John Harper
Oil Spill Clean Up: Boom or Bust for Slicks at Sea
Oil spills at sea are an environmental nightmare. The mix of churning seawater and crude oil make containing and mopping up one of Earth's most polluting substances extremely hazardous.
Despite the best efforts of clean-up crews armed with chemical dispersants, containment booms and skimmers, sorbents to soak up oil, and pumps to remove it, large spills may still pollute the ocean, killing wildlife and leaving ecosystems damaged for decades.
MV Wakashio
When the Japanese cargo ship MV Wakashio ran aground on a coral reef south east of Mauritius in July 2020, its hull split, slowly releasing 1,100 tons of fuel oil into the Indian Ocean. The scale of the accident took weeks to develop, meaning that local and international oil spill specialists were able to remove nearly 75% of the spill. Still, the slick polluted around nine miles of biodiverse shoreline, including mangrove forests at Pointe d'Esny, leading to widespread criticism of the government's response.
Bloomberg
The MV Wakashio bulk carrier vessel, operated by Mitsui OSK Lines Ltd., sits partially submerged in the ocean after running aground close to Pointe d'Esny, Mauritius, on Friday, Aug. 14, 2020.
Proportional Response
Time is a factor, yet clean-up technologies need to do more than clear slicks quickly to prevent them killing turtles or dolphins and despoiling shore habitats. Burning surface oil releases toxic fumes and greenhouse gases. Dispersants rapidly break up and dissolve slicks, but if chemicals and oil droplets sink deeper into the ocean to kill pelagic fish or species living on the sea floor, they destroy ocean ecosystems.
One of the first and most effective strategies is to lay down an inflatable boom to block, divert, and contain the oil. Skimmers are then used to separate the oil layer and store it for removal. They come in all shapes and sizes–belts, drums, ropes, and discs–but the most effective are those made of oleophilic (oil-attracting) materials that split higher volumes of oil from the water.
Skimming can then be coupled with sorbent materials to mop up any oil that is left. Absorbents soak up oil and adsorbents form a layer of oil on their surface for separation. Sorbents can be simple natural substances like sawdust, straw, or even chicken feathers, but they include advanced synthetic materials. The best are both highly oleophilic and water-repellent (hydrophobic), biodegradable, and reusable.
Many of the latest advances are in sorbent technologies, including plant-based skimming materials like the floating Fern Salvinia, and highly absorbent organic peat moss. Reusable sorbents are best and the field-tested Oleo Sponge from the Argonne National Laboratory is a robust polyurethane foam that takes up to 90 times its weight in oil.
Oil has different densities depending on how it has been refined and the Oleo Sponge works with both lighter diesel and crude oil, whether oil is on the surface or below water, and maintains its structure after being wrung out again and again.
Another technological breakthrough is the E-MOP system from the advanced physics institute Fermilab. Oil is first seeded with an iron oxide called magnetite and then electromagnetic fields are produced by a special magnetic boom to physically lift and remove it. Tests show the system was 97.2 percent efficient in separating oil from water.
Cleaning up the trace contamination could then be achieved using bacteria called Alcanivorax borkumensis, a lifeform that feeds on oil and petroleum products. Thankfully, the size and number of large tanker spills is diminishing, down from almost 25 per year in the 1970s to less than two in the 2010s. But the industry cannot diminish its responsibility.
The Danger of History Repeating
The Deepwater Horizon platform explosion in 2010 was the third biggest spill in history. More deep ocean exploration is under consideration and only recently 22,000 tons of oil poured into a river in the Arctic Circle from a Russian power plant. These incidents call for urgency in clean up science because of their environmental devastation, but also prevention technology.
Handout
In this handout image provided be the U.S. Coast Guard, fire boat response crews battle the blazing remnants of the off shore oil rig Deepwater Horizon in the Gulf of Mexico on April 21, 2010 near New Orleans, Louisiana. An estimated leak of 1,000 barrels of oil a day are still leaking into the gulf. Multiple Coast Guard helicopters, planes and cutters responded to rescue the Deepwater Horizon's 126 person crew.
The National Oceanic and Atmospheric Administration now uses sophisticated computer modelling software to predict how oil spreads in water, how it degrades, and affects the marine environment. It also employs autonomous 'saildrones' to gather oceanic data, that could be used to improve shipping safety, detect spills, and provide real time data on spread and ecosystem health.
