Life cycle assessment of integrated recycling schemes for plastic containers and packaging with consideration of resin composition

Many life cycle assessment studies have evaluated and compared the environmental performance of various technologies for recycling plastic containers and packaging in Japan and other countries. However, no studies have evaluated the combination of recycling technologies in consideration of the resin composition in terms of the quantity of each recycled product so as to maximize their environmental potential. In this study, 27 scenarios of recycling schemes for household waste plastic containers and packaging are developed through integrating a conventional recycling scheme with additional recycling schemes. The conventional recycling scheme involves municipal curbside collection and either the material recycling or feedstock recycling of waste plastics. The additional recycling schemes are feedstock recycling in steel works of the residue from conventional material recycling processes, and corporate voluntary collection and independent material recycling of specific types of plastic trays. Life cycle assessment based on the modeling of recycling processes considering the resin composition in terms of the quantity of each recycled product is applied to evaluate and compare these scenarios from the viewpoints of fossil resource consumption and CO₂ emission. The results show that the environmental loads are reduced in all scenarios including the additional recycling schemes compared with the conventional recycling scheme. However, the independent plastic tray recycling scheme exhibits lower additional environmental savings when the residue recycling scheme is integrated with the conventional material recycling scheme. This is because both additional recycling schemes aim to utilize polystyrene and polyethylene terephthalate, which would otherwise be incinerated as residue from material recycling processes. The evaluation of the environmental loads of plastic recycling with consideration of the resin composition in terms of the quantity of each recycled product makes it possible to investigate recycling schemes that integrate different technologies to maximize their environmental potential.     

Hydrothermal recycling of waste and performance of the recycled wooden particleboards

Recycling today constitutes the most environmentally friendly method of managing wood waste. A large proportion of the wood waste generated consists of used furniture and other constructed wooden items, which are composed mainly of particleboard, a material which can potentially be reused. In the current research, four different hydrothermal treatments were applied in order to recover wood particles from laboratory particleboards and use them in the production of new (recycled) ones. Quality was evaluated by determining the main properties of the original (control) and the recycled boards. Furthermore, the impact of a second recycling process on the properties of recycled particleboards was studied. With the exception of the modulus of elasticity in static bending, all of the mechanical properties of the recycled boards tested decreased in comparison with the control boards. Furthermore, the recycling process had an adverse effect on their hygroscopic properties and a beneficial effect on the formaldehyde content of the recycled boards. The results indicated that when the 1st and 2nd particleboard recycling processes were compared, it was the 2nd recycling process that caused the strongest deterioration in the quality of the recycled boards. Further research is needed in order to explain the causes of the recycled board quality falloff and also to determine the factors in the recycling process that influence the quality degradation of the recycled boards.     

Direction of CRT waste glass processing: electronics recycling industry communication

Cathode Ray Tube, CRT, waste glass recycling has plagued glass manufacturers, electronics recyclers and electronics waste policy makers for decades because the total supply of waste glass exceeds demand, and the formulations of CRT glass are ill suited for most reuse options. The solutions are to separate the undesirable components (e.g. lead oxide) in the waste and create demand for new products. Achieving this is no simple feat, however, as there are many obstacles: limited knowledge of waste glass composition; limited automation in the recycling process; transportation of recycled material; and a weak and underdeveloped market. Thus one of the main goals of this paper is to advise electronic glass recyclers on how to best manage a diverse supply of glass waste and successfully market to end users. Further, this paper offers future directions for academic and industry research. To develop the recommendations offered here, a combination of approaches were used: (1) a thorough study of historic trends in CRT glass chemistry; (2) bulk glass collection and analysis of cullet from a large-scale glass recycler; (3) conversations with industry members and a review of potential applications; and (4) evaluation of the economic viability of specific uses for recycled CRT glass. If academia and industry can solve these problems (for example by creating a database of composition organized by manufacturer and glass source) then the reuse of CRT glass can be increased.     

Correlation analysis between sulphate content and leaching of sulphates in recycled aggregates from construction and demolition wastes

In some recycled aggregates applications, such as component of new concrete or roads, the total content of soluble sulphates should be measured and controlled. Restrictions are usually motivated by the resistance or stability of the new structure, and in most cases, structural concerns can be remedied by the use of techniques such as sulphur-resistant cements. However, environmental risk assessment from recycling and reuse construction products is often forgotten. The purpose of this study is to analyse the content of soluble sulphate on eleven recycled aggregates and six samples prepared in laboratory by the addition of different gypsum percentages. As points of reference, two natural aggregates were tested. An analysis of the content of the leachable amount of heavy metals regulated by European regulation was included. As a result, the correlation between solubility and leachability data allow suggest a limiting gypsum amount of 4.4% on recycled aggregates. This limit satisfies EU Landfill Directive criteria, which is currently used as reference by public Spanish Government for recycled aggregates in construction works.     

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.     

Compressive strength and resistance to chloride ion penetration and carbonation of recycled aggregate concrete with varying amount of fly ash and fine recycled aggregate

Construction and demolition waste has been dramatically increased in the last decade, and social and environmental concerns on the recycling have consequently been increased. Recent technology has greatly improved the recycling process for waste concrete. This study investigates the fundamental characteristics of concrete using recycled concrete aggregate (RCA) for its application to structural concrete members. The specimens used 100% coarse RCA, various replacement levels of natural aggregate with fine RCA, and several levels of fly ash addition. Compressive strength of mortar and concrete which used RCA gradually decreased as the amount of the recycled materials increased. Regardless of curing conditions and fly ash addition, the 28 days strength of the recycled aggregate concrete was greater than the design strength, 40 MPa, with a complete replacement of coarse aggregate and a replacement level of natural fine aggregate by fine RCA up to 60%. The recycled aggregate concrete achieved sufficient resistance to the chloride ion penetration. The measured carbonation depth did not indicate a clear relationship to the fine RCA replacement ratio but the recycled aggregate concrete could also attain adequate carbonation resistance. Based on the results from the experimental investigations, it is believed that the recycled aggregate concrete can be successfully applied to structural concrete members.     

Recycling of biodiesel fuel wastewater for use as a liquid fertilizer for hydroponics

Wastewater is discharged during washing processes in the production of biodiesel fuel (BDF) using alkaline catalysts. It can be recycled as a liquid fertilizer for hydroponics by adding essential components for plant growth. The effects of the liquid fertilizer on plant growth were investigated. Liquid fertilizer containing a smaller amount of the BDF wastewater had a similar effect on plant growth as the standard nutrient solutions. This result reveals that BDF wastewater can be recycled for use as a liquid fertilizer for hydroponics. However, fertilizer with a larger amount of the BDF wastewater showed poor and varied plant growth due to the growth of microorganisms in the contaminated wastewater. Hence, when BDF wastewater becomes contaminated during storage, sterilization is necessary to recycle it as a liquid fertilizer. Moreover, contamination during storage should be avoided for successful recycling.     

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.     

国内外线路板电子元件去除及贵金属提取现状分析

围绕线路板的处置和资源化利用,介绍了国内外线路板电子元器件去除及贵金属提取现状,对现有回收方式的原理、效益和推广程度进行了阐述.     

Processes in informal end-processing of e-waste generated from personal computers in Vietnam

Informal treatment of e-waste plays an important role in many countries which have no or weak formal waste management structures. One of the challenges for assessing informal e-waste recycling technologies is to identify their disadvantages and potential technology improvement. The analysis of informal recycling processes starts with a balance of input and output materials for each of the processes. Main obstacles are the fact that in most cases, mixed or variety materials serve as input and, secondly by nature, the informal sector does not systematically measure and monitor the process. This study presents the processes and available data for informal e-waste recycling of desktop personal computer as it consists of components made of plastic and many metals within the Vietnamese context. To identify the most relevant processes, critical flows and technology gap, two scenarios are compared: (1) current situation in which recycling activities are taken in recycling craft villages and (2) appropriately selected BAT. The selected materials from e-waste cover a wide range of recycling processes and technologies: Printed Circuit Board treatment, metal (ferrous metal, aluminum and copper) and plastic recycling.

     

Closed-loop recycling of construction and demolition waste in Germany in view of stricter environmental threshold values.

Recycling of construction and demolition waste contributes decisively to the saving of natural mineral resources. In Germany, processed mineral construction and demolition waste from structural engineering is used nearly exclusively in civil engineering (earthwork and road construction sector) as open-loop recycling. Due to the planned stricter limit values for the protection of soil and water, however, this recycling path in civil engineering may no longer be applicable in the future. According to some new guidelines and standards adopted recently, recycled aggregates may also be used for concrete production in the structural engineering sector (closed-loop recycling). Wastes from the structural engineering sector can thus be kept in a closed cycle, and their disposal on a landfill can be avoided. The present report focuses on the determination of maximum waste volumes that may be handled by this new recycling option. Potential adverse effects on the saving of resources and climate protection have been analysed. For this purpose, materials flow analysis and ecobalancing methods have been used.     

废旧塑料的再生及其在制管行业中的应用

总结了再生、降解、焚烧及填埋等几种废旧塑料处置方式的特点,指出对于品种单一、老化程度低的废旧塑料应优先选择再生利用.重点介绍了废旧聚氯乙烯塑料、聚乙烯塑料、聚丙烯塑料、氯化聚氯乙烯塑料的再生及其在制管行业中的利用情况进展.     

Amino-Modified Halloysite Nanotubes to Reduce Polymer Degradation and Improve the Performance of Mechanically Recycled Poly(lactic acid)

From an environmental point of view, mechanical recycling is, in general, a good end-of-life option for poly(lactic acid) (PLA), one of the most important biobased polymers. However, the degradation of PLA during the service life and, especially, during the mechanical recycling process, leads to a decrease in the properties of PLA, thus reducing the applications of the recycled plastic. The main aim of this work was to study the addition of small amounts of halloysite nanotubes, during the recycling step, as the basis of a cost-effective method for improving the properties of the recycled PLA. Raw halloysite was modified with an aminosilane, and 2% by weight of both raw and modified halloysite were melt compounded with PLA previously subjected to accelerated ageing. The addition of the nanotubes led to recycled materials with improved properties because halloysite reduces the degradation of PLA by blocking the carboxyl groups, generated during the ageing and washing steps, which catalyze the degradation during the recycling process. This effect was more intense in the silanized nanotubes, because the carboxyl groups were effectively blocked by acid–base interactions with the amino groups of the chemical modification. The properties of the recycled plastic with only 2 wt% of silanized halloysite were very close to those of the virgin plastic.     

Evaluation of material recycling for plastics: environmental aspects

“Zero emissions” is a concept envisaging the creation of a sustainable society with minimal disposal of resources. In order to realize zero emissions for plastics, it is important to establish a method for quantitatively evaluating candidate recycling processes. In this study, the principle of the substitution factor (SF) is introduced. A quantitative evaluation of the recycling process for plastics was then carried out. The production process for monofilament plastics was examined. The recycling of plastics discarded during the production process could be substituted in small amounts for virgin materials, giving reduced CO₂ emissions. Furthermore, production using recycled material mixed with virgin material was more effective in reducing CO₂ emissions than when recycled materials only were used. Received: November 19, 1999 / Accepted: November 28, 2000     

Waste battery treatment options: Comparing their environmental performance

Waste consumer batteries are recycled using different routes based on hydrometallurgical and pyrometallurgical processes. Two hydrometallurgical and two pyrometallurgical treatment scenarios are compared starting from an average composition of Belgian waste batteries. The environmental performance is compared using life cycle analysis (LCA). The recycling rate is studied through mass balance calculation.Each treatment scenario results in a specific recycling rate. The environmental impact and benefits also vary between the treatment options. There is no such thing as a typical hydrometallurgical or pyrometallurgical treatment. When applying a hydrometallurgical treatment scenario, the focus lies on zinc and iron recycling. When allowing manganese recycling, the energy demand of the hydrometallurgical process increases considerably. Both pyrometallurgical options recycle zinc, iron and manganese. According to the LCA, none of the treatment scenarios performs generally better or worse than the others. Each option has specific advantages and disadvantages. The Batteries Directive 2006/66/EC sets out a recycling rate of 50% for consumer waste batteries. Based on metal recycling alone, the mass balances show that the target is difficult to obtain.     

切割刃料碳化硅的再生处理工艺研究

采用化学反应除杂和水力沉降粒度重新分级的方法,通过酸洗、碱洗、水力分级、pH值调节、干燥、配料等一系列处理工艺,对废砂浆中的碳化硅进行再生处理,得到的再生切割刃料各项性能指标满足切割工业使用要求,实现了资源再利用和循环发展.     

A simple model for complex waste recycling scenarios in developing economies

Future uncertainties involved in the current waste management activities in the developing nations have been addressed through determining plastic waste recovery, recycling and landfilling scenarios in two case study countries — Bangladesh and India. In order to discern and comprehend the material in-flow and out-flow of such complex successive plastics recoveries and recyclings, within the closed-loop recycling systems present in these two countries, a simple mathematical model is developed. The model is based on limited published information, on extensive fieldwork in Dhaka, Calcutta and Delhi, and on experimental data. An environmental legislative factor has been included in the model which will allow balancing of the quality of recycled products and the amount of landfilling non-recyclable plastics. The model has the potential to create and predict a sound waste database for these countries. Bangladesh has been chosen as a model developing country for this study. The mathematical model can be used in future decision making processes within the plastics recycling arena of the countries concerned to achieve an environmentally sound and cost effective waste management option.     

Importance of recycling education: a curriculum development at WSU

The use of recyclable materials has been continuously increasing worldwide due to economic, environmental, and technological developments. Not reusing recyclable materials means that they will be degraded or corroded, and then completely destroyed by nature, thus representing a waste of resources and much environmental damage. To increase both academic and public awareness of recycling, the authors have developed a three-credit-hour recycling course entitled “Recycling of Engineering Materials” at the College of Engineering at Wichita State University, which was taught in spring 2008 and 2010. The lectures focused on basic characterization and separation techniques of recyclable materials, recycled products, environmental concerns, and potential commercial applications. Throughout the lectures, students were expected to gain an understanding of recycling concepts, processing techniques, recent progress on recycling, as well as health issues relating to toxic and hazardous materials and their handling procedures. The survey results confirmed that the course is well established and understood by the undergraduate and graduate students.     

Recycling of carbon fiber-reinforced plastic using supercritical and subcritical fluids

The recycling of waste plastics is important for the prevention of the exhaustion of fossil resources. In this paper, recycling techniques of carbon fiber-reinforced plastic (CFRP) using supercritical and subcritical fluids were reviewed. The matrix resin of CFRP such as epoxy resin or resol resin was decomposed by supercritical and subcritical fluids, and the carbon fiber without thermal damage was recovered from CFRP. Mainly, water or alcohol was used as decomposition medium.     

Waste electrical and electronic equipment (WEEE) management in Korea: generation, collection, and recycling systems

In Korea, generation of waste electrical and electronic equipment (WEEE), or electronic waste (e-waste), has rapidly increased in recent years. The management of WEEE has become a major issue of concern for solid waste communities due to the volumes of waste being generated and the potential environmental impacts associated with the toxic chemicals found in most electronic devices. Special attention must be paid when dealing with WEEE because of toxic materials that it contains (e.g., heavy metals, polybrominated diphenyl ethers, phthalates, and polyvinyl chloride). If managed improperly, the disposal of WEEE can adversely affect the environment and human health. Environmental regulatory agencies; electronic equipment manufacturers, retailers, and recyclers; environmental nongovernmental organizations; and many others are much interested in updated statistics with regard to how much WEEE is generated, stored, recycled, and disposed of. In Korea, an extended producer responsibility policy was introduced in 2003 not only to reduce the amount of electronic products requiring disposal, but also to promote resource recovery from WEEE; the policy currently applies to a total of ten electrical and electronic product categories. This article presents an overview of the current recycling practices and management of electrical and electronic waste in Korea. Specifically, the generation rates, recycling systems and processes, and recent regulations of WEEE are discussed. We estimated that 1 263 000 refrigerators, 701 000 washing machines, 1 181 000 televisions, and 109 000 airconditioning units were retired and handled by the WEEE management system in 2006. More than 40% of the products were collected and recycled by producers. Four major producers’ recycling centers and other WEEE recycling facilities are currently in operation, and these process a large faction of WEEE for the recovery of valuable materials. Much attention should still be paid to pollution prevention and resource conservation with respect to WEEE. Several suggestions are made in order to deal with electronic waste management problems effectively and to prevent potential impacts.