Mass Balance and Chemical Recycling: How Recycled Content Gets Attributed

Chemical (advanced) recycling processes - pyrolysis, gasification, depolymerisation - break plastic waste down to oils, gases or monomers that re-enter polymer production mixed with virgin feedstock. The output plastic is molecularly indistinguishable from virgin, so its recycled content exists only as an accounting attribution: mass balance. A certified system tracks the recycled input entering a production complex and allocates recycled shares to outputs under defined rules, so that total claims never exceed total recycled input.

Article 7's targets can be met with chemically recycled content where the implementing methodology recognises the attribution - the mechanism on which the contact-sensitive categories' future supply partly depends. The rules of allocation are therefore among the most consequential technical decisions left in the regulation, and this guide explains the models over which the argument runs.

Three models span the argument. Proportional (pro-rata) allocation spreads recycled input across all outputs in proportion to mass - conservative, simple, and limiting for packaging claims because fuel and other outputs take their share. Fuel-excluded allocation first removes outputs used as fuels from the reckoning, concentrating the recycled attribution on material outputs; the exclusion of fuel use is a settled direction in Union policy discussion because crediting recycled content to material that was burned defeats the mandate's purpose. Free (flexible) allocation within a site lets the operator attribute recycled shares to chosen product lines - the most commercially powerful and the most audit-sensitive, defensible only inside strict site-level bookkeeping with the total-claims ceiling absolute. Which blend the methodology adopts, per process type, decides the effective supply of attributable content for a decade.

Mass-balance claims travel on certification: schemes such as ISCC PLUS certify sites, chain-of-custody models and bookkeeping, and the claim that reaches a packaging manufacturer is only as strong as the weakest certificate in its chain. The file discipline mirrors the calculation guide's: the content figure resolves to certificates whose scopes name the process, the site and the period; allocation statements accompany consignments; and the manufacturer's own books reconcile inputs claimed against outputs sold without double counting - the cardinal sin of mass-balance systems, policed by scheme audits and, increasingly, by customer audits behind them. Buyers should contract for audit access and for notification when a supplier's certification scope changes; a suspended certificate upstream silently invalidates claims downstream until somebody checks.

Three questions sort credible offers from arithmetic. What is the site's actual recycled input share this year - not capacity, not ambition? Which allocation model does the certificate apply, and does the claim offered to you survive it? And what would make the claim fall - certificate scope, site closure, an audit finding - and who tells you, how fast? A supplier who answers all three precisely is selling attribution you can file. A supplier who answers with adjectives is selling you the audit finding of 2031, at 2027 prices. The technology deserves its place in the system; the discipline around its accounting is what will earn that place, claim by claim.

Depolymerisation - returning PET or other condensation polymers to their monomers and re-polymerising - sits closest to mechanical recycling in character: the output is a true recycled polymer with a traceable material lineage, and several frameworks treat its attribution more directly than the pyrolysis-oil route. Buyers should still ask the allocation questions, because plant configurations mix inputs, but the audit conversation is shorter. As capacity in both families scales through the late 2020s, the methodology's treatment of each will shape investment for a decade; the desk tracks the implementing work in the acts calendar, and this guide will be re-issued against the adopted rules rather than left standing on the consultation landscape.