The world's first carbon-absorbing concrete house

JAPAN The house in the mountainous area has a unique design with 3-meter high walls built from about 2,050 carbon-absorbing concrete blocks.

A house in Karuizawa, a mountain town near Nagano, Japan, has walls made of the world's first CO2-absorbing concrete called (CO2-SUICOM), Interesting Engineering reported on April 8. The house is located along the road, in a 110 m long plot of land. Karuizawa is one of Japan's oldest and most famous mountain resort towns.

This new type of concrete is made by replacing part of the cement with an industrial by-product, while adding CO2 absorbing materials, thereby reducing emissions from the production process. They are jointly developed by the companies Kajima, Chugoku Electric Power, Denka and Landes.

The strength of CO2-absorbing concrete is equivalent to that of regular concrete. To fabricate, shaped concrete is placed into a curing chamber. Then, CO2 is pumped into the chamber for absorption by concrete. CO2 from various sources can be used directly. While conventional concrete blocks emit about 300 kg of CO2 per m3, CO2-SUICOM can achieve carbon neutrality (the amount of carbon emitted equals the amount of carbon absorbed). Absorbed CO2 is kept fixed inside the concrete and will not escape into the atmosphere.

Nendo designed concrete walls that resemble screens. About 2,050 concrete blocks are arranged in many rows to form 5 3 m high walls. The construction team adjusted the angle of the blocks to control visibility. Depending on how the blocks are arranged, they control what is visible and what needs to be hidden, ensuring ventilation and also privacy.

Nendo uses carbon-absorbing concrete in construction to contribute to reducing CO2 emissions in the world. According to a study published on ResearchGate in 2023, the world's cement and concrete production produces about 8% of total carbon emissions. CO2 emissions from energy used in the cement industry in 2020 accounted for about 1.2% of Japan's total emissions.