A new house in the Bahamas is being built using an alternative concrete that sucks carbon dioxide out of the air. The house helps combat climate change and there are plans to build 999 more similar houses in the area. That’s the latest endeavor from NBA Lakers legend and actor Rick Fox, now on the tiny island nation where he grew up.
Fox is the CEO and co-founder of sustainable building materials startup Partanna. If they succeed in the Bahamas, they aim to make it an everyday building material alternative to concrete, thereby reducing construction pollution.
Concrete happens to be a major source of greenhouse gas emissions that contribute to more intense storms, wildfires, and other disasters caused by climate change. The culprit is actually cement, the main component of concrete and which alone accounts for more than 8% of global carbon dioxide emissions.
"I entered the world of concrete out of sheer necessity to survive and to innovate in my home country," Fox said. "In 2019, Hurricane Dorian hit the Bahamas, destroying 75% of the homes on the hardest-hit island of Abaco and displacing thousands of people. Fox was in Los Angeles. The nearest thing I could do was run to CNN and shout from the rooftops that we need to do better."
Soon after, he met Sam Marshall, a California architect whose home was damaged in the 2018 Woolsey Fire, one of the most destructive fires in the state's history. Fox said Marshall had "caught lightning in a bottle." Working with materials scientists, they developed a way to make concrete without carbon-intensive cement. Together they founded the company Partanna.
The pair are tight-lipped about the process, but the main ingredients are brine from desalination plants and slag, a by-product of steel production. By eliminating cement, Partanna avoids the CO2 emissions that come with it. Making cement creates a lot of climate pollution because the cement must be heated to very high temperatures in kilns and the cement triggers chemical reactions that release more carbon dioxide from the limestone.
Partanna says its mixture cures at ambient temperatures, so it doesn't need to use as much energy. It also says the binder component in the mixture absorbs carbon dioxide from the air and traps it in the material. In a home or building, this material continuously breathes in carbon dioxide. Even if the building is demolished, the material retains CO2 and can be reused as aggregate to create more replacement concrete.
The startup can therefore call its materials and new homes "carbon negative buildings." The 1,250-square-foot building is said to absorb as much carbon dioxide in a year as 5,200 mature trees.
To be sure, carbon accounting for trees is tricky. A Guardian investigation earlier this year found that 90% of rainforest offsets certified by Verra, one of the world's leading carbon credit certifiers, were "of no value" because they likely did not result in actual reductions in pollution. Verra is also working on carbon credit certification for Partanna. Fox said the carbon dioxide captured by Partanna is easier to quantify than forest offsets and is not as fragile as forests, which need to be protected from clearing in order to store carbon.
It is worth noting that Partanna’s main ingredients, slag and brine, come from energy-intensive steel and desalination facilities, which themselves generate large amounts of carbon dioxide emissions. Partanna does not include these emissions in its carbon footprint. "This has nothing to do with us... these are scraps and we use them for good causes."
It's a good thing they're using waste, said Dwarak Ravikumar, assistant professor in Arizona State University's School of Sustainable Engineering and the Built Environment. Even so, we need to analyze this in depth from a systems perspective to understand the overall impact on climate. Companies must share data so researchers can assess Partanna's entire environmental footprint and the scalability of its strategy, he said. Not only are we at the forefront of climate change, we are also at the forefront of solutions."
Fox isn't the only one working on making building materials more sustainable than traditional concrete. Microsoft announced last month that it was testing low-carbon concrete for its data centers. Other startups are also working to extract carbon dioxide from the atmosphere and sequester it in concrete.
Partanna says its advantage is that its material is made from salt water. The material actually becomes stronger when exposed to seawater, an attractive property for a country made up of many low-lying islands facing worsening storms and rising sea levels.
"We are not only at the forefront of climate change, we are at the forefront of solutions," Bahamas Prime Minister and Minister of Finance Philip Davis said in a Partanna press release.
The Bahamas government is working with Partanna to build 1,000 homes, starting with a further 29 homes by next year. No one has lived in the first house in Nassau yet; it's just a prototype. But the next batch of homes is expected to be part of a plan to help first-time buyers.