ISO 22095‑2: What This New Mass Balance Standard Actually Means — and Why It Matters

March 4, 2026

ISO 22095-2 (“Chain of custody — Mass balance — Requirements and guidelines” formerly known as ISO/DIS 13662) is attracting a lot of attention… and a fair bit of confusion! Here’s the essential point up front: ISO 22095-2 is not a mass balance standard you “take and implement” as an operator. 

Instead, it’s what you might call a meta standard: a structured set of requirements and considerations for the developers of mass balance systems and standards (referred to as “requirements setters”), telling them what to include, define, differentiate, and disclose when they create or update a mass balance program. In other words, it’s a design guide for credible mass balance frameworks, not an operations manual for day-to-day mass balance accounting.  

What does the standard do?

ISO 22095-2 lays out requirements and guidelines for the mass balance chain of custody (CoC) model, including how to attribute specified characteristics to material flows, and how to differentiate mass balance from other CoC models, such as controlled blending and book and claim. 

It outlines the two implementation methods applicable to mass balance systems: the rolling average method and the credit method, both asking requirements setters to clearly define system boundaries (e.g., geographical area, balancing or claim period), methodologies for consumption and conversion factors, as well as attribution principles. 

The standard reminds us: CoC is not only the handoff of certified material between separate companies; it also governs how certified materials are accounted for within a site or corporate system boundary. That means an organization may apply mass balance internally (e.g., coprocessing certified and non-certified inputs and attributing characteristics across multiple product streams), and yet ship a segregated, mass-balanced certified output to its customer. In this case, mass balance is the CoC model within the facility (and the product carries a “mass balance” certification claim) while segregation is the CoC model used for the transfer of the certified product to the customer. 

How can the standard be used? 

If you are developing or revising a mass balance program, ISO 22095-2 provides a checklist of design obligations:

• Define boundaries (geographic and temporal), 
• Choose and justify attribution approaches, 
• Set conversion factors, 
• Reconcile inputs/outputs, 
• Implement systems to avoid double-counting, and 
• Apply a designation system to communicate the chain of custody system used. 

The intent is to harmonize expectations so certification programs do not talk past each other, or worse, enable double-counting. 

In practice, the emergence of ISO 22095-2 should help align developers of mass balance CoC systems across sectors and geographies. This alignment matters: without common definitions, understandings, and guardrails, mass balance risks becoming a patchwork of incompatible claims that confuse customers and regulators. 

How does ISO 22095-2 mesh with other ISO standards?

The parent chain of custody standard, ISO 22095, defines common terminology and models, and the newly published ISO 22095-2 provides mass balance requirements and guidelines at the model level (including rolling average and credit methods), further underscoring that ISO is standardizing how mass balance systems should be designed and governed rather than prescribing a single operational method for every user. A similar approach was taken in developing ISO 22095-3, which provides requirements to establish a book and claim CoC system. 

What do we need next?

The standard clearly lays out the differences between mass balance and controlled blending, which is often conflated with rolling average mass balance. The ISO community should continue to refine guidance around controlled blending because the concept is underdefined in the parent standard ISO 22095, leaving room for divergent interpretations in programs and certification schemes. As ISO 22095-2 informs the design of mass balance systems across sectors, further refining of control blending definitions and control points would help reduce noise at the interfaces between models and prevent accidental overstating of claims.

For help navigating the complex topic of chain of custody systems, contact [email protected].