Bacteria and fungi help desert sand stick together

Agriculture in the UAE is associated with many challenges.

Most of the country is desert and only about 5% of its land is suitable for agriculture. This means that the UAE can produce only 10% to 15% of its food supply and relies heavily on imports, which is never ideal. And if this sounds like a distant, localized problem that only affects somewhere far away, think again. With rapid deforestation and global warming, more and more territories around the world are becoming desert, and this problem could become much more identifiable sooner than we think.

There isn’t much rain in the UAE, to say the least, and even with irrigation, growing in sand is very challenging. Sand does not contain many nutrients and its grains do not stick together like particles in fertile soil do. This is why sandy soil is very prone to erosion, as it simply cannot hold water for long, allowing it to quickly seep through the spaces between the grains.

Researchers from Switzerland’s Empa Institute and Abu Dhabi’s Khalifa University took on the challenge of finding a way to make sand more suitable for crops.

They call their technology “living sand” and the idea behind it is clever and simple: if things don’t stick, add something sticky. In this case, the researchers introduced specific bacteria and fungi into the sand to help hold it together. These microorganisms produce a whole network of fibers and biopolymers that spread between the sand particles and make them more cohesive. In very simple terms, it is very similar to mixing sand with a natural glue.

To test this technology, scientists used laboratory sand and sand collected from the dunes of Abu Dhabi. The resulting material was significantly more stable than pure sand, and the bacterial treatment slowed water movement six times.

These microorganisms also need nutrients to grow and spread, but that part seems to have an easy solution. According to the researchers, sugars from organic waste could be a potential source of these nutrients, so “food” for bacteria is already widely available.

The researchers also tried another method. They used bacteria that produce nanocellulose to form so-called geotextiles. Basically, these are very thin sheets of cellulose that are then combined with sand to form layers. This layered structure makes the sand more stable and also helps it retain water. This time the results were even more impressive: the water filtered 28 times slower. The most obvious drawback of this method, for now, is the time it takes.

None of these technologies magically turn sand into highly fertile soil or prove that crops actually grow in it, at least not at this stage of the study. Compared to real soil, even treated sand is still not as strong and stable, but that was not the current goal. The idea is to give the sand enough cohesion and water-holding capacity to create conditions in which plants can potentially grow. Therefore, this study is a first step rather than a complete solution, but it is already a big step forward.

“This approach allows us to introduce organic matter and water into the sand and stabilize it a little. Ideally, this will allow the growth of more microorganisms and plants, thus starting the process of making the soil more resistant and fertile,” says Gustav Nyström, head of the Cellulose and Wood Materials laboratory at Empa and one of the authors of the study.

The study is still in the laboratory stage, so the next step will be to test whether sand treated with bacteria and fungi can support plant growth in a greenhouse and field environment.

An article about the research was recently published in the journal carbohydrate polymers.

Source: Empa