Steam Cracker Co-Processing Mass Balance Basics
Co-processing plastic pyrolysis oil in steam crackers requires yield-based mass balance attribution under ISCC PLUS rules to substantiate circular claims.
Credit Balance Rolling Window
Meaning
Temporal boundaries for credit validity govern how long a chemical recycler can retain mass balance surpluses before they must be allocated or expired. Under mass balance certification schemes, a credit balance rolling window dictates the maximum duration that a producer can hold recycled polymer credits. This period is typically set at twelve months, preventing the infinite accumulation or hoarding of credits.
The boundary of this window is strictly chronological, meaning that unused credits must be written off or allocated to products before the window closes.
Duration Constraint
Strict time-based limits prevent the decoupling of physical processing from the sale of certified resins. Within the rules of the credit balance rolling window, producers must coordinate their plastic waste intake with the market demand for circular polymers. This constraint ensures that the environmental claims of recycled content are temporally linked to the actual recycling activity.
Inventory Risk
Moulders and converters face supply volatility when credit balances are allowed to expire. Because the credit balance rolling window forces chemical companies to use or lose their recycled credits, it can lead to periods of high credit availability followed by sudden shortages. When chemical producers run low on credits as a window closes, they may raise prices or restrict the availability of certified resins.
This fluctuation makes long-term sourcing contracts difficult to manage for high-volume injection moulding operations.
Supply Stability
Planning polymer purchases requires a clear understanding of when major credit blocks will expire. In the context of the credit balance rolling window, chemical manufacturers must optimize their feedstock processing schedules to avoid sudden drops in certified resin inventory. When the window is managed efficiently, moulders receive a stable flow of mass-balanced resin without facing unexpected premium surges or supply interruptions.
Maintaining this equilibrium supports continuous high-speed production runs of sustainable plastic parts, which helps converters meet their contractual obligations without incurring penalty fees from brand owners.