Material flow analysis

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The material flow analysis is an instrument for the implementation and execution of a successful material flow management . The different objectives of the individual forms of material flow management result in a multitude of methodological approaches for modeling material flow systems.

Material and energy balances

The simplest approach to depicting material systems is material and energy balances , which are created in practice in the form of operational, process and product balances ( life cycle assessment ). Material and energy balances are the practical application of the first law of thermodynamics ( thermodynamics ). Company balances depict the material flows of an individual company for a certain balance period (Fresner, J. et al. (2009), page 65). Process balances are the result of a material and energetic balancing of individual or several process steps connected one after the other in a plant or a process. Product balances, on the other hand, depict the material flows of a product over the entire product life cycle (often today the product life cycle assessment is simply referred to as life cycle assessment).

Capture

The accounting is based on a completely empirical recording of all material and energy flows and stocks and can be carried out for accounting purposes. Assuming a mass and possibly energetic balance maintenance, the empirically collected data can be checked for consistency or missing values ​​can be calculated as a difference from the mass balance. Such a model is therefore suitable to a limited extent for mapping internal dependencies. In operational practice, however, the mass and energy balance often cannot be balanced or only with the inclusion of economically and ecologically meaningless materials. In addition, the effort involved in the survey is disproportionate to the newly obtained statements.

Modeling

Static

The static modeling requires knowledge of the transformation processes, i. In other words, it creates a process model based on the mapping of the interdependencies of the input, output and inventory values. By solving linear systems of equations, all other flows can be calculated from a few, empirically collected material flows. The static modeling enables the calculation of material flows in cycles (e.g. recycling flows) and is scenario-capable. In this way, however, only linear dependencies can be mapped, while non-linear dependencies also occur in real production processes (see dependencies of input and output flows on technical or chemical process parameters in the chemical industry).

Dynamic

The dynamic modeling supplements the previously static process models with time-dependent calculations. The easiest way to dynamize static process models is to establish an accrual calculation. Further approaches dispense with a purely linear description of transformation processes and introduce non-linear dependencies. Such systems can no longer be solved by linear systems of equations, but require other methods, such as the iteration of systems.

Practical

In the literature, only a few, relatively imprecise statements are formulated on this. For the data collection procedure (Spengler, T. (1998), p. 27) suggests: “By interviewing the responsible employees and using EDP, all auxiliary and operating materials, materials, energies, waste, exhaust air, noise and Wastewater that exceeds the company's balance sheet limits is recorded with quantitative information. "In addition, reference is made to:" When creating the process balance, an allocation of the material and energy flows to the individual process steps must be provided. "How this recommendation is to be implemented, however, will be provided not executed. The most important aspect in the dedicated recording of the material and energy flows relevant for the respective organization is the establishment of suitable measuring points at the neuralgic points of the process. For example, for the detection of the waste streams of a production company, an investigation period of z. B. Weighing of the collecting containers carried out 4 weeks to give precise information about the waste quantities occurring at the individual points of the production process. Only in this way can statements be made about particularly critical processes or process steps. The ratio of effort to benefit can be determined in advance by a qualitative assessment of the potential to be expected. As a rule, however, the decision to carry out a material flow analysis understood in this way is very much dependent on the company's ecological and economic target system. Material flow analyzes are a good basis for analyzing operational environmental impacts within the framework of operational environmental management (e.g. according to ISO 14001 or EMAS) to describe material losses and to localize starting points for improvements.

Material flow networks

Material flow networks are a methodically mature approach to mapping complex material flow systems . Material flow networks take up some methodological questions from the approaches above, but do not use any linear systems of equations, but use special graphs based on so-called Petri networks .

presentation

One approach for the description of material systems are so-called flow charts as in the (flow sheets) process technology for display of material and energy flows are used. Flow diagrams can describe processes or plants both qualitatively and quantitatively. An example of a qualitative-quantitative descriptive flow diagram are the so-called Sankey diagrams , in which the arrow width of the material flows corresponds to their quantity. Material and energy balances as well as flow diagrams are purely descriptive models of material flow systems. However, they are the basis of a systematic evaluation of the efficiency of the use of materials ( cleaner production ).

See also

literature

  • T. Spengler: Industrial material flow management: economic planning and control of material and energy flows in production companies. Habilitation thesis. University of Karlsruhe, Faculty of Economics, 1998.
  • J. Fresner, T. Bürki, H. Sittig: Resource efficiency in production - reducing costs through cleaner production. Symposion Publishing, 2009, ISBN 978-3-939707-48-6 .

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