Seven Quintillion Bricks

For the millions of people living along the edge of the Sahara in Africa, the desert and its infinite sand has always been just part of the landscape. But now, in the age of climate change, the dunes which have always stood guard over their villages are on the attack. Changing winds and temperatures are causing the sands to move rapidly south, far past their previous borders. This onslaught is a danger to the entire human race's future, as well as the safety and livelihood of the people it most directly affects.
But, as is so wonderfully often the case, an architecture student has the solution. Magnus Larsson, who studies at the Architectural Association proposes a radical and elegant solution to the massive problem. He wants to build a 6000 km long "green wall" across the continent that would provide protection and improvement for the African people. It would not be built by humans, but by bacteria.
My least favorite high school class was geology. I always hated memorizing the specific characteristics of hundreds of different rocks, only to forget everything the second after I turned my final exam in. But I do remember learning about sandstone. Unlike most other rocks, sandstone is created biologically. Some rocks are made from the calcium in animals' bones, but sandstone is actively created by the bacteria Bascillus Pasteurii. Through its digestive process, the bacteria turn sand into stone by partially digesting parts of the grain and filling the spaces between the grains with the products of their snacks. This then solidifies to form sandstone. And it's not like this is a new process; it's been happening naturally for millions of years.

So, now we have our construction workers. They're self sufficient when given the proper food and they won't try to form unions. And you only need to buy them once because bacteria can theoretically replicate itself infinitely if it has a food supply to match.

Magnus wants to flush the bacteria into the outer dunes of the Sahara, but with some supervision and control. He predicts that they will do two things within a few days: create a habitable environment for the desert-dwellers and provide protection for the rest of the continent.

These structures will come in a few different forms. To create livable spaces, he must have some level of control over the product. One idea is to sort of blow up big balloons under and on the surface of the still-pliable dunes, let the stone solidify around the balloons, and then pop them, leaving a cavernous and habitable space. This would allow space for people to live, trees to grow, and moisture for farming to collect. In a matter of years, there could be a brand-new environment "printed" across the African continent, sheltering people and improving lives.
The inspirations for the sanditecture comes from another area of geology. Tafoni are small cavernous structures naturally found in sandstone, with wide entrances and round, concave sides. These would give the structure natural stability while allowing fresh air, sunlight, and moisture in.
In places where people would not need to live, the bacteria would be basically set loose. They would do what they do best, and when they run out of nutrients, they would die.
While Larsson's plans are regarded as being a bit far-fetched, they provide an example of just what biology and architecture can do when they team up to solve some of the world's biggest problems. It's estimated that there are more than 7500000000000000000 grains of sand on the planet and 5000000000000000000000000000000 bacterial cells, and we're only just beginning to discover a couple uses for them.

(wrong sand people)