Can Concrete Store Carbon?

Concrete Has Always Supported Buildings. Can It Also Store Carbon?

Concrete forms the foundations of modern cities. It supports homes, bridges, tunnels, hospitals, and public infrastructure, making it one of the most widely used construction materials in the world. Yet producing cement, the primary binding ingredient in concrete, also contributes significantly to global carbon emissions. For decades, engineers have focused on reducing this impact by improving manufacturing efficiency, developing alternative cement formulations, and incorporating recycled materials into concrete production.

Holcim is investigating a different approach. Rather than concentrating solely on reducing emissions during manufacturing, the company is exploring whether concrete itself can retain carbon throughout its service life. Its answer is a concrete formulation containing biochar, a stable carbon-rich material produced from organic biomass. Instead of treating carbon only as an emission to reduce, the material is designed to incorporate and retain part of that carbon within the finished concrete.

Turning Biomass Into Stable Carbon

The innovation begins with biochar, a material produced through a process known as pyrolysis. During pyrolysis, organic biomass such as agricultural or forestry waste is heated in an oxygen-limited environment. Because oxygen is absent, the material does not burn in the conventional sense. Instead, much of the carbon contained within the biomass is converted into a stable solid form rather than being released into the atmosphere as carbon dioxide.

According to Holcim, each kilogram of biochar can prevent the release of up to three kilograms of carbon dioxide. Once produced, the biochar is incorporated into cement, mortar, and concrete formulations while continuing to retain its stored carbon. Rather than functioning simply as another construction ingredient, biochar allows the finished material to act as a long-term carbon reservoir while still performing its structural role.

The significance of this process lies in the transformation itself. Organic waste that would otherwise decompose or be burned becomes part of a durable construction material, extending carbon storage over the lifetime of the structure.

A Different Direction for Low-Carbon Concrete

Many lower-carbon concrete technologies aim to reduce emissions by replacing part of the cement with supplementary materials or by improving manufacturing efficiency. Holcim's approach introduces a different concept. Instead of focusing exclusively on lowering emissions during production, the concrete also incorporates a material specifically intended to retain carbon within the finished product.

The company demonstrated this concept through its net-zero biochar concrete, which received its first full-scale application during the 2025 Venice Architecture Biennale. The material was used in the Basic Services Unit, a housing prototype designed by architect Alejandro Aravena and the architectural practice ELEMENTAL. According to Holcim, the project also incorporated 100% recycled aggregates, combining recycled construction materials with biochar in a single concrete formulation.

This demonstrates how several sustainability strategies—including recycled aggregates, renewable biomass, and advanced concrete engineering—can be integrated into one building material rather than developed as separate solutions.

A New Role for Construction Materials

Holcim's biochar concrete is not simply an alternative concrete mix. It reflects a broader shift in materials science, where engineers are exploring whether construction materials can actively contribute to environmental objectives rather than only reducing their environmental impact.

At the same time, the technology remains at an early stage of adoption. Its long-term role will depend on factors such as the sustainable production of biochar, wider industrial implementation, continued evaluation of structural performance, and how the material performs across different construction applications. These questions are likely to shape future research as carbon-storing construction materials move from demonstration projects toward broader use.

Rather than redefining what concrete is, Holcim's work explores what concrete may be capable of becoming: a structural material that also participates in long-term carbon management.