Deserts are often considered as one of the least resourceful and hostile to life areas on Earth. Most resources of hot deserts are found under the sizzling and arid surfaces. Underground water sources, valuable minerals or oil are usually tough to localise and tap in to for habitants of these sandy regions. The world’s largest hot desert is Sahara. Located in north Africa it stretches through multiple countries including Morocco in the western part. The most common building element of arid terrains is Sand. Sahara desert’s sand is a weathering product of the mountains that were eroded away from the southern side of Sahara. Sand dunes are composed almost exclusively of rounded quartz grains but also contain mica, amphibole, calcite, ankerite, feldspar and dolomite. Sand is defined by size with particles ranging from 2 mm up to 0.6 mm.
For some organisms uninviting conditions found in Sahara are enough to maintain life. Hiding just below the surface from overwhelming heat, tiny, living things – too small to see without magnification – are utilising everything there is, including the sand in order to survive.
One of them is Microcoleus – Cyanobacteria, bacterias that obtain their energy through photosynthesis with oxygen as a byproduct.
This thread-like organism uses its body to intertwine, weaving an organic microscopic mesh of fine filaments that holds down the sand. By threading their way through the soil, they hold the surface together, creating a biological desert crust. Crusted surfaces can then resist hurricane-force winds without letting the soil blow into the air. These crusts also increase water filtration and add nutrients to the soil.
During the dry period lasting for months without water, Microcoleus hides a couple of sand-grains deep below the surface using the sand and protection. To survive for extended amount of time it desiccates (dries out) and shrinks until it contains only 1-2% of water to await next wet period in suspended animation. Amid this inactive time Cyanobacteria are still bombarded by harmful UV light. In order to defend themselves they produce a thick layer of protective pigments that act like a sunscreen. As soon as rains come, these thread-like bacterias instantly soak up the water and are brought back to life turning the surface green.
More than 6% of the world’s total land area is salt-affected; most of this salt-affected land has arisen from natural causes and the accumulation of salts over long periods of time in arid and semiarid zones. It is much easier to find microbic life in these areas. The puddles, as well as the surrounding salt crusts, can be found coloured brown, green and pink with Halophilic bacteria (salt-loving) inside them. The salt crust functions as a greenhouse window, allowing filtered light to penetrate it. While at the same time it traps the moisture generated from extensive evaporation.
Sand has been used by men for quite long time, in modern history and until now mostly in cement. Concrete and cement production contributes to up to 5% of worldwide man-made emissions of CO2, making it unsustainable solution. Increasingly large cement factory stand behind new constructions, concrete takes over traditional methods of building. Changing what used to be ecological and native to region in to emitters of green house gases among other disadvantages.
fig.7 Loudaya, Morocco Cement Plant Source
It is difficult to find an alternative to concrete or brick, mainly because these materials were engineered over centuries to be very good at their jobs. On the other hand, designers and scientists are progressively experimenting with new materials that could one day be a more environment friendly replacement.
fig.8 Attempts at rethinking usage of sand. Links can be found at the end of the page.
Similarly to naturally occurring bacterias in desert, some of the researchers used organic matter as binding substance for sand, creating much more solid material than the natural desert crust. The most interesting and well studied is a combination of regular sand with bacteria. This method is a microbial-induced casting procedure, which uses bacterium Bacillus Pasteruii for cementing sand, transforming it in to stone-like formations.
This biodegradable substance has similar qualities to concrete, but can be broken up and used as a fertiliser for crops. It also produces no greenhouse gases and uses a widely available raw material. This low-footprint biological processes may very well be replacing energy intensive methods (burning fossil fuel) of production building materials in arid regions.
fig.11 How to create biostone Source // fig.12 Energy consumption Source
Sustainable production is in core of this concept, therefore to avoid unnecessary transportation of main ingredient (and the heaviest), fabrication should happen on building site. Achievable formations using this chemical reaction would vary depending on the digital design. Fabrication methods would have to be adapted accordingly. Some of the presented approaches are already tested, some remain as unproven theories which require further exploration and some are still waiting to be discovered.
Possible fabrications methods:
- 3d printing, for more complex elements.
- Moulding sand blocks, for repetitive elements.
- Hollow piles used to pump bacteria in to sand dunes for underground caverns and excavated structures.
- Robotics. Tunnel digging robots. This could require 3d scanning the dune, for example with a drone for it’s general dimension in order to proceed with the design. Process would be similar to reversed carving with digitally designed paths for robots to dig their way through sand, leaving bacteria and nutrition behind.
- Using machinery that would lay down flat multilayer cemented sand. Which then could be cut in to right segments or perforated.
Similar researches are carried out for potential mars or moon expeditions, where sand/moon-dust is widely available. Resourcefulness and sustainability lay in heart of these concepts. One earth they have potential of bringing back ecological and sustainable solutions into arid regions. However, this method also provides new possibilities for creating valuable spaces. Where light and air conditions are unique and suitable for climate. Structures built out of the surrounding would blend in, provide shelter and prevent progressing desertification in the most affected regions.
More research on Bacillus Pasteurii in combination with Cyanobacteria could lead to producing a living material for one the most inhospitable areas on earth. Cyanobacteria could work as a surface material, producing oxygen and protecting the structure from winds and sun as it already does as desert crust.
fig.12 Potential result of described method Source
Further information on selected projects: