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.
Chemical Recycling Accounting
Meaning
Traceability protocols for mass balance systems ensure the transparent attribution of recycled content to polymers derived from co-processed fossil and circular feedstocks. This methodology underpins the certification of resins where physical segregation of recycled material is technically impossible. In the production of circular polymers, chemical recycling accounting governs how the mass of inputted plastic waste is distributed among the output streams.
The boundary of this system is the chemical complex or cracker boundary, ensuring that credits are not transferred across unrelated operations.
Allocation Protocol
Mass balance rules dictate how manufacturers allocate recycled content to specific product lines. Under chemical recycling accounting, companies use mathematical models to distribute the certified recycled share of inputs to high-value polymers. This allows moulders to purchase certified resins carrying specific recycled percentage claims.
Auditing Procedure
Independent verifiers scrutinize the records of chemical plants to confirm that recycled inputs match the volume of sold recycled credits. The verification of chemical recycling accounting prevents double-counting and ensures that the mass balance calculations remain accurate. High-precision documentation must track each tonne of pyrolysis oil injected into the steam cracker.
When audits reveal discrepancies, the plant must adjust its balance sheet or face decertification, which would immediately disrupt the supply of certified resins to the moulding industry.
Material Traceability
Moulders depend on robust certifications to justify premium pricing to brands seeking circular packaging. By adhering to chemical recycling accounting, converters can use mass-balance certified polypropylene or polyethylene on standard injection moulding machines without adjusting process variables. Because the material is chemically identical to virgin polymer, it exhibits no changes in viscosity, shrinkage or mechanical strength.
This integration eliminates the tooling modifications and high scrap rates associated with physically recycled regrind, allowing manufacturers to maintain high production speeds without investing in new equipment or secondary processing lines.