By Erica Yokoyama
Dispersant is one the most commonly used cleanup methods, said Nobuharu Kagami, an executive director of the Japan Association of Marine Safety. 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. Dispersants are regulated to be less toxic to the marine environment, Kagami said, but they are not normally used in environmentally vulnerable spots. 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.
Mop up the oil
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 tarballs,” said Kuniaki Sasaki, an expert at the Ocean & Beach Foundation who has been involved in major accidents including the 1997 Nakhodka spill in the Sea of Japan. 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. And both systems are only really effective in calm conditions.
In the Wakashio case, the recovery was complicated because the shoreline included areas of rocks, sand, silt and mangrove, said Richard Johnson, a technical director of International Tanker Owners Pollution Federation Ltd., one of the organizations supervising the Mauritius clean-up effort.
How about ‘bioremediation’?
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 effective in degrading oil components such as resin and asphaltene, and they can also harm the ecosystem. The bacteria use up dissolved oxygen that other marine life also need. More experiments are needed before “dispersing bacteria into the ocean,” Yamazoe said.
Design ships not to leak
One of the biggest innovations designed to curb maritime pollution was the decision in 1992 by the International Maritime Organization to make it compulsory for large tankers to have a double hull, giving greater protection in case the outer hull was punctured by a collision or a reef. Regulations have been tightened several times since, but cannot prevent environmental contamination in a case like the Wakashio, which broke in two.
Don’t sail close to the shore
One effective way to reduce the risk of your shore being coated in oil is to ban ships from sailing too close. 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 problem is that ship owners want to save time and money by taking the shortest route and international treaties allow merchant ships to sail within a few miles of national coastlines.
Stop using oil
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. And developing large ocean-going vessels powered by renewable energy is in its infancy.
“It’s still hard to operate oil-free pure EV ships for commercial use, especially for long distances,” said Yasumasa Suetsugu, a chief technology officer for a consortium including Mitsui O.S.K. Lines Ltd., Mitsubishi Corp. and five other Japanese companies that are trying to develop electric vessels. The group hopes to launch a lithium ion battery-powered tanker in 2022 that could operate within Tokyo Bay.
Fukuoka-based Eco Marine Power is among those working on vessels driven by solar and wind energy, but Greg Atkinson, chief technology officer of the shipbuilder, says these ships aren’t yet able to meet the energy requirements of global carriers, “especially huge cargo ships like Wakashio.”