Environmental problems have been considered as a serious situation in the construction. Waste management is pressing harder with the alarming signal warning the industry. Reuse, recycling and reduce ...the wastes consider as the only methods to recover those waste generated; however, the implementations still have much room for improvement. This paper reviews the technology on construction waste recycling and their viability. Ten material recycling practices are studied, including: (i) asphalt, (ii) brick, (iii) concrete, (iv) ferrous metal, (v) glass, (vi) masonry, (vii) non-ferrous metal, (viii) paper and cardboard, (ix) plastic and (x) timber. The viable technology of the construction material recycling should be provided an easy reference for future applications.
This study outlines a recycling initiative conducted at Rekular GmbH, focusing on the recycling of 100 refrigerators. The recycling process employed a combination of manual dismantling, depollution, ...and mechanical processing techniques. Manual dismantling followed a predefined protocol to extract various materials, while the mechanical and physical processes involved shredding, zigzag, magnetic, and eddy current separation (ECS) to liberate and separate different materials. The resulting ferrous, non-ferrous and polymer product fractions were analyzed and categorized, providing valuable insights into the quality of interim products in the refrigerator recycling process. Simulations were then performed using FactSageTM version 8.2 and HSC Chemistry 10 version 10.3.7.1 software to simulate the recovery of metals from the ferrous and non-ferrous fractions using pyro metallurgical and hydrometallurgical methods. An electric arc furnace (EAF) was utilized for iron (Fe), while a re-smelter process for aluminium (Al), and the black copper route was simulated for copper (Cu) recovery. The recovery rates including metallurgical, mechanical, and physical processes are as follows: Fe (78%), Al (68.4%), and Cu (52.4%). In contrast, the recovery rates through metallurgical processes are as follows: Al (99%), Fe (79%), and Cu (88%). This discrepancy is attributed to losses of these elements resulting from incomplete liberation in mechanical processing. Additionally, a product/centric approach was applied and the recycling index reached 76% for recovery the Al, Cu, and Fe metals in a refrigerator recycling process. Turning to the environmental impact evaluation within the life cycle assessment (LCA), the process unit with the highest emissions per refrigerator in the recycling process was the use of nitrogen during the shredding process, accounting for 3.7 kg CO2 eq/refrigerator. Subsequently, the consumption of medium voltage electricity from the German grid during mechanical and physical separations contributed to 0.6 kg CO2 eq/refrigerator. The EAF, and electrolytic refining stages in the metallurgical recovery process also had a notable impact, generating 10.7 kg CO2 eq/refrigerator.
•A model of the Dutch post-consumer plastic packaging recycling system has been established.•Both the amounts of produced milled goods and their polymeric compositions can be predicted.•The ...end-of-life fates of 35 individual packaging types have been resolved.•The origins of the polymeric contaminants in recycled plastics have been determined.•Most contaminants originate from packaging components and are hence design-related.
The Dutch post-consumer plastic packaging recycling network has been described in detail (both on the level of packaging types and of materials) from the household potential to the polymeric composition of the recycled milled goods. The compositional analyses of 173 different samples of post-consumer plastic packaging from different locations in the network were combined to indicatively describe the complete network with material flow analysis, data reconciliation techniques and process technological parameters. The derived potential of post-consumer plastic packages in the Netherlands in 2014 amounted to 341 Gg net (or 20.2 kg net.cap−1.a−1). The complete recycling network produced 75.2 Gg milled goods, 28.1 Gg side products and 16.7 Gg process waste. Hence the net recycling chain yield for post-consumer plastic packages equalled 30%. The end-of-life fates for 35 different plastic packaging types were resolved. Additionally, the polymeric compositions of the milled goods and the recovered masses were derived with this model. These compositions were compared with experimentally determined polymeric compositions of recycled milled goods, which confirmed that the model predicts these compositions reasonably well. Also the modelled recovered masses corresponded reasonably well with those measured experimentally. The model clarified the origin of polymeric contaminants in recycled plastics, either sorting faults or packaging components, which gives directions for future improvement measures.
•Waste tire rubber as environmentally-friendly and low-cost modifier of thermoset polymers.•Recent advances and future developments in thermoset/waste tire rubber composites.•Structure-property ...relationship for thermoset/waste tire rubber systems.•Possible routes to tailoring of performance properties of thermoset/waste tire rubber systems.
Nowadays, waste tire rubber (WTR) management is a growing and serious problem. Therefore, research works focused on the development of cost-effective and environmentally-friendly methods of WTR recycling are fully justified. Incorporation of WTR into polymer matrices and composite materials attracts much attention, because this approach allows sustainable development of industrially applicable waste tires recycling technologies. Generally, utilization of WTR as a filler for polymer composites noticeably reduces materials costs, while suitable modification/functionalization of WTR may significantly enhance the performance of plastics and rubbers. This work aims to summarize the literature reports related to the thermoset/WTR composites based on various matrices such as: polyurethanes, epoxy and other resins. It particularly focuses on compatibilization strategies in thermosets/WTR systems and their impact on the chemistry and physical interfacial interactions between thermoset matrix and WTR filler phase, what significantly affecting performance properties of prepared materials. Moreover, future trends and limitation related to thermoset/WTR composites development are discussed.
•A vast body of literature exists in the area of solid waste sorting for recycling.•Automation of municipal solid waste (MSW) sorting process is an active research area.•This paper reports a detailed ...review of automated sorting of source-separated MSW.•This paper presents sensors, actuators, and processes used in automated sorting.•Automated waste sorting to deal with increasing global waste generation is discussed.
A crucial prerequisite for recycling forming an integral part of municipal solid waste (MSW) management is sorting of useful materials from source-separated MSW. Researchers have been exploring automated sorting techniques to improve the overall efficiency of recycling process. This paper reviews recent advances in physical processes, sensors, and actuators used as well as control and autonomy related issues in the area of automated sorting and recycling of source-separated MSW. We believe that this paper will provide a comprehensive overview of the state of the art and will help future system designers in the area. In this paper, we also present research challenges in the field of automated waste sorting and recycling.
The increasing consumption of plastics and plastic products results in correspondingly substantial volumes of waste, which poses considerable environmental burdens. With the ongoing environmental ...actions, the application of circular economy on this waste stream is becoming inevitable. In this paper, the topics of plastics recycling, circular economy on plastics, and challenges to plastic waste recycling are critically reviewed. In the first part of this paper, the development of research on plastic recycling was viewed from 1950 until 2020 using the scientific database Web of Science, and 682 related studies were found and used to assess the changing research priorities along that timeline. The following sections discuss the potentials and requirements to enhance the quality of the produced recycled plastic, in connection with the factors that currently limit it. In conclusion, the quality of recycled plastic is generally determined by the homogeneity of the recovered plastic feed. There are various strategies which could be implemented to overcome the hindrances identified in the paper and to improve the quality of the recycled plastic, such as working on enhanced product designs for minimised waste heterogeneity and controlling the materials’ degree of contamination by applying advanced sorting.
•Molten metal pyrolysis recycles aluminium-laminated plastics.•The polypropylene layer pyrolyses to waxes.•A 4,000 t/y or larger plants is economic; 20% internal rate of return (IRR).
Aluminium ...laminated (AL) pouch packages and aluminium laminated Tetra-Pak cartons are considered unrecyclable, reducing their otherwise excellent lifecycle performance. This paper describes experimental results on pilot plant trials to recycle AL packages with a molten metal pyrolysis reactor. The experimental evidence shows that both package formats can be recycled and that clean aluminium can be recovered. However, the recovered aluminium from Al pouches may require mechanical cleaning as the consumer's information is printed onto the aluminium, leaving a carbon residue on the recovered aluminium. On the other hand, over 90% of the polypropylene plastic layer on the AL packaging pyrolysed into waxes, pointing to excellent kinetics. Moreover, an economic analysis of a 4,000 t/y commercial-scale plant demonstrates that a molten metal AL recycling plant is economically viable, achieving an internal rate of return (IRR) of over 20%.
•Mg-Al-O@Fe3O4 catalyst shows high catalytic efficiency in the glycolysis of PET.•High monomer yield is obtained in the presence of 0.5 wt% of catalyst within 90 min.•Magnetic Mg-Al-O@Fe3O4 micro ...catalyst can be consecutively used for two times.•Deactivated Mg-Al-O@Fe3O4 micro catalyst can be regenerated by heat treatment.•Nanostructured Mg-Al-O@Fe3O4 micro catalyst is cheap and environmentally benign.
Magnetic Mg-Al-O@Fe3O4 micro particles were synthesized by coating nanosized Mg-Al double oxides onto Fe3O4 micro particles. The formed hierarchical structure gave Mg-Al-O@Fe3O4 micro particles a high active surface area, which enabled these micro particles to work efficiently as a catalyst in the glycolysis of poly(ethylene terephthalate) (PET). The bis(hydroxyethyl) terephthalate (BHET) yield reached above 80 mol% in the presence of 0.5 wt% of Mg-Al-O@Fe3O4 micro catalyst in the reaction system within 90 min at 240 °C. After the reaction, Mg-Al-O@Fe3O4 micro catalyst was easily retrieved by a magnetic decantation and can be repetitively used for two times with a high catalytic efficiency. After that, the deactivated Mg-Al-O@Fe3O4 micro catalyst can be regenerated by heat treatment. The regenerated Mg-Al-O@Fe3O4 micro catalyst displays a comparable catalytic performance as that of the virgin catalyst. In addition, the Mg-Al double oxides and Fe3O4 micro particles are low-cost and environmentally benign. Therefore, the Mg-Al-O@Fe3O4 micro catalyst may contribute to an economically and environmentally improved large-scale circular recycling of PET fiber waste.
Following the circular economy hierarchy of reduce and reuse, recycling is the third layer to close the loops for materials and decouple their value from consumption. Polymeric materials (“plastics”) ...are in principle well suited for recycling, as they can be reprocessed with relatively low energy input as a material, cleaved back into their monomers or converted back to feedstock. Today, these approaches still fall short in quantitatively diverting waste towards reuse. This perspective describes the industry challenges for recycling back into high value applications of polymers, and the portfolio of existing and emerging technology solutions. Sustainable design of products and polymers, recycling technologies, appropriate business models, and enabling technologies converge at the frontier of plastics recycling, for a transformation of the industry towards circularity and greenhouse gas emission neutrality.
Plastics today face the dual challenge of a global waste issue and lifecycle greenhouse gas emission contributions. Recycling both diverts plastics from waste and supports transitioning the whole industry to climate neutrality. The frontier of plastics recycling, from an industry perspective, is reconciling these goals with uncompromised material quality, to replace virgin plastics in their applications at scale.
Alcoholysis of poly(ethylene terephthalate) (PET) waste to produce monomers, including methanolysis to yield dimethyl terephthalate (DMT) and glycolysis to generate bis-2-hydroxyethyl terephthalate ...(BHET), is a promising strategy in PET waste management. Here, we introduce an efficient PET-alcoholysis approach utilizing an oxygen-vacancy (Vo)-rich catalyst under air, achieving space time yield (STY) of 505.2 gDMT·gcat−1·h−1 and 957.1 gBHET·gcat−1·h−1, these results represent 51-fold and 28-fold performance enhancements compared to reactions conducted under N2. In situ spectroscopy, in combination with density functional theory calculations, elucidates the reaction pathways of PET depolymerization. The process involves O2-assisted activation of CH3OH to form CH3OH* and OOH* species at Vo-Zn2+–O–Fe3+ sites, highlighting the critical role of Vo-Zn2+–O–Fe3+ sites in ester bond activation and C–O bond cleavage. Moreover, a life cycle assessment demonstrates the viability of our approach in closed-loop recycling, achieving 56.0% energy savings and 44.5% reduction in greenhouse-gas emissions. Notably, utilizing PET textile scrap further leads to 58.4% reduction in initial total operating costs. This research offers a sustainable solution to the challenge of PET waste accumulation.Polyester waste is increasingly accumulating in the environment, and alcoholysis recycling offers a sustainable management solution. This study demonstrates the use of an oxygen vacancy-rich catalyst to transform waste blended polyester/textiles into high-value monomers.
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