# BBCA vs CML calculation of some biobased material are strange **URL:** \ **Category:** Product LCA, EPDs & Data\ **Tags:** epd, building-lca\ **Created:** [March 23, 2026, 9:01am UTC](https://community.oneclicklca.com/t/bbca-vs-cml-calculation-of-some-biobased-material-are-strange/2873 "2026-03-23T09:01:28Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Nicolas\_TERZIAN](https://avatars.discourse-cdn.com/v4/letter/n/c6cbf5/32.png) [@Nicolas\_TERZIAN](https://community.oneclicklca.com/u/Nicolas_TERZIAN)\ **Post date:** [March 23, 2026, 9:01am UTC](https://community.oneclicklca.com/t/bbca-vs-cml-calculation-of-some-biobased-material-are-strange/2873/1 "2026-03-23T09:01:28Z")
Hi, I’ve a question about some results of BBCA calculation tool (french method “carbon energy”). I don’t understand why certain bio-based materials, calculated using the BBCA method – which is supposed to subtract biogenic carbon from the result – have a higher impact than their impact calculated using a CML method (BREEAM or HQE). This is the case, for example, with STEICO Flex F 036 and IsoHemp PAL36EX. Is there a specific reason for this, or is it a calculation or data error? Could you please correct this if necessary? Regards, ---
**Author:** ![quentin.judalet](https://avatars.discourse-cdn.com/v4/letter/q/87869e/32.png) [@quentin.judalet](https://community.oneclicklca.com/u/quentin.judalet)\ **Post date:** [March 24, 2026, 10:17am UTC](https://community.oneclicklca.com/t/bbca-vs-cml-calculation-of-some-biobased-material-are-strange/2873/2 "2026-03-24T10:17:17Z")
Hi Nicolas, Thank you for raising this question. In general, both methodologies can account for biogenic carbon **provided that it is already included in the underlying EPD/FDES dataset**. In other words, the treatment of biogenic carbon is primarily driven by the inventory data and the modelling rules applied in the declaration. However, it is important to highlight that **CML-based methods do not explicitly report GWP biogenic as a separate indicator**. Biogenic carbon is therefore only reflected **indirectly within the total GWP result** , assuming it has been integrated upstream in the dataset. As such, CML does not allow for a transparent distinction between fossil and biogenic carbon contributions. Regarding the specific datapoints you mentioned: - They are compatible with the LCA calculation framework implemented in One Click LCA. - Their use in a specific LCA calculation tool in One Click LCA depends on the applicable version of EN 15804: These differences are important, as **EN 15804+A2 introduces a mandatory split of GWP into fossil, biogenic, and LULUC components** , whereas +A1 does not. The way biogenic carbon is reflected in the total results is determined by the calculation methodology applied in One Click LCA. I hope this clarifies the topic. Kind regards, ---
**Author:** ![Nicolas\_TERZIAN](https://avatars.discourse-cdn.com/v4/letter/n/c6cbf5/32.png) [@Nicolas\_TERZIAN](https://community.oneclicklca.com/u/Nicolas_TERZIAN)\ **Post date:** [March 24, 2026, 10:42am UTC](https://community.oneclicklca.com/t/bbca-vs-cml-calculation-of-some-biobased-material-are-strange/2873/3 "2026-03-24T10:42:41Z")
Hi Quentin, Thank you for your answer. However I wasn’t speaking about biogenic/fossil GWP, but about carbone storage in biobased materials. The BBCA method substract this carbon from the GWP total. Therefore the GWP result is supposed to be lower than their CML result, which is usually true, except for these two materials. ![Capture d’écran 2026-03-24 113932](https://europe1.discourse-cdn.com/flex013/uploads/oneclicklca/original/1X/8a86eff540784e1a3faf6a8e3423ae2071f98886.png) That’s why I was wondering if there might be a mistake in data source. Like an additive carbon storage instead of a substractive one. I hope this clarifies my question. Regards, ---
**Author:** ![quentin.judalet](https://avatars.discourse-cdn.com/v4/letter/q/87869e/32.png) [@quentin.judalet](https://community.oneclicklca.com/u/quentin.judalet)\ **Post date:** [March 24, 2026, 4:02pm UTC](https://community.oneclicklca.com/t/bbca-vs-cml-calculation-of-some-biobased-material-are-strange/2873/4 "2026-03-24T16:02:21Z")
Hi Nicolas, Thanks for the extra info! Because this involves specific project tools and data, it’s best to loop in our support team at **[support@oneclicklca.com](mailto:support@oneclicklca.com)**. Once you send over the **project name and the tools/data you’re using** , we can take a closer look at those results and get back to you with a detailed explanation. Kind regards