Particleboard manufacturing: an innovative way to recycle paper sludge

This paper presents the results on a study to use paper mill sludge for particleboard production. Single-layer board and three-layer board, with paper sludge on the surface, were fabricated. Four levels of mixing ratios of paper sludge to wood particles (0:100, 15:85, 30:70, and 45:55) were used. The boards were produced with 3% and 4% methylene diphenyl diisocyanate (MDI), and 10% and 12% urea-formaldehyde (UF) adhesives. The bending and shear strengths, water absorption, and thickness swelling of the boards were investigated. The results indicated that the mechanical properties of the boards were negatively affected by the paper sludge amount. Overall, UF-bonded particleboards gave superior mechanical performance, water resistance, and thickness swell than MDI-bonded particleboards. The strengths of the UF-bonded board decreased much more than those of MDI-bonded board as paper sludge content increased. The three-layer boards made from 15% paper sludge with 12% UF satisfied fully the minimum requirements set by EN, ASTM D 1037-99, and ANSI A208.1 standards for general uses.     

Effect of carbon dioxide injection on production of wood cement composites from waste medium density fiberboard (MDF)

The possibility of recycling waste medium density fiberboard (MDF) into wood-cement composites was evaluated. Both new fibers and recycled steam exploded MDF fibers had poor compatibility with cement if no treatment was applied, due to interference of the hydration process by the water soluble components of the fiber. However, this issue was resolved when a rapid hardening process with carbon dioxide injection was adopted. It appears that the rapid carbonation allowed the board to develop considerable strength before the adverse effects of the wood extractives could take effect. After 3-5 min of carbon dioxide injection, the composites reached 22-27% of total carbonation and developed 50-70% of their final (28-day) strength. Composites containing recycled MDF fibers had slightly lower splitting tensile strength and lower tensile toughness properties than those containing new fibers especially at a high fiber/cement ratio. Composites containing recycled MDF fibers also showed lower values of water absorption. Unlike composites cured conventionally, composites cured under CO(2) injection developed higher strength and toughness with increased fiber content. Incorporation of recycled MDF fibers into wood cement composites with CO(2) injection during the production stage presents a viable option for recycling of this difficult to manage waste material.     

Reutilization of thermostable polyester wastes by means of agglomeration with phenolic resins

We report on the possibility of obtaining organic polymeric matrixes allowing the development of new high performance fire-resistant products by recycling downsized thermostable waste materials. Phenolic resins have been used as binders for recycled waste. Furthermore, considering that reinforced plastic triturations have superior properties (chemical, mechanical, water resistance, etc.) to wood agglomerates, significant advantages over conventional materials are anticipated. In summary, we propose a viable solution to some of the known problems caused by the consumption of wood and to the needs of strengthened plastic processing engineering. Using resins as a binder, several fire-resistant prototypes were prepared from polyester waste, and their mechanical properties, thermal stability, and fire-resistant properties were analyzed.     

Online sorting of recovered wood waste by automated XRF-technology: part II. Sorting efficiencies

Sorting of waste wood is an important process practiced at recycling facilities in order to detect and divert contaminants from recycled wood products. Contaminants of concern include arsenic, chromium and copper found in chemically preserved wood. The objective of this research was to evaluate the sorting efficiencies of both treated and untreated parts of the wood waste stream, and metal (As, Cr and Cu) mass recoveries by the use of automated X-ray fluorescence (XRF) systems. A full-scale system was used for experimentation. This unit consisted of an XRF-detection chamber mounted on the top of a conveyor and a pneumatic slide-way diverter which sorted wood into presumed treated and presumed untreated piles. A randomized block design was used to evaluate the operational conveyance parameters of the system, including wood feed rate and conveyor belt speed. Results indicated that online sorting efficiencies of waste wood by XRF technology were high based on number and weight of pieces (70-87% and 75-92% for treated wood and 66-97% and 68-96% for untreated wood, respectively). These sorting efficiencies achieved mass recovery for metals of 81-99% for As, 75-95% for Cu and 82-99% of Cr. The incorrect sorting of wood was attributed almost equally to deficiencies in the detection and conveyance/diversion systems. Even with its deficiencies, the system was capable of producing a recyclable portion that met residential soil quality levels established for Florida, for an infeed that contained 5% of treated wood.     

Characterization of composites based on expanded polystyrene wastes and wood flour

This paper aims to evaluate the potential for the use of recycled expanded polystyrene and wood flour as materials for the development of wood plastic composites. The effects of wood flour loading and coupling agent addition on the mechanical properties and morphology of wood thermoplastic composites were examined. In addition, a methodology for the thermo-mechanical recycling of expanded polystyrene waste was developed. The results show that the mechanical properties decreased as the wood flour loading increased. On the other hand, the use of poly(styrene-co-maleic anhydride), SMA, as a coupling agent improved the compatibility between the wood flour and polystyrene matrix and the mechanical properties subsequently improved. A morphological study revealed the positive effect of the coupling agent on the interfacial bonding. The density values obtained for the composites were compared with the theoretical values and showed agreement with the rule of mixtures. Based on the findings of this work, it appears that both recycled materials can be used to manufacture composites with high mechanical properties and low density.     

Use of recycled plastics in wood plastic composites – A review

The use of recycled and waste thermoplastics has been recently considered for producing wood plastic composites (WPCs). They have great potential for WPCs manufacturing according to results of some limited researches. This paper presents a detailed review about some essential properties of waste and recycled plastics, important for WPCs production, and of research published on the effect of recycled plastics on the physical and mechanical properties of WPCs.     

Influence of RFID tags on recyclability of plastic packaging

The use of Radio Frequency IDentification Technology (RFID) in the packaging sector is an important logistical improvement regarding the advantages offered by this technology in comparison with barcodes. Nevertheless, the presence of these devices in plastic packaging, and consequently in plastic waste, can cause several problems in the recycling plants due to the materials included in these devices.In this study, the mentioned recycling constraints have been experimentally identified in a pilot scale recycling study consisting in three recycling tests with an increasing presence of RFID tags. Differences in each test were evaluated. Furthermore, the quality of the recycled material of each test was studied through the injection and testing of tests probes.The results of the pilot scale recycling tests did not show a decrease in the quality of the recycled plastic due to the presence of RFID tags. Nevertheless, several operational problems during the recycling process were observed such as the obstruction of the screens, which lessened the process yield and created process interruptions, as well as the loss of extruded plastic during the process.These recycling constraints cannot be directly extrapolated to the industrial plants due to the different working scales. Nevertheless, technological solutions are proposed in order to avoid these recycling constraints if they appear.     

Effect of Xylanase–Laccase Synergistic Pretreatment on Physical–Mechanical Properties of Environment-Friendly Self-bonded Bamboo Particleboards

Diminishing wood supply and high formaldehyde emission from synthetic adhesive-bonded lignocellulose boards have become concerns. In this research, new adhesive-free boards made from xylanase–laccase-modified bamboo particles were developed. The bamboo particles were pretreated first with xylanase and then with laccase. The synergistic pretreatment was performed according to a Taguchi experiment that included six variables: xylanase treatment (enzyme concentration: 10, 20, 30 U/g; reaction pH: 8, 9, 10; reaction time: 30, 60, 90 min) and laccase treatment (enzyme concentration: 10, 20, 30 U/g; reaction pH: 2, 3, 4; reaction time: 30, 60, 90 min). The particles were hot-pressed to harvest the self-bonded boards, whose physical–mechanical properties were evaluated. The results showed that all six variables (except laccase reaction time) caused significant effects at 0.05 level on physical–mechanical properties of boards. The optimum pretreatment parameters were determined to be xylanase (20 U/g, pH 9, 60 min) and laccase (20 U/g, pH 4, 60 min). The optimized flexural strength, flexural modulus, internal bonding, and 2 h thickness swelling of boards met the highest requirements in Chinese national standard GB/T 4897 (2015) for particleboards. The performance of proposed boards was also better than that of reported self-bonded bamboo particleboards with only a laccase pretreatment.     

Rheological, Mechanical and Thermal Behaviour of Wood Polymer Composites Based on Recycled Polypropylene

The aim of this paper was to investigate the effect of recycled polypropylene (PP) on the rheological, mechanical and thermal properties of wood flour polypropylene composites. Beforehand, the influence of wood flour treated with a coupling agent on the rheological behaviour had been looked at. By analysing moduli and viscosity curves and studying the thermal and mechanical properties of samples with 10% filler it was possible to see that the recycled PP that was added change in either its physical properties or its rheology. In the other wood plastic composites (WPC) studied, slight changes in the rheology behaviour were observed. However, the same processing parameters may be used with and without recycled PP. Recycled PP is appropriate for these kinds of composites to maintain the optimal rheological properties that make it easier to process the material by extrusion. Furthermore, it is also possible to maintain the thermal and mechanical properties in comparison with the behaviour of virgin PP/wood flour composites.     

Economic and Environmental Benefits of Using Hardwood Sawmill Waste as a Raw Material for Particleboard Production

Annually, sawmills and other wood-processing factories generate a significant amount of scrap materials which are sent to landfills or incinerated. The amount of residue generated in Australia annually is estimated at 200,000 tonnes. A research project conducted at RMIT University explored utilizing these waste materials as particleboard furnish. The research team has now established a methodology for making particleboard in the laboratory using 100% hardwood sawmill residues, developing a particleboard product made in the laboratory which has acceptable mechanical properties and density profiles in accordance with the Australian Standards. However, this board product has some perceived issues which have been hindering ready commercial uptake. The current product requires a 10% higher resin load, has a 10% higher board density, and requires 10% longer pressing times compared to normal softwood particleboard. The paper presents an analysis of the current production process of particleboard to investigate the economic feasibility of particleboard production using hardwood sawmill residues. A major challenge in the analysis is converting the environmental benefit of utilizing large quantities of sawmill residue to a monetary term. Investigation of the global impact of particleboard by considering emission of carbon dioxide to the atmosphere is also included. A comparison is presented between different methods of disposing wood residues to understand the environmental benefit of using hardwood residue in particleboard.     

Use of recycled plastic in concrete: a review

Numerous waste materials are generated from manufacturing processes, service industries and municipal solid wastes. The increasing awareness about the environment has tremendously contributed to the concerns related with disposal of the generated wastes. Solid waste management is one of the major environmental concerns in the world. With the scarcity of space for landfilling and due to its ever increasing cost, waste utilization has become an attractive alternative to disposal. Research is being carried out on the utilization of waste products in concrete. Such waste products include discarded tires, plastic, glass, steel, burnt foundry sand, and coal combustion by-products (CCBs). Each of these waste products has provided a specific effect on the properties of fresh and hardened concrete. The use of waste products in concrete not only makes it economical, but also helps in reducing disposal problems. Reuse of bulky wastes is considered the best environmental alternative for solving the problem of disposal. One such waste is plastic, which could be used in various applications. However, efforts have also been made to explore its use in concrete/asphalt concrete. The development of new construction materials using recycled plastics is important to both the construction and the plastic recycling industries. This paper presents a detailed review about waste and recycled plastics, waste management options, and research published on the effect of recycled plastic on the fresh and hardened properties of concrete. The effect of recycled and waste plastic on bulk density, air content, workability, compressive strength, splitting tensile strength, modulus of elasticity, impact resistance, permeability, and abrasion resistance is discussed in this paper.     

Developing Biocomposites Panels from Food Packaging and Textiles Wastes: Physical and Biological Performance

The urban solid waste problem has been one of the biggest environmental challenges these days. In this context, developing biocomposites with improved performance by using various sources and wastes has been intensified in the last decades for economic and environmental points of view. In this study, physical behavior, fungal decay and termite attack tests were conducted in laboratory conditions to investigate the performance of composites developed from TetraPak and textile wastes. All the results were compared to standard wood products. The water swelling properties strongly decreased in the manufactured TetraPak composites when compared with the conventional particleboard panels. The fungal decay resistance tests revealed that the stand alone TetraPak based composites were not completely resistant to wood-decaying fungi. A significant amelioration in the decay durability was observed for the manufactured TetraPak composites compared to the standard wood samples. Durability classes were determined according to the criteria given in the European standard (CEN/TS15083-1). Interestingly, the data indicated that the increment of the wool waste proportion in the produced boards lead to a significant enhancement counter the test fungi. The results of termite screening test showed further considerable resistance for whole TetraPak based composites against termites when compared to traditional wood samples. Such panels could be an available alternative without any additives for wood based composite structures and it can be used in a wide range of applications.     

Development of composite materials by mechanochemical treatment of post-consumer plastic waste

Improvement of mechanical properties of recycled mixed plastic waste is one of the fundamental goals in any recycling process. However, polymer immiscibility makes the development of any effective reprocessing method difficult. In this work, a polymer milling process with liquid CO2 was applied to polymeric mixed waste, obtaining a powder material which was successfully utilized as a matrix for a new composite material. Developed materials have interesting mechanical properties and material performance can easily be improved. Investigations on selected mixtures of PP and PE clearly showed evidence of chemical compatibilization.     

Recycled Natural Fiber Polypropylene Composites: Water Absorption/Desorption Kinetics and Dimensional Stability

Detailed analysis of the effects of recycling process on long-term water absorption, thickness swelling and water desorption behavior of natural fiber polypropylene composites is reported. Composite materials containing polypropylene and wood flour, rice hulls or bagasse fibers were produced at constant fiber loading and were exposed to a simulated recycling process consisting of up to five times grinding and reprocessing under controlled conditions. A wide range of analytical methods including water absorption/desorption tests, thickness swelling tests, density measurement, scanning electron microscopy, image analysis, contact angle, fiber length analysis and Fourier transform infrared spectroscopy was employed to understand the hygroscopic behavior of the recycled composites. Water absorption and thickness swelling behaviors were modeled using existing predictive models. Results indicated that generally the recycled composites had considerably lower water absorption and thickness swellings as compared with the original composites which were attributed to changes in physical and chemical properties of the composites induced by the recycling process.     

Mineral wool waste in Europe: a review of mineral wool waste quantity,quality, and current recycling methods

The construction and demolition (C&D) industry has been identified as a major source of waste. European Union legislation states that, by 2020, 70 % of C&D waste must be prepared for reuse, recycled or recovered. European Union member states must increase their C&D waste recycling percentages in order to meet this binding target. Utilization of mineral wool waste, often considered unrecyclable, could improve the recycling percentage of C&D waste. In this article, mineral wool production and waste volumes are estimated based on information from the Eurostat database. A literature survey is conducted to collect information about mineral wool material properties, current recycling methods, and barriers to recycling of mineral wool, and suitable methods for separating mineral wool from C&D waste streams and the economic viability of mineral wool recycling are discussed. It is noted that accurate estimation of mineral wool waste volumes is problematic due to the fragmented nature of available data. Based on the literature review, current methods for recycling mineral wool waste include utilization of mineral wool waste as a raw material in various products. Barriers to recycling include economic questions and issues related to the purity and health effects of mineral wool waste. Material properties of mineral wool waste, such as fire resistance, could provide improved properties in products utilizing mineral wool waste as a raw material.     

Experimental study of rubber tire aggregates effect on compressive and dynamic load-bearing properties of cylindrical concrete specimens

Sustainable development has become a major focus for engineers and planners as part of their collective efforts in finding, developing and integrating environmental-friendly solutions for material recycling and waste management into design and construction of civil engineering infrastructure. In the past three decades, there has been an increase in recycling and application of waste materials into the concrete to decrease costs and improve material properties of the concrete. Significant growth in automobile manufacturing industry and increased rubber tire supply for vehicles suggested the application of waste tire particles as concrete aggregates to minimize the ecological footprint of the rubber tire waste due to its recycling process difficulties. In this paper, the effect of rubber tire particles on compressive and dynamic strength of concrete specimens with different particle percentiles was tested on more than 55 cylindrical specimens. To achieve the optimal mix design properties of rubber tire concrete specimens, both fine and coarse aggregates got replaced by fine and coarse rubber particles. Introduction of rubber tire particles as coarse and fine aggregate reduces the brittleness of the concrete and provides more flexible aggregate bonding which ultimately improves the dynamic resistance of the concrete. It increases the concrete workability and provides environmental-friendly and cost-effective solutions in using recycled materials for concrete construction applications.     

Improving the layout of recycling centres by use of lean production principles

There has been increased focus on recycling in Sweden during recent years. This focus can be attributed to external environmental factors such as tougher legislation, but also to the potential gains for raw materials suppliers. Recycling centres are important components in the Swedish total recycling system. Recycling centres are manned facilities for waste collection where visitors can bring, sort and discard worn products as well as large-sized, hazardous, and electrical waste. The aim of this paper was to identify and describe the main flows and layout types at Swedish recycling centres. The aim was also to adapt and apply production theory for designing and managing recycling centre operations. More specifically, this means using lean production principles to help develop guidelines for recycling centre design and efficient control.Empirical data for this research was primarily collected through interviews and questionnaires among both visitors and employees at 16 Swedish recycling centres. Furthermore, adapted observation protocols have been used in order to explore visitor activities. There was also close collaboration with a local recycling centre company, which shared their layout experiences with the researchers in this project.The recycling centres studied had a variety of problems such as queues of visitors, overloading of material and improper sorting. The study shows that in order to decrease the problems, the recycling centres should be designed and managed according to lean production principles, i.e. through choosing more suitable layout choices with visible and linear flows, providing better visitor information, and providing suitable technical equipment. Improvements can be achieved through proper planning of the layout and control of the flow of vehicles, with the result of increased efficiency and capacity, shorter visits, and cleaner waste fractions. The benefits of a lean production mindset include increased visitor capacity, waste flexibility, improved sorting quality, shorter time for visits and improved working conditions.     

Quantitative characterization of recyclable resources dismantled from waste liquid crystal display products

Currently only limited materials, such as common metals and plastics, are recovered from waste flat-panel displays, thus necessitating the development of a comprehensive recycling process. This study aims to establish a statistical database about the types and amounts of valuable resources in waste liquid crystal display (LCD) products. To obtain these data, the waste LCD products were disassembled into four components: plastics, printed circuit boards, metals, and other materials, including their panels, and the weight of each component was measured. Overall, the product weight decreased with increasing manufacturing year regardless of the product screen size; however, the decreasing rate varied from 14 to 73%. The metal weight ratios decreased significantly by 24–31%. Meanwhile, regardless of the manufacturing year, the plastic weight ratios remained almost constant at about 20%. On the other hand, the weight ratio of the other components increased by 26–46% with increasing manufacturing year suggesting that rare-earth metal recycling has become more important. These statistical analyses are expected to contribute to the development of an eco-friendly, high-efficiency dismantling/separation process that will enable higher value recycling and minimal waste disposal.     

生活垃圾分类背景下对广州市废玻璃回收利用的思考

废玻璃是一种载能节能、低碳环保、可重复利用和再生利用的再生资源,广州市通过补贴政策、两网融合等手段,促进废玻璃回收利用,随着生活垃圾分类纵深推进,为了进一步提高废玻璃回收利用,从废玻璃回收利用现状入手,对比了北京、上海生活垃圾中废弃玻璃的占比情况,针对目前存在问题,提出废玻璃回收利用分析与建议。     

Flammability Properties of Virgin and Recycled Polycarbonate (PC) and Acrylonitrile–Butadiene–Styrene (ABS) Recovered from End-of-Life Electronics

Acrylonitrile–Butadiene–Styrene (ABS), Polycarbonate (PC) and their alloys are widely used in automotive industry, computer and equipment housings. With increasing disposal of end-of-life electronic equipment, there is also an increased demand for recycling of these materials so that they do not pose environmental challenge as solid waste. One of the recycling approaches is mechanical recycling of these thermoplastics where recycled plastic is melt blended with virgin materials to obtain a high quality product. Besides obtaining desirable mechanical properties, such blends should also conform to fire safety standards. In this work, a series of blends were prepared using PC and ABS recovered from discarded computers and virgin materials using a twin-screw extruder. Their flammability properties were evaluated using burner flammability tests and Ohio State University (OSU) release rate tests. It was found that the extinguishing time, burning extent and weight loss appears to progressively decrease with the addition of both virgin or recycled PC to virgin or recycled ABS. It was also seen that the addition of the 70% of PC, virgin or recycled, to ABS virgin or recycled, appears to significantly decrease heat release and smoke evolution. The results of this study indicate that recycled polycarbonate can be used as an additive for virgin or recycled ABS, as a means of giving flame resistance to ABS in high-value applications. This result is significant when related to the result obtained by a separate study indicating that up to 25% of recycled material can be used without degradation of mechanical properties in the presence of 15% short glass fiber reinforcement.