Mixed Plastic Waste Research Articles

Effects of temperature zones on pyrolysis products of mixed plastic waste

Effects of temperature zones on pyrolysis products of mixed plastic waste

Feasibility of gasifying mixed plastic waste for hydrogen production and carbon capture and storage

Waste plastic gasification for hydrogen production combined with carbon capture and storage is one technology option to address the plastic waste challenge. Here, we conducted a techno-economic analysis and life cycle assessment to assess this option. The minimum hydrogen selling price of a 2000 oven-dry metric ton/day mixed plastic waste plant with carbon capture and storage is US$2.26–2.94 kg−1 hydrogen, which can compete with fossil fuel hydrogen with carbon capture and storage (US$1.21–2.62 kg−1 hydrogen) and current electrolysis hydrogen (US$3.20–7.70 kg−1 hydrogen). An improvement analysis outlines the roadmap for reducing the average minimum hydrogen selling price from US$2.60 to US$1.46 kg−1 hydrogen, which can be further lowered to US$1.06 kg−1 hydrogen if carbon credits are close to the carbon capture and storage costs along with low feedstock cost. The life cycle assessment results show that hydrogen derived from mixed plastic waste has lower environmental impacts than single-stream plastics.

Clariant unveils portfolio for purifying pyrolysis oil derived from mixed plastic waste

Clariant unveils portfolio for purifying pyrolysis oil derived from mixed plastic waste

Hands-on Laboratory Experiments for Demonstrating Mixed Plastic Recycling

Plastic waste is a growing concern in recent years due to the massive increase in single-use plastic applications. Despite the ever-increasing amount of waste, recycling plastics is not a simple process due to difficulties in sorting, which results in significantly downgraded material properties. This hands-on lab experiment showcases the important knowledge steps in a typical recycling process, including waste collection, plastic separation and sorting methods, processing techniques, and characterization methods including scanning electron microscopy (SEM) and tensile testing. Additionally, this lab demonstrates the importance of miscibility between materials and provides evidence that small amounts of block copolymers (BCPs) can compatibilize immiscible mixed plastic waste, leading to enhanced material properties of recycled products. Through these engaging hands-on lessons, students can not only obtain a better understanding about the challenge and industrial solution of mixed plastic waste recycling, but also realize the importance for protecting environments through waste management.

Conversion of Mixed Waste Plastic into Fuel Oil Production from Pyrolysis

Pyrolysis is the thermochemical decomposition of organic materials at high temperatures in the absence of oxygen. The process usually takes place in a sealed vessel under high pressure. Pyrolysis involves the simultaneous change of chemical composition and physical phase and irreversible. Excessive pyrolysis which leaves most of the carbon as a residue is called carbonization. Pyrolysis can deal with a variety of organic materials including plastic waste, food waste, crop waste, used cooking oil, used engine oil, etc. Pyrolysis is used to transform a variety of household items and industrial residues into fuel by recovering them. During pyrolysis, the molecules of the object vibrate at high frequencies to the extent that the molecules break down. The rate of pyrolysis also increases with the increase of temperature. The temperature of household items ranges from 370°C to above 410°C. Industrial applications have temperatures above 430°C. Pyrolysis is the transformation of waste biomass into a liquid fuel form. The density of the product fuel is 0.89gram/millilitre. The fuel produced has a long carbon chain length C9-C24 which is determined by Gas Chromatography and Mass Spectrometer (GC/MS). The produced fuel functional group and energy fuel heat enthalpy value is shown in the Fourier Transform Infrared Spectroscopy (FTIR) analysis result. The fuel produced can also be used as an internal combustion engine. The feed stock can be used as feed for refineries or as power generation feed for power plants. The objective of this research is to address the problem of waste plastic by using economical technology pyrolysis for waste reduction and energy recovery. Along with these environmental problems can also be solved. With the help of economical technology, we can save the environment and the problem of inflation of petrol in our country can also be reduced to some extent.

Supplementary Data for "Feasibility of gasifying mixed plastic waste for hydrogen production and carbon capture and storage" in Communications Earth & Environment

Supplementary Data for "Feasibility of gasifying mixed plastic waste for hydrogen production and carbon capture and storage" in Communications Earth & Environment

Discernment of synergism in co-pyrolysis of HDPE and PP waste plastics for production of pyro-oil: Mechanistic investigation with economic analysis and health risk assessment

Plastic waste is a major environmental challenge globally as it can hazard the soil, groundwater, marine, and land creatures. It also emits several toxic gases in open environment when heated up. The ceaseless demands for plastic materials due to wide applications generated a high volume of plastic waste which can impact sustainability development. The present study reports synergism in co-pyrolysis of mixed waste plastic for production of value-added products with economic analysis and health risk assessment. The characterization results of mass spectroscopy and NMR revealed that the product contains different types of hydrocarbons such as paraffins, aromatic, cyclic olefins, and lower hydrocarbons. The physicochemical characterization of pyro-oil showed similar fuel properties to that of commercial diesel (CD). Blending of pyro-oil obtained from HDPE:PP (20:80) improved the fuel quality that results in high brake thermal efficiency (BTE) and reduced brake-specific fuel consumption (BSFC). At the maximum load condition, ∼19.17% and 29.43% enhancement in BTE were observed with 10% and 20% PO blending, respectively. Also, ∼23.4% of fuel consumption was reduced when 20% PO blend was used with CD. The results showed that the maximum CO emission of 30.93% could be reduced by blending 10% PO. The engine performance and combustion characteristics revealed that PO blended fuels emit low percentage of CO, NOx, CO2, and HC – which essentially suggest a better life style by minimizing the health risks via reduction in greenhouse gas emission that may cause cardiovascular collapse, seizures, coma, and sometimes death. Thus, the present study will help in valorization and mitigation of generated waste plastics through energy conservation and boost the circular economy. The economic analysis based on the present investigation showed that ∼₹9.73 (0.12$) profit per litter can be achieved in the first year itself, while the profit in the 2nd and 5th year could be increased up to ₹54.43 (0.68$) and ₹67.73 (0.85$), respectively.

Supplementary Data for "Feasibility of gasifying mixed plastic waste for hydrogen production and carbon capture and storage" in Communications Earth & Environment

Supplementary Data for "Feasibility of gasifying mixed plastic waste for hydrogen production and carbon capture and storage" in Communications Earth & Environment

Mixed plastics waste valorization through tandem chemical oxidation and biological funneling.

Mixed plastics waste represents an abundant and largely untapped feedstock for the production of valuable products. The chemical diversity and complexity of these materials, however, present major barriers to realizing this opportunity. In this work, we show that metal-catalyzed autoxidation depolymerizes comingled polymers into a mixture of oxygenated small molecules that are advantaged substrates for biological conversion. We engineer a robust soil bacterium, Pseudomonas putida, to funnel these oxygenated compounds into a single exemplary chemical product, either β-ketoadipate or polyhydroxyalkanoates. This hybrid process establishes a strategy for the selective conversion of mixed plastics waste into useful chemical products.

Conversion of mixed waste plastic into fuel for diesel engines through pyrolysis process: A review

During the last decade, massive production of plastic materials causes a significant amount of waste. This growing trend in waste plastic, and the related negative effect on environment raised many concerns leading to propose different solutions for its disposal, recycle and re-use. Among different methods, landfilling, incineration and mechanical recycling are more conventional, however due to their environmental problems or economic issues, they would not be the best solutions for waste plastic management. The paper presents a review of a more effective process to recover the energy contained in these materials, with a focus of their use for producing fuel thorough the pyrolysis process. This conversion process does not only represent an environmentally friendly solution for the management of waste plastics, but also allows producing a liquid product which can be used for several energy-related applications. The focus of this review paper is to identify an optimum approach for production of maximum waste plastic pyrolysis oil with the characteristic similar to diesel fuel through investigation on various previous studies in this area. To reach this target, a review of the recent studies related to pyrolysis of waste plastics was carried out, and the main parameters affecting the liquid product yield were investigated. Then, the quality of several waste plastic oil (WPO) was compared to the conventional diesel fuels, based on the information reported about their physico-chemical properties, and their application in the diesel engine based on the parameters such as combustion, performance, and emission have been studied.

Potential Analysis of the Plastics Value Chain for Enhanced Recycling Rates: A Case Study in Iceland

In light of the circular economy gaining momentum, plastics recycling is regarded as a key solution to keep materials in the loop. Continuous efforts are needed to achieve the packaging waste recycling targets set by the European Union. Hence, this work evaluates the potential of the Icelandic plastics value chain for enhanced recycling rates. In addition to identifying the main challenges and opportunities, a feasibility study was conducted on the expansion of the deposit-return system to Skyr cups, allowing for closed-loop solutions. Based on the status quo, proposals for the improvement of the current waste and recycling system are made. Insights were acquired by semi-structured interviews with nine key stakeholders in Iceland, representing vital groups that influence the plastics value chain. The obtained answers followed the same trend, pointing out that a circular economy within the boundaries of Iceland is currently not feasible. This is mainly due to the strong dependence on international partners in all parts of the value chain except waste collection. However, major improvements are required to enhance the current waste collection rate of 28%. No conclusive evidence was found to justify the suitability of Skyr cups for the deposit-return system, as the disadvantages outweigh theoretically higher collection and recycling rates. Moreover, the extended producer responsibility scheme implemented with the Icelandic Recycling Fund is a valuable tool to enforce a design for recycling of products, enabling higher recycling rates. Despite one recycler operating in Iceland, Icelandic stakeholders consider sorting and treatment of mixed plastic waste as economically more efficient by collaborating with experts throughout Europe. Therefore, they expect that the current practice of exporting the majority of the domestic waste will prevail. On the contrary, the authors propose a comprehensive waste treatment and recycling scheme within Iceland, which requires a sorting step prior to three possible pathways, being (1) mechanical recycling, (2) alternative fuel, and (3) waste-to-energy. The aim of the proposed scheme is a reduction in greenhouse gas impact of plastics entering the waste stage by an efficient and flexible design of the relevant technologies within Iceland.

Study for Recycling Water Treatment Membranes and Compnents towards a Circular Economy-Case of Macaronesia Area.

Desalination is an opportunity to get fresh water for irrigation and for drinking. Reverse Osmosis (RO) for sea water desalination is a solution for the high demand for water in Atlantic islands. The most efficient process to get desalinated water is RO; however, it is necessary to study what to do with the RO membranes used at the end of their life. This paper confirms the possibility to recycle them. The main categories of recycling by thermal processing commonly used in the industry include incineration and pyrolysis to produce energy, gas and fuel. These processes can be applied to mixed plastic waste, such as the combination of materials used in the manufacture of RO membranes. Recycling RO elements from desalination plants is shown to be an opportunity and pioneering initiatives are already underway in Europe. Energy recovery, via incineration, is feasible nowadays and it is a possibility to recycle RO membranes. On the other hand, the recycling of RO elements, via the pyrolytic industry, for fuel production could be centralized in a new industry already planned in the Macaronesia area and all obsolete osmosis membranes could be sent there for recycling. Recycling RO membranes is a very important opportunity for the environment and economy of the zone. This is a new business in water treatments with membranes, very interesting for decreasing the residues and the carbon footprint. The importance of this work is applied to sea water membranes, brackish water ones, and also wastewater tertiaries RO elements at the end of their life.

Investigation of an Upcycling Strategy for Mixed Plastic Wastes from Urban Collection

AbstractIn this work, an upcycling strategy, aimed to upgrade the performances of recyclates deriving from sorting and mechanical recycling of mixed plastic waste recovered from the urban collection (UPW), is explored. To this aim, UPW samples are firstly analyzed to get information on their polymer constituents (type and relative amount), and then they are upcycled with the addition of different amounts of a polymer compatibilizer, a CaCO3‐based moisture absorber, and/or odor removers. All used additives give interesting benefits on processability and quality of the recycled UPW. In particular, the stiffness is increased up to ca. 22%, with the addition of 5 wt% of compatibilizer, and up to ca. 36%, with the addition of 5 wt% of moisture absorber, which also give better processability thanks to its moisture removal action. The odor absorber significantly reduces the smell of the recyclates, as found in preliminary odor recognition test sensory evaluation.

The Effect of Ultraviolet Light Stabilizers on Color Stability, Melt Properties and Tensile Properties of Mixed Waste Plastics Blends

Plastic waste disposal is among the most challenging problems of the current era. Therefore, new methods and applications for the utilization of waste plastics are increasingly needed. To find them, it is essential to research and develop the material properties of recycled plastics. The effect of different ultraviolet light (UV) stabilizers on the color stability, melt properties and tensile properties of mixed waste plastics blends was studied in this paper. The mixed waste plastics collected from two different waste sources were prepared as specimens by injection molding, and studied with two different types and loading amounts of UV stabilizers. UV absorbers (UVAs) and hindered amine light stabilizers (HALS) were used as UV stabilizers. A specimen produced without the addition of a UV stabilizer was used as a reference specimen of both the blends. After the accelerated weathering, the addition of a UVA provided an improved, smaller change in color than the addition of HALS. Among the tensile properties, the addition of UV stabilizers clearly improved the tensile strength and tensile modulus for almost all the studied specimens. Additionally, the melt properties of both the studied plastic blends were found to be increased by the addition of UV stabilizers.

SolvX: Solvothermal conversion of mixed waste plastics in supercritical toluene in presence of Pd/C catalyst

As the world's ability to cope with the fast-rising output of disposable plastic products is limited, plastic pollution has emerged as one of the most important environmental challenges. Catalytic solvothermal conversion (SolvX) could potentially utilize mixed waste plastics (MWPs) for sustainable fuels and chemical production. In this study, the effect of SolvX reaction time (1 – 5 h), Pd/C catalyst loading (0 – 10 wt%), and hydrogen loading (0–75 bar) on MWPs were investigated using supercritical toluene as solvent at temperature 350 °C. Four major waste plastics including low-density polyethylene (#4), polypropylene (#5), polystyrene (#6), and polyurethane (#7) were used as feedstock for this study. Along with SolvX conversion, the liquid products (crude oils) were characterized for elemental composition changes using ultimate analysis, boiling point distribution via thermogravimetric analysis, functional groups alteration using Fourier transform infrared spectroscopy, and product identification via gas chromatography-mass spectrometry. The results showed that the addition of catalyst and hydrogen have positive effects on the SolvX conversion. According to the elemental analysis, the SolvX crude oils' higher heating values (HHV) range from 32 to 38 MJ/Kg. The range of boiling points demonstrates that Pd/C increases the formation of lighter hydrocarbons. Additionally, a proposed catalytic SolvX reaction mechanism shows that the aromaticity raised with the increment of residence time and Pd/C enhances hydrodenitrogenation and deoxygenation at higher hydrogen loading.

Chemical recycling of mixed plastic waste via catalytic pyrolysis

The recovery rate of plastic waste has increased over recent years, however, there are still a large amounts of waste disposed in landfills or littered in the environment. As a result, advanced thermochemical technologies, such as catalytic pyrolysis, have become a promising approach to solve plastic waste management issues. This work aims to assess inexpensive catalysts derived from waste biomass for pyrolysis of mixed plastic waste for high-value products. Conventional thermal pyrolysis at high temperatures, i.e. 800 °C only increased the gas yield (up to 52 wt% from the 32 wt% obtained at 500 °C) but had no significant effect on the proportion of individual compounds in the gas fraction. A two-stage catalytic pyrolysis of mixed plastic waste at 600 °C (first stage) combined with biochar catalyst held isothermally at 800 °C (second stage) significantly enhanced the cracking process compared to thermal pyrolysis. In presence of the biochar catalyst, the gas yield increased up to 85 wt% mainly by an increase in the yield of hydrogen (from 0.2 wt% to 3.3 wt%) and methane (from 1.4 wt% to 55 wt%). Biochar also removed all the benzoic acid in the wax fraction. Therefore, the use of biochar derived from biomass waste as a catalyst opens-up an opportunity to develop a sustainable and efficient process to valorise waste.

Plasma gasification versus incineration of plastic waste: Energy, economic and environmental analysis

The rise in plastic waste production and its mismanagement poses huge environmental issues. Thermochemical techniques can minimize the amount of plastic waste discarded in landfills, reduce carbon footprints, increase conversion efficiency, and be cost-effective. Studies that compare the economic feasibility and environmental impact of treatment of mixed plastic waste for power generation via thermochemical methods are limited. The present study compares the electricity generation potential, economic feasibility, and environmental performance of plasma gasification and incineration of mixed plastic waste in China. The prominent findings show that plasma gasification's total power generation potential is 4378.6 GWh, while incineration is 491.2 GWh. The economic feasibility analysis shows that both projects are feasible with a positive net present value. Plasma gasification is highly beneficial with a higher net present value ($309.1 million), return on investment (32.1%), internal rate of return (27%), lower payback period (5.3 years), and levelized cost of energy ($0.230/kWh). The environmental assessment indicates that compared to the environmental impact, the environmental benefits of both projects are little. Relative to incineration, the environmental performance of plasma gasification is promising. This paper can give scientific guidance for optimal investment and decision-making on the environmental sustainability of mixed plastic waste treatment.

Thermal Degradation and Organic Chlorine Removal from Mixed Plastic Wastes

Plastic waste accumulation has been growing due to the increase in plastic generation and the lack of infrastructure for recycling. One of the approaches is to treat the mixed plastic waste (MPW) through thermal processes to produce feedstocks for other applications. However, the presence of polyvinyl chloride (PVC) in MPW would produce HCl during processing and has negative impacts (emission, catalyst poisoning, etc.). In addition, due to the high heterogeneity of MPW, it is difficult to generate consistent experimental data. In this study, MPW was homogenized through double compounding–extrusion and then formed into a sheet to be treated at 400 °C. The solid products at various mass losses were characterized by heat and chlorine content, Fourier-transform infrared (FTIR) spectroscopy, and elemental composition analysis. It was found that the thermal degradation of MPW started at ~260 °C. The chlorine removal efficiency increased with mass loss and reached an asymptotic value of ~84% at ~28% mass loss, and the remaining chlorine can be attributed to inorganic sources. A PVC de-chlorination model was developed for MPW using TGA data for PVC and MPW to determine organic chlorine removal efficiency. These results show that PVC de-chlorination was not affected by other plastics at this temperature. As the mass loss increases, the heat content first increases and then decreases. It was found that mass loss is a universal parameter for organic chlorine removal efficiency and heat content. The elemental composition analysis and FTIR spectroscopy also shed more light into the chemical changes during MPW thermal degradation.

Greenhouse gas benefits from direct chemical recycling of mixed plastic waste

Dealing with heterogeneous plastic waste – i.e., high polymer heterogeneity, additives, and contaminants – and lowering greenhouse gas (GHG) emissions from plastic production requires integrated solutions. Here, we quantified current and future GHG footprints of direct chemical conversion of heterogeneous post-consumer plastic waste feedstock to olefins, a base material for plastics. The net GHG footprint of this recycling system is −0.04 kg CO2-eq./kg waste feedstock treated, including credits from avoided production of virgin olefins, electricity, heat, and credits for the partial biogenic content of the waste feedstock. Comparing chemical recycling of this feedstock to incineration with energy recovery presents GHG benefits of 0.82 kg CO2-eq./kg waste feedstock treated. These benefits were found to increase to 1.37 kg CO2-eq./kg waste feedstock treated for year 2030 when including (i) decarbonization of steam and electricity production and (ii) process optimizations to increase olefin yield through carbon capture and utilization and conversion of side-products.

Morpho-structural and thermo-mechanical characterization of recycled polypropylene and polystyrene from mixed post-consumer plastic waste

In this work, a complete sorting and characterization of dirty non-recyclable mixed plastic (plasmix fraction) from municipal solid waste was performed. The procedure comprised a visual inspection and identification of the materials presented in the mixed plastic bales, and subsequent moisture and dirt content determination. Afterwards, both polypropylene and polystyrene fractions obtained from the sorting process were recycled and physico-mechanically and thermally characterized for the assessment of recycled material quality. The dirty non-recyclable mixed plastic from municipal solid waste was composed of polypropylene (28.89 %), polyethylene terephthalate (22.02 %), polystyrene (9.65 %) and rigid polyethylene (4.68 %). Regarding the moisture and dirt content of the mixed plastic fraction, the results were highly variable, mainly due to the heterogeneity of the material, its origin, atmospheric conditions, etc. The average sum of both parameters (moisture and dirt) was around 15 %. The mechanical properties were within the expected range for each type of polymer, noting that polystyrene recycled materials are more brittle than recycled polypropylene. The recycling of non-food polypropylene wastes yielded a material with higher impact resistance (70 kJ m−2) and Young´s modulus (1934 MPa) as compared to that obtained from the recycling of food packages. Concerning the polystyrene recyclates, it is worth mentioning that recycled materials obtained from foamed residues (expanded polystyrene and extruded polystyrene showed approximately twice the tensile strength with respect to the recycled materials from high impact polystyrene and general-purpose polystyrene residues. In some cases, infrared and thermal analyses revealed cross-contamination with traces of other polymers.