Synthetic Eelgrass

Inundation of biota in coastal waters by heavy smothering deposits of oil requires cleanup to enable ecological recovery within normal time scales. Conventional floating curtain and sorbent oil booms deployed to prevent such inundation have proven only marginally effective. Currents have advected oil under them. Wave have induced snap loadings destroying them, or advected oil over them. The capacity of conventional sorbent booms is limited to their outer surface. Such booms are discarded with the oil they adsorb, because the oil cannot be economically separated from them. To protect coastal wetlands, a new form of floating, sorbent barrier, called synthetic eelgrass (SE), is proposed to interdict and sequester floating oil before it can inundate the coast. Oil so captured can be recovered enabling SE to be reused, repeatedly. The form of this new barrier was suggested by natural sessile life. Zostera marina, common eelgrass, survives in seas by its flexibility and compliance to wave induced forces. Leukonoid sponges, filter feeders that remove nutrients from seawater passing through them, suggest a higher saturation limit to adsorbed oil on a sorbent that is an open-cell foam with a high surface area to volume ratio. Like eelgrass, SE has long, slender, buoyant blades, rising from the seabed to the surface, where it can extend over some surface area. These blades of SE, called filaments, are intrinsically buoyant strips of ethylene methyl acrylate (EMA), an amorphous thermoplastic elastomer, a non-polar material, which is oleophilic and hydroscopic. Besides crude oil, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and organic compounds such as lipids, amino acids, fatty acids, fats and soaps can be adsorbed on EMA. SE acts as a sponge. Because EMA's Youngs modulus is small, adsorbed oil can be squeezed out of SE, and SE can be reused, repeatedly. Filaments of SE are attached to a line, anchored at both ends to the seabed. Thousands of filaments, placed side by side, along this line can be deployed and recovered much as demersal longline fishermen do. While recovering or deploying a line of SE, an existing barrier would not be breeched provided two or more parallel lines of SE had been placed in close proximity. Being reusable, synthetic eelgrass provides an economical means of interdicting, sequestering, and recovering oil, and other non-polar chemicals, spilled in water before they can inundate the environment.