Materials and recyclability

    Mass balance

    A chain-of-custody method that allocates a quantity of recycled feedstock to a share of output, used to evidence chemically recycled content.

    Mass balance accounting lets a producer that mixes recycled and virgin feedstock in a continuous process claim a corresponding proportion of output as recycled. It exists because chemical recycling and many polymer processes cannot physically segregate recycled molecules.

    The credibility of a mass-balance claim rests entirely on the allocation rule and the certification scheme behind it. Fuel-use exempt allocation, polymer-only allocation and proportional allocation produce very different numbers from the same input, so the scheme and rule should be recorded alongside the percentage.

    Regulators are still converging on which allocation rules are acceptable for statutory recycled content targets, so companies relying on mass balance should keep the underlying certificates and be prepared for a rule change.

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