ISCC PLUS Mass Balance: How Bio Content Is Attributed

One system, separate books

A chemical plant is not a set of sealed pipes for each feedstock. Material enters, mixes in process inventories, and leaves as product; tracking individual molecules is not feasible at scale. Mass balance accepts that physical reality and applies bookkeeping instead, keeping a credit account for the certified input and drawing against it as output is sold.

How attribution is assigned

The certified input creates a credit in proportion to what entered the system. Output draws against that credit, so the attributed quantity can never exceed the input it came from. This is the safeguard that stops one delivery of certified feedstock from being claimed several times over, and it is the first thing an auditor tests. That single constraint explains why attributed volume behaves as a limited quantity.

The document chain

The claim travels through documents rather than through the container. Sustainability declarations identify quantities and periods, purchase records tie them to lots, and internal ledgers show what has been consumed and what remains claimable. Because the attribute is not visible in the product, the chain of documents is the product as far as a claim is concerned.

What it does not mean

Mass balance does not mean the drum in the store is physically bio-based, and it does not support a statement about the exact carbon content of a specific container. It supports a statement about an attributed quantity over a defined period. Buyers who understand that distinction write defensible claims, and buyers who do not tend to overstate them in marketing. Clear wording in a purchase specification prevents most of these mistakes before a customer sees them.

What an auditor checks

An auditor typically follows the credit from receipt to claim, checks that consumption and sales reconcile, and looks for the boundary of the system. Findings are usually about clarity rather than fraud: a system boundary that was never written down, or a ledger that mixes two accounting periods, makes an otherwise sound claim difficult to verify. Preparing for that sequence in advance is usually enough to avoid a repeat visit.