New studies have shown that gently applying electricity can significantly fortify marine coastlines for many years, helping to minimize erosion risks linked to climate change and rising sea levels. This innovative method creates natural cement among sand grains, effectively turning them into sturdy, immovable rock. Mollusks, like clams and mussels, use a similar technique to create their shells from minerals found naturally in seawater.
Recent research conducted at Northwestern University reveals that a mild electric shock can enhance the resilience of marine coastlines for generations, greatly mitigating the risks of erosion caused by climate change and rising seas.
The research team drew inspiration from clams, mussels, and other marine animals known for using dissolved minerals in seawater to create their shells.
In a similar vein, the scientists utilized those same naturally dissolved minerals to establish a natural cement between sand grains that were soaked in seawater. However, instead of relying on metabolic energy like mollusks, they employed electrical energy to induce a chemical reaction.
During experiments in the lab, a mild electric current rapidly altered the structure of marine sand, transforming it into a solid, rock-like material. The researchers are optimistic that this method could provide a long-lasting and cost-effective solution for reinforcing coastlines worldwide.
This study is set to be published on Thursday (August 22) in Communications Earth and the Environment, a journal from the Nature Portfolio.
“Over 40% of the global population resides in coastal regions,” noted Alessandro Rotta Loria, the lead researcher from Northwestern. “Erosion poses a significant threat to these communities due to climate change and rising sea levels, leading to the deterioration of infrastructure and loss of land, resulting in billions of dollars in damages each year. Current methods to combat erosion usually involve building protective barriers or injecting external compounds into the ground.”
“My objective was to create a new method for coastal protection that doesn’t involve constructing barriers and could naturally solidify marine sands without using traditional cement. By applying mild electric stimulation to marine soils, we have systematically and mechanistically shown that we can cement them by transforming naturally dissolved minerals from seawater into solid mineral binders—effectively creating a natural cement.”
Rotta Loria holds the position of Louis Berger Assistant Professor of Civil and Environmental Engineering at Northwestern University’s McCormick School of Engineering. The research paper’s first author, Andony Landivar Macias, previously a Ph.D. candidate in Rotta Loria’s lab, co-authored the study alongside Steven Jacobsen, a mineralogist and professor of Earth and planetary sciences at Northwestern’s Weinberg College of Arts and Sciences.
Sea walls erode too
With the increasing severity of storms and rising ocean levels, climate change is steadily eroding coastlines. A 2020 study by the European Commission’s Joint Research Centre predicted that nearly 26% of the world’s beaches could disappear by the end of this century.
To address this problem, communities have mostly relied on two strategies: constructing protective barriers like sea walls or injecting cement to strengthen sand-based marine substrates. However, both approaches face significant challenges. These traditional methods are not only prohibitively expensive but also tend to be ineffective over time.
“Sea walls can also experience erosion,” Rotta Loria explained. “Over time, the sand beneath these barriers erodes, leading to potential collapse. Often, protective structures consist of heavy stones, costing millions per mile, but the sand beneath can turn to liquid due to various environmental factors, leading to the displacement of these structures.”
“Injecting cement and binders into the earth comes with irreversible environmental consequences and usually requires extensive pressure and energy.”
Transforming ions into glue
To overcome these challenges, Rotta Loria and his team devised a straightforward technique inspired by coral and mollusks. Seawater naturally contains many ions and dissolved minerals. When a mild electric current (between 2 to 3 volts) is applied, it triggers chemical reactions that convert some of these elements into solid calcium carbonate—similar to what mollusks use to build their shells. With a slightly higher voltage (about 4 volts), they can produce magnesium hydroxide and hydromagnesite, which are common minerals found in various rocks.
When these minerals come together in sand, they act like an adhesive, binding the particles closely. In laboratory tests, this process has been successful with various sand types—from ordinary silica and calcareous sands to iron-rich sands often found near volcanic areas.
“After treatment, the sand resembles rock,” Rotta Loria remarked. “It becomes solid and immovable, rather than loose and granular. The minerals are substantially stronger than concrete, so the treated sand could be as durable and strong as a sea wall.”
Although the mineral formation occurs rapidly upon applying the current, extended electric treatments yield even more impressive results. “We have observed remarkable improvements after just a few days of stimulation,” Rotta Loria noted. “Afterward, the treated sand should remain in place without needing further maintenance.”
Eco-friendly and reversible
Rotta Loria believes that the fortified sand will maintain its stability, providing protection to coastlines and properties for decades.
He also reassured that the method poses no risk to marine life since the voltages used are too mild to be felt. Similar techniques have been utilized to enhance underwater structures and restore coral reefs without harming marine organisms.
If communities decide to revert to untreated sand, Rotta Loria has a reversible solution. By switching the electrodes on the battery, the electricity can dissolve the minerals, reversing the cementing process.
“The minerals precipitate as we raise the pH locally around the cathodic interfaces in seawater,” Rotta Loria explained. “If the anode is switched with the cathode, localized reductions in pH lead to the dissolution of the previously formed minerals.”
Cost-effective with various applications
This process presents an affordable alternative to traditional methods. Estimates put the cost of Rotta Loria’s technique at only $3 to $6 per cubic meter of electrically solidified ground, significantly lower than existing methods that can reach up to $70 for the same quantity.
Research in Rotta Loria’s lab indicates that this method could also repair cracks in reinforced concrete structures. Many coastal infrastructures are made of such materials, which degrade due to the effects of rising sea levels, erosion, and harsh weather conditions. When these structures crack, his approach could fix the damage with just one application of electricity instead of needing complete reconstruction.
“The potential applications for this technique are numerous,” Rotta Loria said. “We can enhance the seabed beneath sea walls, stabilize sand dunes, and secure unstable soil slopes. This method could also reinforce protective structures, marine foundations, and much more. There are countless ways to use this to safeguard coastal regions.”
In the future, Rotta Loria’s team plans to test this technique in real-world beach settings.
The study, “Electrodeposition of calcareous cement from seawater in marine silica sands,” received support from the Army Research Office (grant number W911NF2210291) and Northwestern’s Center for Engineering Sustainability and Resilience.
