‘Natural cement’: Scientists electrocute sand to stop coastline erosion

Climate change and rising sea levels are wreaking havoc on the coastal regions around the globe.

Erosion has become a constant threat, eroding beaches, damaging infrastructure, and costing billions of dollars each year. In fact, studies project that nearly 26% of the world’s beaches may disappear by the end of the century.

Northwestern University researchers have developed a new sustainable solution to tackle this issue.

The lead author, Alessandro Rotta Loria, told Interesting Engineering (IE) that the “lack of sustainable and efficient approaches to mitigate coastal erosion” spurred this study.

Inspired by the natural processes used by clams and mussels to build their shells, they have developed a method to strengthen marine coastlines. This method applies a gentle electric current to marine soils.

The researchers are optimistic that this approach could provide a long-lasting, affordable, and environmentally friendly solution for reinforcing global coastlines.

How it works

Clams and mussels use dissolved minerals in seawater to form their strong shells.

Likewise, the researchers used the naturally existing dissolved minerals to form a natural cement between seawater-soaked sand grains.

For this, they used electrical energy to kick-start the chemical process.

Seawater is naturally rich in a variety of ions and dissolved minerals. Therefore, a moderate electrical current (2 to 3 volts) can cause chemical reactions in seawater.  The electricity has the capacity to transform some of its ingredients into solid calcium carbonate, the same material used to make mollusk shells.

With a higher voltage of 4 volts, these constituents can be turned into magnesium hydroxide and hydromagnesite — a common mineral found in various stones.

In the presence of sand, these minerals come together and hold the sand particles together.

“By applying a mild electric stimulation to marine soils, we systematically and mechanistically proved that it is possible to cement them by turning naturally dissolved minerals in seawater into solid mineral binders — a natural cement,” Loria noted in the press release.

This means that sand transformed from grainy and loose particles to a rock-like, immovable solid. Together, it could form a strong “sea wall,” safeguarding coastlines and property for decades.

The team showcased that this process proved to be effective with various types of sand, ranging from common silica and calcareous sands to iron sands.

Method protects sea life

Loria stated that there is no risk of harm to sea life as the voltages used in the process are too low to be felt.

“By modulating the applied electrical currents, it is possible to achieve minimal impacts on the environment. Notably, approaches leveraging the same mineralization process have been used for decades to grow artificial coral reefs in various marine regions around the world and evidence proves that the use of mild electrical stimulations in seawater does not affect marine life,” Loria told IE.

Interestingly, this method is also reversible. This innovative approach offers a more sustainable and cost-effective alternative to traditional methods like building sea walls or injecting cement into the ground.

Calculations estimate that the cost of electrically cementing one cubic meter of ground ranges from $3 to $6.

Loria added: “We are working to develop a number of technologies that will enable implementations at the large scale. For instance, the use of electrically conductive geotextiles that could be deployed over unstable marine soil masses for stabilization purposes.”

“The next steps of this research consist of delving deeper into a number of fundamental scientific questions and at the same time commence the scale-up of this technology.”

The findings were published in the journal Communications Earth and the Environment.