Zapping Sand to Create Rock: A Solution for Coastal Erosion

Coastal erosion poses a significant threat to shorelines worldwide, reports ScienceNews. This challenge worsens with rising sea levels — an aspect of contemporary climate change. Traditional methods of combating erosion include building seawalls or trucking in sand to replenish eroded beaches. However, as Alessandro Rotta Loria, a civil engineer at Northwestern University, points out, these solutions are short-lived. The injections of materials like plastics can harm the environment.

An innovative alternative involves low voltage electricity, applied to saturated sand. According to research by Rotta Loria and colleagues, this technique prompts mineral formation that binds sediments together. The study was published on August 22 in Communications Earth & Environment. The minerals are composed of components already found in seawater.

Applying a mere 4 volts to a mixture of sand and seawater over 28 days encourages mineralization. The researchers utilized a rod-like electrode about 2 centimeters in diameter, effective in creating rock tubes reaching up to 80 centimeters across. The predominant minerals formed include calcium carbonate and magnesium hydroxide. "It is, in essence, limestone," Rotta Loria explains.

Testing indicates that the rock produced has about one-tenth the strength of concrete. Despite its relatively low strength, this material could effectively combat coastal erosion. The mineralization reinforces sandy areas beneath cliffs, reducing the timeframe for cliff retreat. Additionally, it provides stability to the foundations of coastal homes, whether they are constructed on slabs or stilts. The technology shows potential to repair cracks in existing concrete structures.

This mineralization technique is environmentally friendly, as the low voltages applied do not affect marine life. Additionally, initial cost estimates suggest an economical processing rate — around $3 to $6 per cubic meter of seawater-saturated sand. In contrast, traditional sand replenishment methods can cost between $14 and $30 per cubic meter, adding to the financial burden of coastal protection, which can amount to billions over time.

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