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.
Mass Balance Ledger
Meaning
Inventory tracking databases for chemical recycling record the flow of certified circular feedstocks and the corresponding generation of recycled polymer credits. Within a petrochemical complex, a mass balance ledger functions as the central registry where input volumes of recycled pyrolysis oil are balanced against sold volumes of certified resins. This tool records transactions in physical units, usually metric tonnes, and tracks the conversion factors of different cracking units.
The boundary of this ledger is the physical and administrative envelope of the certified chemical manufacturing site.
Record Keeping
Accurate documentation is essential for demonstrating that no double-counting of recycled material has occurred. Within the mass balance ledger, every batch of incoming circular feedstock is logged with its origin, mass and carbon-equivalent yield. This record-keeping system ensures that a company does not sell more tonnes than it processes.
Balance Sheet
The difference between inputs and outputs is managed through continuous credit balances that must be reconciled. Inside the mass balance ledger, a positive balance indicates that the plant has processed more recycled oil than it has sold as certified product. If the balance becomes negative, the plant must immediately halt the sale of mass-balanced polymers or purchase credits from other certified locations.
This balance sheet must be maintained with high precision to prevent regulatory non-compliance.
Industrial Integration
Moulders benefit from this accounting system because it allows them to purchase certified sustainable resins that are physically identical to fossil-based polymers. Since the mass balance ledger verifies the environmental claims at the refinery level, the moulder does not need to invest in separate storage silos or run specialized processing trials. The certified resin behaves perfectly on standard injection moulding machines, maintaining consistent cycle times and part dimensions.
This integration allows brands to achieve their sustainability targets without sacrificing manufacturing throughput or risking tool damage from inconsistent polymer melt flows.