Allocation Logic
Accounting methodologies for sustainable materials allow for the mixing of recycled and virgin inputs during a complex manufacturing process. The mass balance arithmetic provides the mathematical proof that the volume of certified product leaving a factory matches the volume of sustainable raw material entering it. This system is used when the physical separation of different fibre types is technically impossible or too expensive.
Credit Conversion
Calculations are based on a simple input-output model where every ton of sustainable material is converted into a credit. When using mass balance arithmetic, a company must subtract the processing losses and moisture changes from the total mass before allocating credits to the final products. If a mill buys ten tons of certified fibre and loses one ton during pulping, they can only sell nine tons of certified paper.
These credits can be transferred between different product lines as long as the total balance remains zero or positive at the end of the reporting period. This flexibility allows for the gradual transition of a large mill toward more sustainable sourcing without the need for new tanks or pipes. The integrity of the system depends on frequent audits of the ledger books.
Sustainability Reporting
Transparency is maintained through a clear paper trail that links the forest certificate to the final invoice. While mass balance arithmetic does not guarantee that a specific sheet of paper contains recycled fibre, it ensures the overall market volume is accurate. This approach supports the growth of circular economies in the paper industry.
