Creating sustainable cities from waste

 Wael Al Awar, founder of the architecture firm waiwai (UAE PAVILION )

UAE pioneers are using natural resources to develop new building materials—and address an impending ecological crisis.

THE GULF’S CONSTRUCTION frenzy continues, but while more cities rise from the ground, a new wave of sustainability pioneers is emerging, keen to reconnect the region’s future with its natural resources.

Take Dubai and Tokyo-based architecture firm waiwai, attracting plaudits for its building blocks made of magnesium-based cement, produced from brine generated by the UAE’s desalination plants. Centuries ago, chunks of material were hewn from salt flats—or sabkha—and used to build Siwa, a medieval city in Egypt. Rather than disrupt today’s delicate ecosystem, waiwai principal architect Wael Al Awar focused on the desalination byproduct, which contains the same minerals.

“I think all architects have a duty to find local solutions to help tackle the ecological crisis and utilizing waste brine makes a lot of sense for the MENA region,” says Al Awar, explaining how the idea crystallized when he was diving in the waters of the Gulf. “When the UAE was first built, sabkha was used to bind the coral used as a construction material. This suggested the magnesium salts in the seawater had the potential to be used as an eco-friendly alternative to lime in cement.”

What’s more, not only could this new cement be made using less heat—and therefore less energy—than one using limestone, but it would also involve the upcycling of a byproduct that would otherwise have to be disposed of at a further environmental cost. Significantly, Al Awar points out, the UAE produces around 20% of the world’s industrial waste brine.

“Given that ordinary Portland cement (OPC) is responsible for almost 8% of the world’s annual human-made COemissions, it is almost existential that we develop materials to avoid the repetition of those emissions,” proclaims Dr Kemal Celik, assistant professor of civil and urban engineering at New York University Abu Dhabi (NYUAD), and part of a team at the university’s Advanced Materials and Building Efficiency Research Laboratory (AMBER Lab).

A desalination byproduct sabhka is being repurposed into CalMag, a new sustainable cement. (UAE Pavilion )

A desalination byproduct sabhka is being repurposed into CalMag, a new sustainable cement. (UAE Pavilion )

Dr. Celik, who is collaborating on the project, cast the cement into blocks, which were placed in a carbon dioxide chamber where they absorbed 8.5% of their weight in CO2 to gain structural strength—providing further environmental benefits by sequestering emissions. Tests in the UAE and Tokyo showed that after around 72 hours of carbonation, the magnesium cement—dubbed CalMag— achieves the same structural performance as OPC. 

Although CalMag cannot yet be used for multi-storied buildings—as it is salt-based, it could corrode the steel reinforcement typically used—Al Awar insists precast blocks of the new material could already be used to construct single-story buildings. “I would love the first commercial building to be a domestic dwelling in the UAE,” he says. “I think that this would be fitting, considering sabkha’s provenance.”

Dr. Celik, who believes that Abu Dhabi’s Masdar City is already “a shining example of how ancient Arabic architectural techniques can be interwoven with modern building technologies”, says this new type of cement could solve multiple environmental issues simultaneously, while fulfilling the UAE’s vision to transition to a circular economy.

Dr. Kemal Celik and his team (UAE PAVILION )

Yet the most exciting part of all about CalMag, according to the professor, is its ability to absorb CO2 during the hardening process, making it a potential carbon-negative product. “We are now scaling up the production process and further enhancing its properties to build stronger concrete with less water” he explains.

As a first step towards application, the material was showcased in the National Pavilion of the UAE at the Venice architecture biennale 2021, where visitors were invited to wander through a prototype structure formed by 3000 modules designed to resemble a room made from coral. The exhibit won the prestigious Golden Lion Award for Best National Participation.

CalMag is not the only groundbreaking new material created from natural resources in the UAE, however. Another product, developed by the AMBER lab and the NetBio group at NYUAD, is the BioBrick, which uses desert sand as a primary matrix and incorporates bacterial strains present in the UAE’s seawater. These materials, which take advantage of low-cost and readily available binders and fibers, are an environmentally friendly alternative to concrete blocks, says Dr Celik. Potential applications can be in the embankment of highways and hollow bricks.

This would dovetail with various initiatives designed to reduce the carbon footprint of road construction. In one such project a new type of asphalt, made partly from ground-up rubber tires, is being monitored on a busy two-kilometre stretch of highway by the Abu Dhabi Municipality and the Khalifa University Pavement Engineering team. The UAE currently allows the use of up to 40% recycled aggregate materials in private and public construction projects.

Dr Oussama El-Kadri and Dr Mohamed Al-Sayeh (UAE PAVILION )

Indeed, the UAE is rapidly becoming one big incubator for sustainable living. In another potentially game-changing development, Dr. Oussama El-Kadri and Dr. Mohammad Al-Sayah at American University Sharjah, recently stitched together different organic molecules to create nitrogen-rich sponge-like polymers that have also proven effective in the selective capture of CO2.

Traditionally, polymers are used in pretty much every aspect of urban construction—flooring, window and door seals, pipes, insulation, and so on. “Cities nowadays are using many technologies to reduce the levels of CO2 in the atmosphere and porous materials are very promising candidates,” explains Dr. El-Kadri. “Because of our materials’ high levels of porosity, along with their chemical functionalities, particularly high volumes of CO2 can be captured and stored.”

Dr. El-Kadri says that his research team is now focused on patenting and commercializing the technology, while continuing to work on other new materials that either collect or neutralize other toxins found in our everyday urban lives.

Al Awar, meanwhile, is also continuing to work on developing new building materials, again utilizing plentiful, vernacular waste. He points to Amsterdam, where organic building products are being created using mycelium, the root-like structure of mushrooms, mixed with hemp. “Well, I want to see what we can do in the Middle East using another byproduct—palm fiber” he says.

“These are early days, but, like salt flats, date palms are another thing we have plenty of here.”

Original Article Wired

Urban Development and Clean Energy