United Kingdom

American architects SOM propose a design for a building that absorbs carbon throughout its life cycle

In terms of innovation of sustainable high-rise models within the architecture, engineering and construction industries, a key idea comes from Skidmore, Owings & Merrill (SOM), who unveiled Urban Sequoia that absorbs more carbon emissions than it emits. Built using prefabricated, modular construction, the conceptual structure incorporates carbon storage materials such as bio-brick, hemp concrete, wood and bio-concrete, which would reduce the carbon impact of construction by 50% compared to regular concrete and steel, with the ultimate goal of 95% of eliminate construction emissions. As with roof gardens, the facade and “grey” surfaces of the building can be covered with biomass and algae, which inhale up to 1,000 tons of carbon annually, the equivalent of 48,500 trees. After 50 years, the prototype could absorb more than 400% of the amount of carbon emitted by a typical building. The integrated biomass and algae facades can be converted into biofuel to power heating systems, vehicles and aircraft and can be used to produce biomaterials for roads, sidewalks and pipes, effectively creating a carbon removal economy. I speak with Mina Hasman, Senior Associate Principal and Sustainability Lead at SOM, about this design that is easy to build today.

SOM has developed the Urban Sequoia design. What are the main challenges in getting this done?

With Urban Sequoia, we have positioned SOM as a conduit between the construction industry, research/academic community and emerging technologies to bring ideas, strategies and systems together to make the built environment part of the solution to the climate challenge. Our vision is a network of Urban Sequoias that absorb, store and exchange carbon in all cities in the way trees interact in a forest. This would allow us to move beyond net zero to carbon negative and regenerative cities around the world. The inspiration came from understanding the natural carbon cycle and how nature, especially forests, continuously absorb carbon, and how activities in the construction industry throw the Earth’s core systems out of balance. The built environment currently emits far more carbon than nature can absorb, and we need to reverse that. That’s why we deliberately set out to find a solution that can be achieved today by bringing together existing and emerging technologies and materials from cross-sectoral industries – although we certainly don’t say it will be easy.

What is unique about Urban Sequoia? What new design ideas or technologies does it contain that have not been applied before in the built environment?

The technologies, systems and strategies that the project brings together already exist today, although some, such as Direct Air Capture, have not been used before in our industry and others, such as bio-bricks, have not yet been widely adopted. So far we have studied the culmination and application of these systems in one building, using the high-rise typology as a prototype. While we recognize that tall buildings are not the only solution to urban density, they are an inevitable part of future urban growth, especially in already densely populated cities and/or rapidly densifying cities where land may be limited. By addressing the complexity of a tall building, we are able to find synergies between the optimal building-scale and urban-scale development strategies, which would be replicated in other low and mid-rise building types, as well as in different contexts around the world.

Your idea is to use materials such as bio-brick, hemp concrete, wood and bio-concrete to reduce the carbon impact of construction, and integrated biomass and algae on the facades to sequester carbon. How are they made or grown and used? Describe the processes involved.

To move this closer, there are two categories of systems that need to be combined: existing material alternatives already used by the construction industry, such as biocomposites of hemp concrete or bioconcrete, etc. and emerging technologies and materials, some of which already exist in other sectors. ​and that need to be adapted to work at the building scale, such as Direct Air Capture and Carbon Capture and Storage, algae, bio-brick and carbon fiber. Built using locally sourced natural materials available in every geography, biogenic/biomaterials, such as bio-concrete, bio-brick and hemp concrete. It wouldn’t use regular concrete or steel. The prototype would be built using prefabricated, modular construction with biogenic materials that take longer to cure and are therefore more effective when prefabricated. The building would use the natural stacking effect and the structure would be very efficient to use as little material as possible. The facades would be made from biomass and algae that breathe carbon. The facade would capture carbon using natural processes, complementing the carbon capture technology.

There are important parallels between what we propose to do with Urban Sequoia and the transformation of the modern solar panel industry. The use of homes and buildings as solar panel fixtures led to an explosion of solar power generation technologies, as well as major shifts in how utilities operate across the country as they accommodate solar power generation. Today, solar panels can be found on roofs in virtually every part of the UK and now generate 1.5% of the country’s total electricity. It doesn’t sound like a big number, but it’s close to zero a decade ago. In the same vein, Urban Sequoia shows how new technologies such as carbon capture and storage can be transformed, scaled and made much more effective by integrating them into buildings around the world.