Once the oil comes to shore, the more intensive the cleaning technique. You can risk causing further damage, say Nicky Cariglia, an independent consultant at Marittima, who specializes in marine pollution.
Because oil normally has a lower density than water, it floats on the surface of the ocean. This means that for cleanup action to be most effective, it should happen very quickly after a spill, before the oil disperses.
One method of controlling oil spills at sea, which was used after the Grande America cargo vessel sank in March 2019 some 300 kilometers (186 miles) off the French coast, is essentially scooping up the oil from the water's surface.
This is done using booms, which act like a barrier to prevent the oil from spreading. Once it's contained, boats equipped with so-called skimmer machines can suck up the oil and separate it from the water. After being processed, the oil can even be reused.
Booms were used to prevent oil from spreading after the Grande America cargo ship burned and sank in the Bay of Biscay
It seems like a simple method, but it only works when the oil stays in one place — and under the right conditions. When that's the case, the specialized vessels needed for the process can also make this an expensive and logistically challenging method.
In certain conditions, burning the oil off the water's surface can be the most appropriate method. In Arctic or ice-covered waters, for example, it might be the only option.
In-situ burning (ISB) would also be used to tackle an uncontrolled oil leak, where a lot of oil is spilling fast. When the Deepwater Horizon offshore oil rig caught fire and sank in April 2010, oil gushed from the seabed and caused the largest accidental oil spill in history. ISB proved to be a highly effective technique in responding to the disaster.
But the method also produces toxic fumes which can have a negative impact on the environment. And it comes with challenges, too.
Absorbents can be kinder to the environment: They act like a sponge to soak up the spilled oil. But they're more useful for clearing small amounts of oil on land and are not usually effective in tackling a spill out at sea. In fact, employing these materials on the water can create further pollution.
Experts also disagree over the effectiveness of different absorbent materials, which can range from natural products such as straw to highly engineered synthetics developed by scientists for the purpose of tackling oil spills.