Finkbeiner (2021) comments on our critique (Heijungs et al., 2021) of the amendment to ISO 14044. We summarize hereafter his comment:

• According to him, the ISO amendment does not rule out system expansion (in the sense of expanding the functional unit) in favor of substitution (in the sense of subtracting the avoided impacts of coproducts); instead, it is a clarification that both approaches are allowed.

• The texts by ISO are comparable to legislative documents, which require knowledge of the rules in order to decipher them.

We thank Finkbeiner for this clarification, and we are happy to read that both procedures (system expansion and substitution) are allowed, according to his interpretation.

Yet, the amendment text is not in line with his interpretation, as pointed out by us and by Schaubroeck et al. (2021). Even if the amendment text is not normative and just informative, consistency and correctness is needed throughout the complete ISO text. Moreover, we are worried by the implication that well-trained scientists interpreted in a different way a text that was intended to provide clarity. We consider ourselves as target audience of these standards, and these are apparently not as “crystal-clear” as Finkbeiner appears to think. Hence, it seems that the amendment has failed in its mission “that it should be clarified, that the “subtraction approach” can also be used as system expansion,” as Finkbeiner phrases the amendment’s “actual intention.” A lost opportunity, after all. Let’s hope that future ISO amendments are more consistent, and also understandable to the people who are not familiar with the ISO rules.

Author Contributions

RH drafted and edited the text. KA, EB, MB, JG, SS, TS, and AZ suggested additions and improvements. All authors contributed to the article and approved the submitted version.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s Note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


Keywords: life cycle assessment, allocation, substitution, system expansion, ISO

Citation: Heijungs R, Allacker K, Benetto E, Brandão M, Guinée J, Schaubroeck S, Schaubroeck T and Zamagni A (2021) Response: Commentary: System Expansion and Substitution in LCA: A Lost Opportunity of ISO 14044 Amendment 2. Front. Sustain. 2:768194. doi: 10.3389/frsus.2021.768194

Received: 31 August 2021; Accepted: 29 September 2021;
Published: 30 November 2021.

Copyright © 2021 Heijungs, Allacker, Benetto, Brandão, Guinée, Schaubroeck, Schaubroeck and Zamagni. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Reinout Heijungs,


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