Understanding the real meaning behind recovery rates in recycling
In the recycling and waste management industry, it’s common to hear statements like:
“Our plant achieves 70% recovery.”
It sounds impressive — but do those numbers really mean the same thing everywhere?
Let’s take a closer look at what a mass balance really tells us about efficiency, and why methodology matters more than the number itself.
What recovery actually means
In theory, calculating recovery is simple:
Recovery = (amount of material recovered in the product) / (amount of that material present in the input).
It’s a straightforward ratio — but it hides a practical challenge.
Almost no sorting plant measures the input composition directly.
Why the input isn’t measured directly
To measure the composition of incoming waste in a statistically valid way, one would need to sample thousands of tonnes of material — across multiple deliveries, waste types, and days of operation.
This is logistically and economically impossible.
Therefore, professional facilities use an indirect approach:
the input composition is calculated through the mass balance, based on the known mass and material composition of all output streams —
products, residues, ONF streams, and other fractions.
Only by reconstructing all outputs can we estimate what actually entered the process.
The real challenge: methodology differences
Every sorting plant has its own procedures:
- some take residue samples weekly, others daily,
- some measure ONF separately, others combine it,
- and many use different classification systems or sample sizes.
This means that “70% recovery” in one plant might represent something entirely different than “70% recovery” in another.
So when comparing performance between facilities, we’re often comparing different definitions of recovery.
When does a mass balance make sense?
A mass balance is only meaningful when:
- sampling is statistically representative,
- material analysis is complete and consistent,
- and the methodology is repeatable over time.
Without these elements, “recovery” becomes just a number — disconnected from reality.
From numbers to insight
Accurate and statistically representative mass balancing isn’t just a reporting tool.
It’s the foundation for:
- evaluating true process efficiency,
- identifying losses in specific streams,
- and creating benchmarks that are actually comparable.
Reliable recovery data doesn’t just show how much was sorted — it shows how well the process works.
Looking ahead
In an upcoming article, we’ll explore how different sampling methodologies can drastically change the calculated recovery — and what that reveals about the real efficiency of a sorting plant.