In the race to scale post-consumer recycled content—particularly in plastics—“mass balance” has quickly become one of the most debated concepts in the circular economy. While it may sound technical, for recyclers, policymakers, and brands navigating Extended Producer Responsibility (EPR) laws and recycled content mandates, it’s becoming a critical issue that will define market credibility and investment confidence in the years ahead.
Put simply, mass balance is an accounting approach used to allocate recycled content across outputs when materials are processed in complex, mixed systems—such as chemical recycling or integrated petrochemical production. Rather than tracking recycled feedstock molecule-by-molecule, it ensures that total inputs and outputs “balance” and allows recycled content to be assigned to specific products based on defined rules.
In Europe, rules were defined when the EU’s implementing decision on recycled content under the Single-Use Plastics Directive (SUPD) was adopted, but not all bases have been covered. The “line in the sand” around how mass balance and chemical recycling are likely to be treated under future EU frameworks, particularly the Packaging and Packaging Waste Regulation (PPWR) marks the end of a debate, that has been running, in Europe in various forms, for many years. I was involved in early work for the European Commission on how recycled content under the SUPD should actually be quantified.
But what about in the US? Are there any defined rules? And if not—what does this mean for recyclers, policymakers and brands? How brands choose to calculate mass balance cuts to the heart of how recycled content claims are made—and whether those claims will stand up to regulatory and public scrutiny.
Why do mass balance rules matter now?
Across the United States, policymakers are actively shaping the future of packaging and recycling systems. States like California, Oregon, Colorado and Maine are implementing or advancing EPR schemes, while minimum recycled content requirements—especially for plastics—are gaining traction. At the same time, many US brands are investing in chemical recycling technologies or purchasing recycled content from chemical recycling technologies to meet ambitious recycled content targets, particularly where mechanical recycling struggles to deliver suitable material quality or volume.
Mass balance sits at the intersection of these developments. It is the primary mechanism enabling chemical recycling outputs to be counted as recycled content. But crucially, different approaches to allocation can produce dramatically different recycled content claims from the same underlying inputs. For example, a proportional approach allocates recycled content evenly across outputs, yielding lower but more conservative claims. By contrast, more flexible approaches allow recycled content to be concentrated into selected products, resulting in higher headline percentages.
This trade-off—between credibility and commercial viability—is at the core of the debate now emerging in the US.
A risk of inconsistent claims
One of the key lessons emerging internationally is that inconsistent rules lead to inconsistent claims. In Europe, regulators have begun tightening how mass balance can be applied—placing limits on credit transfers and excluding certain uses (such as fuels) from counting toward recycled content in packaging.
The result is that the same product may carry different recycled content claims depending on the system it is certified under. A product deemed “30% recycled” under one scheme may not qualify under stricter regulatory definitions, even if both rely on mass balance methodologies. For US stakeholders, this should serve as a cautionary tale.
Without clear, harmonized rules, there is a real risk that recycled content claims become difficult to compare, harder to verify, and ultimately less trusted by regulators, investors and consumers. In a market already facing scrutiny over greenwashing, that’s a risk the industry cannot afford.
Not “book and claim”
Mass balance is sometimes compared to “book and claim” systems used in renewable energy markets—but the comparison is inaccurate. Under mass balance, recycled inputs must still physically enter the production system, and outputs are tied to actual material flows within defined boundaries.
However, if those boundaries are too broad—for example, allowing credits to be transferred freely across multiple facilities—the system can begin to resemble a trading mechanism rather than a direct link between recycling and product manufacturing. At that point, the environmental integrity of claims becomes harder to defend. For US policymakers designing EPR frameworks or recycled content standards, this distinction will be crucial.
Getting it right: A call to action
The US has an opportunity to learn from international experience and build a system that balances scalability with credibility from the outset.
Three priorities stand out:
- Define clear allocation rules: Regulators must determine how recycled inputs can be assigned to outputs—and ensure those rules are transparent and enforceable.
- Set appropriate system boundaries: Limiting how far recycled content credits can travel will help maintain the integrity of claims.
- Align with broader circularity goals: Recycled content should not be treated in isolation, but as part of a system that delivers measurable environmental benefits—including emissions reduction and resource efficiency.
For brands buying post-consumer recycled content from chemical recycling technologies, the message is equally clear—now is the time to understand the mass balance approach being used by suppliers. Understand which mass balance model you are using, assess whether your claims would stand up under stricter scrutiny, and prepare for a more regulated future.
The bottom line
Mass balance is not a loophole—it is a necessary tool for scaling post-consumer recycled content in complex industrial systems. But its value depends entirely on how it is implemented.
Get it right, and it can unlock investment, accelerate chemical recycling, and support a more circular plastics economy in the United States.
Get it wrong, and it risks undermining the very credibility the industry is working to build.
