Material flow analysis
Material flow analysis quantifies what enters, circulates, accumulates and leaves a defined system — a company, a supply chain, a territory — over a given period. It rests on one simple, demanding constraint: within a boundary, what comes in equals what goes out plus what accumulates. That constraint is where the method gets its power, because it lets you compute what you never measured.
The principle: the mass balance
Nothing is lost. For every node in the system — a workshop, a processing plant, an entire territory — inputs equal outputs, give or take the change in stock. This is the mass balance, and it is the method’s only starting assumption.
Its consequence is more interesting than its statement. If a value is missing but its neighbours are known, it is fully determined: you do not have to measure it, you deduce it. And when the collected figures do not close, that is not a detail to smooth over — it is information. A source is wrong, or a flow is missing from the diagram.
It is also what separates a flow analysis from a mere chart: a diagram whose nodes do not balance is wrong, and it says so.
What the method lets you say
Find where it leaks
Losses do not show up in a table — they blend into rounding differences. On a flow diagram, a branch peeling off to the side is unmissable. On a food supply chain, it is often the first result that surprises the client.
Measure a dependency
How much of a supply comes from outside the territory, and from whom. A chain that hangs on a single import, a resource whose local deposit is already saturated: the question has no answer until the flows are quantified end to end.
Put a number on a scenario
What happens if collection doubles, if a plant closes, if a resource grows scarce? A consistent flow model can be replayed under other assumptions. A table of figures cannot: you start over by hand.
Make a diagnosis defensible
A documented MFA says where every number came from, what was measured and what was inferred. That is what separates a diagnosis from an estimate, and what a funder or a steering committee will ask for sooner or later.
Where it fits
Material flow analysis is not an isolated discipline: it is the measuring instrument of several fields that, without it, stay declarative.
In industrial ecology, it is used to spot possible synergies between operators on a single site or area — one party’s by-product becoming another’s input. That requires knowing what leaves whom, in what quantity and in what form: that is an MFA.
Applied to a local authority, it goes by urban or territorial metabolism: the territory is read as an organism that extracts, transforms, stores and discharges. It is the frame used by the diagnostics commissioned by regions and national agencies, and the frame of most of our studies.
In the circular economy, it supplies the baseline without which a closing-the-loop target is only an intention: you cannot claim to reduce a flow you have not quantified, nor measure progress without a starting point.
Finally it must be distinguished from material flow accounting, the aggregate exercise standardised by Eurostat that tracks the large tonnages of a national or regional economy. Accounting produces indicators; analysis produces a model, with its nodes and its internal structure. Moving from one to the other is common, and rarely effortless.
How a study is run
Five steps, only one of which is technical — and it is not the one people expect.
1. Set the boundary
Which territory or company, which year, which materials. It is the most decisive step and the most often rushed: a vague boundary makes everything downstream unarguable, because you will never know whether a missing flow is absent data or a badly drawn edge.
2. Draw the system before counting
The nodes — extraction, processing, uses, stocks, exports — and the flows between them. Structure first, numbers second. A correct structure with orders of magnitude beats a wrong structure with decimals.
3. Collect what exists
National and regional statistics, declarations, company accounts, sector interviews, literature. The sources will not agree on the year, the boundary or the unit. That is normal, and it is the real work.
4. Reconcile
Collected figures never add up on the first pass. Reconciliation searches, among all the value sets consistent with the balances, for the one closest to the observed data, each weighted by how much you trust it. What is missing gets computed, and what was computed stays marked as such.
5. Read and publish
An MFA result is read as a flow diagram — the representation that makes orders of magnitude comparable at a glance. Published and interactive, it gets discussed in the room instead of circulating as a frozen PDF.
Step 4 is what separates a drawing tool from an analysis tool. A diagram program demands a number per arrow: without it, no drawing. A reconciliation engine treats each node as an equation, each ratio and each uncertainty as a constraint, and looks for the consistent solution closest to your data. How the mechanism works.
Pitfalls that sink a study
Mistaking precision for accuracy
A figure given to three decimals is no truer than an honest interval. In real systems some flows are never measured: stating that as a range is a result; hiding it behind a single number is a mistake.
The “other” line
When the balance does not close, the temptation is to park the gap in a catch-all item. That throws away exactly the information the gap carries: it says a source is wrong, or a flow is missing from the diagram.
Mixing units
Wet tonnes, dry matter, carbon equivalents, cubic metres: adding two different units in one balance yields a total that means nothing. Conversions must be explicit and documented, never implicit.
Waiting for complete data
The surest way never to deliver the study. In our work, a few dozen measurements are enough to constrain diagrams of several hundred flows. You start with what you have, then look at where the uncertainty is still too wide to conclude.
What the result looks like
Rather than describe it: our studies are published, with their interactive diagrams and their sources. Forest and wood supply, waste for a group of municipalities, regional food systems, biomass at regional scale — these are real flow analyses, commissioned by public bodies and sector organisations, not demonstrations.
Frequently asked questions
What is material flow analysis?
It is a method that quantifies the flows and stocks of materials within a defined system — a company, a supply chain, a territory — over a given period, resting on the conservation of mass: within a boundary, what comes in equals what goes out plus what accumulates. For the industrial case it is standardised as ISO 14051.
How does it differ from life cycle assessment (LCA)?
LCA starts from a product and traces every environmental impact attributable to it, wherever it occurs. MFA starts from a boundary — a territory, a supply chain — and quantifies what actually circulates inside it. One answers “what is this product’s impact”, the other “what is happening here”. They complement each other more than they compete.
What is a mass balance?
It is the founding constraint of the method: for every node in the system, inputs equal outputs, give or take the change in stock. It is what allows unmeasured values to be deduced, and what reveals that a dataset is inconsistent.
What is the difference between material flow analysis and material flow accounting?
Material flow accounting is the aggregate exercise, standardised by Eurostat, that tracks the large tonnages entering and leaving a national or regional economy. Material flow analysis goes down to a particular system and its internal structure: which nodes, which flows between them. The first yields indicators, the second a model.
How much data do you need to start?
Less than people assume. Because the balances constrain the system, an unknown surrounded by known values is fully determined. In our studies a few dozen measurements populate diagrams of several hundred flows. The price is explicit: where information is missing, the result is an interval.
Which software is used for material flow analysis?
STAN (TU Wien) is the academic reference and remains free. MFASankey, built by TerriFlux, is a reconciliation engine in the browser that imports STAN models and publishes interactive results. A spreadsheet is enough for a simple system, but it offers neither constrained reconciliation nor uncertainty handling.
Going further
- The Sankey diagram — the representation an MFA is read in.
- Data reconciliation — how what was never measured gets computed.
- Coming from STAN — the academic reference, and what we added to it.
- Training — our courses on the method and the tool.
- Why flows matter — what this reading changes for a territory.
- Research — the work and the partners behind the method.