The influence of adhesives on recycling

The finiteness of many resources made it necessary to think about how to save them by developing resource-saving technologies, e.g. to recycle materials. To execute the idea of recycling, it is necessary to think about a material recycling of the used products when designing them. This means that all additives of the process have to be designed in the way they do not disturb the later material recycling. Today, adhesives play a decisive role in the production of almost every good, especially for mass-produced articles and therefore it is important to choose adhesives that do not disturb the recycling of the primary materials. In recycling processes which take place at high temperatures (e.g. glass or metal recycling), the influence of the adhesives usually formed by organic polymers can be ignored. In the field of low temperature recycling technologies, the question whether an adhesive is recycling-friendly or not can only be answered by knowing its application and the recycling process. If the recycling processes are known, it is easy to chose suitable adhesives. For plastic and paper recycling, there are a lot of adhesives today that fulfill the requirements of recyclers. In order to simplify recycling for the future, adhesives with “switches enclosed” are being developed which will allow us to disbond system components into separate parts after use for reuse or material recycling.     

Global disposal strategies for waste cathode ray tubes

The collection and management of waste electrical and electronic appliances around the world, and the possible negative environmental consequences have been an issue of current debate. Cathode ray tubes (CRTs) used as display screen for computer monitors and televisions contains large quantities of lead, estimated at between 0.5 and 4 kg, depending on the size of the CRT and has been identified as the most polluting of all electronic waste components. Having failed the tests used in the toxicity characterization of solid wastes, CRTs have been declared ‘hazardous’ and subsequently banned from landfills and incinerators in most developed countries. Presently, large quantities of CRTs are generated globally with only few developed countries having effective take back and sound management program. Meanwhile, large quantities of CRT-containing devices are being moved across frontiers into developing countries in the name of ‘reuse’ and ‘bridging the digital divide’. With near absence of recycling infrastructure for electronic wastes in most developing countries, waste CRTs are disposed of with MSW at open dumps and unsanitary landfills. This paper reviews the current practices in the management of CRTs around the world, with emphasis on the role of regulations, availability of recycling infrastructure, recycling/reuse routes, and export into developing countries. Inappropriate disposal of waste CRTs creates the opportunity for large-scale environmental contamination with heavy metals, especially lead. Appropriate disposal routes are required globally in the management of CRTs in order to mitigate environmental contamination and human exposure to toxins.     

A graphical technique for wastewater minimisation in batch processes

Presented in this paper is a graphical technique for freshwater and wastewater minimisation in completely batch operations. Water minimisation is achieved through the exploitation of inter- and intra-process water reuse and recycle opportunities. In the context of this paper, a completely batch operation is one in which water reuse or recycle can only be effected either at the start or the end of the process. During the course of the operation, water reuse and recycle opportunities are completely nullified. The intrinsic two-dimensionally constrained nature of batch processes is taken into consideration. In the first instance, time dimension is taken as a primary constraint and concentration a secondary constraint. Subsequently, the priority of constraints is reversed so as to demonstrate the effect of the targeting procedure on the final design. Attention is brought to the fact that first and cyclic-state targeting are essential in completely batch operations. Moreover, the exploration and use of inherent storage in batch processes is demonstrated using a real-life case study. Like most graphical techniques, the presented methodology is limited to single contaminants.     

Dealing with electronic waste: modeling the costs and environmental benefits of computer monitor disposal

The importance of information technology to the world economy has brought about a surge in demand for electronic equipment. With rapid technological change, a growing fraction of the increasing stock of many types of electronics becomes obsolete each year. We model the costs and benefits of policies to manage 'e-waste' by focusing on a large component of the electronic waste stream-computer monitors-and the environmental concerns associated with disposal of the lead embodied in cathode ray tubes (CRTs) used in most monitors. We find that the benefits of avoiding health effects associated with CRT disposal appear far outweighed by the costs for a wide range of policies. For the stock of monitors disposed of in the United States in 1998, we find that policies restricting or banning some popular disposal options would increase disposal costs from about US dollar 1 per monitor to between US dollars 3 and US dollars 20 per monitor. Policies to promote a modest amount of recycling of monitor parts, including lead, can be less expensive. In all cases, however, the costs of the policies exceed the value of the avoided health effects of CRT disposal.     

Present status of the recycling of waste electrical and electronic equipment in Korea

In Korea due to rapid economical growth followed by urbanisation, breakage of large traditional families into small nuclear families, continuous changes in equipment features and capabilities causes tremendous increase in sale of new electrical and electronic equipment (EEE) and decrease in sale of used EEE. Subsequently, the ever-increasing quantity of waste electrical and electronic equipment (WEEE) has become a serious social problem and threat to the environment. Therefore, the gradual increase in the generation of WEEE intensifies the interest for recycling to conserve the resources and protect the environment. In view of the above, a review has been made related to the present status of the recycling of waste electrical and electronic equipment in Korea. This paper describes the present status of generation and recycling of waste electrical and electronic equipment, namely TVs, refrigerators, washing machines, air conditioners, personal computers and mobile phones in Korea. The commercial processes and the status of developing new technologies for the recycling of metallic values from waste printed circuit boards (PCBs) is also described briefly. Since 1998, three recycling centers are in full operation to recycle WEEE such as refrigerators, washing machines and air conditioners, having the total capacity of 880,000 units/year. All waste TVs are recently recycled on commission basis by several private recycling plants. The recycling of waste personal computers and mobile phones is insignificant in comparison with the amount of estimated obsolete those. Korea has adopted and enforced the extended producer responsibility (EPR) system. Korea is making consistent efforts to improve the recycling rate to the standards indicated in the EU directives for WEEE. Especially environmentally friendly and energy-saving technologies are being developed to recycle metal values from PCBs of WEEE.     

A review on the use of waste glasses in the production of cement and concrete

The use of recycled waste glasses in Portland cement and concrete has attracted a lot of interest worldwide due to the increased disposal costs and environmental concerns. Being amorphous and containing relatively large quantities of silicon and calcium, glass is, in theory, pozzolanic or even cementitious in nature when it is finely ground. Thus, it can be used as a cement replacement in Portland cement concrete. The use of crushed glasses as aggregates for Portland cement concrete does have some negative effect on properties of the concrete; however, practicle applicability can still be produced even using 100% crushed glass as aggregates. The main concerns for the use of crushed glasses as aggregates for Portland cement concrete is the expansion and cracking caused by the glass aggregates. This paper summarizes the progresses and points out the directions for the proper uses of waste glasses in Portland cement and concrete.     

电子废弃物资源化技术现状

随着电子废弃物数量的日益增加和对电子废弃物资源化利用要求的提高,电子废弃物经历了由堆存到资源化利用的发展过程.目前电子废弃物资源化技术主要包括物理处理法、化学处理法和热处理法等方法,实现电子废弃物的资源化.     

Use of Life Cycle Assessment in Environmental Management

The aim of this paper is to demonstrate how life cycle assessment (LCA) can be used to develop strategic policies that can lead to a minimization of the environmental burden resulting from the provision of services or the manufacture, use, and disposal of products within the economy. We accomplish this aim by presenting a case study that evaluates the greenhouse gas contributions of each stage in the life cycle of containerboard packaging and the potential impact on emissions of various policy options available to decision-makers. Our analysis showed that, in general, the most useful strategy was to recycle the used packaging. However, our analysis also indicated that when measures are taken to eliminate sources of methane emissions, then recycling is no longer beneficial from a greenhouse perspective. This is because the process energy required in the form of gas and electricity is substantially greater for containerboard manufactured from recycled material than it is for virgin fiber.     

Small‐Capacity Gold Production Tests From Waste Desktop Computers

This article describes a procedure for the hydrometallurgical recovery of gold from waste computer printed circuit boards (PCBs) and central processing units (CPUs). The wastes processed within the recovery installation described in this article were derived from desktop computers, the parts of which were manually sorted to select those components found to be rich in gold content. X‐ray fluorescence measurements showed that considerable amounts of gold are contained in the “finger” terminals of the PCBs as well as in the CPUs. This article describes the chemical processes for recovering gold from these parts. In addition, the article covers the emissions control apparatus that is capable of eliminating the nitrogen oxides (NOx) and sulfur dioxide (SO2) emissions produced by the recovery process. The main costs arising from the overall procedure are for personnel utilization. Approximately 60 work hours from one worker are required to process 1.75–1.85 tons of unprocessed desktop computer waste to produce gold in the form of sediments. The quantity of gold recovered from this amount of waste computers can reach up to 35 grams with a standardized purity of 21 karats. The overall recovery procedure takes eight consecutive calendar days to accomplish.     

Twenty years of PET bottle to bottle recycling—An overview

Polyethylene terephthalate (PET) has become the most favourable packaging material world-wide for beverages. The reason for this development is the excellent material properties of the PET material, especially its unbreakability and the very low weight of the bottles compared to glass bottles of the same filling volume. Nowadays, PET bottles are used for softdrinks, mineral water, energy drinks, ice teas as well as for more sensitive beverages like beer, wine and juices. For a long time, however, a bottle-to-bottle recycling of post-consumer PET packaging materials was not possible, because of the lack of knowledge about contamination of packaging polymers during first use or recollection. In addition, the decontamination efficiencies of recycling processes were in most cases unknown. During the last 20 years, PET recollection as well as recycling processes made a huge progress. Today, sophisticated decontamination processes, so-called super-clean recycling processes, are available for PET, which are able to decontaminate post-consumer contaminants to concentration levels of virgin PET materials. In the 1991, the first food contact approval of post-consumer PET in direct food contact applications has been given for post-consumer recycled PET in the USA. Now, 20 years after the first food approval of a PET super-clean recycling process, this article gives an overview over the world-wide progress of the bottle-to-bottle recycling of PET beverage bottles, e.g. the recollection amount of post-consumer PET bottles and the super-clean recycling technologies.     

Management and recycling of waste glass in concrete products: Current situations in Hong Kong

Disposal of more than 300 tonnes waste glass daily derived from post-consumer beverage bottles is one of the major environmental challenges for Hong Kong, and this challenge continues to escalate as limited recycling channels can be identified and the capacity of valuable landfill space is going to be saturated at an alarming rate. For this reason, in the past ten years, a major research effort has been carried out at The Hong Kong Polytechnic University to find practical ways to recycle waste glass for the production of different concrete products such as concrete blocks, self-compacting concrete and architectural mortar. Some of these specialty glass-concrete products have been successfully commercialized and are gaining wider acceptance. This paper gives an overview of the current management and recycling situation of waste glass and the experience of using recycled waste glass in concrete products in Hong Kong.     

Evaluation of life cycle inventory data for recycling systems

This paper reviews databases on material recycling (primary as well as secondary production) used in life cycle assessments (LCA) of waste management systems. A total of 366 datasets, from 1980 to 2010 and covering 14 materials, were collected from databases and reports. Totals for CO₂-equivalent emissions were compared to illustrate variations in the data. It was hypothesised that emissions from material production and the recycling industry had decreased over time due to increasing regulation, energy costs and process optimisation, but the reported datasets did not reveal such a general trend. Data representing the same processes varied considerably between databases, and proper background information was hard to obtain, which in turn made it difficult to explain the large differences observed. Those differences between the highest and lowest estimated CO₂ emissions (equivalents) from the primary production of newsprint, HDPE and glass were 238%, 443% and 452%, respectively. For steel and aluminium the differences were 1761% and 235%, respectively. There is a severe lack of data for some recycled materials; for example, only one dataset existed for secondary cardboard. The study shows that the choice of dataset used to represent the environmental load of a material recycling process and credited emissions from the avoided production of virgin materials is crucial for the outcome of an LCA on waste management. Great care and a high degree of transparency are mandatory, but advice on which datasets to use could not be determined from the study. However, from the gathered data, recycling in general showed lower emission of CO₂ per kg material than primary production, so the recycling of materials (considered in this study) is thus beneficial in most cases.     

Utilization of calcite and waste glass for preparing construction materials with a low environmental load

In this study, porous calcite materials are hydrothermally treated at 200 °C using powder compacts consisting of calcite and glasses composed of silica-rich soda-lime. After treatment, the glasses are converted into calcium aluminosilicate hydrates, such as zeolite phases, which increase their strength. The porosity and morphology of new deposits of hydrothermally solidified materials depend up on the chemical composition of glass. The use of calcite and glass in the hydrothermal treatment plays an important role in the solidification of calcite without thermal decomposition.     

Integrating waste,manufacturing and industrial symbiosis: an analysis of recycling,remanufacturing and waste treatment firms in Texas

The continually increasing volume of the waste stream has led to numerous calls for strategies to close the loop on material use through industrial symbiosis strategies which direct used material and products (wastes) back to production processes. By use of a survey of recycling, remanufacturing and waste treatment firms in Texas, this paper asks if these firms can operate as a bridge between production and consumption/waste to efficiently increase the flow of used materials and products back to production processes at the local level. The results suggest that while most materials and used products are collected locally, only some can be re(consumed) locally. Moreover, the firms face negative perceptions about their activities from industry and the public at large that likely slow both the rate of entry of new firms into these markets and the expansion possibilities of existing firms. In addition, the types of conventions that characterize the interactions of more successful firms are not well developed in this sector(s). It is unlikely that recycling, remanufacturing and waste treatment firms can become central players in the production, consumption and waste cycle loop until society develops production design, marketing and consumption philosophies that include recycling and remanufacturing at a fundamental level.     

Integrating waste, manufacturing and industrial symbiosis: an analysis of recycling, remanufacturing and waste treatment firms in Texas

The continually increasing volume of the waste stream has led to numerous calls for strategies to close the loop on material use through industrial symbiosis strategies which direct used material and products (wastes) back to production processes. By use of a survey of recycling, remanufacturing and waste treatment firms in Texas, this paper asks if these firms can operate as a bridge between production and consumption/waste to efficiently increase the flow of used materials and products back to production processes at the local level. The results suggest that while most materials and used products are collected locally, only some can be re(consumed) locally. Moreover, the firms face negative perceptions about their activities from industry and the public at large that likely slow both the rate of entry of new firms into these markets and the expansion possibilities of existing firms. In addition, the types of conventions that characterize the interactions of more successful firms are not well developed in this sector(s). It is unlikely that recycling, remanufacturing and waste treatment firms can become central players in the production, consumption and waste cycle loop until society develops production design, marketing and consumption philosophies that include recycling and remanufacturing at a fundamental level.     

A life cycle based multi-objective optimization model for the management of computer waste

The accelerating pace of waste generation from used electrical and electronic equipment is of growing global concern. Within this waste stream, computer hardware is quite significant in terms of both volume and risk to the environment because of the hazardous materials within it. The waste management hierarchy of prevention, reuse, recycle, treatment and disposal in landfill is accepted as a universal guideline for waste management. The contemporary concept of integrated solid waste management is very complex comprising of not only the environmental aspects or the technical aspects of the waste management hierarchy, but also incorporating economic, institutional, perceived risk and social issues in the context of complete life cycle of waste. Moreover, when to shift from one stage of hierarchy to another, is an involved decision warranting inclusion of several case specific issues. This paper presents a life cycle based multi-objective model that can help decision makers in integrated waste management. The proposed model has been applied to a case study of computer waste scenario in Delhi, India, which apart from having computer waste from its native population receives large quantities of imported second hand computers. The model has been used to evaluate management cost and reuse time span or life cycle of various streams of computer waste for different objectives of economy, perceived risk and environmental impact. The model results for different scenarios of waste generation have been analyzed to understand the tradeoffs between cost, perceived risk and environmental impact. The optimum life cycle of a computer desktop was observed to be shorter by 25% while optimizing cost than while optimizing impact to the environment or risk perceived by public. Proposed integrated approach can be useful for determining the optimum life cycle of computer waste, as well as optimum configuration of waste management facilities, for urban centers where computer waste related issues are of growing concern.     

A life cycle based multi-objective optimization model for the management of computer waste

The accelerating pace of waste generation from used electrical and electronic equipment is of growing global concern. Within this waste stream, computer hardware is quite significant in terms of both volume and risk to the environment because of the hazardous materials within it. The waste management hierarchy of prevention, reuse, recycle, treatment and disposal in landfill is accepted as a universal guideline for waste management. The contemporary concept of integrated solid waste management is very complex comprising of not only the environmental aspects or the technical aspects of the waste management hierarchy, but also incorporating economic, institutional, perceived risk and social issues in the context of complete life cycle of waste. Moreover, when to shift from one stage of hierarchy to another, is an involved decision warranting inclusion of several case specific issues. This paper presents a life cycle based multi-objective model that can help decision makers in integrated waste management. The proposed model has been applied to a case study of computer waste scenario in Delhi, India, which apart from having computer waste from its native population receives large quantities of imported second hand computers. The model has been used to evaluate management cost and reuse time span or life cycle of various streams of computer waste for different objectives of economy, perceived risk and environmental impact. The model results for different scenarios of waste generation have been analyzed to understand the tradeoffs between cost, perceived risk and environmental impact. The optimum life cycle of a computer desktop was observed to be shorter by 25% while optimizing cost than while optimizing impact to the environment or risk perceived by public. Proposed integrated approach can be useful for determining the optimum life cycle of computer waste, as well as optimum configuration of waste management facilities, for urban centers where computer waste related issues are of growing concern.     

Automobile recycling in the United States: Energy impacts and waste generation

Changes in the trends in the material composition of domestic and imported automobiles and the increasing cost of landfilling the non-recyclable portion of automobiles (automobile shredder residue or ASR) pose questions about the future of automobile recycling in the United States. In response to these challenges, new and innovative approaches to automobile recycling are being developed. This paper presents the findings of a recent study to examine the impacts of these changes on the life cycle energy consumption of automobiles and on the quantity of waste that must be disposed of. Given the recycle status quo, trends in material composition and the viability of recycling the non-metallic components of the typical automobile are of secondary importance when compared to the energy consumed during the life of the automobile. The energy savings resulting from small changes in the fuel efficiency of a vehicle overshadow potential energy losses associated with the adoption of new and possibly non-recyclable materials. Under status quo conditions, the life cycle energy consumed by the typical automobile is projected to decrease from 599 million Btus in 1992 to 565 million Btus in 2000. Energy consumed during the manufacture of the typical car will increase from about 120 to 140 million Btus between 1992 and 2000, while energy used during vehicle operation will decrease from 520 to 480 million Btus. This study projects that energy saved at the recycle step will increase from 41 million Btus in 1992 to 55 million Btus in 2000. This study also investigated the energy impacts of several potential changes to the recycle status quo, including the adoption of technologies to retrieve the heat value of ASR by incineration and the recycle of some or all thermoplastics in the typical automobile. The study estimates that under optimistic conditions —i.e., the recycling of all thermoplastics and the incineration with heat recovery of all remaining ASR —about 8 million Btus could be saved per automobile —i.e., an increase from about 55 to 63 million Btus. In the more realistic scenario —i.e., the recycling of easy-to-remove thermoplastic components (bumper covers and dash-boards) —the potential energy savings are about 1 million Btus per vehicle. It is estimated that the annual quantity of ASR in the United States could be reduced from about 5 billion pounds to as little as 1 billion pounds of ash if all ASR is incinerated. Alternatively, ASR quantity could be reduced to about 4 billion pounds if all thermoplastics in automobiles are recycled. However, in the case of recycling only thermoplastic bumper covers and dashboards, the quantity of ASR would be reduced by only 0.2 billion pounds. A significant reduction or increase in the size of the ASR waste stream will not in itself have a large impact on the solid waste stream in the United States.     

A Framework for Geographically Sensitive and Efficient Recycling Networks

This paper has three primary objectives. First, it seeks to demonstrate that recycling is an important component of sustainable human systems, particularly in the case of electronics, where environmental impacts of disposal are potentially severe. Second, it presents a methodology that could be used to estimate the volumes of electronics or other consumer durable goods that are available for recycling. Third and last, it illustrates, through a case study of Atlanta focused on computers, that metropolitan areas may fruitfully be viewed as opportune centres from which to mine, recycle and reuse cast-off electronic goods. From an environmental and economic development policy perspective, doing so presents an important opportunity to provide new economic opportunities in the most distressed portions of metropolitan areas which have been disproportionately impacted by previous environmentally destructive industrialization practices.     

Exergy losses during recycling and the resource efficiency of product systems

Recycling materials have always some degree of contamination. The presence of contaminations in the recycling streams causes a shift in the original composition of the materials to recycle. As a consequence, their quality may decrease with each recycling step. Additionally, lower quality resources are produced from resource streams that had initially a higher quality. These quality losses cannot be measured by mass balances, as the quality degradation cannot be translated by mass measures alone. To account all losses caused by recycling contaminations, all downstream recycling processes required to bring the materials back to the resource cycles must be included. This article describes a method to calculate the exergy content and exergy losses of metal solutions during recovery and recycling. The losses attributed to recycling, namely the material losses, the contamination losses with other metals, and the consequent need for dilution can be used as indicators of the quality loss of materials and of the efficiency of resource use in product systems. Therefore, exergy is proposed here as a measure of the efficiency of resources use.