National foreword

This British Standard is the UK implementation of ISO 22095‑2:2026.

The UK participation in its preparation was entrusted to Technical Committee SES/1/11.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 January 2026.

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

ISO draws attention to the possibility that the implementation of this document may involve the use of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s) which may be required to implement this document. However, implementers are cautioned that this may not represent the latest information, which may be obtained from the patent database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.

Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISO's adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 308, Chain of custody.

A list of all parts in the ISO 22095 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

Introduction

The mass balance model is one of five chain of custody models outlined in ISO 22095. A mass balance model offers different methods for organisations to mix or co-process inputs with and without specified characteristics while transparently documenting the movement of the inputs and their specified characteristics. This is to ensure that the credits or specified characteristics are appropriately accounted for and attributed to outputs within the same system boundary.

NOTE Mixing and co-processing includes activities where those in the value chain (i.e. brokers) do not physically mix or co-process mass balanced material or products.

A mass balance model is ideally suited for certain situations, such as when identity preserved, segregated, or controlled blending chain of custody models are not feasible. For instance, in some supply chains, materials or products with specified characteristics are mixed or co-processed with materials or products without specified characteristics. New materials or products are then produced. It is not possible to distinguish which of these new materials or products were derived from inputs with, and without, specified characteristics. However, the quantity of input with specified characteristics, such as renewable feedstock or fair trade labour practices, are in the system. Therefore, it becomes appropriate to pass forward those specified characteristics through a chain of custody model. Many industries currently use a mass balance model including transportation, agriculture, textiles, forestry, construction, chemicals, metals, steel, energy, glass, plastics, organics and inorganics.

However, the mass balance model may be applied differently in the market based on the criteria selected. This may create confusion and reduce its credibility among consumers, policy makers, standard setters, and other stakeholders. This document provides guidance to explain the mass balance chain of custody model and limit the risk of confusion on mass balance model communication (for example claims) in the marketplace and throughout the value chain.

This document helps organizations outline technical choices, define system boundaries, and specify methods of attribution. In addition, it provides guidance on communication and claims.

1 Scope

This document provides requirements and guidelines for the application of the mass balance chain of custody model, as defined in ISO 22095, to any material or product flow within mass balance systems, including how to attribute specified characteristics to flows of such processes.

This document provides requirements and guidelines for the following matters, amongst others:

differentiations from controlled blending and book and claim models;
general requirements for organizations active in a mass balance chain of custody model;
system boundaries including geography and time;
conversion factors;
the rolling average percentage method;
the credit method;
transparency, communication and claims.

2 Normative references

3 Terms and definitions

4 Differentiation between chain of custody models

4.1 General

4.2 Differences between the mass balance model and the controlled blending model

4.3 Differences between the mass balance model and the book and claim model

5 Requirements for mass balance chain of custody model

5.1 General

5.2 Set-up of a mass balance system

5.3 System boundary

5.4 Evaluation and claim periods

5.5 Types of data, data sources and data quality

5.6 Material and credit reconciliation

5.7 Conversion and consumption factor

5.8 Avoidance of double counting in mass balance systems

5.9 Returned materials and products

6 Mass balance model implementation methods

6.1 Mass balance model rolling average percentage method

6.2 Mass balance model credit method

7 Claims and communication

7.1 General requirements

7.2 Business-to-business communication

7.3 Business-to-consumer communication

Bibliography

BS ISO 22095-2:2026

Chain of custody - Requirements and guidelines for mass balance

Current

Published:

31 Jan 2026