In recent years, recycling and disposal of end-of-life (EOL) electronic products has attracted considerable attention in response to concerns over resource recovery and environmental impacts of electronic waste (e-waste). In many countries, legislation to make manufacturers responsible for taking e-waste at the end of their useful lives either has been adopted or is being considered. In this paper, by capturing different stages in the life-cycle of EOL electronic products (or, e-waste) generated from private or small-entity users, we develop two different formulations of a reverse logistics network, i.e. system-optimum model and user-optimum model, to estimate both economic and environmental effects of take-back legislation. In this system, e-waste is collected through user drop-off at designated collection sites. While we study the whole reverse logistics network associated with recycling and remanufacturing of e-waste in the system-optimum model and obtain an optimum solution from the policy maker's perspective, we split the logistics network into two distinct parts in the user-optimum model in order to derive an optimum solution from the users' standpoint. Implementing the proposed models on an illustrative example shows how they are capable of estimating the economic and environmental impacts of take-back legislation in various stages of e-waste's life-cycle.

The authors previously analysed a real-world solid waste management (SWM) system using the solid waste optimization life-cycle framework (SWOLF) to identify optimal SWM strategies that meet modelled objectives (e.g.cost, environmental impacts, landfill diversion). While mathematically optimal strategies can support SWM decision making, they may not be readily implementable because of unmodelled objectives (e.g.practical limitations, social preferences, political and management considerations). A mathematical programming technique extending SWOLF is used to systematically identify, for several scenarios, different 'optimal' SWM strategies that are maximally different from each other in terms of waste flows, while meeting modelled objectives and constraints. The performance with respect to unmodelled issues was analysed to demonstrate the flexibility in potential strategies. Practitioner feedback highlighted implementation challenges due to existing practices; however, insights gained from this exercise led to more plausible and acceptable strategies by incrementally modifying the initial SWM alternatives generated.

Policies and regulations such as Extended Producer Responsibility (EPR) have been implemented to potentially increase the recycling rate of electronic waste (e-waste), but the cost and environmental impacts of associated collection, transportation, material recovery, material re-processing, and disposal could outweigh the benefits of recycling if the e-waste management system is not effectively designed and implemented. This paper presents a quantitative, holistic framework to systematically estimate life-cycle impacts and costs associated with e-waste management. This new framework was tested using data from the state of Washington's EPR program to represent e-waste collection, transportation, processing and disposal. Sensitivity of process-level life-cycle model outputs to parameter and input variability was also conducted. Drop-off using fossil-fuel-powered personal vehicles was found to be a key contributor to cost and carbon dioxide emissions. Decision-makers must account for drop-off and consider the feasibility of alternate e-waste aggregation strategies to ensure life-cycle benefits of e-waste recycling are maximized.

Greenhouse gas emissions resulting from municipal solid waste management activities and the associated climate change impacts are getting great attention worldwide. This study investigates greenhouse gas emissions and their distribution during waste collection and transport activities in the Dammam region of Saudi Arabia. Greenhouse gas emissions and associated global warming factors were estimated based on diesel fuel consumption during waste collection and transport activities. Then, waste collection and transport data were used to parameterise a mechanistic collection model that can be used to estimate and predict future fuel consumption and greenhouse gas emissions. For the collection and transport of municipal waste in the study area, the average associated total greenhouse gas emissions were about 24,935 tCO(2)-eq. Global warming factors for three provinces were estimated as 25.23 kg CO2-eq t(-1), 25.04 kg CO2-eq t(-1), and 37.15 kg CO2-eq t(-1), respectively. Lastly, the American Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD) modelling system was used to estimate the atmospheric dispersion of greenhouse gas emissions. Model results revealed that the maximum daily greenhouse gas concentrations ranged between 0.174 and 97.3 mg m(-3), while annual average greenhouse gas concentrations were found to be between 0.012 and 27.7 mg m(-3) within the study domain. The highest greenhouse gas concentrations were observed for the regions involving the municipal solid waste collection routes owing to their higher source emission rates.

Solid waste management (SWM) is a key function of local government and is critical to protecting human health and the environment. Development of effective SWM strategies should consider comprehensive SWM process choices and policy implications on system-level cost and environmental performance. This analysis evaluated cost and select environmental implications of SWM policies for Wake County, North Carolina using a life-cycle approach. A county-specific data set and scenarios were developed to evaluate alternatives for residential municipal SWM, which included combinations of a mixed waste material recovery facility (MRF), anaerobic digestion, and waste-to-energy combustion in addition to existing SWM infrastructure (composting, landfilling, single stream recycling). Multiple landfill diversion and budget levels were considered for each scenario. At maximum diversion, the greenhouse gas (GHG) mitigation costs ranged from 30 to 900 $/MTCO2e; the lower values were when a mixed waste MRF was used, and the higher values when anaerobic digestion was used. Utilization of the mixed waste MRF was sensitive to the efficiency of material separation and operating cost. Maintaining the current separate collection scheme limited the potential for cost and GHG reductions. Municipalities seeking to cost-effectively increase landfill diversion while reducing GHGs should consider waste-to-energy, mixed waste separation, and changes to collection.

This article estimates greenhouse gas emissions and global warming factors resulting from collection of municipal solid waste to the transfer stations or landfills in Istanbul for the year of 2015. The aim of this study is to quantify and compare diesel fuel consumption and estimate the greenhouse gas emissions and global warming factors associated with municipal solid waste collection of the 39 districts of Istanbul. Each district's greenhouse gas emissions resulting from the provision and combustion of diesel fuel was estimated by considering the number of collection trips and distances to municipal solid waste facilities. The estimated greenhouse gases and global warming factors for the districts varied from 61.2 to 2759.1 t CO2-eq and from 4.60 to 15.20 kg CO2-eq t-1, respectively. The total greenhouse gas emission was estimated as 46.4E3 t CO2-eq. Lastly, the collection data from the districts was used to parameterise a collection model that can be used to estimate fuel consumption associated with municipal solid waste collection. This mechanistic model can then be used to predict future fuel consumption and greenhouse gas emissions associated with municipal solid waste collection based on projected population, waste generation, and distance to transfer stations and landfills. The greenhouse gas emissions can be reduced by decreasing the trip numbers and trip distances, building more transfer stations around the city, and making sure that the collection trucks are full in each trip.

Solid waste collection contributes to the cost, emissions, and fossil fuel required to manage municipal solid waste. Mechanistic models to estimate these parameters are necessary to perform integrated assessments of solid waste management alternatives using a life-cycle approach; however, models are only as good as their parameterization. This study presents operational waste collection data that can be used in life-cycle models for areas with similar collection systems, and provides illustrative results from a collection process model using operational data. Fuel use and times associated with various aspects of waste collection were obtained for vehicles collecting mixed residential (residual) waste, recyclables, and yard waste from single-family residences in selected municipalities. The total average fuel economy for similarly-sized diesel collection vehicles was 0.6-1.4km/L (1.4-3.3 mpg (miles per gallon)) for residual waste and 0.8-1 km/L (1.9-2.4 mpg) for recyclables. For residual waste and recyclables collection stops, the average time to collect at each residence using automated collection was 11-12 s and 13-17 s, respectively. The average time between stops was 11-12 s and 10-13 for residuals and recyclables, respectively. A single yard waste route was observed, and all collection times were longer than those measured for either recycling or residual waste. Unload or tip times were obtained or measured at a landfill, transfer station, and material recovery facility (MRF). Average time to unload was 7-9 min at a MRF, 14-22 min at a landfill, and 11 min at a transfer station. Commercial and multi-family collection vehicles tend to have longer stops and spend more time between stops than single-family collection, and a larger portion of fuel is used while driving relative to single-family collection. Roll-off vehicles, which collect more waste per stop, spend longer at each stop and drive longer distances between stops than front-loader vehicles. Diesel roll-offs averaged 2.4 km/L (5.7 mpg) and front-loaders averaged 1.4 km/L (3.3 mpg). (C) 2016 Elsevier B.V. All rights reserved.

A process model was developed using a lifecycle approach to estimate the cost and energy use associated with municipal solid waste collection, which is the most fuel-intensive and often the most costly aspect of solid waste management. The model divides collection service areas into single-family residential, multi-family residential, and commercial sectors with sector-specific, user-defined characteristics, including population, waste generation, and waste composition. Waste is collected by a set of processes (e.g.,residual waste, recyclables collection) defined by costs, collection activity parameters, and energy use. The model overpredicted fuel use by similar to 25% compared with data obtained from actual single-family residential collection routes and their average fuel efficiencies, but was within 10% when modal fuel efficiencies (e.g.,driving, idling) were considered. Adding recyclables or yard waste collection to a mixed waste collection program increased fuel consumption by approximately 75% per metric ton (Mg) and doubled cost, whereas adding both services more than doubled fuel use and tripled cost. Increasing recyclables and residual collection frequency from biweekly to weekly resulted in a predicted 53% increase in fuel consumption and 39% increase in cost. Sensitivity analysis illustrated the relative impact of changing individual parameters (e.g.,route to disposal facility distance, average time at each stop) and highlighted the need for a mechanistic model that is responsive to variations in input values.

Short pulse lasers are used for a variety of therapeutic applications in medicine. Recently ultra-short pulse lasers have gained prominence due to the reduction in collateral thermal damage to surrounding healthy tissue during tissue ablation. In this paper, ultra-short pulsed laser ablation of mouse skin tissue is analyzed by assessing the extent of damage produced due to focused laser beam irradiation. The laser used for this study is a fiber-based desktop laser (Raydiance, Inc.) having a wavelength of 1552 rim and a pulse width of 1.3 ps. The laser beam is focused on the sample surface to a spot size on the order of 10 microns, thus producing high peak intensity necessary for precise clean ablation. A parametric study is performed on in vitro mouse tissue specimens and live anaesthetized mice with mammary tumors through variation of laser parameters such as time-averaged laser power, repetition rate, laser scanning rate and irradiation time. Radial temperature distribution is measured using thermal camera to analyze the heat affected zone. Temperature measurements are performed to assess the peak temperature rise attained during ablation. A detailed histological study is performed using frozen section technique to observe the nature and extent of laser-induced damages.

The objective of this paper is to analyze the temperature distributions and heat affected zone in skin tissue medium when irradiated with either a collimated or a focused laser beam from a short pulse laser source. Experiments are performed on multi-layer tissue phantoms simulating skin tissue with embedded inhomogeneities simulating subsurface tumors and as well as on freshly excised mouse skin tissue samples. Two types of lasers have been used in this study – namely a Q-switched pulsed 1064nm Nd:YAG short pulse laser having a pulse width of 200ns and a 1552nm diode short pulsed laser having a pulse width of 1.3ps. Experimental measurements of axial and radial temperature distribution in the tissue medium are compared with the numerical modeling results. For numerical modeling, the transient radiative transport equation is first solved using a discrete ordinates method for obtaining the intensity distribution and radiative heat flux inside the tissue medium. Then the temperature distribution is obtained by coupling the bio-heat transfer equation with either hyperbolic non-Fourier or parabolic Fourier heat conduction model. The hyperbolic heat conduction equation is solved using MacCormack’s scheme with error terms correction. It is observed that experimentally measured temperature distribution is in good agreement with that predicted by hyperbolic heat conduction model. The experimental measurements demonstrate that converging laser beam focused directly at the subsurface location can produce desired high temperature at that location compared to that produced by collimated laser beam for the same laser parameters. Finally the ablated tissue removal is characterized using histological studies as a function of laser parameters.

Ultra-short pulsed lasers are known for their ability to precisely machine materials including human hard and soft tissues while minimizing the amount of thermal energy deposited to the surroundings. Non-thermal ablation produced by ultra-short pulsed lasers in the femtosecond to picosecond range is very effective for dental applications. As shown in Figure 1, most decay occurs in the dentin, which is found between the outer surface (enamel) and the inner region containing the nerve endings (pulp) [1]. Caries removal and the preparation of cavities in dentistry are primarily performed by the use of mechanical drills. The current techniques are invasive and cause patient discomfort. Due to the vibrations of the drills it is necessary to use local anesthetic for the majority of dental procedures. A continuous water spray is used in conjunction with the drills to balance the temperature rise produced by mechanical vibrations. Drills are somewhat limited in precision causing a large amount of healthy tooth to be lost during any restoration process. Replacing a multitude of mechanical tools with one non-invasive, accurate and painless laser treatment will be a huge advancement to the current dental techniques.