Metals recycling in the United States

Twenty-two metals for which secondary recovery is important, in terms of quantity and/or value, were compared and ranked for rate and efficiency of recycling, and availability of recycled metal. In general, their recycling rates trended upward over the period 1970–1993. Iron, aluminum, copper, gold, platinum, and lead accounted for most of the value of all secondary metal produced, while iron and steel dominated in terms of quantity produced and exported. The factors most influential on recycling rates are profitability, public support, organization of infrastructure, sortability, legislative support, and scrap purity. The share of supply accounted for by secondary metals is expected to surpass that of primary metals sometime in the next decade.     

Energy and carbon balances of wood cascade chains

In this study we analyze the energy and carbon balances of various cascade chains for recovered wood lumber. Post-recovery options include reuse as lumber, reprocessing as particleboard, pulping to form paper products, and burning for energy recovery. We compare energy and carbon balances of chains of cascaded products to the balances of products obtained from virgin wood fiber or from non-wood material. We describe and quantify several mechanisms through which cascading can affect the energy and carbon balances: direct cascade effects due to different properties and logistics of virgin and recovered materials, substitution effects due to the reduced demand for non-wood materials when wood is cascaded, and land use effects due to alternative possible land uses when less timber harvest is needed because of wood cascading. In some analyses we assume the forest is a limiting resource, and in others we include a fixed amount of forest land from which biomass can be harvested for use as material or biofuel. Energy and carbon balances take into account manufacturing processes, recovery and transportation energy, material recovery losses, and forest processes. We find that land use effects have the greatest impact on energy and carbon balances, followed by substitution effects, while direct cascade effects are relatively minor.     

DESIGN OF DESALTING PLANTS FOR CONJUNCTIVE OPERATION1

ABSTRACT The selection of an evaporator design must reflect the balancing of captial cost (primarily in heat exchanger surface and vessels) against operating cost (primarily steam cost) to achieve minimum cost. In a conjunctive plant the tendency is to select a low-capital cost, high-operating cost plant. In addition, it is advantageous to use a high-capacity plant which needs to be operated much less of the time than a plant which is sized just at the needed rate. For example, in the study of a possible system to satisfy a future increase of 450 MGD in water supply to New York Qty, a plant of 750 MGD capacity was selected as optimum. This plant, of the advanced VTE-MSF process type, would have a performance ratio of 9 lb product/1000 Btu as compared to 10-13 normally used for base-loaded plants. Steam would be supplied by a multi-unit dual-purpose nuclear power plant. The most economical type of energy supply would be “interruptible”; the steam would be used by a low pressure turbine to generate electricity during periods of peak electrical demand but would be available to the desalting plant at other times. The low pressure turbine would be available as spinning reserve during desalting plant operation. It is estimated that the desalting plant would have a load factor of 27 per cent over its life.     

Utilization of red mud as catalyst in conversion of waste oil and waste plastics to fuel

The aim of this study was to investigate the possibilities of using a by-product (red mud) from alumina production as a catalyst for recovery of waste. The conversion of waste mineral oil (WMO) and waste mineral oil/municipal waste plastic (WMO/MWP) blends over red mud (RM), a commercial hydrocracking catalyst (silica–alumina), and a commercial hydrotreating catalyst (Ni–Mo/alumina) to fuel has been studied. The effect of the catalyst and the temperature on the product distribution (gas, liquid, and wax) and the properties of liquid products were investigated. In the case of hydrotreatment of WMO, the liquids obtained over RM at both 400° and 425°C had larger amounts of low-boiling hydrocarbons than that of thermal or catalytic treatment with hydrotreating catalyst. Gas chromatography and nuclear magnetic resonance analysis of the liquid products showed that RM had hydrogenation and cracking activity in hydrotreatment of WMO. In coprocessing of WMO with municipal waste plastics, temperature had an important effect as well as the amount of MWP in the blend and the catalyst type. The hydrocracking at 400°C produced no liquid product. In hydrocracking at 425°C, the product distribution varied with catalyst type and MWP amount. The commercial hydrocracking catalyst had more cracking ability in the conversion of WMO/MWP to liquid and gas fuel than RM. In the case of hydrocracking over RM, the largest amount of liquid having satisfactory quality was obtained only from the blend containing 20% MWP.     

Simulation of Live and Dead Phytomass Formation and Transformation in Optimized Agrocenoses

The formation and transformation of live and dead phytomass in agrocenoses with a complex horizontal structure are described. These processes are demonstrated to be specific and to be determined by differences in the horizontal structure. Only agrocenoses of a mosaic structure (with square parcels) have optimal conditions for these processes.     

Motives as Predictors of the Public's Attitudes Toward Solid Waste Issues

/ Surveys focusing on solid-waste-related issues, conducted over a period of several years, provided data from independent samples of residents of a Midwestern, USA, community. The collection of these data yielded useful information about the relationship between residents' recycling motives and their attitudes toward solid waste management in light of several changes in the solid waste infrastructure of the community over that time. The initial survey assessed baseline beliefs and attitudes, while later surveys were conducted after the implementation of a community educational program and a curbside recycling program. The findings indicated that for recyclers and nonrecyclers, different motives predicted endorsement of solid waste programs and policies. Although a similar percentage of recyclers and nonrecyclers were in support of various proposed programs and policies, concern for the environment was found to be positively related to nonrecyclers' support of proposed programs, particularly before these programs were implemented. Prior to program implementation, motives other than environmental altruism were found to be related to recyclers' support of the programs. Additional findings support the idea that educational programs and increased accessibility to recycling opportunities affect the relationship between people's attitudes toward solid waste management and their recycling motives.     

Effect of Recycling on Material Properties of Glass-filled Polyethylene Terephthalate

Recycled plastics are considered low performance materials because their properties are expected to decrease drastically with recycling. The objective of this study was to characterize a 15 wt.% glass filled polyethylene terephthalate (rPET-15GF) using six recycle generations and four recycle ratios. Mechanical properties such as tensile strength, elastic modulus, and percent elongation to failure of the PET composite were determined for various recycle generations and recycle ratios. Results show that the mechanical properties of rPET-15GF decrease slightly per recycle generation. In contrast, thermal properties of rPET-15GF were not at all affected by the recycling process. This data demonstrates that recycled glass filled PET can be used effectively to fabricate components without significantly affecting their mechanical performance.     

Characterization and recycling of polymeric components present in cell phones

The cell phone market is developing at a rapid speed. Today there are more than 1.6 billion consumers in the world, and the lifetime of a cell phone is less than 2 years. As a consequence, there is an increase in the waste associated to this product, and many alternatives to the disposal of the cell phones are being studied, such as recycling which shows to be the most important. It is crucial to know what materials constitute the cell phone in order to carry out recycling and determine environmental and economical issues. This work presents an evaluation of the cell phone components, characterizing the raw materials and some properties of the recycled materials.     

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.