Two processes, two realities: one framework needs to reflect both

The review of mineral carbonation methodologies does valuable work in mapping carbonation pathways and identifying methodological challenges. The analysis is primarily framed around cement recarbonation, the gradual reabsorption of CO₂ that was originally released when cement was produced. That is an important pathway. But it is not the only one, and the differences between pathways matter for how certification rules are designed.

Engineered mineral carbonation, which is what Paebbl does, is a fundamentally different process. We developed an engineered mineral carbonation technology that converts captured CO₂ and reactive minerals such as magnesium silicates into stable carbonate materials and turns these into construction materials (specifically, an SCM replacing up to 30% of cement in concrete mixes).

In our process, there is no prior CO₂ release through calcination, no gradual reabsorption over decades, and no need for complex modelling of how much carbon a material might absorb on its own. The CO₂ is absorbed in a controlled and industrial process, and the amount of CO₂ stored is directly measurable.

The dual value is clear: First, the process permanently sequesters CO₂ through an industrial carbonation step with directly measurable storage. Second, the resulting products displace conventional cement as a supplementary cementitious material (SCM), avoiding the embedded emissions of the clinker they replace. Silicate mineral carbonation is already recognised as a distinct pathway - the methodological design for baseline determination should reflect that.

The “permanence” storage question is already answered in EU law

EU legislation already provides strong recognition of the permanence of mineral carbonation. The Commission Delegated Regulation on permanently chemically bound CO₂ establishes that CO₂ chemically bound in stable mineral carbonates provides a climate benefit comparable to geological storage. It identifies construction materials containing mineral carbonates such as aggregates, cement constituents, concrete, and masonry products, as capable of permanently storing captured CO₂.

Mineral carbonates are thermodynamically stable under normal conditions. Construction materials remain in use for decades or centuries. And construction and demolition waste is predominantly recycled, landfilled, or backfilled - not incinerated. We believe the CRCF methodology development has an opportunity to build directly on this regulatory foundation, ensuring consistency across EU climate policy instruments and providing clarity for mineralisation technologies.

With that in mind, permanence is only one of the four criterias. Engineered mineral carbonation has a clear case on each:

• Quantification - CO₂ stored is directly measured at the point of binding through input flows, reactor conditions, and carbonate content of the output.

• Additionality - the carbonation step adds cost that is only justified by CO₂ revenue, not by SCM performance alone. Without a removal incentive, silicate minerals would not be processed through carbonation reactors.

• Long-term storage - addressed above

• Sustainability - typically documented in third-party-verified EPDs

Mineralisation delivers two climate benefits, not one

When mineralised materials are used as supplementary cementitious materials (SCMs) in concrete mixes, they deliver a dual benefit: permanent storage of captured CO₂, and avoided emissions by replacing carbon-intensive cement clinker. Cement production remains one of the largest sources of embodied emissions in the built environment.

At Paebbl, we believe these two benefits are complementary, not competing. The existence of an emissions reduction benefit through material substitution should not diminish recognition of the removal component. Technologies can legitimately deliver both, reflecting the full climate value of mineralisation in construction materials, just as we do at Paebbl.

We also recognise that transparent accounting matters. A clear line should be drawn between (i) the CO₂ permanently removed and stored, which is the unit eligible for certification under the CRCF, and (ii) the avoided emissions from material substitution, which are captured in lifecycle instruments such as EPDs.

These are two distinct climate effects coming from the same process, and they should be tracked separately rather than treated as mutually exclusive. We have an opportunity to provide clear guidance on how certified removals embedded in products are claimed alongside - but not double-counted with - the emission reduction accounting that already exists in LCA and EPD frameworks.

When mineralised materials are used as supplementary cementitious materials (SCMs) in concrete production, they deliver a dual benefit: permanent storage of captured CO₂, and avoided emissions by replacing carbon-intensive cement clinker. Cement production remains one of the largest sources of embodied emissions in the built environment.

Bridging the gap between carbon removal certification and construction product accounting

There is also a practical question worth addressing early: how CRCF-certified carbon removals in products will interact with the frameworks that the construction industry actually uses to make purchasing and specification decisions.

In Europe, the environmental performance of construction materials is assessed through Environmental Product Declarations (EPDs) developed according to EN 15804. Under the current version, carbon permanently stored in materials is generally not reflected as a negative contribution in the core Global Warming Potential (GWP) indicators. It appears instead as supplementary information outside the main assessment, almost as an afterthought.

The EN 15804-based EPDs, the tool that drives actual construction procurement decisions, do not yet reflect the stored carbon in core impact indicators. Our experience shows that customers really want this information to make these purchasing decisions.

The current set up creates a paradox: a mineralised construction material can be certified as delivering permanent carbon removal, but that benefit may remain invisible in the building-level carbon assessments that increasingly drive procurement. Addressing this by examining how certified removals embedded in products can be transparently reflected in product-level carbon accounting would strengthen transparency in the market.

Engineered mineral carbonation is one of the few carbon removal pathways that can deliver permanent storage and integration into existing industrial supply chains at scale. Getting the certification rules right determines whether these technologies can attract the investment and market recognition needed to contribute meaningfully to Europe's climate neutrality goals.

We welcome the ongoing work on the CRCF and look forward to contributing to the next phase of methodology development.