Architecture

Carbon-capturing concrete walls conceal a quirky Japanese house

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The Block-Wall House is located in Karuizawa, in Japan's Nagano Prefecture
Masahiro Ohgami
The Block-Wall House is located in Karuizawa, in Japan's Nagano Prefecture
Masahiro Ohgami
The Block-Wall House is located on a slightly awkward plot next to a rural road
Masahiro Ohgami
The Block-Wall House's angled screen allows the owners to see out, but makes it a little harder for the casual passerby to see inside
Masahiro Ohgami
The Block-Wall House's screen has a length of 110 m (360 ft)
Masahiro Ohgami
The Block-Wall House's screen is made up of approximately 2,000 blocks staggered in parallel rows
Masahiro Ohgami
The Block-Wall House's interior features very generous glazing throughout, which is given privacy with the concrete screen
Masahiro Ohgami
The Block-Wall House's interior decor is very minimalist and dark, putting the focus on the lush greenery outside
Masahiro Ohgami
View gallery - 7 images

The production of the cement used in concrete is a major contributor to worldwide CO2 emissions and since we're reliant on the stuff for our infrastructure, this is a serious problem. However, Nendo showcases an example of a greener way to build with its Block-Wall House, which was part-built using a novel concrete that actually captures CO2 instead of emitting it.

The Block-Wall House is located in Japan's Nagano Prefecture, next to a rural road. It has a lot of glazing, so in an attempt to offer privacy from passing vehicles and pedestrians, Nendo installed an angled screen that allows the owners to see out, but makes it harder for the casual passerby to see inside. The screen is made up of approximately 2,000 blocks arranged in parallel rows to create five walls with a combined length of 110 m (360 ft). It's this screen that's actually made from the sustainable concrete.

The concrete is made by the Kajima Corporation, in collaboration with the Chugoku Electric Power Co, Denka, and Landes Co, and is named CO2-SUICOM. During its manufacturing process, a special cement mixture is placed in a curing chamber and CO2 is then pumped into the chamber to be absorbed. The absorbed CO2 is then stuck inside the concrete, and will not be released. Crucially, it's also just as strong as regular concrete, unlike Washington State University's somewhat similar effort.

The Block-Wall House's screen is made up of approximately 2,000 blocks staggered in parallel rows
Masahiro Ohgami

"Generally, concrete hardens through a chemical reaction between cement and water," explains Kajima Corporation. "But with CO2-SUICOM, over half the cement is replaced with a material we call γ-C2S. Instead of reacting with water, γ-C2S reacts with the CO2 in the air to harden. After mixing the materials need to create CO2-SUICOM, the concrete can be placed in a location with high CO2 levels so it can capture the CO2 and harden, trapping the gas inside. For example, a thermal power plant or other facility that produces carbon-heavy exhaust gases can redirect the gases into a carbon sequestration chamber, where concrete products made with CO2-SUICOM can be placed to capture the CO2 in the gases."

As is usually the case, the devil is in the details, however. Obviously greener concrete is a good thing in itself and under the right conditions this could be used to create net-zero infrastructure, but if it's not affordable and practical to produce, it's not going to be widely adopted.

On that note, signs are actually quite hopeful. A Kajima Corporation representative told us that the cost of producing CO2-SUICOM concrete is currently about three times higher than standard concrete used in Japan. Work is currently being undertaken on further reducing this cost and the firm believes it will become a lot more affordable in the near future.

The Block-Wall House's interior decor is very minimalist and dark, putting the focus on the lush greenery outside
Masahiro Ohgami

Alongside this new concrete there have also been some other interesting efforts to make our buildings greener, including projects by Provencher Roy, the University of Tokyo and VTT Finland.

Sources: Nendo, Kajima Corporation

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4 comments
TechGazer
How much CO2 is released in production of this material? Lime cement absorbs CO2 because CO2 is driven out during production, so it's eventually approaching net zero, if no CO2 was released providing the energy needed. Some types of rock can absorb CO2, but crushing them to provide enough surface area to absorb much in a reasonable amount of time requires energy. Is that overall more efficient than allowing plants or algae to fix the CO2 and then bury it?
christopher
*All* concrete captures (re-absorbs) CO2 over it's lifetime (not as much as was emitted during manufacture of course), so the PR surrounding this product is just extreme greenwashing that process which always exists anyhow.
TomLeeM
I think the problem with capturing CO2 is that one might capture too much of it. plants need CO2 to grow. I have read that CO2 isn't a pollutant. I think eliminating all CO2 would do more harm than good; IMO I do think this unique home is cool.
Arran King
Yeah, it's great if the total life cycle (including the production) of the concrete is actually a negative, or at least zero, CO2 balance, but I can't believe the eye-burning affront to nature of this atrocity in the midst of a beautiful forest. I thought Japanese culture was strong on harmony!!!

And to make it worse, the place looks like a prison on the inside!!!