Researchers at Empa’s Concrete & Asphalt lab are exploring a groundbreaking approach to carbon-neutral or even carbon-negative concrete. By integrating biochar, derived from biomass carbonization, into concrete in pellet form, they aim to mitigate the construction industry’s carbon footprint. This method could play a crucial role in achieving Switzerland’s goal of climate neutrality by 2050.

To counterbalance challenging emissions from the construction sector, which contributes around eight percent of global greenhouse gas emissions, the team is developing negative emission technologies (NET). Biochar, rich in carbon extracted from the atmosphere during plant growth, is proposed as a viable solution. However, challenges arise due to its porosity, water absorption, and handling difficulties.

Addressing these issues, researchers advocate processing biochar into pellets to enhance practicality. Through a concrete mixer, biochar is mixed with water and cement, resulting in pellets that, when used in concrete, can achieve net-zero emissions with a 20 percent volume proportion. Notably, lightweight concrete with 45 percent carbon pellets exhibits negative emissions of minus 290 kg CO2/m3, a remarkable improvement over conventional concrete.

This innovative carbon-capturing technique aligns with broader initiatives at Empa, emphasizing “Mining the Atmosphere” for synthetic methane production. This holistic approach utilizes solar energy, water, and atmospheric CO2, contributing significantly to meeting climate targets.

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