Flow Analysis Approach Research Articles

Evaluation of the environmental impact of end-of-life refrigerators in Colombia by material flow analysis

The management of waste electrical and electronic equipment (WEEE) represents one of the main environmental challenges on a global scale, due to the rapid growth of this type of waste and the risk it poses to both human health and the environment. Decision makers depend on reliable estimates of the generation of WEEE and the quantification of its environmental impact. However, limited data regarding the amount of equipment in use, annual sales, and the lifespan of electrical and electronic equipment pose important limitations to this assessment. In response to this challenge, this paper develops a combined dynamic material flow analysis and life cycle assessment approach to estimate the volume of end-of-life refrigerators in Colombia and measure their environmental impact. First, the dynamic MFA model is developed to calculate the number of end-of-life refrigerators between 1935 and 2050. Then, the environmental impact is estimated using the CO2 emissions generated in each of the pathways of final disposal at the end of the refrigerators’ useful life. The results highlight the importance of the formal refrigerator recycling system in Colombia, since this achieves a saving of approximately three million tonnes of CO2 emissions during the period of evaluation. They also show that delivering refrigerators to informal recyclers or throwing them into open-air dumps or bodies of water generates a considerable environmental impact in comparison. Additionally, these alternative scenarios imply the loss of more than two hundred thousand tonnes of recyclable material.

The circular economy potential of urban organic waste streams in low- and middle-income countries

There is growing recognition of the potential environmental and socio-economic benefits of applying a circular approach to urban organic waste management through resource recovery. Decisions around planning and implementing circular urban waste systems require estimates of the quantity of resources available in waste streams and their potential market value. However, studies assessing circular economy potential have so-far been conducted mostly in high-income countries, yet cities in low- and middle-income countries have different challenges when developing a circular economy. This paper addresses this gap by estimating the resource recovery potential of organic waste streams in the context of low- and middle-income countries, illustrated with the case of Kampala, Uganda. A simplified material flow analysis approach is used to track the transformation of waste streams, namely faecal sludge, sewage sludge and organic solid waste into the resource recovery products biogas, solid fuel, black soldier fly larvae and compost. Findings indicate that even at current rates of waste collection, the three waste streams combined could annually yield 135,000 tonnes of solid fuel or 39.6 million Nm3 of biogas or 15,000 tonnes of black soldier fly larvae or 108,000 tonnes of compost and revenues from the products could range from 5.1 million USD from compost to 47 million USD from biogas. The results demonstrate how complex information describing urban waste can be presented to facilitate decision making and planning by stakeholders. By highlighting different resource recovery opportunities, application of this approach could provide an incentive for more sustainable urban sanitation and waste management systems.

Application of material flow analysis for the assessment of current municipal solid waste management in Karachi, Pakistan.

This article assesses the status of the solid waste management system (SWMS) in Karachi, the largest city of Pakistan, using the material flow analysis approach, a widely applied method in waste management (WM) studies. It involves a systematic assessment of the material flows of solid waste under the current WM system. A material flow diagram is developed to visualize the input and output waste flows. This study shows the quantification and identification of municipal solid waste (MSW) flow for the year 2019, from the point of generation to the end-use and disposal. Results show that the MSW generation increased from 10,435 to 15,600 metric tonnes per day (TPD) between 2017 to 2019. Approximately, 75% of the waste generated is collected: formally (50%); and informally (25%). The material recovery is low, accounting for only 26.28% of the total waste. There is no official material recovery and recycling facility. Therefore, material recovery solely depends on the informal sector. Results show that 70% of the daily waste ends up in landfills, which is 3120 TPD more than the formally collected waste. This estimated waste of 3120 TPD flows in either due to disposal activities of the backlogged waste or informally collected waste. Overall, Karachi's SWMS performs poorly with a significant need for improvement. This study recommends adopting integrated WM approaches and inclusion of the informal sector to ensure the affordability and sustainability of the WM system.

High specific speed Francis turbine for small hydro purposes - Design methodology based on solving the inverse problem in fluid mechanics and the cavitation test experience

The paper is a result of a research and development project aimed at developing a series of types of high specific speed (90 < nsQ < 100) Francis turbines. The inverse flow analysis approach based on the hodograph theory has been employed in order to develop the blading geometry of quality high enough to minimize the subsequent CFD based optimization process. The three-dimensional turbine blades are developed on meridional stream surfaces determined using the VLM methodology. The mass and momentum conservation equations are written in a curvilinear coordinate system, which is adjusted to the streamlines by means of the Christoffel symbols. The solution is found using the method of characteristics. The developed geometry is optimized by means of the genetic algorithm implemented in CFD software. Model tests were conducted in the Institute of Fluid-Flow Machinery of the Polish Academy of Sciences. Satisfactory coincidence between design assumptions, the CFD based performance assessments and those based on the model test results attained, shows reliability of the methodology adopted. Critical cavitation numbers as established according to different criteria have been applied to plot the sigma permissible isolines on top of the efficiency hill diagram. Physical interpretation of some irregularities in diagnostic characteristics is provided.

Grey emission targets for municipalities based on material cadastres

The building stock contributes significantly to greenhouse gas (GHG) emissions. Considerable progress has been made in the energy-efficient operation of buildings, thus the importance of grey emissions is increasing and will become a future field of action for municipalities as well. So far, there is poor knowledge regarding quantities, fields of actions and impacts. This paper is addressing this gap by applying a bottom-up material flow analysis (MFA) approach on the domestic building stock of Hamburg, and by calculating material-induced grey emissions of alternative building stock compositions as well as impacts of technical and social innovations. Overall, the stock induced grey emissions amount to 41.9 million metric tons of CO2 equivalent. Impact with regard to technical innovations concerning GHG reduction is rather limited. In contrast, impact achieved by ambitious social innovation is quite significant. This means that technical innovations must be considered in a more radical way and merged with social innovations.

Analyzing present and future availability of critical high-tech minerals in waste cellphones: A case study of India

Critical high-tech minerals (CHTMs) are raw materials that are essential for a future clean-energy transition and the manufacture of high-end products. Cellphones, one of the fastest growing electronic products, contain various CHTMs. Since 2019, India has surpassed the United States to become the second largest smartphone market in the world. An increasing and alarming number of excessive waste cellphones will be generated in India in the near future. In this study, the dynamic material flow analysis approach and the Weibull distribution are adopted to analyze the volumes of accumulated waste cellphones and the contained CHTMs based on the differentiation between smartphones and feature phones in India. Moreover, a market supply model is adopted to predict the future trends of CHTMs in waste cellphones. The results show a general upward tendency of waste cellphone volume in India, which indicates that various CHTMs contained in cellphone waste can be properly reused or recycled. Future implications based on the analysis results are provided for efficient cellphone management in India.

A reactive nitrogen budget for forest land and wetlands in Latvia and Estonia

ABSTRACT Human intervention in global nitrogen cycling has led to excess reactive nitrogen (Nr) flows to the environment, impacting terrestrial ecosystems as well as the quality of the atmosphere and waterbodies. This paper presents the results of a study that quantified and compared the main flows of Nr through forest land and wetlands in Latvia and Estonia using substance flow analysis approach based on data from statistics, research results, reports, monitoring programmes, data bases and expert estimations. Input and output flows to and from the forest land and wetlands both in Latvia and Estonia are well balanced, with a trend to be a Nr sink (+1.2 kT N yr−1) for Latvia and a Nr source (−6.5 kT N yr−1) for Estonia. Major input flow to the studied pools in Estonia is a soil nitrogen stock used for forest growth, while in Latvia, it is atmospheric deposition and biological fixation. Major output flow of Nr in both countries occurs via wood and peat for industrial uses. Emissions of Nr to the atmosphere and hydrosphere from forest land and wetlands are significantly lower compared to human-related emissions such as industries, energy production, agriculture, human settlements, and transport.

A unified energy flow analysis considering initial guesses in complex multi-energy carrier systems

Multi-energy flow (MEF) analysis is the most fundamental issue in studying multi-energy carrier (MEC) systems. In the tight coupling MEC systems, the unified energy flow analysis is indispensable to tackle the problems of accuracy and in decomposition. Therefore, on the basis of the comprehensive node classification and modified Jacobian matrix, this paper proposes a unified energy flow analysis approach with Newton method considering initial guesses selection for complex MEC systems including electrical, gas, heating sub-networks. This approach is based on the presented convergence theorem, which can determine in advance whether the initialization can converge to results, since the Newton method, the main approach of the unified energy flow analysis, is sensitive to its initial guesses selection. Once the initialization can not converge, the proposed approach can help selecting proper initial guesses for Newton method to guarantee the convergence of the unified energy flow. Several cases are studied to demonstrate the effectiveness and applicability of the proposed approach on judging and choosing initialization for the unified energy flow analysis.

Electronic waste in the Caribbean: An impending environmental disaster or an opportunity for a circular economy?

Islands are bounded systems, often plagued with several sustainability challenges of limited land and resource availability, as well as pressing waste management issues. Despite these known problems, research aiming to help develop proper e-waste management systems for small island nations is scarce. Focusing on five Caribbean island states, this study provides the first comprehensive view of e-waste generation trends in an island context and explores the factors driving those trends. The study estimates Electrical and Electronic Equipment (EEE) flows for the five island cases over a period of 60 years (1965–2025), including e-waste that these flows have and will generate. A dynamic material flow analysis (MFA) approach has been used to estimate these flows and stocks for 206 product types. The results show that the five Caribbean islands produced double the e-waste per capita per year, i.e., 13 kg/cap/year compared to global average of 6.1 kg/cap/year in 2016. The aggregated amount of e-waste generated per year on these five islands seems to significantly rise in future: from 27,500 tonnes in 2010 to an estimated amount of 59,000 tonnes in 2025. This considerable estimated e-waste generation rate, when not properly managed, is not only harmful for the local environment, but also translates into considerable health impacts and loss of valuable resources. From a sustainability perspective, small islands should consider moving away from a linear to a circular economy that will limit waste generation as well as reliance on the supply of virgin materials from outside.

Analysis of shape memory alloy vibrator using harmonic balance method

Shape memory alloy (SMA) is a very important smart material, which has been widely used in many fields, especially in vibration. Phase transformation can be induced by changing temperature and its stiffness changes accordingly. In this paper, the primary resonance vibration of a one-dimensional SMA oscillator is analyzed using the harmonic balance (HB) method. The amplitude-frequency curves of the SMA oscillator with different temperatures are drawn, and the effect of temperature and frequency on the amplitude is discussed. Then, the energy flow of SMA in the vibration process is researched by the power flow analysis (PFA) approach. The time-averaged input power (TAIP) is calculated using the analytical and numerical method, respectively, and the calculation time is compared. It is found that the difference between the analytical and numerical solutions is not significant in most cases, but the calculation time of analytical solution is only about one-tenth of that of the numerical solution, which is very important in saving computational cost, real-time control and so on. Finally, some other characteristics of energy flow in the SMA oscillator are identified.

Material stocks and flows of power infrastructure development in China

As the world's largest emitter of greenhouse gases with a dominant share of coal-fired power, China is expecting a continuous clean power transition in the next decades. However, the development of power generation, transmission, and distribution infrastructure requires significant amount of construction materials, therefore an understanding of the corresponding materials demand and waste generation would be important. In this paper, we deployed a dynamic, bottom-up, and technology-specific material flow analysis approach to characterize the stocks and flows of four major construction materials (cement, steel, aluminum, and copper) associated with China's power infrastructure development from 1980 to 2050. We found that the material stocks of China's power infrastructure have increased from 30 ± 4 Mt in 1980 to 573 ± 91 Mt in 2018 (an annual growth rate of 7.7%) and will further increase to 1188 Mt and 1487 Mt in 2050, respectively, in the two energy development scenarios we constructed. While thermal and hydro power contributed the most to stocks growth in the past two decades, solar and wind power are expected to contribute more in the future. A more metal-intensive energy future is foreseen due to increasing use of steel and aluminum in renewable energy generation and use of copper and aluminum in power transmission and distribution. These patterns reflect the physical material basis of China's power transition and call for better understanding of the energy-material nexus for addressing the dual challenge of satisfying growing materials demand and addressing increasing amount of waste and environmental impacts in the next decades.

A dynamic analysis of the global warming potential associated with air conditioning at a city scale: an empirical study in Shenzhen, China

Heating, ventilation and air conditioning (HVAC) systems are a major source of energy consumption in buildings, directly and indirectly contributing to greenhouse gas (GHG) emissions. In the urban environment, and depending on local climatic conditions, air conditioning units attribute to these high energy demands. This study analyzes the use of residential air conditioning units and their associated global warming potential (GWP) between 2005 and 2030 for the city of Shenzhen, a fast-growing megacity located in Southern China. A life cycle assessment approach was adopted to quantify the GWP impacts which arise from both direct (refrigerant release) and indirect (energy consumption) sources, in combination with a materials flow analysis approach. The results show that the total GWP (expressed as carbon dioxide equivalents, CO2 eq.) from residential air conditioning systems increased from 2.2 ± 0.2 to 5.1 ± 0.4 million tonnes (Mt) CO2 eq. between 2005 and 2017, with energy consumption and refrigerant release contributing to 72.5% and 27.5% of the total demands, respectively. Immediate measures are required to restrict refrigerant release and reduce the energy consumption of air conditioning units, to help mitigate the predicted additional total emissions of 36.4 Mt. CO2 eq. potentially released between 2018 and 2030. This amount equals to approximately New Zealand's national CO2 emissions in 2017. The findings proposed in this study targets air conditioning units to reduce the GWP emissions in cities, and provide useful data references and insights for local authorities to incentivise measures for improving building energy efficiency management and performance.

Performance test of Pikohidro Cross flow Water Turbine using multilevel double penstock

This study aims to examine the performance of pico hydro scale cross flow water turbines using multilevel double penstock as a conductor of water flow. Multilevel double penstock is used to reduce the transportation process from highways that are affordable to four-wheeled vehicles / cars to the location of the installation of the turbine. This condition causes the need for small-scale water turbine designs with lightweight construction with a kock down system. Overall the picohidro scale turbine construction is needed relatively cheaper transportation costs, so that people who have not been reached by the PLN network can be touched by small and cheap electricity. Turbine construction data has a runner diameter of 170 mm, body dimensions 200 mm x 300 mm x 250 mm, frame 250 mm x 800 mm. Pool tando 600 mm x 1200 mm and penstock length 16m. The power produced is theoretically around 2500 watts, with a data flow of 50 liters / second and a water level of 8 m. 65% efficiency. The research method is analyzing the double penstock water flow, by making paralon pipes in stages, ranging from 5 incci diameter, 4 inches and 3 inches, flow analysis approach using a gradient line, where the incoming water velocity and water velocity come out until entering the transmitting pipe. The performance results of this turbine provide an average actual power of up to 2000 watts. The stability of the inlet water condition is used by the Tando pond as a water bath. If there is excess water in the sediment tank, the water gate is used out, where excess water will automatically flow into the exhaust channel.

Impacts of biogas production on nitrogen flows on Dutch dairy system: Multiple level assessment of nitrogen indicators within the biogas production chain

AbstractBiogas production on dairy farms is promoted as a climate change measure since it captures methane, a greenhouse gas emitted by manure, and produces renewable energy. Digestate is a by‐product of biogas production and is often used for nutrient recycling in a similar way as traditional manure. Despite having similar functions, manure and digestate have different behaviors related to nitrogen recycling and nitrogen emissions which are significant agricultural and environmental concerns of manure. This paper provides an insight into the impact of biogas production on nitrogen emissions and nitrogen recycling issues of the current dairy farming practice. Using the Substance Flow Analysis (SFA) approach, we analyzed the changes on three levels: manure handling, dairy farm, and the whole chain. Four biogas production options on a Dutch dairy farm related to types and sources of feedstocks were considered. We quantified biogas output, nitrogen fertilizer replacement percentage (%) and consequential nitrogen emissions (kgN/year; kgN/m3 biogas produced) of these productions in comparison with the baseline of current dairy farming without biogas. We conclude that biogas production options with additional feedstocks will cause profound changes in the nitrogen recycling on dairy farms and the nitrogen emissions at the chain level. Besides, the results show that determining the optimal biogas production option can be challenging as the evaluation is highly dependent on the used nitrogen indicator and the included level of analysis. Our findings show how SFA and a multilevel perspective can give a broader understanding of environmental trade‐offs.

A Discounted Stochastic Multiplayer Game Approach for Vehicle-to-Grid Voltage Regulation

Along with the diversification of electricity market, the voltage regulation (VR) service is opened up to various qualified providers to meet the enormous demand, among which, the electric vehicle (EV) aggregators (AGGs) can integrate the scattered EVs and play the role of VR sources with a high response speed and low cost. In order to coordinate the VR service providers to satisfy the total VR requirement, auction mechanisms are widely used to select VR sources to achieve better performance. Yet, it is challenging to optimize the strategy of each EV AGG in the auction process due to the stochastic EV mobility, various distribution network topology, and the competition mechanism. To address these challenges, we proposed a discounted stochastic multiplayer game (DSMG) approach to analyze the competition among EV AGGs. Due to the constraint of distribution network topology, the efficiency of the VR sources at different locations can be different. Thus, the impact of distribution network topology on the VR efficiency is investigated by DSO when evaluating the capacity of AGGs. The randomness of EV numbers is considered when predicting the AGGs’ available VR capacity so that the tendency for the AGGs to follow the optimal strategies can be modeled accurately. Accordingly, a linear power flow analysis approach and a battery pool model are developed to address the distribution network topology and EV mobility, respectively. Then, the DSMG approach is used in the VR auction process to optimize the AGGs’ strategies. The existence proof of the stationary Markov perfect equilibrium is presented, and the corresponding algorithms to obtain the equilibrium is proposed. The performance of the proposed DSMG approach is evaluated and compared with other approaches based on the IEEE 33-bus test feeder, IEEE 123-bus test feeder, and the real-world generation and load data from PVWatts Calculator and Market Analysis and Information System, respectively.

Assessing mineral extraction and trade in China from 1992 to 2015: A comparison of material flow analysis and exergoecological approach

Mineral resources have made great contributions to China's economic development since late 20th century. However, China is also facing many challenges in current days, such as mineral depletion and environmental pollution. In order to identify the main minerals that affect China's mineral capital loss and environmental damage as well as to provide some useful information for the formulation of mineral development policy in China, the exergy replacement costs (ERC) and material flow analysis (MFA) principles are applied. In this paper, we analyze the production and international trade of 28 non-fuel minerals and 3 fossil fuels in China from 1992 to 2015. The results showed that (1) the total loss of mineral capital in China is 5.2 billion tonnes of oil equivalent in the period of 1992–2015, and the main minerals that affect mineral capital loss include coal, limestone, iron ore, aluminum, gypsum, potash, salt and zinc; (2) China appears to be a country of self-sufficient for minerals in mass terms, but it is increasingly dependent on imports of high-quality minerals, especially for non-fuels minerals, such as aluminum; (3) it is necessary to consider the quality of minerals when assessing for international environment burden transfer caused by mining activities; and (4) compared with conventional MFA, the change of China's mineral extraction and trade measured under ERC are more sensitive to changes in mineral development policy. Hence, China should improve resources efficiency by (1) giving priority to the management of coal, iron ore, aluminum, limestone et al. to avoid over-exploitation; (2) expanding the sources of mineral resources imports, especially for high-quality non-fuel minerals; and (3) enhancing the technical research and development to reduce energy consumption throughout the life cycle of mineral resources.

Material Flow Analysis as a Decision Supporting Tool for Faecal Sludge Resource Recovery: Mathematical Formulation and Quantification

In this work, a conceptual framework for faecal sludge (FS) management and resource recovery in Dar es Salaam city was developed. Material Flow Analysis (MFA) approach was used to assess and quantify the current materials and nutrients to support on decisions for nutrient recovery and minimize environmental pollution in three unplanned settlements of Manzese, Keko and Kipawa in Dar es Salaam city. Nitrogen and Phosphorus were chosen as indicators for the evaluation of the process. The results showed that about 75% of the Dar es Salaam city population relies on pit latrines and 15% connected to septic tanks, translating to a large amount of faecal sludge being contained onsite. The situational analysis study on faecal sludge management (FSM) showed that the collection, treatment and proper disposal of FS are the major challenges that pose risks to public health. Currently, 57% of faecal sludge generated in Dar es Salaam is disposed to the environment inappropriately. Onsite Sanitation Systems in all study areas are the main polluters, discharging large quantity of nutrients to the environment. About 37.7% of faecal sludge is with large amount of nutrients emptied from onsite sanitation systems discharged to the environment and through seepage to the groundwater.

Information Flow Analysis of Combined Simulink/Stateflow Models

Simulink and its state machine design toolbox Stateflow are widely-used industrial tools for the development of complex embedded systems. Due to the strongly differing execution semantics of Simulink and Stateflow, the analysis of combined models poses a difficult challenge. In this paper, we present a novel approach to relate the semantics of both the dynamic and the controller components and use it to perform an information flow analysis on a combined model consisting of discrete Simulink components and Stateflow controllers. The key idea of our approach is that we analyze the information flow in a given model by computing an over-approximation of the control flow, and deduce whether all control flow conditions combined permit information to flow on a given path or not. Our control flow analysis approach is threefold: (1) we identify timed path conditions which capture the conditions for time-dependent information flow on paths of interest for (discrete) Simulink components, and translate them into a UPPAAL timed automata representation, (2) we translate the Stateflow components to UPPAAL timed automata, and (3) we perform model checking on the resulting set of automata to analyze the existence of paths in the combined model. With our approach, we safely rule out the existence of information flow on specific paths through a model, which enables us to reason about non-interference between model parts and the compliance with security policies. Furthermore, our approach presents a starting point to generate feasible, efficient test cases and to perform compositional verification. We demonstrate the applicability of our approach using two versions of a complex case study from the automotive domain consisting of multiple safety-critical components communicating over a shared bus system.

Integrated assessment of resource-energy-environment nexus in China's iron and steel industry

MESSAGEix model are widely used for forecasting long-term energy consumption and emissions, as well as modelling the possible GHGs mitigations. However, because of the complexity of manufacturing sectors, the MESSAGEix model aggregate detailed technology options and thereby miss linkages across sub-sectors, which leads to energy saving potentials are often not very realistic and cannot be used to design specific policies. Here, we integrate Material/Energy/water Flow Analysis (MEWFA) and nexus approach into the MESSAGEix to estimate resource-energy-environment nexus in China's iron and steel industry. Results show that between 2010 and 2050 energy efficiency measures and route shifting of China's steel industry will decrease raw material input by 14%, energy use by 7%, water consumption by 8%, CO2 emissions by 7%, NOx emissions by 9%, and SO2 emissions by 14%, respectively. However, water withdrawal and PM2.5 emissions will increase by 14% and 20%, respectively. The main reason is that water withdrawal and PM2.5 emissions in the process of BF-BOF are over 4 times lower than the process scrap-EAF. Therefore, policy makers should consider nexus effects when design integrated policy to achieve multiple targets. Finally, future directions on enhancing the representation of manufacturing sectors in IAMs are given.

Construction and demolition waste generation in cities in India: an integrated approach

ABSTRACTThis paper quantifies construction and demolition waste (C&DW) generation rate in Indian cities using bottom-up material flow analysis approach. A dynamic model was applied to different classes of cities in India to investigate how C&DW generation rate varies across different classes of cities. The data on construction and demolition activities in different classes of cities were estimated from information reported in secondary literature. The results show that urban areas in India generated over 150 million tonnes of C&DW in 2016, and almost 50% of waste was generated in small to medium towns. The paper concludes with discussion on opportunities for recycling of C&DW and closing the material loops in Indian cities.