Applying Ecological Input-Output Flow Analysis to Material Flows in Industrial Systems: Part I: Tracing Flows

Input-output mathematics, which allows a modeler to fully consider direct and indirect relationships among conserved flows in a system, has a long history in economics with prominent use dating to Leontief in the 1930s. Nearly all previous industrial applications of input-output analysis have been grounded in the monetary flows of an economy. Here however, because of the central nature of physical flows in the environmental impact of industry, we consider physical flows to be a fundamental component of an industrial economy. Hence, we propose an input-output based approach for modeling physical flows in industry independent of their monetary implications.
In this first part of a two-part article, a framework for using input-output mathematics to model material and energy flows is constructed from a foundation laid by previous research in nutrient and energy cycling in natural ecosystems. The mathematics of input-output flow analysis is presented from an ecological perspective, culminating in two core capabilities: tracing of flows with environs (investigated in this article) and characterizing system behavior with flow metrics (presented in the second article). We assert that environ analysis is an effective means for tracing flows through industrial systems while fully considering direct and indirect flow paths. We explore material flows of aluminum and five other metals in depth using environ analysis in this article.     

Quantitative Evaluation of Data Quality in Regional Material Flow Analysis

A method for quantitative evaluation of data quality in regional material flow analysis (MFA) is presented. The principal idea is that data quality is a multidimensional problem that cannot be judged by individual characteristics such as the data source, given that data from official statistics may not be per se of good quality and expert estimations may not be per se of bad quality, respectively. It appears that MFA data are never totally accurate and may have certain defects that impair the quality of the data in more than one dimension. The concept of MFA information defects is introduced, and these information defects are mathematically formalized as functions of data characteristics. They are quantified on a scale from 0 (no information defect) to 1 (maximum information defect). The proposed method is illustrated in a case study on palladium flows in Austria. A quantitative evaluation of data quality provides opportunities for understanding and assessing MFA results, their a priori information basis, their reliability in decision making, and data uncertainties. It is a formal step toward better reproducibility and more transparency in MFA.     

Global Phosphorus Flows in the Industrial Economy From a Production Perspective

Human activity has quadrupled the mobilization of phosphorus (P), a nonrenewable resource that is not fully recycled biologically or industrially. P is accumulated in both water and solid waste due to fertilizer application and industrial, agricultural, and animal P consumption. This paper characterizes the industrial flows, which, although smaller than the agricultural and animal flows, are an important phosphorus source contributing to the pollution of surface waters. We present the quantification of the network of flows as constrained by mass balances of the global annual metabolism of phosphorus, based on global consumption for 2004, all of which eventually ends up as waste and in the soil and water systems. We find that on a yearly basis, 18.9 million metric tons (MMT) of P is produced, of which close to 75% goes to fertilizer and the rest to industrial and others uses. Phosphoric acid is the precursor for many of the intermediate and end uses of phosphate compounds described in this study and accounts for almost 80% of all P consumed. Eventually, all of the P goes to waste: 18.5 MMT ends up in the soil as solid waste, and 1.32 MMT is emissions to air and water. Besides quantifying P flows through our economy, we also consider some possible measures that could be taken to increase the degree of recovery and optimization of this resource and others that are closely related, such as the recovery of sulfur from gypsum and wastewater (sludge), and fluorine from wet phosphoric acid production.     

Food Consumption and Nutrient Flows: Nitrogen in Sweden Since the 1870s

Changes in food consumption and related processes have a significant impact on the flow of nitrogen in the environment. This study identifies both flows within the system and emissions to the hydrosphere and atmosphere. A case study of an average inhabitant of the city of Linköping, Sweden, covers the years 1870, 1900, 1950, and 2000 and includes changes in food consumption and processing, agricultural production, and organic waste handling practices. Emissions to the hydrosphere from organic waste handling increased from 0.57 kilograms of nitrogen per capita per year (kg N/cap per year) to 3.1 kg N/cap per year, whereas the total flow of nitrogen to waste deposits grew from a negligible amount to 1.7 kg N/cap per year. The largest flow of nitrogen during the entire period came from fodder. The input of chemical fertilizer rose gradually to a high level of 15 kg N/cap per year in the year 2000. The total load per capita disposed of to the environment decreased during these 130 years by about 30%.     

Future Redistribution of Cadmium to Arable Swedish Soils: A Substance Stock Analysis

This article describes a stock-based methodology designed to analyze the redistribution of substance stocks to environmental compartments. The methodology is then applied to investigate the requirements and possibilities for avoiding undesired future accumulation of cadmium in Swedish arable soils. A prospective decomposition analysis of human cadmium mobilization is thus performed to estimate the potential amounts that can end up in arable soils through different flows from the cadmium stocks identified. The requirements for cadmium abatement to achieve prescribed goals for accumulation limits are determined and compared with past and current achievements and with the varying qualities of possible abatement methods.
A stock-based methodology adds some important information to traditional scenario techniques based on substance flow analysis. The most obvious is that the fact that stocks are limited actually matters for long-term accumulation of cadmium in arable land. The methodology may also contribute certain indicators, for instance, on abatement requirements, which could serve as a complement to regulation and local quality measures on specific flows at an aggregated policy level. The stock perspective also sheds new light on actions such as increased recycling.
Concerning the specific example used in the study, it is possible to achieve a future addition of cadmium in Swedish agricultural soils that is significantly lower than in the past, although the amount depends to a large degree on activities and policies outside Sweden. Considerable uncertainty exists regarding future depositions from air, especially that from distributed small-scale emissions from fuel burning and reemission of already deposited cadmium from natural media. Measures must also be taken to guarantee a continued low addition in the form of mineral phosphorus fertilizers.     

Full Mode and Attribution Mode in Environmental Analysis

Several tools exist for the analysis of the environmental impacts of chains or networks of processes. These relatively simple tools include materials flow accounting (MFA), substance flow analysis (SFA), life-cycle assessment (LCA), energy analysis, and environmentally extended input-output analysis (IOA), all based on fixed input-output relations. They are characterized by the nature of their flow objects, such as products, materials, energy, substances, or money flows, and by their spatial and temporal characteristics. These characteristics are insufficient for their methodological characterization, and sometimes lead to inappropriate use. More clarity is desirable, both for clearer guidance of applications and for a more consistent methodology development. In addition to the nature of the flow object and to spatial and temporal characteristics, another key feature concerns the way in which processes are included in a system to be analyzed.
The inclusion of processes can be done in two fundamentally different ways: according to a full mode of analysis, with the inclusion of all flows and related processes to their full extent as present in a region in a specific period of time; and according to an attribution mode, taking processes into account insofar as these are required for a given social demand, function, or activity, in principle whenever and wherever these processes take place. This distinction, which cuts across families of tools that traditionally belong together, appears to have significant methodological and practical implications. Thus the distinction between the two modes of analysis, however crucial it may be, strengthens the idea of one coherent family of tools for environmental systems analysis.     

Particle Flow Analysis

Several authors have highlighted the potential risks of nanoparticles (NPs). Still, little is known about the magnitude of emissions of NPs from society. Here, the method of explorative particle flow analysis (PFA), a modification of the more well‐known substance flow analysis (SFA), is suggested. In explorative PFA, particle number instead of mass is used as flow and stock metric and explorative scenarios are used to account for potential technology diffusion and, consequently, potentially higher emissions. The method has been applied in a case study of the use phase of titanium dioxide (TiO₂) NPs in paint, sunscreen and self‐cleaning cement. The results indicate that the current largest emissions of TiO₂ NPs originate from the use of sunscreen. One scenario implies that, in the future, the largest flows and stocks of TiO₂ NPs could be related to self‐cleaning cement. Gaps in current knowledge are identified and suggestions for future research are given.     

降水量变化对蒙古栎落叶分解过程的间接影响

分析了在4种不同降水量条件下蒙古栎叶凋落物基质质量的变化,并应用分解袋法研究其凋落物在蒙古栎次生林内的分解过程.结果表明：与对照相比,降水量减少条件下,蒙古栎叶凋落物的初始N、P、K浓度显著升高,初始木质素浓度显著降低,凋落物分解速率大,N、P、K矿化率高,N和P固持时间缩短;降水量增加情况下,其凋落物初始N浓度显著降低、木质素浓度显著升高,N、P、K矿化率低,N和P固持时间延长.4种类型叶片凋落物的质量损失过程均符合指数降解模型,分解速率可以由凋落物木质素/N来预测.相关性分析显示,木质素浓度高、N浓度低的两种凋落物的分解速率与N浓度相关性最大;而木质素浓度低、N浓度高的两种凋落物的分解速率与木质素浓度相关性最大.说明降水量的变化显著地改变了蒙古栎叶凋落物的基质质量,进而间接地改变了凋落物的分解过程.     

Decomposition Analysis of Finnish Material Flows: 1960–1996

To the extent that environmental impacts are the consequence of the magnitude of total material input into production in an economy, they can be lessened by reducing the use of materials—by concentrating on what has been called qualitative growth. This article presents a summary of Finnish resource use over the period 1960–1996 as a means of evaluating the trends in material use and providing a basis for assessments of sustainability. It adapts the technique of decomposition analysis developed in the field of energy studies to distinguish the effects of changes in aggregate economic activity ("activity effect"), composition of industrial activity ("structural effect") and materials intensity of use ("intensity effect") on a sectoral basis.p
According to the analysis presented here, materials consumption in Finland has grown substantially between 1960 and 1996 in the electricity, gas and water supply, pulp and paper production, civil engineering, and mining and quarrying sectors. In the same period, the ratio of GDP/mass of material mobilized has improved by 175 percent. Economic growth has caused the largest increases in materials use in the building of infrastructures; for example roads, waterways, means of supplying electricity, gas, and water, and in the production of paper and paper products. The least growth took place in the transport, basic metals production, and mining and quarrying sectors.     

Cadmium Flows Caused by the Worldwide Production of Primary Zinc Metal

Material flows of the economic cycle can contain toxic substances, which enter the economy as impurities in raw materials or are intentionally added as minor or even main constituents during the manufacture of industrial or consumer goods. Cadmium, predominantly associated with zinc minerals, is a by-product of the primary zinc production. Cadmium is generated when zinc is extracted from zinc ores and concentrates, an intermediate product resulting from flotation processing after the zinc ore has been mined and milled. Information on the amount of cadmium generated from zinc extraction is rarely published. In this article, we assess generation and fate of cadmium accumulating worldwide in the production of primary zinc from ores and concentrates. Model calculations for the beginning of the 21st century show that annually about 30,000 tonnes of cadmium were generated, but only approximately 16,000 tonnes were converted to primary cadmium metal, key material for the production of other cadmium compounds (e.g., cadmium oxide), and cadmium-containing goods (e.g., nickel−cadmium batteries). Hence, about 14,000 tonnes of cadmium must have been transferred somewhere else. The fate of about 5,500 tonnes can be plausibly explained, but it is difficult to determine what happens to the rest.     

A Novel Approach to Characterize Data Uncertainty in Material Flow Analysis and its Application to Plastics Flows in Austria

Material flow analysis (MFA) is widely used to investigate flows and stocks of resources or pollutants in a defined system. Data availability to quantify material flows on a national or global level is often limited owing to data scarcity or lacking data. MFA input data are therefore considered inherently uncertain. In this work, an approach to characterize the uncertainty of MFA input data is presented and applied to a case study on plastics flows in major Austrian consumption sectors in the year 2010. The developed approach consists of data quality assessment as a basis for estimating the uncertainty of input data. Four different implementations of the approach with respect to the translation of indicator scores to uncertainty ranges (linear‐ vs. exponential‐type functions) and underlying probability distributions (normal vs. log‐normal) are examined. The case study results indicate that the way of deriving uncertainty estimates for material flows has a stronger effect on the uncertainty ranges of the resulting plastics flows than the assumptions about the underlying probability distributions. Because these uncertainty estimates originate from data quality evaluation as well as uncertainty characterization, it is crucial to use a well‐defined approach, building on several steps to ensure the consistent translation of the data quality underlying material flow calculations into their associated uncertainties. Although subjectivity is inherent in uncertainty assessment in MFA, the proposed approach is consistent and provides a comprehensive documentation of the choices underlying the uncertainty analysis, which is essential to interpret the results and use MFA as a decision support tool.     

Material Flows and Energy Analysis of Glass Containers Discarded in New Jersey,USA

The use of glass cullet (crushed recycled glass containers) as aggregate in construction projects and landfills has increased rapidly even though the use of cullet as feedstock in new glass container and fiberglass production is energetically more sound. The effect of increased use of cullet as aggregate has not yet been thoroughly assessed. The objectives of this study were to model and quantify glass container flows across New Jersey and the associated life cycle energy consumption, and then compare life cycle energy consumption for two different recycling scenarios and three different end‐use/disposal scenarios. The results of a material flow analysis showed that in 2008 only about 11% of the glass containers consumed in New Jersey were used as glass container or fiberglass feedstock, while five times more were used as construction aggregate. However, a lower system energy requirement can be achieved by increased use of cullet as container feedstock compared to construction aggregate, even when the cullet is transported 1,600 miles to a glass container manufacturer. Based on the uncertainty analysis, there is about an 80% probability for the scenario with increased use as container feedstock to have a lower system energy requirement when compared with all other scenarios. To achieve increased use of cullet as glass container feedstock in New Jersey, the quality of the cullet must be improved.     

The Waste Input-Output Approach to Materials Flow Analysis

Abstract: A general analytical model of materials flow analysis (MFA) incorporating physical waste input-output is proposed that is fully consistent with the mass balance principle. Exploiting the triangular nature of the matrix of input coefficients, which is obtained by rearranging the ordering of sectors according to degrees of fabrication, the material composition matrix is derived, which gives the material composition of products. A formal mathematical definition of materials (or the objects, the flow of which is to be accounted for by MFA) is also introduced, which excludes the occurrence of double accounting in economy-wide MFAs involving diverse inputs. By using the model, monetary input-output (IO) tables can easily be converted into a physical material flow account (or physical input-output tables [PIOT]) of an arbitrary number of materials, and the material composition of a product can be decomposed into its input origin. The first point represents substantial saving in the otherwise prohibitive cost that is associated with independent compilation of PIOT. The proposed methodology is applied to Japanese IO data for the flow of 11 base metals and their scrap (available as e-supplement on the JIE Web site).     

Quantifying Phosphorus Flow Pathways Through Socioeconomic Systems at the County Level in China

Phosphorus (P) is a key factor in aquatic eutrophication, and P contamination has become a common issue worldwide. Many developing countries, including China, have made great efforts in the anti‐P contamination battle. In this article we mainly discuss the P flow in Wuwei, a typical county in China with insufficient wastewater treatment, using the method of static substance flow analysis. We show that characterizing P metabolic pathways and flows at the county level can provide useful information about P pollution. Through complex calculations, we found that Wuwei County released 3,552 metric tons (t) of P into the local aquatic environment in 2008 and that its P load (3.35 kilograms P per capita per year [kg P/cap/yr] or 19.43 kilograms P per hectare per year [kg‐P/ha/yr]) was greater than both the adjoining counties’ and Chaohu City's average levels combined. The agricultural subsystem discharged the largest quantity of P (2,572 t) and had a relatively low production conversion efficiency (32%) and P waste recycling rate (36%). The rural residential and small‐scale livestock breeding systems also accounted for substantial portions of P discharge. Anti‐P contamination efforts should consequently focus on those three subsystems. Based on the results of this case study, we also discuss the feasibility of potential efforts to reduce P contamination.     

Towards an Integrated Regional Materials Flow Accounting Model

A key challenge in attaining regional sustainability is to reduce both the direct and the indirect environmental impacts associated with economic and household activity in the region. Knowing what these flows are and how they change over time is a prerequisite for this task.
This article describes the early development of an integrated regional materials flow accounting framework. The framework is based on a hybrid (material and economic) multiregional input-output model. Using readily available economic and materials data sets together with transport and logistics data, the framework attempts to provide estimates of household resource flows for any U.K. region at quite detailed levels of product and material disaggregation. It is also capable of disaggregating these flows according to specific socioeconomic criteria such as income level or occupation of the head of household. Allied to appropriate energy and life-cycle assessment data sets, the model could, in addition, be used to map both direct and indirect environmental impacts associated with these flows.
The benefits of such an approach are likely to be a considerable reduction of uncertainties in (1) our knowledge of the household metabolism, and hence our predictions of regional household waste generation; (2) our assessment of the impacts of contemplated changes in industrial process siting, and thereby on other aspects of local and regional planning; and (3) our understanding of the impacts of changes in the pattern of demand for different materials and products. It is concluded that the use of such an integrated assessment tool has much to contribute to the debate on regional sustainability.     

Applying Fuzzy and Probabilistic Uncertainty Concepts to the Material Flow Analysis of Palladium in Austria

Material flow analysis (MFA) is a widely applied tool to investigate resource and recycling systems of metals and minerals. Owing to data limitations and restricted system understanding, MFA results are inherently uncertain. To demonstrate the systematic implementation of uncertainty analysis in MFA, two mathematical concepts for the quantification of uncertainties were applied to Austrian palladium (Pd) resource flows and evaluated: (1) uncertainty ranges expressed by fuzzy sets and (2) uncertainty ranges defined by normal distributions given as mean values and standard deviations. Whereas normal distributions represent the traditional approach for quantifying uncertainties in MFA, fuzzy sets may offer additional benefits in relation to uncertainty quantification in cases of scarce information. With respect to the Pd case study, the fuzzy representation of uncertain quantities is more consistent with the actual data availability in cases of incomplete databases, and fuzzy sets serve to highlight the effect of uncertainty on resource efficiency indicators derived from the MFA results. For both approaches, data reconciliation procedures offer the potential to reduce uncertainty and evaluate the plausibility of the model results. With respect to Pd resource management, improved formal collection of end‐of‐life (EOL) consumer products is identified as a key factor in increasing the recycling efficiency. In particular, the partial export of EOL vehicles represents a substantial loss of Pd from the Austrian resource system, whereas approximately 70% of the Pd in the EOL consumer products is recovered in waste management. In conclusion, systematic uncertainty analysis is an integral part of MFA required to provide robust decision support in resource management.     

基于物质流分析的废纸回收利用体系生态成本研究

废弃物回收利用在一定程度上对缓解资源和环境危机起到积极的作用,已经成为可持续发展的重要举措,但生产过程中消耗的资源、能源,排放的污染物同样也会对自然环境产生负面影响。为解决此问题,以废纸回收利用体系为例,基于物质流分析方法构建了生态成本核算模型,为废弃物回收利用体系优化提供基础。在对生态成本相关研究归纳总结的基础上,定义了生态成本的概念,界定了生态成本的研究内容,并分析基于物质流核算生态成本的可行性。生态成本是对生态负荷的价值化,主要分为资源耗减成本、污染产生和环境保护成本以及生态环境损害成本3部分。污染产生和环境保护成本可以通过将总成本按比例分配给正、负产品的方式求得,资源耗减成本和环境损害成本借助LIME方法核算,总生态成本是回收利用体系内部各项生态成本的总和。生态成本核算是评价生态负荷的重要手段,在废纸回收利用体系物质流动图的基础上,分析各生产流程生态成本的构成情况。提出的生态成本核算模型不仅适用于废纸回收利用体系,其他废弃物也同样适用。通过生态成本的核算,寻找到对生态环境影响较大的工序、流程,为废弃物回收利用体系经济与环境的双赢提供理论与实践指导。     

Recycling Rates of Aluminum in the United States

Recycling rates of aluminum are defined in different (sometimes inconsistent) ways and poorly quantified. To address this situation, the definitions and calculation methods of four groups of indicators are specified for the United States: (1) indicators used to measure recycling efficiencies of old aluminum scrap at the end‐of‐life (EOL) stage, including EOL collection rate (CR), EOL processing rate, EOL recycling rate, and EOL domestic recycling rate; (2) indicators used to compare generation or use of new with old scrap, including new to old scrap ratio, new scrap ratio (NSR), and old scrap ratio; (3) indicators used to compare production or use of primary aluminum with secondary aluminum, including four recycling input rates (RIRs); and (4) indicators used to track the sinks of aluminum metal in the U.S. anthroposphere. I find that the central estimate of EOL CR varies between 38% and 65% in the United States from 1980 to 2009 and shares a relatively similar historical trend with the primary aluminum price. The RIR is shown to be significantly reduced if excluding secondary aluminum produced from new scrap resulting from the relatively high NSR. In 2003, a time when approximately 73% of all of the aluminum produced globally since 1950 was considered to still be “in service,” approximately 68% to 69% of all metallic aluminum that had entered the U.S. anthroposphere since 1900 was still in use: 67% in domestic in‐use stock and 1% to 2% exported as scrap. Only 6% to 7% was definitely lost to the environment, although the destination of 25% of the aluminum was unknown. It was either exported as EOL products, was currently hibernating, or was lost during collection.     

Heavy-Metal Balances, Part II: Management of Cadmium, Copper, Lead, and Zinc in European Agro-Ecosystems

The aim of sustainable heavy-metal management in agroecosystems is to ensure that the soil continues to fulfill its functions: in agricultural production, in environmental processes such as the cycling of elements, and as a habitat of numerous organisms. To understand and manage heavy-metal flows effectively, a consistent approach to modeling the flows is needed within the particular agro-system under study. General aspects of heavy-metal balance studies in agro-ecosystems were described in part I of this study. In this article (part II), several European studies of heavy-metal balances at varying spatial scales and in a variety of agro-ecosystems are reviewed. Sectoral studies at the national and international levels provide information for economic analyses and generic regulations; however, policies implemented at these levels often ignore farm characteristics and individual management options. Field-scale and farm-gate balances give farmers specific feedback on effective options for better heavy-metal management. Heavy-metal balances could be incorporated in an environmental management system of certified farms. In this way, farm certification may well serve as a basis from which to develop policy to address environmental issues in agriculture.