Material flow analysis

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Material flow analysis (MFA) (also referred to as substance flow analysis (SFA)) is an analytical method to quantify flows and stocks of materials or substances in a well-defined system. MFA is an important tool to study the bio-physical aspects of human activity on different spatial and temporal scales. It is considered a core method of industrial ecology and urban metabolism. Typical applications of MFA include the study of material, substance, or product flows across different industrial sectors or within ecosystems. MFA can also be applied to a single industrial installation, for example, for tracking nutrient flows through a waste water treatment plant. Examples for policy-relevant applications of MFA include the determination of material use indicators for different societies and the assessment of strategies for improving the material flow systems in form of material flow management. Since 1990, the number of publications using material flow analysis as main method of investigation has grown steadily. Major journals that publish MFA-related work include the Journal of Industrial Ecology, Ecological Economics, Environmental Science and Technology, and Resources, Conservation, and Recycling.[1]

Description of the method

Motivation

Human needs such as shelter, food, transport, or communication require materials like wood, starch, sugar, iron and steel, copper, or semiconductors. As society develops and economic activity grows, production, use, and disposal of the materials employed increases to a scale where unwanted impacts on environment and society cannot be neglected anymore, neither locally nor globally. Material flows are at the core of local environmental problems such as leaching from landfills or oil spills. Rising concern about global warming put a previously unimportant waste flow, carbon dioxide, on top of the political and scientific agenda. Moreover, the gradual shift from traditional to urban mining in developed countries requires a detailed assessment of in-use and obsolete stocks of materials within human society. Scientists, industries, government bodies, and other organisations therefore need a tool that complements economic accounting and modelling. They need a systematic method to keep track of and display stocks and flows of the materials entering, staying within and leaving the different processes in the anthroposphere. Material flow analysis is such a method.

Basic principles

MFA is based on two fundamental and well-established scientific principles, the systems approach and mass balance. [2] [3] The system definition is the starting point of every MFA study.

System definition

An elementary MFA system without quantification.
File:MFASystem 2.png
A more general MFA system without quantification.

An MFA system is a model of an industrial plant, an industrial sector or a region of concern. The level of detail of the system model is chosen to fit the purpose of the study. An MFA system always consists of the system boundary, one or more processes, material flows between processes, and stocks of materials within processes. Exchange between the system and its environment happens via flows that cross the system boundary. Contrary to chemical engineering, where a system represents a specific industrial installation, systems and processes in MFA can represent much larger and more abstract entities as long as they are well-defined. The explicit system definition helps the practitioner to locate the available quantitative information in the system, either as stocks within certain processes or as flows between processes.

MFA system descriptions can be refined by disaggregating processes or simplified by aggregating processes.

Next to specifying the arrangement of processes, stocks, and flows in the system definition, the practitioner also needs to indicate the scale and the indicator element or material of the system studied. The spatial scale describes the geographic entity that is covered by the system. A system representing a certain industrial sector can be applied to the USA, China, certain world regions, or the world as a whole. The temporal scale describes the point in time or the time span for which the system is quantified. The indicator element or material of the system is the physical entity that is measured and for which the mass balance holds. As the name says, an indicator element is a certain chemical element such as cadmium or a substance such as CO2. In general, a material or a product can also be used as indicator as long as a process balance can be established for it. Examples for more general indicators are goods such as passenger cars, materials like steel, or other physical quantities such as energy flows.

MFA requires practitioners to make precise use of the terms 'material', 'substance', or 'good'. We refer to the definitions given in chapter 2.1 in the book by Brunner and Rechberger,[4] one of the main references for the MFA method.

  • A chemical element is "a pure chemical substance consisting of one type of atom distinguished by its atomic number".[5]
  • A substance is "any (chemical) element or compound composed of uniform units. All substances are characterized by a unique and identical constitution and are thus homogeneous." From chapter 2.1.1 in Brunner&Rechberger.[4]
  • A good is defined as "economic entity of matter with a positive or negative economic value. Goods are made up of one or several substances". From chapter 2.1.2 in Brunner&Rechberger.[4]
  • The term material in MFA "serves as an umbrella term for both substances and goods." From chapter 2.1.3 in Brunner&Rechberger.[4]
File:MFASystem 3.png
A typical MFA system with quantification.

Process balance

One of the main purposes of MFA is to understand the metabolism of the elements of the system. Unlike purely economic accounting, MFA also covers non-economic waste flows, emissions to the environment, and stocks of obsolete products. The process balance is a first order physical principle that turns MFA into a powerful accounting and analysis tool. The processes in the system determine which balances apply. For a process ‘oil refinery’, for example, one can establish a mass balance for each chemical element, while this is not possible for a nuclear power station. A car factory respects the balance for steel, but a steel mill does not.

When quantifying MFA systems either by measurements or from statistical data, mass other process balances have to be checked to ensure the correctness of the quantification and to reveal possible data inconsistencies or even misconceptions in the system such as the omission of a flow or a process. Conflicting information can be reconciled using data validation and reconciliation, and the STAN-software offers basic reconciliation functionality that is suitable for many MFA application.[6]

Examples for MFA applications on different spatial and temporal scales

MFA studies are conducted on various spatial and temporal scales and for a variety of elements, substances, and goods. They cover a wide range of process chains and material cycles. Several examples:

  • MFA on a national or regional scale (also referred to as material flow accounting): In this type of study, the material exchanges between an economy and the natural environment are analyzed. Several indicators are calculated in order to assess the level of resource intensity of the system.
  • Corporate material flow analysis, or MFA along an industrial supply chain involves a number of companies: The goal of material flow analysis within a company is to quantify and then optimize the production processes so that materials and energy are used more efficiently manner, e.g., by recycling and waste reduction. Companies can use the results obtained by material flow analysis to reduce their operational costs and improve environmental performance.
  • In the life cycle of a product: The life cycle inventory, whose compilation is at the core of life cycle assessment, follows the MFA methodology as it is based on an explicit system definition and process balances.

Historical development

  • Mass balance or the conservation of matter has been postulated already in ancient Greece, and it was introduced into modern chemistry by Antoine Lavoisier (cf. chapter 2.1.3 in Brunner&Rechberger.[4]), from where it found its way to chemical engineering and finally to environmental science.
  • Other seminal contributions were made by Sanctorius and Theodor Weyl.
  • Dennis Meadows made a wide audience aware of the physical foundation of the economy when he co-authored the bestseller Limits to Growth in 1971. Meadows et al. based their predictions on an analysis of resource stocks; see in the glossary of environmental science.
  • The methdology of MFA was developed during the 80ies and 90ies. Development happened simultaneously in different research groups. Central publications on the MFA methodology include Baccini and Bader (1996),[7] Brunner and Rechberger (2012 [1991]),[8] and van der Voet et al. (2002).[9]
  • Friedrich Schmidt-Bleek, who worked at the Wuppertal Institute,[10] developed the MFA-related concept of Material Input Per Service unit (MIPS).[11]
  • The UNEP Resource Panel[12] was set up in 2007 by the United Nations Environment Program, and was first headed by Ernst Ulrich von Weizsaecker and Ashok Khosla. In analogy to the Intergovernmental Panel on Climate Change (IPCC)[13] it brings together experts from many disciplines and institutions to review the current state of research on societal metabolism and to communicate the latest findings to policymakers and stakeholders.

Recent development

  • MFA concepts have been or are being incorporated in national accounts in several countries and regions such as the EU[14] and Japan.[15] MFA is also used in the System of Integrated Environmental and Economic Accounting.
  • Several international conferences or other meetings provide a platform for researchers and policymakers to meet and exchange results and ideas, including the World Resources Forum,[16] a bi-annual international conference on material flow analysis and sustainable development.
  • MFA-IO is an approach to establish an MFA system of the whole economy using monetary and physical Input-Output tables.[17]
  • The Sustainable Europe Research Institute (SERI) in Vienna, Austria, has developed a data base called materialflows.net.[18]
  • Dynamic MFA aims for long-term quantification of MFA systems and uses historic development patterns of physical stocks and flows to create robust scenarios for the years and decades to come.[19]
  • Japan has developed into a hotspot for MFA research. The country has scarce mineral resources and is therefore dependent on imports of energy carriers, ores, and other raw materials. The Japanese government fosters research on material cycles and also inaugurated the 3-R concept.[20]

Relation to other methods

MFA is complementary to life cycle assessment (LCA) and input-output (I/O) models. Some overlaps between the different methods exist as they all share the system approach and to some extent the mass balance principle. The methods mainly differ in purpose, scope, and data requirements.

MFA studies often cover the entire cycle (mining, production, manufacturing, use, waste handling) of a certain substance within a given geographical boundary and time frame. Material stocks are considered explicitly in MFA, which makes this method suitable for studies involving resource scarcity and recycling from old scrap. The common use of time series (dynamic modelling) and lifetime models makes MFA a suitable tool for assessing long-term trends in material use.

  • Compared to I/O analyses, the number of processes considered in MFA systems is usually much lower. On the other hand, mass balance ensures that flows of by-products or waste are not overlooked in MFA studies, whereas in I/O tables these flows are often not included due to their lack in economic value. Physical I/O models are much less common than economic ones. Material stocks are not covered by IO analysis, only the addition to stock can be included in form of capital accumulation.
  • Life cycle assessments and inventories focus on the various material demands and subsequent impacts for single products, whereas MFA studies typically focus on a single material in many different products. Impact assessment is traditionally not part of MFA, but there have been recent attempts to include it.

See also

References

Notes

  1. ↑ http://www.journals.elsevier.com/resources-conservation-and-recycling/
  2. ↑ Marina Fischer-Kowalski, The Intellectual History of Materials Flow Analysis, Part I, 1860-1970, Journal of Industrial Ecology 2(1), 1998, pp 61-78, doi:10.1162/jiec.1998.2.1.61.
  3. ↑ Marina Fischer-Kowalski, The Intellectual History of Materials Flow Analysis, Part II, 1970-1998, Journal of Industrial Ecology 2(4), 1998, pp 107-136, doi:10.1162/jiec.1998.2.4.107.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "chemical element".
  6. ↑ http://www.stan2web.net/
  7. ↑ Baccini and Bader 1996, 'Regionaler Stoffhaushalt' (Regional metabolism), Spektrum Akademischer Verlag, Heidelberg (Germany), ISBN 3-86025-235-6
  8. ↑ Brunner and Rechberger, 'Metabolism of the Anthroposphere', MIT Press. ISBN 9780262016650
  9. ↑ 'Predicting future emissions based on characteristics of stocks', Ecological Economics, 2002, 41(2), 223-234.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Schmidt-Bleek Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  18. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  19. ↑ Daniel B. Müller, Stock dynamics for forecasting material flows--Case study for housing in The Netherlands, Ecological Economics 59(1), 2006, pp 142-156, doi:10.1016/j.ecolecon.2005.09.025.
  20. ↑ Lua error in package.lua at line 80: module 'strict' not found.

Further reading

  • Lua error in package.lua at line 80: module 'strict' not found.

External links

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