Applicability of Coastal Protection Techniques Using Eco-Friendly Porous Materials

Global warming has accelerated the rise in sea levels, leading to widespread coastal erosion worldwide. Cement concrete, the predominant material employed for coastal protection, is a major source of greenhouse gas emissions, thereby perpetuating a self-reinforcing cycle that further contributes to sea level rise. In addition, elevated atmospheric carbon dioxide concentrations increase the dissolution of CO₂in seawater, where it releases hydrogen ions and consequently exacerbates ocean acidification. Within concrete, cement reacts with water to form calcium hydroxide, which remains stable for decades but gradually leaches into seawater. This dissolution alters the marine carbonate system by converting abundant bicarbonate ions into carbonate ions. Although carbonate ions typically constitute less than 1% of total dissolved inorganic carbon in neutral seawater, their concentration markedly increases in the vicinity of cement-based structures. Such chemical alterations create favorable conditions for the proliferation of coralline algae, which utilize the excess carbonate ions for calcification and growth. Given the detrimental effects of cement concrete on ocean acidification, marine desertification, and global warming, the development of sustainable alternatives for coastal protection is urgently required. This study introduces permeable polyurethane concrete—a porous, eco-friendly composite formed by binding aggregates with a biopolymer synthesized from vegetable oil—and examines its material characteristics and potential applications in mitigating coastal environmental degradation.