GHG inventory in the plastics industry under ISCC PLUS

The adoption of the ISCC PLUS GHG inventory in the plastics industry requires combining life cycle accounting (PCF), chain of custody traceability and robust data governance. In chains with physical mixing of currents (bio/circular and fossil), the model of mass balance of ISCC PLUS enables scale without renovating assets, as long as the bookkeeping is consistent, auditable and that commercial claims follow the rules of the scheme.

What changes with ISCC PLUS in plastic

ISCC PLUS is a voluntary scheme aimed at chemicals and plastics, among other sectors not directly covered by RED II. It validates traceability and reporting of renewable/circular content via three chain of custody methods (physical segregation, controlled blending e mass balance). For plastic, mass balance is the most used path because it allows the attribution of sustainable characteristics to output batches in plants where the streams are physically mixed — as long as the entire chain is certified and the mass balance is closed within the defined period.

How GHG inventory integrates with mass balance

At the level of ISCC PLUS GHG inventory, the company needs to transform real consumption into emissions per product (PCF, product carbon footprint) and link these results to the chain of custody. The logic is:

1. Measure primary data (electrical energy, steam/fuels, utilities, reagents, losses, water/effluent) By stage (cracking, purification, polymerization, conversions).
2. Apply emission factors and PCI/LHV consistent with recognized standards (p. ex., ISO 14067, GHG Protocol Product Standard, sector guides).
3. Close the mass balance (inflows/outflows/losses/stocks) of the period and assign sustainable content in batches in accordance with ISCC PLUS rules.
4. Connect the PCF of each grade of resin/intermediate to the bookkeeping system (bookkeeping) and at certified declarations used for sale.

Recommended Accounting Standards (and why use them together)

To give comparability and credibility to the PCF, the primary reference is the ISO 14067, that defines principles, requirements and guidelines for quantifying and reporting the carbon footprint of products in alignment with ISO 14040/44. in parallel, O GHG Protocol Product Standard details requirements for quantifying and reporting emissions throughout a product's life cycle, and is widely adopted in the market. The chemical sector still has TfS PCF Guideline, that harmonizes assumptions and data granularity between chemical suppliers and customers. Together, these three pillars reduce methodological divergences and support ISCC audits with consistent evidence trails.

Scope and boundaries: what goes into your PCF

For each resin or chemical intermediate, delimit:

• Process boundary (gate-to-gate or cradle-to-gate, according to the intended use of the PCF).
• Unit steps (cracking/furnace, separations, polymerization, extrusion).
• Utilities (electricity, vapor, cooling water, compressed ar) with technically defensible measurement or apportionment.
• Process inputs (catalysts, solvents, additives, enzymes, control agents) with confirmed emission factors and documented sources.
• Effluent and waste treatment (including purges and torches where applicable).
  The result must be expressed in kgCO₂e/kg of product (e, when it makes sense for comparison, also in Co.₂e/MJ), maintaining inventories and calculation memories organized by period and line.

Chain of custody and claims: the role of mass balance

No mass balance, certified materials (bio/circular) and non-certified can be physically mixed, but remain segregated in the ledger. Each period has rules for assigning credits/percentages to output batches, respecting losses and conversions. As allegations (ex.: “bio-attributed”, “circularly assigned”) must reflect exactly what was assigned in the system and in the period, in accordance with the ISCC PLUS chain of custody document and its certification guidelines. This coherence between bookkeeping, PCF and claims are critical for audits and to avoid non-conformities.

Step by step to assemble the inventory (from data to allegation)

1. Data mapping: lift gauges, utility reports and material notes for each stage. List gaps and prioritize direct measurement where consumption is relevant to PCF.
2. FEs and PCI Plan: select factor sources and hierarchies (supplier primary data when auditable; sectoral secondary when necessary) and document versions and dates.
3. Cost center/step structure: organize the apportionment of utilities and support inputs according to technical criteria (hours of operation, thermal load, treated dough, etc.).
4. PCF calculation: consolidate the modules (energy, inputs, losses, effluents) and normalize per kg of each grade of resin.
5. Mass balance closure: reconcile inflows/outflows/losses/inventories; apply bio/circular content assignment to batches as per ISCC PLUS rules.
6. Report and evidence: generate spreadsheets with audit trail (raw data, transformations, factors, base versions) e sustainability statements accompanying the sale.
7. Review and audit: run internal checks, historical comparisons and spot checks before external audit.

Critical Items in Chemical and Polymerization Plants

• Electricity and steam: are typically the biggest “drivers” of the PCF. Seek granularity by process area and consider efficiency improvements and lower carbon intensity contracts.
• Cracking/furnaces: evaluate thermal integration opportunities, heat recovery and load scheduling.
• Solvent balancing and purging: Small leaks and burns can affect the PCF; document hypotheses and monitor improvements.
• Water/effluents: Consumption reductions and better treatment can reduce indirect emissions; keep factors and scopes aligned with the method.
• Critical input data (catalysts/additives): obtain primary FEs from vendors when possible; where not, follow sector guides (TfS) to ensure comparability between chemical chains.

How the ISCC PLUS GHG Inventory Accelerates Decarbonization

Com ISCC PLUS GHG inventory well implemented, its operation:

• Verifies bio/circular content with independent audit, at the same time as delivering Comparable PCFs to customers;
• Directs CAPEX/OPEX for the biggest levers (ovens, utilities, losses), based on measurable data;
• Evita greenwashing by aligning claims with the chain of custody system and mass balance results;
• Responds to sustainable purchasing of large clients that require PCF according to recognized standards (ISO 14067 + GHG Protocol) and specific methodologies for the chemical sector (TfS).

Governance, update and trends

Establish a annual cycle methodological update (FE versions, border adjustments, efficiency gains). Train purchases, manufacture, logistics and marketing about what you can — and what you can’t — claim. Monitor developments in PCF guides for the chemical sector (TfS) and ISCC itself on mass balance, that have been refining terminology and controls to increase market confidence.

Conclusion O ISCC PLUS GHG inventory is the backbone of a credible strategy for plastics and chemicals: connects first-party data to recognized PCF standards and chain of custody via mass balancing, enabling scale, traceability and responsible communication. With data governance, clear hierarchy of factors and audit discipline, your company turns pressure for decarbonization into competitive advantage — and in numbers that resist any due diligence.

We carry out GHG inventories for the plastics industry with adherence to ISCC PLUS and best practices for PCF (Product Carbon Footprint). We structure primary energy and input data (cracking, polymers, utilities, losses), we apply mass balance chain of custody when there is physical mixing of currents and we connect the results to recognized standards (ISO 14067) and sector guides (TfS PCF Guideline for the chemical industry). We do scope mapping, the design of the bookkeeping and FE/PCI reconciliation, ensuring auditable traceability and correct communication of claims in line with the official ISCC PLUS documentation. Thereby, your company gets comparable numbers, ready for audit and to respond to customers who require proof of footprint on resins and packaging.

Learn more about GHG inventory in our blog, and more about ISCC on here.