Commingled Waste Research Articles

A single-step upcycling of PVC-containing municipal solid waste compositions for greener chemicals and clean solids as fuel or oil absorbent

Polyvinyl chloride (PVC) containing municipal solid waste (MSW) streams are difficult to recycle and mostly landfilled due to various detrimental effects PVC causes to waste recycling. In this work, a single-step upcycling of PVC-containing commingled wastes in tetrahydrofuran was investigated using cellulose, PVC, polyethylene (PE), polypropylene (PP), and polystyrene (PS) to model the wastes. During the co-conversion, in-situ produced HCl derived from PVC decomposition acted as an acid catalyst to selectively decompose cellulose into liquid mainly containing levoglucosan (LGA) and furfural. It was also found that the presence of PE, PP, and PS in the mixture synergistically enhanced the cellulose-derived monomer productions and increased the reaction rate for producing the monomers by suppressing secondary reactions of HCl in the solvent. The maximum LGA yield from co-conversion of cellulose, PVC, and PS was 35.4% after a 5 min reaction compared to the 31.7% obtained without PS in the mixture. In addition to converting cellulose to chemicals, PVC-derived polyaromatics and partly decomposed PE, PP, and PS were recovered as solids. The dechlorinated solids had higher heating values up to 46.11 MJ/kg, achieved by co-converting cellulose, PVC, and PP. When used as oil absorbents in water, the solid recovered from converting cellulose, PVC, and PE mixture showed the highest absorption capability. Overall, the presented approach offers a promising way for upcycling PVC-containing wastes in which PVC properties and its molecular structure are leveraged to enhance the conversion.

Potential greenhouse gas emissions and reduction from municipal solid waste management in Phnom Penh municipality

AbstractThis study evaluates greenhouse gas (GHG) emissions and reduction potential from municipal solid waste management (MSWM) following the IPCC 2006 guidelines. Under different MSWM scenarios of Phnom Penh municipality, this study quantifies GHG emissions from transportation, open burning, composting, recycling, anaerobic digestion (AD), incineration, and landfilling municipal solid waste. The study also considers the GHG emissions avoided as a benefit of recycling and electricity generation from incineration and AD. Various waste separation rates are used to evaluate the effectiveness of source segregation in GHG mitigation. The results show that the most significant net GHG emission saving is under scenario 5, avoiding about 1.15 M kg CO2‐eq/day with treatment affords 389 t/day of organic waste, 714 t/day of mixed recyclables, 777 t/day of digestible food waste, and 1,280 t/day of commingled waste via composting, recycling, AD, and incineration, respectively. The worst‐case scenario represents the current MSWM method, which generates the highest GHG emissions of 3.13 M kg CO2‐eq/day. This is due to the open burning of uncollected waste (211 t/day) and landfilling (2,835 t/day). Based on the analysis, an integrated MSWM system along with source separation for recycling and resource recovery purposes is highly recommended as it leads to the most significant reduction in environmental impacts. The findings of this study provide valuable insights into the practical implications of policy frameworks for MSWM, specifically in terms of GHG emissions reduction. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.

Commingling of Waste Rock and Tailings to Improve “Dry Stack” Performance: Design and Evaluation of Mixtures

Mine tailings are typically deposited as slurry and stored in impoundment dams. These structures pose a serious geotechnical risk, and are difficult to successfully reclaim at the end of mining. An increasingly common alternative to traditional tailings disposal is “dry stacking”: the placement of tailings dewatered using filtration in a self-supporting stack. It has been demonstrated that the addition of rock (termed “commingling”) to a filtered tailings stack has the potential to improve the geotechnical performance of the stack and may make large-scale dry stacking more economically viable. This paper discusses the application of commingling to tailings dry stacking, specifically relating to the design and evaluation of commingled blends of waste rock and tailings. The authors present a review of existing mix design theory, and present an extended theoretical model to predict the structure and behavior of blends of waste rock and tailings, based upon mix ratio and density. This paper is based upon established theory, but is extended to consider the case of loosely placed materials and the effect of volume change on structural configuration. The extended model may be used to describe the geotechnical behavior of commingled filtered tailings and waste rock. It is postulated that the geotechnical behavior of blends, and the primary mechanism of volume change, is governed by particle configuration. A brief discussion of experimental methods to evaluate the structure and configuration of commingled mine wastes is also presented.

Qualitative and quantitative contaminants assessment in recycled pellets from post‐consumer plastic waste by means of spectroscopic and thermal characterization

AbstractThe complexity of any plastic recycling initiative lies in the heterogeneous nature of the post‐consumer commingled plastic waste stream: recycling treatments are challenging without prior reliable sorting. A suitable identification system should be able to recognize different plastics and blends. Nowadays, the main technique used as quality control in plastic waste sorting centers is differential scanning calorimetry, whose result can be purely qualitative or semi‐quantitative, since only the crystalline fraction is evaluated. Moreover, the time required for data acquisition is relatively long. Infrared spectroscopy is an alternative, faster technique extensively used in applied research, but not widely utilized in industry. In this work, the cross‐use of infrared spectroscopy and calorimetry is tested in a real, practical case: the quality control of recycled pellets (namely composed of polyolefins only), which represent the output of a commingled plastic recycling plant and are used as secondary raw materials for different applications. Appropriate infrared spectroscopy calibration curves were built to allow the quantitative analysis with respect to the most common polymers found in the commingled plastic waste stream; the composition and contaminants in the recycled pellets were thereby determined and tracked through different production batches through the cross‐use of the two techniques outlined above.

Upcycling of waste artificial turf forhigh‐performancewood‐plastic composites

AbstractPlastic recycling is an essential tool to address the issue of plastic waste pollution. Unfortunately, current mechanical recycling processes for commingled plastic waste such as waste artificial turf (WAT) are limited by the inherent dilemma of separation challenge, high cost, and low‐quality products. In this work, solid‐phase shear milling (S3M) process was applied to prepare high‐performance WAT/wood flour (WF) composites, which addressed the challenges of poor compatibility and poor mechanical performance. Due to the strong shear force of S3M equipment, the strong hydrogen bonding in WF fibers was broken and the particle size of the WAT/WF mixture decreased from 452 to 47 μm. The well‐dispersed WF significantly improved the mechanical strength of WAT/WF composites from 17.6 to 26.4 MPa and melt processing ability. Moreover, the maximum tensile strength and modulus of the composites further improved to 32.6 and 2477 MPa through solid‐phase stretching with a 4% draw ratio. Compared with traditional WAT/WF composites, our research achieved the enhancement of 85.2% and 81.3% for tensile strength and modulus respectively. This work not only provides a promising strategy to resolve WAT environment pollution but also prepared value‐added high‐performance products for wood‐plastic applications.

Fabrication of high-performance HDPE/CWPF blend film via the assistance of OBC and solid-state drawing

To achieving highly efficient reuse of commingled waste plastic films (CWPF) in high-density polyethylene (HDPE), elastomer-olefin block copolymer (OBC) was adopted to improve the compatibility between CWPF and HDPE, and solid-state drawing was further used to improve the mechanical properties of the blends. The results showed that OBC could form core-shell structure with CWPF, as a bridge layer to simultaneously connect CWPF and HDPE, and form epitaxial crystallization induced by HDPE crystals, thereby greatly enhancing the compatibility between CWPF and HDPE, and improving the tensile strength, elongation at break and impact strength of HDPE/CWPF blend. In the subsequent solid-state drawing, depending on the fluidity of OBC at the drawing temperature of 100 °C, more CWPF were covered, efficiently reducing the defects caused by CWPF along the transverse direction (TD) and increasing the elongation at break of the stretched sheet along this direction. With the increase of draw ratio, lamellae in fibril along TD and shish-kebab-like structure along the flow direction (FD) formed, greatly improving the tensile strength of the blend along both TD and FD. And the long period (Lp), amorphous region (La) and lateral dimension (Llateral) decreased, but lamella thickness (Lc) increased. This work provides good bases for obtaining novel and low-cost HDPE based material as well as high-effect recycling of CWPF.

Fabrication of high-performance piezoelectric composite from commingled waste plastic films via a novel physicomechanical technology

The highly efficient and environmentally friendly reuse of waste plastics is always a big challenge worldwide, especially for commingled waste plastics. In this study, based on a novel pan-milling equipment, a simple, efficient and green physicomechanical technology, i.e. solid-state shear milling (S3M) technology, was established to realize the high-quality reuse of the commingled waste plastic films (CWPF) composed of polypropylene (PP), nylon 6 (PA6), polyethylene terephthalate (PET) and polyethylene (PE), as well as their good complexation with BaTiO3. Under the strong 3D-shear force of this milling equipment, the proper phase size of CWPF and the good compatibility between the components in CWPF were achieved, endowing the milled CWPF powders with significantly improved reprocessability. After milling for 30 cycles, ascribing to the formation of the fibrous phases, the tensile strength of the reprocessed CWPF sheet reached 18.7 MPa, increasing by 285% compared with the one without milling. Through co-milling, BaTiO3 piezoelectric particles were successfully incorporated into CWPF, and high-performance CWPF/BaTiO3 composite sheets were obtained. With 15 vol% BaTiO3, the composite sheet has the flexural strength of 17 MPa and compressive strength of 90 MPa, and could directly produce 95 V and 1.56 μA piezoelectric outputs to power 20 LED bulbs, or to charge a 1 μF commercial capacitor to 6.03 V within 100 s, surpassing most of BaTiO3 containing piezoelectric energy harvesters reported thus far, thus having great potential applications in the piezoelectric field, e.g. piezoelectric road.

Recyclable waste collection—Increasing ecopoint filling capacity to reduce energy for transportation

Urban waste production is increasing around the world. In the present Covid-19 context, an emergent flow of waste growth, as well as of pollution in general, stems from confinement and the use of protective masks. Although part of the waste is considered commingled, much is recyclable, if properly disposed off. Hence, recycling plays today, more than ever, an extremely important role, not only in terms of pollution prevention, but also from the point of view of the circular economy and of resources use efficiency. Thus, this work is focused on developing an approach to assist in recycling wastes. As a management option, recycling depends on a collective behavior, that relies on individual acts. Therefore, the individual use of plastic/metal compaction systems can help reaching the recycling targets, even as a complement to conventional commingled waste bins. Thus, we present a proposal for a plastic/metal collection station with a built-in compaction element that allows one to compact separated waste, individually, in an easily accessible drawer. Sorting and compaction of waste before collection will then result in a reduction of the number of collection/transportations stops, which will also translate into higher efficiency, reduction of costs, optimization of transported tons/km ratio, and profitability.

One-Pot Conversion of Pvc-Containing Commingled Wastes for Versatile Value-Added Products

One-Pot Conversion of Pvc-Containing Commingled Wastes for Versatile Value-Added Products

Hydraulic conductivity testing and destructive sampling of field-scale mine waste test piles

A commingled waste rock and tailings test pile and a waste rock test pile were evaluated to determine saturated hydraulic conductivity and destructively sampled to measure dry density. The commingled test pile contained a mixture of filtered tailings and waste rock blended to isolate waste rock particles as inclusions within the tailings matrix. Test piles were constructed in the shape of truncated 5 m high pyramids with 25 m base sides and flat 5 m × 5 m top surfaces, and instrumented to monitor water content (and additional geochemical indicator parameters) within the test pile and seepage from the base of the pile. Piles were decommissioned after 26 months of operation. Saturated hydraulic conductivities were measured using sealed double-ring infiltrometers (2.4 m square outer ring and 1 m square inner ring). Tensiometers and embedded water content sensors were used to measure progression of the wetting front, and the final location of the wetting front in the commingled test pile was directly measured during decommissioning. Field-measured saturated hydraulic conductivities were compared to laboratory-measured results intended to simulate the test piles. Despite having a lower average density, the commingled waste rock and tailings had a hydraulic conductivity approximately 2.5 times lower than the waste rock.

Black soldier fly larvae for treatment and segregation of commingled municipal solid waste at different environmental conditions

The commingled nature of the municipal solid waste in many developing nations is one of the primary reasons behind the failure to its successful management. Although there are technologies to effectively treat and process well-segregated and classified waste, they are ineffective in managing the commingled waste. Commingled waste has neither calorific value enough to support waste-to-energy operations nor is it suitable for producing quality compost to generate market value. In this article, a novel Black Soldier Fly Larva (BSFL) -based technology has been proposed and tested to auto-segregate and treat the biodegradable fraction of the Commingled Municipal Solid Waste (CMSW). Several BSFL feeding experiments on five different CMSW compositions were conducted at various temperatures and relative humidity conditions. BSFL could selectively consume the biodegradable fraction of the CMSW to convert it into its body mass and separate itself from the rest of the waste, which mainly consisted of inert and recyclable waste fractions that can be further treated using appropriate waste treatment technology. The mature larvae or the pre-pupae grown at the expense of the biodegradable waste fraction can find several commercial uses. The larvae's consumption rate and weight gain were dependent on the environmental conditions; 30 °C and relative humidity of 65–75% provided the highest consumption rate and most significant weight gain. The batch experiments in the laboratory proved that BSFL could be promising for the treatment of CMSW. The experimental data presented may help design a process for further scaling up an effective treatment method for CMSW, which might benefit many developing nations in managing their waste effectively and economically.

How does separate collection efficiency influence biological stability of commingled Italian municipal solid waste?

Italy developed over the last two decades a fairly efficient separate collection system but still about 30% of municipal solid waste (MSW) collected is destined to landfilling. Italian Regulation adopts the Dynamic Respirometric index (DRI) as the key parameter for evaluating the waste biological stability of MSW prior to landfilling. On the basis of a recent literature survey, this paper aims at evaluating how much DRI (used as aerobic waste stability index) and the biochemical methane potential (used as anaerobic waste stability index) of commingled (mixed) waste, respectively before and after a simulated biological treatment, are influenced by separate collection. Experimental data confirm that enhanced separate collection results in a reduction of the putrescible content of commingled waste. However, the reduction of DRI due to separate collection only (about 20%) is insufficient to approve direct landfilling without any biological pretreatment since the required standard is not achieved, while its implementation decreases efficiently both indices in the order of 50–75%. It is also delineated that only the joint use of an aerobic and an anaerobic index gives complete and reliable information on commingled waste stability, which optimizes the treatment of municipal waste for increasing the overall sustainability of the system.

An effective method of processing immiscible polymer blends into strong fiber

A unique methodology employing a “nearly co‐continuous morphology” for processing immiscible polymers into strong fiber is presented, and an immiscible polypropylene/polystyrene (PP/PS) blend is used as a model system to demonstrate the effectiveness of this methodology. The “nearly co‐continuous morphology” is easier to obtain than the fully co‐continuous structure, and yet, it provides an engineering solution to the production of strong fiber from an immiscible polymer blend. In addition, a process different from traditional melt spinning is used to prepare fiber with good mechanical properties. Traditional melt spinning involves large jet stretch and therefore introduces large interfacial orientation but little molecular orientation in polymer blends. To address this issue, the PP/PS blend is spun with nearly zero jet stretch and after solidification undergoes hot drawing at temperature close to the glass transition temperature of PS. This process sequence imparts a large degree of molecular orientation to the PP phase and produces a strong fiber. The proposed methodology can be extended to other blend systems and provides a potential route for directly recycling commingled polymer waste without preseparation or compatibilization. POLYM. ENG. SCI., 59:2052–2061, 2019. © 2019 Society of Plastics Engineers

Current status of circularity for aluminum from household waste in Austria

Aluminum (Al) represents the metal with the highest consumption growth in the last few decades. Beside its increasing usage in the transport (lightweight construction of vehicles) and building sector, Al is used ever more frequently for household goods like packaging material, which represents a readily available source for secondary aluminum due to its short lifetime.The present paper investigates the extent to which this potential source for recycling of Al is already utilized in Austria and highlights areas for future improvements. Thereto a detailed material flow analysis for Al used in packaging & household non-packaging in 2013 was conducted. In practice, all Al flows starting from market entrance through waste collection and processing until its final recycling or disposal have been investigated. The results indicate that about 25,100 t/a (2.96 kg/cap/a) of Al packaging & household non-packaging arose as waste. At present about 9800 t/a, or 39%, are recycled as secondary Al, of which 26% is regained from separate collection and sorting, 8% from bottom ash and 5% from mechanical treatment. The type of Al packaging & household non-packaging affects the recycling rate: 82% of the total recycled quantities come from rigid packaging & household non-packaging, while only 3% of the total recycled Al derives from flexible materials. A significant amount of Al was lost during thermal waste treatment due to oxidation (10%) and insufficient recovery of Al from both waste incineration bottom ash and municipal solid waste treated in mechanical biological treatment plants (49%). Overall it can be concluded that once Al ends up in commingled waste the recovery of Al becomes less likely and its material quality is reduced. Although Austria can refer to a highly developed recycling system, the Austrian packaging industry, collection and recovery systems and waste management need to increase their efforts to comply with future recycling targets.

Sustainable Solid Waste Management in Sports Events: A Case Study of Football Matches in Thailand

The International Olympic Committee has adopted Agenda 21 as a countermeasure to the environmental impact caused by sports events. This research addresses its lack of a concrete solid waste management framework by investigating solid waste generated, collected and sorted by the football stadiums in the Thai Premier League. The participation behaviors of spectators were examined by means of a structured questionnaire along with in-depth interviews with key stakeholders in solid waste management. In addition, relevant policies were reviewed. Results suggest that due to the lack of waste separation, less than 15% of the recyclable waste at stadiums proceed to recycling, with the rest going to landfills in the form of commingled solid waste. Carbon dioxide emissions corresponding to the waste produced was estimated by the IPCC’s first-order decay method. Field observations suggest that recycling can be increased by means of a prior-sorting behavior, and this was confirmed by the spectator survey. In-depth interviews with key stakeholders underlined the lack of proper incentives, regulations and environmental awareness to support proper solid waste management. We propose a sustainable solid waste management framework comprised of responsive policies, incentives and public participation focusing on the current deficiencies of solid waste management and increasing opportunities for resource recovery and recycling at sporting events.

Pyrolysis of commingled waste textile fibers in a batch reactor: Analysis of the pyrolysis gases and solid product

ABSTRACTThe main object of this study was the investigation of the thermal recycling of commingled waste textile fibers, with the aim of the production of useful end products. Differential scanning calorimetry/Thermo gravimetric analysis (DSC/TGA) was applied to determine the thermal degradation characteristics of the commingled waste textile fibers and there are two peaks located at the temperature ranges of 299–360°C and 399–500°C. Commingled waste fiber was pyrolyzed in a nitrogen atmosphere in relation to three different temperatures (500, 600, and 700°C), heating rates (25 and 50°C min−1), and retention times (15 and 30 min). The effect of the experimental conditions such as pyrolysis temperature, heating rates, and retention time on the formation of char and gas--liquid products was investigated and the product yields were determined from the rate of the weight loss. The highest conversion rate 82.9 wt.% liquid--gas product and 17.1 wt.% char product was achieved at 700°C. Pyrolysis gases were taken for every 7, 15, and 25 min and were analyzed for major components such as CO, CO2, CH4, and H2 by gas chromatography. The pyrolysis char called as carbon black derived from the pyrolysis of commingled waste textile fibers was analyzed for a range of properties, including the elemental analysis, moisture content, ash content, calorific value, and trace metal analysis.

Determining the amount of waste plastics in the feed of Austrian waste-to-energy facilities.

Although thermal recovery of waste plastics is widely practiced in many European countries, reliable information on the amount of waste plastics in the feed of waste-to-energy plants is rare. In most cases the amount of plastics present in commingled waste, such as municipal solid waste, commercial, or industrial waste, is estimated based on a few waste sorting campaigns, which are of limited significance with regard to the characterisation of plastic flows. In the present study, an alternative approach, the so-called Balance Method, is used to determine the total amount of plastics thermally recovered in Austria’s waste incineration facilities in 2014. The results indicate that the plastics content in the waste feed may vary considerably among different plants but also over time. Monthly averages determined range between 8 and 26 wt% of waste plastics. The study reveals an average waste plastics content in the feed of Austria’s waste-to-energy plants of 16.5 wt%, which is considerably above findings from sorting campaigns conducted in Austria. In total, about 385 kt of waste plastics were thermally recovered in all Austrian waste-to-energy plants in 2014, which equals to 45 kg plastics cap-1. In addition, the amount of plastics co-combusted in industrial plants yields a total thermal utilisation rate of 70 kg cap-1 a-1 for Austria. This is significantly above published rates, for example, in Germany reported rates for 2013 are in the range of only 40 kg of waste plastics combusted per capita.

Economic and life cycle analysis of municipal solid waste management for small islands: On-site management scenarios versus off-site transportation

<div> <p>A comparative economic and life cycle based analysis of five management scenarios for the solid waste generated in the island of Syros was conducted. The LCA part was performed with the LCA – IWM software. The four on-site waste management scenarios were: i) source separation of recyclable materials in combination with landfill disposal of the residuals (existing situation), ii) aerobic, windrow type, biological treatment (composting) with landfilling of residues, iii) anaerobic biological treatment (digestion) with landfilling of residues iv) aerobic mechanical biological treatment (MBT) and landfilling of residues. The off-site management scenario examined the transportation of the whole commingled wastes off the island for processing and disposal to the main mechanical and biological pretreatment plant in Athens. The results of analysis showed that the optimum waste management scenario in terms of environmental burdens (based on six environmental impact categories) and economics was off-site transportation, even when the specific landfill tax is included in calculations. The second best scenario in terms of environmental performance included the on-site aerobic MBT plant while the worst scenario was direct landfilling with mixed dry recyclables’ recycling. On-site anaerobic digestion had less environmental burdens and was more expensive than open windrow composting. Threshold distances were calculated below which the transportation of municipal solid wastes from a small island is financially and environmentally beneficial.</p> </div> <p> </p>

Fast Pyroylysis of Polyolefin Waste over Cracking Catalysts for Producing Hydrocarbon Fuels Using a Fluidized-bed Reactor

Abstract A mixture of post-commercial polyolefin waste (PE/PP/PS) was pyrolyzed over various micro- and mesoporous catalysts using a fluidized-bed reactor operating isothermally at ambient pressure. The yield of volatile hydrocarbons with zeolitic nano-catalysts (n-ZSM-5 > n-MOR > n-USY) were higher than with non-zeolitic catalysts (MCM-41 > ASA). MCM-41 with large mesopores and ASA with weaker acid sites resulted in a highly olefinic product mixture with a wide carbon number distribution, whereas n-USY yielded a saturate-rich product mixture with a wide carbon number distribution and substantial coke levels. A novel developed model based on kinetic and mechanistic considerations which take into account chemical reactions and catalyst deactivation for the catalytic degradation of commingled polyolefin waste has been investigated. This model represents the benefits of product selectivity for the chemical composition such as alkanes, alkenes, aromatics and coke in relation to the performance and the particle size selection of the catalyst used as well as the effect of the fluidizing gas and reaction temperature.

A methodology for developing strategic municipal solid waste management plans with an application in Greece

A rational approach for developing optimal municipal solid waste (MSW) management plans comprises the strategic and the detailed planning phases. The present paper focuses on the former, the objective of which is to screen management alternatives so as to select the ones that are able to fulfil all legal and other management requirements with reasonable cost. The analysis considers the transportation, treatment and final disposal of the commingled wastes that remain after the application of material recovery at the source programmes and comprises 10 elements, four of which are region-dependent and the remaining ones application-dependent. These elements and their inter-dependencies are described and the entire methodology is applied to Greece. The application considers the existing regional plans and shows that they are incompatible with the existing EU Directives, as well as overly expensive. To address this problem, a new plan is developed in accordance with the rational planning principles of the present methodology. The comparative evaluation of the above alternatives shows that the existing regional plans, in addition to being incompatible with the applicable EU Directives, require 4.3 to 4.8 times (3.7 to 4.4 billion €) higher capital investment and their annual cost is at least 2.1 to 2.3 times (590 to 735 million € year(-1)) higher in comparison with the new national plan.