Stopping Ocean Oil Spills
By Michael Gregson
Sri Lanka seems to have dodged a bullet – thanks to the skill of the Navy and their Indian colleagues. Fortunately they managed to extinguish the fire aboard the New Diamond supertanker before it reached its cargo of 2 million barrels of oil.
Divers have fixed a fuel leak from the engine of a fire-damaged oil tanker off the island's east coast, in a salvage operation after the huge week-long blaze.
While the Navy said no crude oil has escaped the cargo of the New Diamond, leaked diesel fuel had created a two-kilometre-long slick in the Indian Ocean.
Sri Lanka's Meteorology Department had already modelled the impact of 70,000 tonnes of crude oil - a quarter of the ship's cargo - spilling into the ocean.
The simulation, a worst case scenario according to authorities, found that such a spill would not immediately threaten the country's east coast.
But Dharshani Lahandapura, Chair of Sri Lanka's Federal Marine Environment Protection Authority, told Reuters that any spill from the ship would be catastrophic for marine life.
“It will be a huge environmental and economic disaster if this happens,” she said.
Sri Lanka's environmental authorities fear a marine disaster if the tanker is allowed to transfer its oil to another ship in the country's waters. They are seeking to avoid damage to the coastline like that suffered by Mauritius after a Japanese bulk carrier, MV Wakashio, struck a coral reef off the Indian Ocean Island on July 25 and began spilling oil on 6 August.
It has been more than half a century since the world looked on in horror as the Torrey Canyon spilled some 100,000 tons of crude oil onto the coast of Britain. But when just 1,000 tons of fuel oil leaked from the bulk carrier Wakashio, it still caused the worst ecological disaster in the island nation’s history.
So why is it so difficult to find a fast and effective way to tackle one of the most damaging of industrial accidents?
Spraying dispersants is one the most commonly used clean-up methods. The chemicals break down the oil into smaller molecules, which disperse in the ocean and are eventually degraded by natural bacteria and microorganisms into carbon dioxide and water. In spills near the coast, where most ship accidents take place, the chemical also may not have time to act fully and the mixture of oil, solvents and emulsifiers can end up penetrating further into the ecosystem.
Oil recovery using machines is probably the fastest way of cleaning up most of a spill, but it needs to happen quickly before oil solidifies and turns into tar balls. Booms are also used to contain slicks and prevent them from reaching the shore. But vacuum tankers that suck up spilled oil can also damage the environment as they remove everything, not just oil. Both systems are only really effective in calm conditions.
Bioremediation is a more recent innovation, a nature-based method that increasingly attracts attention from environmentalists. The idea is to pump oil-eating bacteria into the ocean and foreshore to speed up the natural effect of the sea’s own organisms.
Bioremediation can help when the oil is already diffused, especially in warmer, tropical waters. “The performance of oil-degrading microorganisms are affected a lot by environmental factors like temperature, oxygen or nutrients such as phosphorus and nitrogen,” said Atsushi Yamazoe, a manager at Japan’s National Institute of Technology and Evaluation.
But the bacteria aren’t always effective and they can also harm the ecosystem. More experiments are needed before “dispersing bacteria into the ocean,” Yamazoe told Bloomberg News.
One effective way of reducing the risk of coastal contamination is to ban ships from sailing too close to shore. That isn’t possible if the ship has to dock in port to load or offload, but the Wakashio was sailing from China to Brazil via Singapore and didn’t need to be near Mauritius.
The best solution ultimately would be to stop using oil altogether, both to power ships, or to carry in the hold. Ship owners are increasingly turning to liquefied natural gas as an alternative, which may eventually be replaced by fuels such as bio-methane. While leaked gas from such vessels would just evaporate, the fuel could still contribute to global warming. But at least there wouldn’t be any oil slicks.