Material Flow Analysis

Introduction

Material flow analysis (MFA) is a methodology to analyze the flow of "materials" in-and-out of a system.

Built upon the law of conservation of energy, where energy can never be created or destroyed, only transferred, you can use material-balance equations to model complex systems such as the Seed Eco-Home.

See Material flow Analysis on Wikipedia for additional information.

Motivation

Due to the law of the conservation of matter, the results of an MFA can be controlled by a simple material balance.

It's this distinct characteristic of MFA that makes it attractive for decision-making.

Unanswered Research Questions

• Can the formal concept of "Material flow analysis (MFA)" prove useful in the design of close-looped sustainable systems?

Definitions & Terms

Taken from Chapter 2.1 of Practical handbook of material flow analysis:

1. Substance — any (chemical) element or compound composed of uniform units (e.g. Carbon (C), Nitrogen (N), Carbon Dioxide (CO₂), and Ammonium (NH₃)).
2. Good — economic entities of matter with a positive or negative economic value (e.g. wood, drinking water, mineral ores, concrete, and automobiles)
3. Material — umbrella term for Substance and Good
4. Process — transformation, transportation, or storage of Materials.
   1. Stock — material reservoirs (mass) within the analyzed System, and they have the physical unit of kilograms. A stock is part of a Process comprising the mass that is stored within the process.
5. Flow and Flux
   1. Flow — a "mass flow rate." Ratio of mass per time that flows through a conductor (e.g. water pipe). Physical unit examples include kg/sec or t/year.
   2. Flux — a flow per "cross section." For the water pipe, this means that the flow is related to the cross section of the pipe. The flux might then be given in units of kg/(sec * m²). Flux can be considered as a specific flow.
   3. Imports and Exports - Flows and Fluxes entering and exiting a System Boundary respectively.
6. Transfer Coefficient
7. System and System Boundaries
   1. System — Object under MFA investigation.
      1. Note, poor results of MFA can often be traced back to an unsuitable system definition.
   2. System Boundary — encloses the object under investigation defined in space (spatial boundary) or time (temporal boundary).
8. Activities
9. Anthroposphere and Metabolism
10. Material Flow Analysis
11. Materials Accounting

Diagrams

Box and Arrow

Using mainly simple boxes and arrows to represent materials flows with a few observed conventions:

• Usually, processes are defined as black boxes
  • This means processes within the box are not taken into account
  • Only the inputs and the outputs are of interest
• Arrows between boxes are for flows and fluxes of materials
  • They have a label describing the material (e.g. "Gasoline")
  • Ovals are used for the rates of the flows or fluxes, and the surrounding oval may be omitted due to space constraints.

Taken from section 2.1.4 Process of Practical Handbook of Material Flow Analysis.

Sankey

Sankey diagrams use the width of arrows to denote the rate of the flow or flux of materials in a linked node diagram.

Resources

• Practical Handbook of Material Flow Analysis by Paul H. Brunner and Helmut Rechberger