SOM Proposes Carbon-Eating 'Urban Sequoia' Skyscraper at COP26

It eats carbon dioxide and is made of all-natural materials. What's wrong with this picture?

An artist mockup of a concept for buildings and their urban context to absorb carbon at an unprecedented rate.
Urban Sequoia.


Watching the 2021 United Nations Climate Change Conference (COP26) was a little depressing at times. There was so much "blah blah blah" from nations and corporations making vague pledges of net-zero by 2050, which we have called the new never. If we are going to have any chance to keep the 1.5 degrees Celsius (2.7 degrees Fahrenheit) goal alive, we have to change the way we do things right now.

This is why I am alternating between being excited and depressed by "Urban Sequoia," a proposal by Skidmore, Owings & Merrill (SOM) presented at COP26.

SOM asks the questions in a press release:

"What if the built environment could be a solution to the climate crisis, rather than part of the problem? What if buildings could act like trees – capturing carbon, purifying the air, and regenerating the environment? Taking inspiration from natural processes and ecosystems, Urban Sequoia envisions “forests” of buildings that sequester carbon and produce biomaterials to create a new carbon economy and a resilient urban environment."

Being net-zero or carbon neutral is so 2020. According to SOM Partner Chris Cooper, “We are quickly evolving beyond the idea of being carbon neutral. The time has passed to talk about neutrality. Our proposal for Urban Sequoia – and ultimately entire ‘forests’ of Sequoias – makes buildings, and therefore our cities, part of the solution by designing them to sequester carbon, effectively changing the course of climate change.”

The building shown is designed to sequester 1,000 tons of carbon per year, using nature-based materials that absorb carbon over time. It is built of materials like hempcrete, timber, biocrete, and bio-brick.

A graphic of SOM's proposal of a carbon-capturing building.


A labeled version of the building section, which is not in the press release but on many websites, describes some of the systems, including "carbon sequestration driven by natural photosynthesis" which I assume is the pumping of algae around the building. There is direct air capture of carbon dioxide (CO2), driven by the stack effect in the core of the tower. There are "circular materials."

SOM states:

"This solution allows us to move beyond net zero to deliver carbon-absorbing buildings, increasing the amount of carbon removed from the atmosphere over time. After 60 years, the prototype would absorb up to 400 percent more carbon than it could have emitted during construction. The captured carbon can be put to use in various industrial applications, completing the carbon cycle and forming the basis of a new carbon-removal economy. With integrated biomass and algae, the facades could turn the building into a biofuel source that powers heating systems, cars, and airplanes; and a bioprotein source usable in many industries."
A view looking up at a building designed by SOM that is proposed to capture carbon.


Yasemin Kologlu, principal at SOM, says, “The power of this idea is how achievable it is. Our proposal brings together new design ideas with nature-based solutions, emerging and current carbon absorption technologies and integrates them in ways not done before in the built environment.”

But, with apologies to Kologlu, is this achievable? Nobody has built a timber building this high. Algae systems like this have never been built. Direct air capture of CO2 doesn't work like this. It's all as one commenter called it, "magical eco-tech."  

Mina Hasman, senior associate principal, says, “If the Urban Sequoia became the baseline for new buildings, we could realign our industry to become the driving force in the fight against climate change.”

building section


But it can't become a baseline, because these technologies don't exist. As one commenter noted after looking at this drawing: "WTF is this ... CO2 doesn't magically get filtered into an exportable substance via stack effect ... but no active capture is mentioned ... and does this industrial use just re-emit or does it sequester? ... magic arrows of frustration."

Another noted: "Much easier said than done - but it sure looks pretty, and people like to believe anything." An important English expert on sustainable building said "Sorry Lloyd, can't come up with anything printable."

But I think my biggest problem with this is that it comes from Skidmore Owings and Merrill, one of the world's most important firms. If you look at its impressive website, it is full of glassy gorgeous towers including New York City's One World Trade Center. There are airports, schools, and hospitals. (Lots of airports, a controversial subject on its own.) Millions of square feet of steel, concrete, and glass.

Urban Sequioa detail


Had Urban Sequoia come up in an Evolo Skyscraper Competition, I would have raved about its ingenuity. When it comes from SOM, it smells like what Alex Steffen called "predatory delay," which he defined as "the blocking or slowing of needed change, in order to make money off unsustainable, unjust systems in the meantime." I have noted that it is not a delay due to the absence of action, but delay as a plan of action—a way of keeping things the way they are for the people who are benefiting now, at the expense of the next and future generations.

It's where one can say, "Don't worry, we really are thinking hard about how to fix the architectural world, someday this will all work, but in the meantime, we will keep building airports and glass towers, with our eyes set on 2050 or maybe even 2100 while we ignore 2030." It lets us keep doing what we are doing now because all this great green technology in our buildings will somehow suck the carbon our current buildings are emitting out of the air in the future. If Swedish climate activist Greta Thunberg was an architect, she might call it green techno-blah blah blah.

SOM has the talent and ingenuity to build carbon positive buildings using technologies that are proven, legal, and actually exist. Show us those—that is what we need now.