Zapping the coastline with electricity sounds like a fool’s errand, but solid science suggests that this approach could strengthen coastlines for generations to come.
Coastal erosion threatens millions of people. It’s a persistent challenge for people living on coasts worldwide, threatening not only shorelines but also the people and infrastructure along them. Simply put, many of our coastslines are going away.
According to a 2020 study by the European Commission’s Joint Research Centre, nearly 26% of the Earth’s beaches will be washed away by the end of this century. Traditional solutions, such as seawalls and beach replenishment, can work, but they’re usually temporary and can be costly and resource-intensive.
Now, there could be a better way. A recent study published in Communications Earth & Environment proposes a novel method that could revolutionize how we protect our coastlines: using electricity to create a natural cement from seawater.
Currents and water
“Over 40% of the world’s population lives in coastal areas,” said Northwestern University’s Alessandro Rotta Loria, who led the study. “Because of climate change and sea-level rise, erosion is an enormous threat to these communities. Through the disintegration of infrastructure and loss of land, erosion causes billions of dollars in damage per year worldwide.”
Drawing inspiration from marine organisms like corals and mollusks, which naturally build strong structures from the minerals in seawater, researchers explored whether a similar process could be applied to coastal sand. Their approach, known as “electrodeposition,” uses a mild electrical current to trigger the precipitation of minerals from seawater within the pores of the sand. This process effectively turns the sand into a type of natural cement, reinforcing it and making it more erosion-resistant.
“My aim was to develop an approach capable of changing the status quo in coastal protection — one that didn’t require the construction of protection structures and could cement marine substrates without using actual cement,” Rotta Loria said. “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.”
When an electrical current is applied to seawater-soaked sand, it initiates chemical reactions that cause minerals like calcium carbonate and magnesium hydroxide to solidify. These minerals then bind the sand particles together, enhancing the sand’s strength and stability. By adjusting the strength and duration of the electrical current, the researchers found that they could control the amount and distribution of the mineral deposits, tailoring the process to different conditions and needs.
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Solidified sand
When these minerals combine with sand, they stick the sand particles together like glue. The process also worked with different kinds of sands in the lab, such as iron sands that are common near volcanoes and silica and calcareous sands. According to the study, one surprising discovery was the formation of hydromagnesite, a mineral that further contributes to the sand’s strength. The research demonstrated that this new method could significantly increase sand’s resistance to erosion, turning it into a much more durable material.
“After being treated, the sand looks like a rock,” Rotta Loria said. “It is still and solid, instead of granular and incohesive. The minerals themselves are much stronger than concrete, so the resulting sand could become as strong and solid as a sea wall.”
While the minerals form instantaneously after the current is applied, longer electric stimulations garner more substantial results.
“We have noticed remarkable outcomes from just a few days of stimulations,” Rotta Loria said. “Then, the treated sand should stay in place, without needing further interventions.
An alternative with potential
This new method offers several advantages over traditional erosion control techniques. For one, it mimics natural processes, potentially reducing the environmental impact compared to more invasive methods. It also holds promise for being a more sustainable and cost-effective solution, as renewable energy sources can power it and it does not require the constant upkeep that other methods do.
The team’s research shows this approach can also repair cracked structures made of reinforced concrete, which disintegrates due to complex effects of sea-level rise, erosion, and extreme weather. Much of the existing shoreside infrastructure is made of reinforced concrete and if these structures crack, the new approach bypasses the need to rebuild the infrastructure fully. Instead, one pulse of electricity can heal potentially destructive cracks.
“The applications of this approach are countless,” Rotta Loria said. “We can use it to strengthen the seabed beneath sea walls or stabilize sand dunes and retain unstable soil slopes. We could also use it to strengthen protection structures, marine foundations and so many other things. There are many ways to apply this to protect coastal areas.”
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