The "Oscar" for engineering achievements goes to … Empa!

Concrete could store considerable amounts of CO₂ if conventional aggregates were replaced by pellets made from biochar. Picture: Empa

Cement production is responsible for around eight percent of global CO₂ emissions. In order to reduce this proportion in future, Empa is investigating the potential of CO₂-neutral or even CO₂-negative concrete. A team from the Concrete and Asphalt lab has therefore developed a process with which biochar can be integrated into concrete. Although first concrete products with biochar already exist, the biochar is often added untreated. “Biochar is very porous and therefore not only absorbs a lot of water, but also expensive additives that are used in concrete production,” says Empa researcher Mateusz Wyrzykowski. The researchers are therefore focusing on pellets made of biochar, water and cement that could replace part of the conventional aggregate in concrete.

The results so far are promising: The carbon pellets can be used to produce CO₂-neutral or even CO₂-negative concrete, which can be used like conventional concrete in buildings and infrastructure. "We are currently working with partners on the industrial production of our CO₂-negative pellets. The first application in a building will be in the new NEST unit, Beyond Zero,“ says Pietro Lura, Head of Empa's Concrete and Asphalt lab. The unit will be part of Empa and Eawag's modular research and innovation building NEST. It showcases promising CO₂-reduced and CO₂-negative innovations that can be used in the construction sector – and how buildings can even act as carbon sinks in the future.

However, a holistic approach goes beyond biochar as a carbon store. As part of the large-scale research initiative, Mining the Atmosphere, Empa is working on a concept in which excess CO₂ is to be extracted directly from the atmosphere and used to produce various materials and products. The aim is to create a completely new global economic model and a corresponding industrial sector in which CO₂ serves as the raw material of the future.

The captured CO₂ is first converted into basic chemicals such as methane or methanol. These in turn can be further processed to replace conventional building materials and petrochemical products. At the end of their life cycle, these carbon-rich materials are to be stored in special landfills to permanently bind the (once atmospheric) carbon. Synthetically produced methane can also be used to transport energy from sunny regions to countries with seasonal energy shortages.

However, according to the Empa researchers, large-scale implementation requires further progress in materials science and process development, particularly in order to make optimal use of decentralized and fluctuating renewable energies. Moreover, a focus on new business models, economic incentives and suitable regulatory frameworks is necessary to make a low-carbon society a reality.