Material flow analysis of used personal computers in Japan

Most personal computers (PCs) are discarded by consumers after the data files have been moved to a new PC. Therefore, a used PC collection scheme should be created that does not depend on the distribution route of new PCs. In Japan, manufacturers’ voluntary take-back recycling schemes were established in 2001 (for business PCs) and 2003 (for household PCs). At the same time, the export of used PCs from Japan increased, affecting the domestic PC reuse market. These regulatory and economic conditions would have changed the flow of used PCs.In this paper, we developed a method of minimizing the errors in estimating the material flow of used PCs. The method’s features include utilization of both input and output flow data and elimination of subjective estimation as much as possible. Flow rate data from existing surveys were used for estimating the flow of used PCs in Japan for fiscal years (FY) 2000, 2001, and 2004. The results show that 3.92 million and 4.88 million used PCs were discarded in FY 2000 and 2001, respectively. Approximately two-thirds of the discarded PCs were disposed of or recycled within the country, one-fourth was reused within the country, and 8% were exported. In FY 2004, 7.47 million used PCs were discarded. The ratio of domestic disposal and recycling decreased to 37% in FY 2004, whereas the domestic reuse and export ratios increased to 37% and 26%, respectively. Flows from businesses to retailers in FY 2004 increased dramatically, which led to increased domestic reuse. An increase in the flow of used PCs from lease and rental companies to secondhand shops has led to increased exports. Results of interviews with members of PC reuse companies were and trade statistics were used to verify the results of our estimation of domestic reuse and export of used PCs.     

Substance flow analysis of coplanar PCBs released from waste incineration processes

Previous reports have focused on the emission of coplanar polychlorinated biphenyls (Co-PCBs) which have a toxic mechanism similar to that of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/DFs) released from municipal solid waste (MSW) incineration. Such emissions accounted for a small percentage of all the dioxins (PCDDs/DFs and Co-PCBs) recorded at the toxicity equivalent (TEQ) level. There is, however, very little information about Co-PCBs, such as the quantities being released and their effect on overall environmental pollution. The aim of this research has been to clarify the substance flow of Co-PCBs from MSW incineration processes. The results reveal that whereas the input of Co-PCBs into the MSW incineration facilities in Kyoto City was 0.13–0.29 μg-TEQ per ton waste, the total output of Co-PCBs (the sum of Co-PCBs released from emission gas, fly ash, and bottom ash) was 4.9 μg-TEQ per ton waste. The total output was therefore found to be higher than the total input. Over 90% of the total PCBs were decomposed in the incineration process. In comparing the profiles of congeners and homologues, those in the MSW were found to be similar to those detected in the atmosphere and products containing PCBs, but different from those in the MSW incineration gas. Received: August 26, 1998 / Accepted: March 2, 1999     

Numerical modelling of multiphase flow and transport processes in landfills.

Waste material in municipal landfills can be described as heterogeneous porous media, where flow and transport processes of gases and liquids are combined with local material degradation. This paper deals with the basic formulation of a multiphase flow and transport model applicable to the numerical analysis of coupled transport and reaction processes inside landfills. The transport model treats landfills within the framework of continuum mechanics, where flow and transport processes are described on a macroscopic level. The composition of organic and inorganic matter in the solid phase and its degradation are modelled on a microscopic scale. The degradation model captures the different reaction schemes of various microbial activities. Subsequently, transport and reaction processes have to be coupled, since emissions at the surface and from the drainage layer depend on the flow of leachate and gas, the transport of various substances and heat, and the biodegradation of organic matter. The theoretical considerations presented here are fundamental to the development of numerical models for the simulation of multiphase flow and transport processes inside landfills coupled with biochemical reactions and heat generation. The implicit modelling of leachate and gas flows including growth and decay of micro-organisms are innovative contributions to landfill modelling     

Material flow indicators to measure progress toward a sound material-cycle society

This article reviews recent progress in material flow analysis and its use in providing resource productivity indicators and is based on developments in Japanese policy toward a sound material-cycle society and in international forums such as within the Organisation for Economic Development and Cooperation, covering both institutional and methodological issues. Indicators derived from economy-wide material flow accounts such as direct material inputs are useful to demonstrate the absolute size of a physical economy and to reinforce the need to both reduce consumption of natural resources and limit waste generation. Interpretation of material flows as resources and potential environmental impacts is discussed, and linkages between the size of material flows and specific environmental impacts and damage must be further elaborated for use in environmental policy. Lessons learned from the practical use of resource productivity indicators are also discussed. Additional indicators are needed that can be used to evaluate the performance of microeconomic contributors. The need for an integrated approach that links upstream resource issues and downstream waste issues through the 3Rs concept or the circular economy/society concept is attracting increasing attention. Consequently, the accumulation of reliable scientific knowledge and data in this field in a fully international context is essential.     

A multi-component two-phase flow algorithm for use in landfill processes modelling

This paper describes the finite difference algorithm that has been developed for the flow sub-model of the University of Southampton landfill degradation and transport model LDAT. The liquid and gas phase flow components are first decoupled from the solid phase of the full multi-phase, multi-component landfill process constitutive equations and are then rearranged into a format that can be applied as a calculation procedure within the framework of a three dimensional array of finite difference rectangular elements.The algorithm contains a source term which accommodates the non-flow landfill processes of degradation, gas solubility, and leachate chemical equilibrium, sub-models that have been described in White and Beaven (2013).The paper includes an illustration of the application of the flow sub-model in the context of the leachate recirculation tests carried out at the Beddington landfill project. This illustration demonstrates the ability of the sub-model to track movement in the gas phase as well as the liquid phase, and to simulate multi-directional flow patterns that are different in each of the phases.     

国外物质流分析研究进展

回顾了国外物质流分析研究的起源和发展,并对其主流研究方法作一概述;探讨了物质流分析研究框架及指标体系的发展及应用,对30余个国家的指标体系使用情况做一统计;总结了国外已研究物质流分析的主要国家物质流分析信息的应用情况;指出了国外物质流分析研究的不足之处。     

Comparative analysis of anaerobically digested wastes flow properties

The flow curve of anaerobically digested wastes from different origins was determined through rheological measurements. Regardless of their origin, samples can be divided into two families: simple non-Newtonian liquids well modelled by basic power law below 10%DC and viscoelastic liquids with a yield stress, well modelled by a Herschel–Bulkley model above. In all the cases, the rheological behaviour is driven by both the organic content and the volatile fraction (organic content/solid content), indicating that anaerobic digestion tends to smooth the rheological characteristics of organic wastes, whichever their origins.     

Research for MSW flow analysis in developing nations

Developing nations have various problems regarding municipal solid waste (MSW). Therefore, to carry out a systematic review of the MSW problems in the target area and to formulate a well-considered management plan, it is extremely important to understand the present MSW flow in the region. One of the authors participated in the nine solid waste management (SWM) studies in developing nations undertaken under the technical cooperation program of the Japan International Cooperation Agency (JICA). Based on these studies, this paper reviews the results of research in developing countries regarding different MSW streams, the factors that cause the differences, and the elements considered to have the most impact on those streams. This research identifies several issues regarding MSW streams in developing nations. The MSW generation rate per capita in developing countries is generally said to grow in proportion to the GNP. However, the findings of this research show no correlation between the two; instead, there is a relationship between the GNP and the collection rate. To formulate proper future MSW management plans in countries with low collection rates, it is very important to forecast the rates of self-disposed and recycled waste, and their fluctuations. These are affected by urban structure, collection services, etc. Received: January 27, 2000 / Accepted: July 19, 2000     

Ammonia flow analysis in the domestic fertilizer industry of South Korea

Journal of Material Cycles and Waste Management - In this study, an ammonia flow analysis that presents how ammonia is used or handled in the South Korean fertilizer industry is developed using...     

Assessing computer waste generation in Chile using material flow analysis

The quantities of e-waste are expected to increase sharply in Chile. The purpose of this paper is to provide a quantitative data basis on generated e-waste quantities. A material flow analysis was carried out assessing the generation of e-waste from computer equipment (desktop and laptop PCs as well as CRT and LCD-monitors). Import and sales data were collected from the Chilean Customs database as well as from publications by the International Data Corporation. A survey was conducted to determine consumers’ choices with respect to storage, re-use and disposal of computer equipment. The generation of e-waste was assessed in a baseline as well as upper and lower scenarios until 2020.The results for the baseline scenario show that about 10,000 and 20,000 tons of computer waste may be generated in the years 2010 and 2020, respectively. The cumulative e-waste generation will be four to five times higher in the upcoming decade (2010–2019) than during the current decade (2000–2009). By 2020, the shares of LCD-monitors and laptops will increase more rapidly replacing other e-waste including the CRT-monitors. The model also shows the principal flows of computer equipment from production and sale to recycling and disposal. The re-use of computer equipment plays an important role in Chile. An appropriate recycling scheme will have to be introduced to provide adequate solutions for the growing rate of e-waste generation.     

Thermodynamic analysis of the role of chlorine and sulfur environments during combustion and incineration processes

 In order to control the emission of trace metals from combustion and incineration systems, sorbents and filters are sometimes used. However, the effectiveness of these methods is greatly affected by the volatility of the metals and the way in which they speciate during combustion, and afterwards during condensation, and physical or chemical sorption. Although there has been a lot of research into the mechanisms by which trace metals speciate and subsequently appear in submicron particles, the details of these mechanisms are not yet thoroughly understood. In this study, a chemical equilibrium approach was used to qualitatively determine the speciation of lead, cadmium, and chromium in Cl and S environments. The reaction conditions of sorbents were also tested numerically in order to understand the reaction behavior of metals with sorbents. This article reports the influence of different concentrations of Cl and SO₂ on Pb, Cd, and Cr speciation, as representatives of other trace elements. The partitioning behavior of metals during combustion was also examined for Cl and S. The results obtained indicate that most metals exist in the vapor phase, even at low temperatures, when chlorine is present. However, the addition of SO₂ enhances the formation of the condensed phase, except at extremely high temperatures. This observation was not significant for Cd or Cr. The higher the concentration of Cl the higher the retention of trace metals in the vapor phase, even at low temperatures. Results from comparisons of the reactivities of mixed metals with Cl indicate that the presence of Fe limits the reactivity of most trace metals with Cl except at higher concentrations. In the presence of Fe, alkali metals are the first to react with Cl. If Fe is not present, most trace metals react with Cl, and the activity increases with higher concentrations. On the other hand, the partitioning characteristics of S show that its presence generally means that metals remain in the condensed phase. Sulfur is more reactive with alkali metals than with other trace metals. Received: June 6, 2001 / Accepted: April 30, 2002     

Potential e-waste generated from households in Indonesia using material flow analysis

Waste of electronic and electrical equipment (e-waste) generated in Indonesia is expected to increase due to high growth of the Indonesian economy and fast development in technology. As Indonesia has not yet had specified criteria on e-waste, in this study, e-waste is defined as any obsolete or unwanted electronic and electrical equipment that is introduced into the recycling and disposal process. The objective of this study is to estimate the e-waste generated in Indonesian households using the method of material flow analysis. The amount of generated e-waste could be used for constructing an e-waste recycling management system in Indonesia. E-waste materials that need to be treated could be known. In this study, some types of equipment, such as television, washing machine, refrigerator, personal computer, and mobile phone, were chosen to be tracers. Using the modified material flow analysis model proposed by Steubing et al. (Waste Manage 30:473–482, 38), the potential e-waste that was generated from households was estimated. The total estimated accumulation of generated e-waste from households in 2015 and 2025 is about 285,000 and 622,000 tonnes, respectively. If a proper recycling system was in place, a new source for valuable materials recovery would be created, as well as protecting the environment and health.     

Sensitivity analysis and literature review of parameters controlling local biodegradation processes in municipal solid waste landfills

The local gas production rate in municipal landfills is influenced by a large number of processes, which have been modelled by a local mechanistic reaction model based on Monod kinetics. This type of model, however, requires over 40 input parameters. The aim of this research was to review published values for these input parameters, and to analyse the sensitivity of the model to changes in each of them. Included were rate constants based on Monod kinetics, general rate-controlling variables, and parameters that influence the local pH and temperature of the waste. Mathematical functions that describe the influence of water content, temperature, and pH on biodegradation rates were calibrated on the basis of literature data. The results of the sensitivity analysis suggest that the parameters with the largest impact on model output are the hydrolysis constant k(Hy), the kinetic constants [Formula: see text] , [Formula: see text] , [Formula: see text] , K(i,ac,Hy), and [Formula: see text] , the water content, temperature, pH, initial concentration of X(me), the enthalpy of formation of the original organic matter, as well as the protein content and buffering capacity of the waste. These parameters, therefore, should be carefully selected when similar modelling studies are performed.     

Estimating construction and demolition debris generation using a materials flow analysis approach

The magnitude and composition of a region’s construction and demolition (C&D) debris should be understood when developing rules, policies and strategies for managing this segment of the solid waste stream. In the US, several national estimates have been conducted using a weight-per-construction-area approximation; national estimates using alternative procedures such as those used for other segments of the solid waste stream have not been reported for C&D debris. This paper presents an evaluation of a materials flow analysis (MFA) approach for estimating C&D debris generation and composition for a large region (the US). The consumption of construction materials in the US and typical waste factors used for construction materials purchasing were used to estimate the mass of solid waste generated as a result of construction activities. Debris from demolition activities was predicted from various historical construction materials consumption data and estimates of average service lives of the materials. The MFA approach estimated that approximately 610–780 × 10⁶ Mg of C&D debris was generated in 2002. This predicted mass exceeds previous estimates using other C&D debris predictive methodologies and reflects the large waste stream that exists.     

Separate collection and bio-waste valorization in the Italian poultry sector by material flow analysis

Journal of Material Cycles and Waste Management - Poultry meat production and consumption face several challenges under economic, social and environmental perspectives, and increasing concerns are...     

A simplified material flow analysis employing local expert judgment and its impact on uncertainty

Material flow analysis (MFA) is an effective tool for waste management, but low- and middle-income countries lack essential data for MFA. This study proposed a simplified MFA (sMFA) utilizing local expert judgment (LEJ) and examining the impact of simplification on its uncertainty. A stochastic sMFA model was developed for nitrogen and phosphorus in urban Mandalay, Myanmar. This model was compared with the intensive MFA (iMFA) model employing intensive surveys for primary data collection. For the total loadings to the environment, the medians of the sMFA were higher by 3% and 11%, respectively, for nitrogen and phosphorus than those of the iMFA. The widths of the 80% confidence intervals of these loadings in the sMFA, normalized by those in the iMFA, were − 0.05 and − 0.11, respectively. The three largest flows to the environment were the same for the two models: on-site sanitation effluent/leakage, greywater, and industrial wastewater. Large median gaps between the models were observed for industrial wastewater, fecal sludge, and human excreta, associated with informal waste management, whereby LEJ did not work well. Overall, the sMFA demonstrated a good estimation of nitrogen and phosphorus flows with limited increase of uncertainty, still requiring focused attention on informal waste streams.

Graphical abstract

     

Scenario assessment of neodymium recycling in Japan based on substance flow analysis and future demand forecast

With the increasing demand for energy-saving technologies, neodymium-iron-boron magnets have been widely utilized in high-efficiency motors. However, the reserves of neodymium, which is a rare earth element (REE), are limited; thus, a strategy for scaling up the REE supply is highly required. In this study, a scenario assessment was conducted to evaluate the effect of material recycling of neodymium from final product waste. Domestic substance flow analysis of neodymium was conducted by focusing on the waste flow of the final product. Moreover, the demand and waste of neodymium until 2050 were forecasted using various multivariate analysis methods. The results showed that the domestic waste of neodymium was forecasted to be 3866–4217 tons/year by 2050. However, material recycling of neodymium from final product waste may cause an additional increase in production by “circular economy rebound”. Considering that CO₂ reduction has also been a global challenge to prevent global warming, the rebound effect was calculated. Therefore, a scenario assessment was conducted to evaluate the influence of this rebound effect by estimating the CO₂ reduction. The results of this study are expected to make a significant contribution to the establishment of a new strategy for neodymium recycling.

     

Substance flow analysis of brominated flame retardants and related compounds in waste TV sets in Japan

We conducted time-series substance flow analysis of two types of brominated flame retardants (BFRs)--polybrominated diphenyl ethers (PBDEs) and tetrabromobisphenol A (TBBPA)--and two types of related compounds--Sb (used with BFRs for flame inhibition) and polybrominated dibenzo dioxins and furans (PBDDs/DFs: unintended byproducts)--in five size categories of waste TV sets in Japan. Two scenarios were created with BFR substitutions and compared to a "business as usual" scenario in order to obtain basic information for strategic product management. The results showed that the use of DecaBDE in rear and front covers of TV sets began in fiscal 1987-1990 and 1993-1996, respectively, and that TBBPA was used to some extent as a substitute for DecaBDE in the 90s. The amount of waste Br in the plastic covers is predicted to increase until at least fiscal 2020 due to the increasing size of TV sets. Although substitution of BFRs with non-BFRs in Japan by 2006 will reduce waste Br, the amount in waste TV sets will not peak until fiscal 2009. The results will help inform decisions in Japan regarding the recovery and disposal of waste TV sets. The methods used would benefit waste managers faced with similar issues in other countries.     

Material Flows in Sweden 2004

This paper presents and discusses the method and results of account for material flows in Sweden for the year 2004. The results show that it is possible to compile material flow data from existing sources in the Swedish statistical system. By using the European classification system of goods, the Combined Nomenclature, as the basic unit of the data collection, both data collection and aggregation into material flow categories were made possible. Although these data exist in the statistical system, they are not easily available for the scientific community. This is due to several reasons, such as the aggregation of data in the system of statistics not corresponding to the material flow account structure and the fact that data on import and export of materials are organised differently than data for domestic extraction. Almost 50% of the material flows in Sweden are flows of minerals, mainly construction minerals followed by iron ores. Most of the extracted iron ores are exported. In comparison with other European countries this generates a unique situation with Sweden as the only net exporter of iron ores. The flow of biomass in terms of wood is also considerable (26% of the Swedish material flows in 2004). The domestic material consumption (inflow) per capita in 2004 was 8 tonnes minerals, 6 tonnes biomass and almost 3 tonnes of fossil fuels. Of the material flows of fossil fuels petroleum and natural gas dominates with 90%.     

A material flow analysis on current electrical and electronic waste disposal from Hong Kong households

A material flow study on five types of household electrical and electronic equipment, namely television, washing machine, air conditioner, refrigerator and personal computer (TWARC) was conducted to assist the Government of Hong Kong to establish an e-waste take-back system. This study is the first systematic attempt on identifying key TWARC waste disposal outlets and trade practices of key parties involved in Hong Kong. Results from two questionnaire surveys, on local households and private e-waste traders, were used to establish the material flow of household TWARC waste. The study revealed that the majority of obsolete TWARC were sold by households to private e-waste collectors and that the current e-waste collection network is efficient and popular with local households. However, about 65,000 tonnes/yr or 80% of household generated TWARC waste are being exported overseas by private e-waste traders, with some believed to be imported into developing countries where crude recycling methods are practiced. Should Hong Kong establish a formal recycling network with tight regulatory control on imports and exports, the potential risks of current e-waste recycling practices on e-waste recycling workers, local residents and the environment can be greatly reduced.