If you’ve ever built a sandcastle, you’ll have seen a demonstration of a simple fact: when you make a building, you also make a hole. With a sandcastle, it’s a hole in the sand of roughly equivalent size. You probably make it circular and use it as a moat. The same is true for every building. All the stone, sand, or clay had to be extracted from somewhere else.
As a general rule, the closer the extraction site is to the building, the more sustainable it is likely to be. This is often a given in traditional building. Mud houses, built in many parts of the world and common in the UK in the past, can be made from the ground they stand on. As a child in Madagascar, I helped our night guard Hary as he dug a pit latrine, made mud bricks out of the spoil, and then used them to build the hut to go over the top. (I say I helped. He may have seen it differently.)
That is not how we build in developed countries. “When people build a house in this country, they first dig a hole and dispose of the excavated soil. Afterwards, they bring in tonnes of sand, gravel and cement to pour in the foundation and walls.”
That’s Gnanli Landrou, who built mud and grass homes in his youth in Togo. He went on to study a Phd in Switzerland, where he has developed this basic idea into a more modern form, by creating a sustainable alternative to cement. Using the powder he has developed, which he calls Cleancrete, the earth removed from the building site can be liquified and poured in the same way as concrete. It can be used for floors and non load bearing walls, and it comes in with 90% lower carbon emissions, for half the price. He anticipates it being used alongside concrete, using the stronger concrete for structural elements, and clay walls using Cleancrete in-between.
This addresses two sources of construction pollution at once – the CO2 from cement production, and the impact of extracting and trucking in materials from elsewhere.
That’s a potentially revolutionary idea, and the invention is finding its way from the lab to building sites at the moment. A home is being built in Switzerland, a clinic in Togo and a resort in Zanzibar. These real world trials will prove the usefulness of Landrou’s solution. If successful, production can be scaled up. Landrou’s company, Oxara, has already had lots of interest and bigger partnerships may be on the way.
Cement production is a huge source of global CO2 emissions, and because they’re part of the chemistry of the process, they can’t be solved with renewable energy. There’s a lot of competition for a solution, with the X-Prize involved, and market leaders like Cemex developing alternatives. There is likely to be a whole portfolio of new materials available in time, and I’d love it if one of them was Landrou’s, inspired by mud building from Togo.
- For more, see this BBC podcast People Fixing the World
- More on building with dirt
- This video is from 2019, but gives a good sense of Landrou’s work: