Potential environmental impacts of light-emitting diodes (LEDs): metallic resources, toxicity, and hazardous waste classification

Light-emitting diodes (LEDs) are advertised as environmentally friendly because they are energy efficient and mercury-free. This study aimed to determine if LEDs engender other forms of environmental and human health impacts, and to characterize variation across different LEDs based on color and intensity. The objectives are as follows: (i) to use standardized leachability tests to examine whether LEDs are to be categorized as hazardous waste under existing United States federal and California state regulations; and (ii) to use material life cycle impact and hazard assessment methods to evaluate resource depletion and toxicity potentials of LEDs based on their metallic constituents. According to federal standards, LEDs are not hazardous except for low-intensity red LEDs, which leached Pb at levels exceeding regulatory limits (186 mg/L; regulatory limit: 5). However, according to California regulations, excessive levels of copper (up to 3892 mg/kg; limit: 2500), Pb (up to 8103 mg/kg; limit: 1000), nickel (up to 4797 mg/kg; limit: 2000), or silver (up to 721 mg/kg; limit: 500) render all except low-intensity yellow LEDs hazardous. The environmental burden associated with resource depletion potentials derives primarily from gold and silver, whereas the burden from toxicity potentials is associated primarily with arsenic, copper, nickel, lead, iron, and silver. Establishing benchmark levels of these substances can help manufacturers implement design for environment through informed materials substitution, can motivate recyclers and waste management teams to recognize resource value and occupational hazards, and can inform policymakers who establish waste management policies for LEDs.     

Low-Cost Magnetic Fe3O4/Chitosan Nanocomposites for Adsorptive Removal of Carcinogenic Diazo Dye

Theoretical Foundations of Chemical Engineering - The eco-friendly adsorptive removal of Congo red (CR) from aqueous medium using Fe3O4/chitosan nanocomposites was investigated. The nanocomposites...     

Measurement and analysis of product energy efficiency to assist energy star criteria development: An example for desktop computers

The Energy Star labeling program contributes to reducing economic and environmental impacts. Although product-specific criteria for the label are developed by taking into account potential energy savings, more robust criteria need to be developed to minimize energy consumption (and consequential global warming potential (GWP)). The objectives of this study are: (i) to measure what we refer to as the technical and cost efficiencies of products with respect to the relative Energy Star criteria achievement rate and GWP, respectively; and (ii) to analyze the relationship between these efficiencies and product design features, using stochastic frontier analysis (SFA) and data envelopment analysis (DEA). As an example, these analyses are applied to data for desktop computers. The results indicate that desktop computer manufacturers currently achieve energy savings that exceed those required by the Energy Star label. The principal product design features affecting the efficiencies are primarily the efficiency and power capacity of the power supply and the number of cores in the central processing unit. This study can help the program develop more robust criteria that ultimately reduce GWP and can provide guidance to manufacturers to strategically improve energy efficiency.     

Column study on Cr(VI)-reduction using the brown seaweed Ecklonia biomass

The potential use of the brown seaweed, Ecklonia, biomass as a bioreductant for reducing Cr(VI) was examined in a continuous packed-bed column. The effects of the operating parameters, such as influent Cr(VI) concentration, influent pH, biomass concentration, flow rate and temperature, on the Cr(VI) reduction were investigated. Increases in the influent Cr(VI) concentration and flow rate or a decrease in the biomass concentration inside the column led to a higher breakthrough of the Cr(VI) ions in the effluent. Particularly, the influent pH and temperature most significantly affected on the breakthrough curve of Cr(VI); a decrease in the influent pH or an increase in the temperature enhanced the Cr(VI) reduction in the column. For process application, a non-parametric model using neural network was used to predict the breakthrough curves of the column. Finally, the potential of the column packed with Ecklonia biomass for Cr(VI) detoxification was demonstrated.     

Environmental and risk screening for prioritizing pollution prevention opportunities in the U.S. printed wiring board manufacturing industry

Modern manufacturing of printed wiring boards (PWBs) involves extensive use of various hazardous chemicals in different manufacturing steps such as board preparation, circuit design transfer, etching and plating processes. Two complementary environmental screening methods developed by the U.S. EPA, namely: (i) the Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI) and (ii) Risk-Screening Environmental Indicators (RSEI), are used to quantify geographic and chemical environmental impacts in the U.S. PWB manufacturing industry based on Toxics Release Inventory (TRI) data. Although the release weight percentages of industrial chemicals such as methanol, glycol ethers and dimethylformamide comprise the larger fraction of reported air and water emissions, results indicate that lead, copper and their compounds' releases correspond to the highest environmental impact from toxicity potentials and risk-screening scores. Combining these results with further knowledge of PWB manufacturing, select alternative chemical processes and materials for pollution prevention are discussed. Examples of effective pollution prevention options in the PWB industry include spent etchant recovery technologies, and process and material substitutions. In addition, geographic assessment of environmental burden highlights states where promotion of pollution prevention strategies and emissions regulations can have the greatest effect to curb the PWB industry's toxic release impacts.     

Positive and negative effects of excessive water reuse to be considered in water network synthesis

Water network synthesis has focused on maximizing water reuse to minimize freshwater consumption, even though the adverse effect of water use has not been examined until now. This study evaluates and analyzes the positive and negative effects of excessive water reuse on the environmental and economic performance of a water network system. Life cycle assessment and life cycle costing are used to evaluate the environmental impacts and economic costs of the three water systems with the different levels of water reuse. Networking for low water reuse enhances both environmental and economic performance of a water system. However, networking for excessive water reuse deteriorates the economic performance of the water system, even though this networking enhances its environmental performance. Therefore, the positive and negative effects of excessive water reuse should be taken into account in developing new pinch analysis methodologies and mathematical optimization models for water network synthesis.     

Cooperative water network system to reduce carbon footprint

Much effort has been made in reducing the carbon footprint to mitigate climate change. However, water network synthesis has been focused on reducing the consumption and cost of freshwater within each industrial plant. The objective of this study is to illustrate the necessity of the cooperation of industrial plants to reduce the total carbon footprint of their water supply systems. A mathematical optimization model to minimize global warming potentials is developed to synthesize (1) a cooperative water network system (WNS) integrated over two plants and (2) an individual WNS consisting of two WNSs separated for each plant. The cooperative WNS is compared to the individual WNS. The cooperation reduces their carbon footprint and is economically feasible and profitable. A strategy for implementing the cooperation is suggested for the fair distribution of costs and benefits. As a consequence, industrial plants should cooperate with their neighbor plants to further reduce the carbon footprint.