What is the Cut-off Method?

The cut-off method is an allocation approach for handling recycled materials in LCA. It separates recycling loops by assigning all recycling impacts and benefits to the product system using the recycled material, while the original product system ends at disposal.

This method draws a clear line through circular material flows. The original product carries production and use-phase impacts but gets no credit for providing recyclable material. The subsequent product using recycled content benefits from avoided virgin production but accounts for reprocessing impacts.

How It Works#

A product made from virgin aluminium accounts for bauxite mining, alumina refining, and primary smelting. At end-of-life, the aluminium gets collected and sent to recycling. The original product’s LCA stops there.

A different product using recycled aluminium accounts for collection, sorting, and remelting. These recycling process impacts belong to the system using recycled content. In exchange, that system avoids primary production impacts.

The “cut-off” occurs at the point where material leaves one product system and enters another. Impacts don’t follow the physical material through multiple lifecycles. Each product system gets evaluated independently.

Rationale#

The cut-off method creates an incentive structure. Product systems benefit from using recycled content through lower material impacts. This encourages design for recyclability and use of recycled materials.

Without this approach, recycled content might show higher impacts than virgin materials due to collection and reprocessing burdens. Virgin production impacts would be allocated across multiple lifecycles, diluting them. The cut-off method prevents this perverse incentive.

Market reality supports the cut-off approach. Companies purchase recycled materials based on current market availability, not historical virgin production. The decision relevant impacts are reprocessing costs, not sunk primary production.

Application to EPDs#

Environmental Product Declarations commonly use cut-off methods. A steel EPD reports impacts for virgin steel production or for production from scrap, but not a complex allocation across multiple lifecycles.

This enables straightforward comparison. Specifiers can see whether products use recycled content and what processing impacts result. The method rewards manufacturers using recycled materials.

Construction standards like EN 15804 specify cut-off approaches for Module D benefits. Recycling potential gets reported separately from product impacts, avoiding complex allocation rules.

Comparison to Other Methods#

Several allocation approaches handle recycling differently:

Closed-loop allocation splits impacts when material returns to the same product system. If your aluminium cans get recycled into new cans, you might allocate primary production impacts across multiple lifecycles based on recycling rates.

Economic allocation splits impacts based on relative market values of virgin and recycled materials. Higher-value recycled materials receive proportionally higher impact shares.

System expansion avoids allocation by expanding boundaries. The recycling system gets credited with avoided virgin production. Both product systems share in this credit.

Each method creates different incentives and results. The cut-off method provides simplicity and clear market signals favouring recycled content use.

Advantages#

The cut-off method offers several benefits:

Simplicity – no complex allocation calculations across product lifecycles. Each system has clear boundaries.

Market alignment – reflects how companies actually make material sourcing decisions based on current recycled material availability.

Incentive compatibility – encourages both design for recycling and use of recycled content by clearly rewarding recycled material use.

Practical implementation – EPD programmes can standardise the approach, enabling consistent product comparison.

Limitations#

The method creates some issues:

No credit for recyclability – products designed for easy recycling don’t receive credit in their own LCA. The benefit accrues to future products, not the original design.

Discontinuous at zero – switching from 0% to 1% recycled content creates a sudden impact reduction. The boundary between virgin and recycled becomes arbitrary.

Lost information – the historical environmental burden of virgin production disappears from recycled material. Multiple recycling loops erase primary production impacts entirely.

Downcycling ignored – materials degrading to lower-value applications lose this effect. Each use treats recycled material equally regardless of quality changes.

Module D in EPDs#

EN 15804 addresses cut-off limitations through Module D reporting. This separate module shows environmental benefits and loads beyond the product system boundary.

A product’s main EPD (Modules A-C) uses cut-off allocation. Module D separately reports potential benefits from recycling, reuse, or energy recovery. This preserves cut-off incentives while informing about end-of-life potential.

Module D results don’t add to the product total. They provide additional information for designers considering whole-building or whole-life impacts. The separation maintains clear product boundaries while enabling broader system analysis.

When to Use Cut-off#

The cut-off method suits:

• Product comparisons where consistency matters
• EPDs and standardised declarations
• Situations favouring recycled content use
• Market-facing environmental information
• Simplified LCA with clear boundaries

Other approaches might suit:

• Detailed academic studies examining allocation sensitivity
• Policy analysis of recycling system design
• Situations where historical virgin production matters
• Analysis of material quality degradation through cycles

Implementation Details#

Applying cut-off requires clear definitions:

Virgin material production includes all processes from raw material extraction through primary production. For aluminium, this means bauxite mining through primary smelting.

Recycled material production includes collection, sorting, and reprocessing. For aluminium, this means scrap collection and remelting. Primary production impacts don’t appear.

Mixed content uses proportional impacts. A product with 60% recycled content gets 60% recycled material impacts plus 40% virgin material impacts.

Quality adjustments might reduce credited benefits if recycled material requires additional processing or has inferior properties. The adjustment should reflect real processing differences.

Data Requirements#

Cut-off implementation needs:

• Recycled content percentages for materials
• Virgin material production datasets
• Recycled material reprocessing datasets
• Clear documentation of boundary decisions

Standard LCA databases like ecoinvent provide cut-off datasets. These separate virgin and recycled material processes, enabling straightforward implementation.

Product-specific data improves accuracy. Generic recycling processes represent averages. Site-specific reprocessing data shows actual performance.

The method requires transparency. State that you’re using cut-off allocation. Document recycled content percentages. Let users understand what’s included and excluded from boundaries.