical condition of soils, especially those used for agricultural purposes.

Food well-being: a review of its conceptualization and measurement

PurposeThis study aimed to improve understanding of the phenomenon of food well-being (FWB) (conceptualization, measurement, antecedents and outcomes) so as to lead future empirical work on measurement, development and theory testing. The hope is to improve the societal benefits of FWB and sustainable food system transformation.Design/methodology/approachA domain-based systematic review of FWB was conducted using databases (Web of Science, ABI/INFORM, EBSCO and Scopus). The well-established theory, context, characteristics and methodology framework were used to structure the review.FindingsThis study synthesized conceptual definitions and measurements of consumer FWB from hedonic, eudemonistic and mixed research streams and a nomological network that distinguishes this construct from its antecedents and outcomes.Practical implicationsThis study provides recommendations for consumers, food designers, retailers and policymakers to improve FWB.Originality/valueThis study assessed the conceptualizations of FWB from hedonic, eudemonistic and mixed perspectives for conceptual clarity. It summarized ten measurement tools for FWB-allied concepts (Well-being Related to Food Questionnaires, Satisfaction with Food-Related Life Scale and World Health Organization-Five Well-Being Index), which revealed the need for novel measurement. This study developed a holistic nomological network of FWB by identifying the categories of antecedents (food-related, consumer-related and contextual factors) and outcomes (general well-being, life satisfaction and food consumption). This study provides a research agenda for FWB measurement and theoretical development.

Pyrolysis of Polyolefin-Enriched Mixed Plastic Waste Streams: Effects of Pretreatments and Presence of Hydrogen during Pyrolysis

Pyrolysis of Polyolefin-Enriched Mixed Plastic Waste Streams: Effects of Pretreatments and Presence of Hydrogen during Pyrolysis

Design and Implementation of a Cost-Effective, Safe, and Precise Lean-Rich Generating System for NOX Storage Reduction Catalyst Evaluation: Performance Analysis, Statistical Modeling, and Multiple Response Optimization – A Guideline for Future Research and Application

Design and Implementation of a Cost-Effective, Safe, and Precise Lean-Rich Generating System for NOX Storage Reduction Catalyst Evaluation: Performance Analysis, Statistical Modeling, and Multiple Response Optimization – A Guideline for Future Research and Application

Enabling simultaneous CO2 and water vapor removal by MOF-801/Pebax mixed matrix membranes: Molecular simulation and experimental study

Enabling simultaneous CO2 and water vapor removal by MOF-801/Pebax mixed matrix membranes: Molecular simulation and experimental study

Chemical recycling of polymer contaminated poly(ethylene terephthalate) by neutral hydrolysis

Plastic recycling is gaining traction to reduce the demand for fossil resources for plastic production. Poly(ethylene terephthalate) (PET), mainly used in the packaging and textile sectors, is often isolated in the sinking fraction during the density-based separation of mixed plastic waste streams. The heterogeneity of the sinking fraction makes direct mechanical recycling of PET impossible. Therefore, neutral hydrolysis of PET was investigated in the presence of other polymer contaminants to study their impact on the neutral hydrolysis of PET. PA6, PC, POM, and PVC were found to decompose during hydrolysis, whereas ABS, PMMA and a mixture of PE, PP and PS was chemically inert during the hydrolysis treatment. The subsequent BHET synthesis with excess ethylene glycol was performed directly on a mix of the polymer contaminated hydrolysis products or a hydrolyzed post-consumer plastic waste fraction. BHET was successfully formed in the plethora of decomposition products in the synthesis, and a subsequent recrystallization recovered the BHET in high purity with only water being used as solvent. This demonstrated a robust method to handle PET fractions in mixed plastic waste that can be applied without purification prior to BHET synthesis - enabling chemical recycling of PET. Abbreviations: ABS, Poly(acetonitrile-butadiene-styrene); ATR-FTIR, Attenuated Total Reflectance Fourier Transformed Infrared Spectroscopy; BC, Bis(2-Hydroxyethyl) terephthalate crystals; BHET, Bis(2-Hydroxyethyl) terephthalate; DMSO, Deuterated dimethyl sulfoxide; DSC, Differential Scanning Calorimetry; EG, Ethylene glycol; 1H NMR, Proton Nuclear Magnetic Resonance; Hm, Melting enthalpy; Oligo, Oligomers; PA6, Polyamide 6; PC, Polycarbonate; PE, Polyethylene; PET, Poly(ethylene terephthalate); PMMA, Poly(methyl methacrylate); POM, Polyoxymethylene; PP, Polypropylene; PS, Polystyrene; P, Purity; PVC, Poly(vinyl chloride); rpm, Revolutions per minute; SPHP, Solid Phase Hydrolysis Product; Ti(IV)OBu, Titanium(IV) butoxide; Tm, Melting temperature; TPA, Terephthalic acid; Wt, Weight; Y, Solid Phase Hydrolysis Product yield; Yt, Bis(2-Hydroxyethyl) terephthalate yield; ν, IR stretching mode; δ, IR bending mode; ω, IR wagging mode.

An in Silico Investigation into Polyester Adsorption onto Alumina toward an Improved Understanding of Hydrogenolysis Catalysts.

Chemical recycling of end-of-life plastic wastes through hydrogenolysis is a promising pathway for achieving a circular plastics economy and reducing overall energy costs. Understanding molecular interactions at the inorganic-organic depolymerization interface is crucial for enhancing catalyst performance and overcoming challenges posed by mixed plastic waste streams. We investigated a fundamental step in the depolymerization process: physisorption of polymers onto the metal oxide support preceding diffusion to and reaction at the catalyst-support junction. Molecular dynamics simulations, augmented with well-tempered metadynamics, were conducted to explore the adsorption of polylactic acid (PLA) and polyethylene terephthalate (PET) oligomers onto a hydroxylated alumina support surface. Our findings revealed multiple layers of highly oriented solvent molecules (1,4-dioxane) above the surface, creating significant barriers to polyester adsorption. Disrupting and displacing these solvent layers led PET oligomers to adsorb closer to and interact stronger with the surface than PLA oligomers, possibly contributing to the higher reaction temperatures needed to achieve full conversion in PET versus PLA hydrogenolysis. We further suggest an experimental approach to validate our results of solvent layering behavior through predictions of X-ray reflectivity that are consistent with our initial experiments. The insights gained in this study can be leveraged to refine our understanding of catalytic mechanisms to predict depolymerization reactivity and selectivity and improve future hydrogenolysis catalyst designs.

Evaluation of Autonomous Driving Safety by Operational Design Domains (ODD) in Mixed Traffic

This study derived effective driving behavior indicators to assess the driving safety of autonomous vehicles (AV). A variety of operation design domains (ODD) in urban road networks, which include intersections, illegal parking, bus stop, bicycle lanes, and pedestrian crossings, were taken into consideration in traffic simulation analyses. Both longitudinal and interaction driving indicators were investigated to identify the driving performance of AVs in terms of traffic safety in mixed traffic stream based on simulation experiments. As a result of identifying the appropriate evaluation indicator, time-varying stochastic volatility (VF) headway time was selected as a representative evaluation indicator for left turn and straight through signalized intersections among ODDs related to intersection types. VF headway time is suitable for evaluating driving ability by measuring the variation in driving safety in terms of interaction with the leading vehicle. In addition to ODDs associated with intersection type, U-turns, additional lane segments, illegal parking, bus stops, and merging lane have common characteristics that increase the likelihood of interactions with neighboring vehicles. The VF headway time for these ODDs was derived as driving safety in terms of interaction between vehicles. The results of this study would be valuable in establishing a guideline for driving performance evaluation of AVs. The study found that unsignalized left turns, signalized right turns, and roundabouts had the highest risk scores of 0.554, 0.525, and 0.501, respectively, indicating these as the most vulnerable ODDs for AVs. Additionally, intersection and mid-block crosswalks, as well as bicycle lanes, showed high risk scores due to frequent interactions with pedestrians and cyclists. These areas are particularly risky because they involve unpredictable movements from non-vehicular road users, which require AVs to make rapid adjustments in speed and trajectory. These findings provide a foundation for improving AV algorithms to enhance safety and establishing objective criteria for AV policy-making.

Tailoring the Properties of Chemically Recyclable Polyethylene-Like Multiblock Polymers by Modulating the Branch Structure.

Developing plastics that fill the need of polyolefins yet are more easily recyclable is a critical need to address the plastic waste crisis. However, most efforts in this vein have focused on high-density polyethylene (PE), while many different types of PE exist. To create broadly sustainable PE with modular properties, we present the synthesis, characterization, and demonstration of materials applications for chemically recyclable PE-like multiblock polymers prepared from distinct hard and soft blocks using ruthenium-catalyzed dehydrogenative polymerization. By altering the branching pattern within the soft blocks, a series of PE-like multiblock polymers were synthesized with tunable glass transition temperatures (Tg) while maintaining consistent high melting temperatures (Tm). A clear U-shape trend between Tg and mechanical properties was found, showcasing their potential as sustainable materials with tailored properties spanning commercial linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE). These materials offer adjustable adhesive strength to metal and demonstrate chemical recyclability and selective depolymerization in mixed plastic streams, promoting circularity and separation.

Tailoring the Properties of Chemically Recyclable Polyethylene‐Like Multiblock Polymers by Modulating the Branch Structure

AbstractDeveloping plastics that fill the need of polyolefins yet are more easily recyclable is a critical need to address the plastic waste crisis. However, most efforts in this vein have focused on high‐density polyethylene (PE), while many different types of PE exist. To create broadly sustainable PE with modular properties, we present the synthesis, characterization, and demonstration of materials applications for chemically recyclable PE‐like multiblock polymers prepared from distinct hard and soft blocks using ruthenium‐catalyzed dehydrogenative polymerization. By altering the branching pattern within the soft blocks, a series of PE‐like multiblock polymers were synthesized with tunable glass transition temperatures (Tg) while maintaining consistent high melting temperatures (Tm). A clear U‐shape trend between Tg and mechanical properties was found, showcasing their potential as sustainable materials with tailored properties spanning commercial linear low‐density polyethylene (LLDPE) and low‐density polyethylene (LDPE). These materials offer adjustable adhesive strength to metal and demonstrate chemical recyclability and selective depolymerization in mixed plastic streams, promoting circularity and separation.

High-speed microactuation in a supersonic dual-stream jet flow

Supersonic shear layers experience instabilities that generate significant adverse effects; in complex configurations, these instabilities have global impacts as they foster compounding complications with other independent flow features. We consider the flow near the exit of a dual-stream rectangular nozzle. The supersonic core and sonic bypass streams mix downstream of a splitter plate trailing edge (SPTE) just above an adjacent deck. We perform two-dimensional direct numerical simulations with laminar inflow conditions to parametrically explore the influence of active flow control, considering various actuation angles and locations. The goal is to alleviate the prominent tone associated with vortices shed at the SPTE; these vortices initiate an unsteady shock system that affects the entire flow field through a shock-induced separation and the downstream evolution of plume shear layers. Resolvent analysis is performed on the baseline flow. The identified optimal response guides the placement of steady-blowing actuators. Since the resolvent analysis fundamentally investigates the input–output dynamics of a system, it is also utilized to uncover actuation-induced changes in the forcing–response dynamics. Spectral analysis shows that the baseline flow fluctuating energy is concentrated in the shedding instability. Actuating at optimal angles based on location disperses this energy into various flow features; this affects the shedding itself, and the structure and unsteadiness of the shock system, and thus the response of the deck and nozzle wall boundary layers and the plume. The resolvent analysis indicates, and Navier–Stokes solutions confirm, that favourable control is obtained by either indirectly or directly mitigating the baseline instability.

Environmental And Health Implications of Waste Disposal Sites In The Lesotho Lowlands

Many Southern African countries, including Lesotho, face severe health and environmental issues attributed to waste disposal. The purpose of this study is to assessed the environmental and health impacts on residents living in proximity to disposal sites in the lowlands of Lesotho. A descriptive cross-sectional design was employed, using a semi-structured questionnaire and observation method. A mapping device was used, and photographs were taken to validate the findings. Descriptive statistics and the Chi-square test (?²) were employed to analyze the data. Results indicate that in Lesotho, some landfill sites are located as close as 50 meters from residential areas, and most (60%) received hazardous mixed waste streams. Waste burning and backyard dumping were the most frequently used disposal methods by residents. Several perceived health outcomes and environmental issues were noted, with respiratory and gastrointestinal health issues being the most prevalent. There was a statistically significant association between waste burning and respiratory diseases (P < 0.010) and between backyard dumping and gastrointestinal diseases (P < 0.003). The study concludes that regulatory instruments need to be revised and enforced, requiring hazardous waste producers to take responsibility for end-of-life waste and banning the entry of such waste into disposal sites. The application of waste management strategies to initiate other preferable end-of-life waste procedures, such as recycling of WEEE and waste-to-energy technologies for organic waste in Lesotho, could improve the quality of health for residents and their environment.

Combined thermochemical-biotechnological approach for the valorization of polyolefins into polyhydroxyalkanoates: Development of an integrated bioconversion process by microbial consortia

Waste management of persistent polymers such as polyolefins (PO)1 still represents a major challenge, often leading to material loss from the value chain and contributing to plastic pollution. This study investigated an integrated process to valorize PO pyrolysis side stream. PO wax was recovered and used as a feedstock for a microbial bioconversion process. A modified emulsification protocol (using two-surfactants system) allowed the successful dispersion and bioconversion of PO wax without the need of the extra oxidation step. Enrichment of plastic landfill inocula allowed to develop efficient mixed microbial consortia (MMC) able to grow on PO wax. Adaptive laboratory evolution improved 4 times cell growth, leading to 2.6-17.3 times shorter lag phase. The bioconversion process using the adapted MMC was performed in a 2L-bioreactor with PO wax-emulsified media (10gL-1) at neutral pH and 20% pO2. 87% of substrate was consumed within 12h and complete consumption was achieved within 48h (4 times faster than previously reported). A maximum of 2.95 gCDW L-1of biomass was produced, while the intracellular triglycerides reached a maximum of 105.5mgL-1 at 30h. Moreover, the conversion of PO wax into polyhydroxyalkanoates (PHAs) was demonstrated and the production was maximized by statistical optimization. Maximum PHA titer of 384 0.1mgL-1 was achieved, which represents a 1.5-17 times improvement from previous reports. This integrated thermochemical-biotechnological approach might represent an interesting strategy to valorize and upcycle currently unrecyclable PO-rich mixed plastic waste streams, thus improving the circularity of the plastic sector.

Vision-based sorting in mixed food-inorganic waste stream

Vision-based sorting in mixed food-inorganic waste stream

Hydrogen underground storage for grid electricity storage: An optimization study on techno-economic analysis

Hydrogen underground storage for grid electricity storage: An optimization study on techno-economic analysis

Supercritical Carbon Dioxide Mixing Loss Characteristics Near the Critical Point

Abstract This paper aims to study the mixing loss characteristic of sCO2 near the critical point and shed light on the non-ideal fluid effect on the mixing losses. As a simplified model of the mixing process in the trailing edge or tip leakage flow in turbomachines, a case of mixing in a constant area adiabatic duct involving two streams of parallel flows is studied by control volume analysis. Both perfect gas and non-ideal fluid calculations are carried out for comparisons. The isolated and coupled effects of the two mixing streams' temperature, velocity, and pressure differences on the loss are investigated. The study shows that non-ideal fluid mixing produces significantly higher losses when compared to the equivalent perfect gas estimation. It also reveals that the non-ideal fluid mixing loss is sensitive to the average thermodynamic states of the mixing streams. A significant variation of the mixing loss coefficient is reported if the static state of any of the two streams is near the critical point, which is mainly caused by the significant variation of the temperature gradient regarding the entropy along the isobar. The results also show that the change in the mixing loss due to the variation of one property difference between mixing streams is almost independent of the other property difference. The results from this simple case contribute to understanding the mixing loss behaviour differences between perfect gas and non-ideal fluids in sCO2 turbomachinery and hold significance for the development of mean-line models.

A study of mixed convection magnetohydrodynamics Williamson nanofluid flow over a nonlinear permeable elongating sheet over a porous medium with viscous dissipation

AbstractConvection, that is, mixed magnetohydrodynamics stream of Williamson nanofluid in excess of a nonlinearly stretchable permeable sheet, has been studied using a mathematical model that includes thermal radiation, viscous dissipation, heat source/sink, chemical reaction, and suction are all examples of thermal radiation are all examples of how heat is dissipated. By availing the controlling similarity transformations, suitable similarity transformations partial differential equations are reduced into the solution of a set of ordinary differential equations that are nonlinear using the homotopy analysis method. There is also a clear approach to get series solutions to converge. There was a strong correlation between the current and past outcomes. Graphs and tables are used to illustrate the nature of the flow field beneath various conditions.