Mass Balance: Accounting Method Supports Circular Packaging
As the packaging industry progresses toward a circular economy, mass balance is gaining traction for its ability to track sustainable inputs without disrupting existing supply chains. Originally developed for the chemical sector to improve yields, mass balance is now being adopted across the packaging industry to attribute recycled or renewable content to raw materials in a quantifiable, scalable manner.
But what exactly is mass balance? How does it work in packaging? And why is it becoming such a pivotal tool in achieving circularity?
What Is Mass Balance?
At its core, mass balance is an accounting method that tracks the flow of materials through a production system. Rather than separating renewable (e.g., bio-based plastic feedstocks) or recycled content inputs from virgin materials throughout the manufacturing process—a logistically and technically challenging task—mass balance allows producers to blend these inputs and assign sustainability attributes proportionally to final products, such as plastic bottles.
This means that producers can say, for example, their packaging contains 30% recycled content—even if it can't be seen or measured in each item. It's a bookkeeping method that supports sustainability without modifying existing production processes or supply streams.
Mass balance is integral to many sustainability applications, ranging from fair-trade coffee and cocoa to deforestation-free palm oil, coconut oil, and FSC-certified paper. Mass balance enables companies to make sustainability claims across diverse product categories while managing complex global supply chains where certified and conventional materials cannot be easily segregated and are often mixed during processing, storage, or transportation.
Another example is the use of green energy in the power grid. You can't physically tell whether the electricity lighting your home came from a wind turbine or a coal plant. But if enough renewable energy is added to the grid, your provider can legally and ethically attribute a portion of that clean energy to your bill. Mass balance works similarly, but for plastics, paper, and other packaging materials.
Why It Matters
The global push for sustainable packaging is intensifying. Regulatory frameworks such as U.S. state minimum post-consumer recycled (PCR) content requirements, extended producer responsibility (EPR) packaging rules, and the EU's Packaging and Packaging Waste Regulation are setting ambitious targets for recycled content, carbon reduction, and material traceability. At the same time, brand owners are pledging to reduce their environmental impact, aiming for net-zero emissions, 100% recyclable packaging, or renewable inputs.
Mass balance offers a bridge between aspiration and implementation. It enables companies to:
- Utilize recycled or bio-based feedstocks without retooling entire manufacturing operations.
- Make certified sustainability claims through third-party standards such as ISCC PLUS or RSB.
- Align with upcoming regulations that demand transparent sourcing and material traceability.
- Support innovation in chemical or advanced recycling and bio-based polymers.
How It Works
Here's how a mass balance system typically functions in a chemical recycling system for producing raw materials for packaging. A chemical producer introduces a sustainable feedstock, such as chemically recycled plastic waste or a bio-based monomer, into its production stream. The sustainable input is physically mixed with conventional (fossil fuel-based) materials in existing infrastructure. Once comingled, the actual molecules cannot be separated or individually identified at this stage.
Using an audited mass balance model, a proportion of the final output is certified as containing recycled or renewable content, even though it's indistinguishable from the conventional version. Third-party auditors verify the input amounts and sources, ensuring no more sustainable material is claimed than was added. Certified packaging can then carry a sustainability marker, such as "ISCC PLUS certified recycled content" or "Recycled Material Standard (RMS) label."
This method ensures environmental integrity while maintaining commercial flexibility—a crucial balance for industries that need to scale quickly without massive capital investment.
Skepticism and Concern
Mass balance is not without its critics. Some claim it's too abstract for consumers to understand, offers too much flexibility in reporting and allocation of credits, or worry that it opens the door to greenwashing.
Recycled inputs are converted into credits, with each credit representing a certain weight or volume of the recycled material added to the process. Under mass balance, these credits can be assigned to specific product batches, whether they contain some or none of the actual recycled molecules.
Another concern is the differences in certification schemes. One certification method may allow a company to make a recycled content claim even if some of the chemical outputs generate fuel or other byproducts instead of plastic. Meanwhile, another certification program for recycled content may reject processes that produce fuel or energy products or exclude those byproducts from the chemical outputs.
Founded by the Ellen MacArthur Foundation, the U.S. Plastics Pact—part of the global National Plastic Pacts network—accepts the mass balance method for tracking recycled content. However, in keeping with its PCR certification principles, the methodology must count fuel outputs as yield loss in the recycling process and comply with the ISO 22095 chain-of-custody standard.
Regulatory Landscape
Regulators seem to be divided on the role of mass balance calculations in determining recycled content in packaging.
In August 2024, the U.S. EPA updated its standards for the use of its voluntary Safer Choice label for commercial and household cleaning and laundry products. The new standard addresses packaging, mandating a minimum of 15% PCR content by weight for plastic packaging. The "by weight" measure precludes the use of recycled content from chemical recycling and mass balance accounting.
In comments about proposed revisions to the Federal Trade Commission's Guides for the Use of Environmental Marketing Claims (Green Guides), the EPA rejected the mass balance approach because "it is not widely implemented or accepted worldwide. Allowing producers to advertise that a product contains recycled content based on the amount of recycled material purchased is deceptive. It would be clearer to focus on calculations that involve the actual amount of material used."
At the state level, jurisdictions (especially those with EPR packaging and minimum PCR content laws) differ on their acceptance of mass balance and chemical recycling. California and New Jersey tend to be more restrictive toward chemical recycling, with New Jersey prohibiting outputs via pyrolysis and gasification processes from counting as PCR. Other states, such as Washington and Colorado, either accept mass balance accounting with recognized third-party certifications or are in the process of creating rules around it.
In July 2025, the European Commission published a draft document allowing the use of a mass balance fuel-exempt method for allocating recycled content in single-use plastic beverage bottles. The adoption of the proposed legislation will enable chemical recycling and will help economic operators meet the ambitious recycled content targets in the EU. While the EU prefers mechanical recycling, it recognizes that chemical recycling is a valuable alternative for applications with higher quality standards, such as food-grade packaging.
In the UK, businesses can use mass balance accounting to demonstrate the amount of recycled content in chemically recycled plastic associated with the Plastic Packaging Tax. Plastic containing at least 30% recycled content is not taxed.
Explaining Mass Balance: LEGO's Language
Since mass balance may not be the easiest thing for consumers to grasp, organizations may want to take a cue from LEGO. In its 2024 annual report, the toymaker reported that half of its materials for plastic bricks and other components came from sustainable sources, and 47% were certified mass balance. That's a huge increase from 2023, when only 18% were certified mass balance.
Beyond those figures, LEGO explains what mass balance is, how it works (including an animated video), and how it fits into its long-term sustainability goals on its website. The company notes, "the mass balance approach is a stepping stone that helps us continue our transition to using more and more renewable raw materials, but it's not the end goal. However, it is the best option we have today to increase the amount of renewable raw material we buy and decrease the amount of virgin fossil fuel we use."
The brands mentioned in this report are trademarks of their respective owners. Inclusion of these brands in this report is not meant to imply an association with or endorsement from the respective trademark owners.