Frequently Asked Questions

Frequently Asked Questions on Construction Stored Carbon

Frequently Asked Questions

Carbon removal, also known as carbon sequestration, means removing or extracting CO2 from the atmosphere, with natural or technical solutions, and then sequestering it on a long-term basis. This reduces the concentration of CO2 in the atmosphere and lowers global temperatures.

To maintain a livable earth with a livable climate, more is needed than just reducing emissions. Both the current surplus of CO2 and the emissions we make now will have to be removed from the air. The EU says:
EN: “Removing several hundred million tonnes of CO2 out of the atmosphere will become increasingly necessary every year.”

Natural climate solutions work with plants and ecosystems that remove CO2 from the air as they grow. The biomass in which this CO2 is sequestered is much more than just a reservoir for CO2. It serves as a building block for a new economy: sustainable agriculture, forestry, housing and ‘sea building’. Consequently, sequestering CO2 with nature has many more benefits, e.g. for biodiversity, nitrogen, water, climate adaptation, circularity, health and reduction of emissions.

If bio-based building materials are harvested from sustainably managed forests and agricultural land, the trees and plants can grow back. Then the ecosystem actually stores more through harvesting than without it. All the harvest you then use as building materials will remain stored in structures for 50, 100 or even 500 years. By rewarding bio-based construction as a climate solution with the right preconditions, four things happen:
An incentive arises to sustainably manage vulnerable ecosystems (forests and agricultural land) through timber harvesting and/or crop cultivation, increasing the health and CO2 storage of ecosystems;
An incentive arises to build more forests and grow crops for bio-based construction;
An incentive arises to use building materials better, to reuse them and sequester CO2 for longer;
An incentive is created for more harvest to go to the construction sector, instead of paper and energy. Thus, it takes much longer for the captured CO2 to be emitted.
For these four reasons, bio-based construction is a climate solution.

The potential of bio-based building to contribute to solving climate change can only be realised if there is funding for it. This is because currently, biobased building is more expensive and unknown to many people in the construction industry. With only public funding, the transition to bio-based building will be too slow. Private parties can contribute to this transition financing in a CO2 storage market, within conditions set by the European Commission and international standards. They then buy CO2 storage in building materials and thereby enable this storage. This solution is called the ‘voluntary carbon market’ and already exists, for both reducing emissions and sequestering CO2.

The voluntary market for reducing emissions has been under fire for some time. Overly complex calculations and models for hypothetical scenarios, human rights violations, overestimations and, above all, carbon credits that are far too cheap. As a result, buying carbon credits can be seen as an excuse to keep emitting, rather than a contribution to a transition.
The CO2 storage market is different. Under the leadership of the European Commission, there is now a framework in place that guarantees real, long-term CO2 storage. The price for these high-quality ‘carbon removal credits’ is many times higher than the old carbon credits: at least €150 per tonne of stored CO2.

The European Commission has introduced so-called ‘QUALITY’ criteria, which stand for robust quantification, additionality, long-term storage, and sustainability. Part of the standard requirements include, for example, verification that every tonne of quantified and promised CO2 storage has actually materialised.
In the construction sector, this is relatively easy to verify. A comprehensive system already exists in the Netherlands to verify that the environmental performance of a construction project meets the legal requirements. To this system, the rewarding of CO2 storage links seamlessly.

The process of getting funding for CO2 storage involves three steps:
In the design phase, you can make a calculation of CO2 storage in the bio-based materials you plan to use. You do this based on your design, material volumes and validated, internationally recognised product data. With only a calculation, you cannot yet receive a certificate or financing, but you can use the calculation and expected financial value in the design and tender process.
Once a final design and building permit are in place, you can get a certificate for the calculated CO2 storage. In that case, you have to provide proof first, for instance to substantiate the sustainability and reusability of your materials. Based on this certificate, you can pre-sell the CO2 storage through sales agreements.
The moment the building project is completed and a verification has taken place, the CO2 storage is declared real. The buyer then officially owns the purchased CO2 storage.
The whole process from quantification to financing is recorded in the registry of a certificate-issuing organisation. There are many of these worldwide; in the Netherlands, you have two: National Carbon Market Foundation and Oncra (platform of Climate Cleanup Foundation). At the moment, only Oncra has a method for certifying bio-based building at the building level.

Oncra uses Oxford University’s ‘Oxford Offsetting Principles’ to prevent greenwashing. These principles impose requirements on buyers before they are allowed to invest in carbon credits. In addition, Oncra is the only certificate provider in the world to apply a second requirement, as an interpretation of the Oxford Offsetting Principles: fossil companies on the ‘Carbon Underground 200’ list are not allowed to buy Oncra-certified carbon storage.

The organisation clearing CO2, such as a construction company, has a contract with Oncra for the certification of a specific project. This includes mutual obligations for truthful delivery of data, selling CO2 storage and monitoring CO2 storage.
The buyer of CO2 storage then enters into a contract per transaction or series of transactions with the seller, in which Oncra guarantees the correct delivery and verification of data. Each transaction is not valid until Oncra has entered the transaction in its register and prepared a transaction receipt. This prevents double counting and fraud.

In the field of carbon accounting and certification of CO2 storage, ISO standards and the European Carbon Removal Certification Framework are leading. There are also market standards such as ICROA and ICVCM that monitor the integrity of the voluntary carbon market.
For quantifying and verifying CO2 storage in bio-based building materials, EN15804+A2 is leading, a European standard that underpins sustainability legislation in the European and Dutch construction sector.

Climate Cleanup is a foundation with ANBI status that helps entrepreneurs reverse climate change. Oncra is a platform and framework of Climate Cleanup through which certificates are issued for projects that store CO2. Climate Cleanup ensures the independent and transparent assessment of projects.

Oncra stands for ‘Open Natural Carbon Removal Accounting’, an acronym for the five basic principles of the framework. The Climate Cleanup Foundation’s goal with Oncra is to make carbon accounting and finance accessible and understandable to all. Visit to read more.

To promote the transition to a circular, bio-based construction sector, funding must land where the transition power is greatest. One such place is in the development of construction projects, where the choice is between bio-based or conventional materials. The project developer, Ballast Nedam Development in the case of the first CSC pilot, uses the extra funding to complete the budget for the bio-based alternative and pay the manufacturer a fair price for the bio-based materials supplied. Thus, the whole chain benefits, either indirectly. An additional argument for landing the funding with the project developer is the availability and reliability of data. The project developer has an overview of a large part of the chain and access to all the necessary data to draw up a reliable certificate.

Climate Cleanup operates on a not-for-profit basis and only charges for accounting, validation, registration and verification costs when selling CO2 storage. For these pilot projects, those costs are zero because the projects are part of a research project funded by Built by Nature.

Every euro goes to enabling more carbon removal and storage. Suppliers get a fair price, more demand and can scale up. Clients and investors can budget without having to choose conventional, polluting options. Ballast Nedam Development is not taking part in this research project for the sake of money, but to accelerate the sustainability of both its own operations and the entire construction and real estate sector.

Each construction project differs immensely in terms of Net Carbon Removal Benefit, depending on the building typology (high-rise, urban sprawl, etc.) and the materials used. For the ‘Natuurhuis’ pilots we expect an average net storage of 50 tonnes of CO2 per home.

Dutch authorities estimate that an additional 900.000 houses must be constructed to keep up with housing demand. If these houses all store 50 tonnes of CO2, this would constitute a net carbon sink of 45 Mt CO2. Additionally, this would roughly avoid around 54 Mt of CO2 emissions, based on an average substitution factor of 1.2 (see Leskinen et al., 2018).

Aside from potential financial benefits, residents of biobased buildings are not connected to the sale of stored CO2 in any way. They are still free to live in their houses (and renovate them) as they see fit, within the boundaries of regulations and contractual agreements.

Yes, anyone can buy the CO2 as long as they comply with the Oxford Offsetting Principles and Oncra’s no-fossil-buyer criterion.