A system model defines the rules for how environmental burdens are allocated when materials or energy flow between different life cycle systems. In practice, the most consequential question is: who bears the environmental burden of recycling?
ecoinvent offers three system models — cut-off, APOS, and consequential — each with different answers to this question. Root uses the cut-off system model.
The cut-off system model explained
In the cut-off model, the rule is straightforward:
The producer of a material bears the full burden of producing it from virgin resources
The user of a recycled material receives it "burden-free" — they inherit zero impact from the previous life of that material
The "cut" happens at the point of recycling: the original product's burden ends there, and the new product's life starts with a clean slate
Example
If your product contains 50% recycled aluminium:
Under cut-off, the recycled aluminium carries no upstream burden in your footprint
You only account for the processing and transport of the recycled material itself
The original burden of producing primary aluminium stays with whoever used it first
This is why switching to recycled content in your BOM can meaningfully reduce your product footprint in Root.
Cut-off vs the other system models
System model | Recycled content burden | End-of-life credit |
Cut-off (Root default) | Zero — recycled input is burden-free | No credit for recyclability of output |
APOS (Allocation at Point of Substitution) | Partial — shared between producer and user | Partial credit for recyclable output |
Consequential | Based on market effects — more complex | Based on substitution of marginal supply |
Why Root uses cut-off
The cut-off system model is the most widely used in industry for product LCA and corporate reporting because:
It is simple and transparent — rules are clear and consistently applied
It is conservative — it doesn't allow companies to claim credits that depend on uncertain future recycling outcomes
It is compatible with major reporting frameworks — including most EPD programme operators and CSRD-aligned methodologies
It aligns with the EF (Environmental Footprint) methodology, which Root uses as its characterisation framework
What this means for your product data
Recycled input materials will generally show a lower impact than virgin equivalents in your BOM
Your product's recyclability at end-of-life does not reduce your current footprint (unless you explicitly model end-of-life)
If you are comparing Root results to an LCA conducted under APOS or consequential, expect differences — this is a methodological difference, not an error
FAQ
Can I switch system models in Root?
No. Root standardises on the cut-off system model for consistency across all users and to align with the EF methodology. Using a single system model ensures that results are comparable across companies and products.
Does the cut-off model penalise companies that use virgin materials?
The cut-off model does not penalise or reward — it simply reflects reality. A product made from virgin materials will show the full upstream burden of those materials. A product using recycled content will show a lower burden. This is an accurate representation of the current supply chain impacts.