Mass Balance and the Future of Recycled Content
What Is Mass Balance?
Mass balance is an accounting method used to allocate recycled content across products when materials move through complex, mixed processing systems, such as chemical recycling or integrated petrochemical plants. Instead of tracking each unit of recycled material individually, the system ensures that total inputs and outputs align, then assigns recycled content to specific products according to predetermined rules. This approach has become central to debates in the circular economy, particularly as it relates to plastics recycling, Extended Producer Responsibility (EPR) laws, and recycled content mandates.
The European Precedent
In Europe, mass balance rules were established through the EU’s implementing decision on recycled content under the Single-Use Plastics Directive, though gaps remain. The treatment of mass balance and chemical recycling under future frameworks like the Packaging and Packaging Waste Regulation represents the culmination of a long-running European debate. The author notes direct involvement in early Commission work on quantifying recycled content under this directive.
Why This Matters for the US Now
US states including California, Oregon, Colorado, and Maine are developing or expanding EPR programs, and minimum recycled content requirements for plastics are becoming more common. Simultaneously, many brands are turning to chemical recycling—either through direct investment or by purchasing recycled content—to meet ambitious targets, especially where mechanical recycling cannot provide sufficient quality or volume.
Mass balance is the key mechanism that allows chemical recycling outputs to count as recycled content. However, the choice of allocation method matters enormously: a proportional approach spreads recycled content evenly across all outputs, producing modest but defensible claims, while more flexible approaches can concentrate recycled content into select products, generating much higher headline figures from the same raw inputs. This creates a fundamental tension between credibility and commercial appeal.
The Risk of Inconsistency
International experience shows that inconsistent rules produce inconsistent and potentially misleading claims. European regulators have already moved to tighten mass balance application, restricting credit transfers and excluding certain outputs (like fuels) from counting toward packaging recycled content. As a result, identical products can receive different recycled content percentages depending on which certification scheme applies. Without harmonized US rules, recycled content claims risk becoming incomparable, difficult to verify, and increasingly distrusted by regulators, investors, and consumers—a serious liability in a market already under pressure over greenwashing.
Not the Same as “Book and Claim”
Mass balance is sometimes likened to book-and-claim systems in renewable energy markets, but this comparison is misleading. Mass balance requires that recycled inputs physically enter the production system, with outputs tied to real material flows within defined boundaries. If those boundaries become too expansive—for instance, allowing credits to move freely between unrelated facilities—the system starts functioning more like a trading scheme than a genuine link between recycling and manufacturing, weakening the environmental credibility of any resulting claims.
A Call to Action
The piece argues the US can learn from Europe by building credibility into its system from the start, through three priorities: establishing clear, transparent, and enforceable allocation rules; setting appropriate boundaries on how far recycled content credits can be transferred; and aligning recycled content policy with broader circularity goals like emissions reduction. Brands sourcing recycled content from chemical recycling suppliers are urged to understand the mass balance methods being used and assess whether their claims would withstand stricter future scrutiny. Done well, mass balance can unlock investment and accelerate circularity; done poorly, it risks undermining industry credibility entirely.
www.resource-recycling.com/analysis/opinion/2026/06/05/mass-balance-matters-why-different-rules-can-lead-to-different-outcomes/