Mass balance is a chain-of-custody method in which recycled and virgin materials are mixed in production, and the recycled share is tracked through bookkeeping and then assigned to specific products.
It works like green electricity: the recycled input entering the system is measured, and an equivalent quantity of output can be sold as recycled, even though the physical product may contain a different proportion. Mass balance is mainly used in chemical recycling, where recycled oil is processed together with fossil feedstock in very large plants. Schemes such as ISCC PLUS certify it. Mechanical recycling normally uses segregation or controlled blending instead, where the recycled material is physically present in the product, which makes claims simpler to explain.
