After an oil spill, the number one priority is finding a way to contain and remove the oil. Boat operators sometimes deploy physical booms to trap the oil so that it can be siphoned or burned off of the water's surface. But, because oil in water is tricky to contain, other methods for corraling it call for adding manmade chemicals to the water.

In a technique called dispersion, chemicals and wave action break down the oil into smaller particles, which then disperse and slowly biodegrade over a large area. Then, there is chemical herding. To clean up an oil spill with a chemical herder, crews spray a compound around the perimeter of the spill. The compound stays on the surface and causes the oil to thicken. Once it’s thick enough, it can be burned off. Chemical herding requires calm water, which makes it unreliable in some spills, but, unlike mechanical removal or dispersion, it gets all the oil. The technique has been around since the 1970s, but, until now, the chemicals used to herd the oil, called soap surfectants, didn't break down over time. After the oil burned off, they’d still be in the ecosystem.

Researchers at the City College of New York, led by chemist George John and chemical engineer Charles Maldarelli, have developed a way to clean up oil using a chemical herder made of phytol, a molecule in chlorophyll that makes algae green. It’s the first non-toxic, natural way to remediate oil spills.

“We didn’t want to add anything to the environment that would make it worse, so we decided to make molecules that came from natural products, so they would automatically biodegrade,” Maldarelli says. "We like the idea of using a molecule that's abundant in nature to arm against something humans have done to the environment."

The researchers settled on phytol, which they harvest from algae. It is a natural molecule that cleaves off as the chlorophyll breaks down, so they knew it would be stable in the environment. The phytol didn’t quite do the job on its own, so they added a plant-based fat, which helped align the molecules in a way that broke the water's surface tension.

In their Manhattan lab, the team tested the natural herder on fake oil spills, to see if it could condense the oil as effectively as current chemical herders. They dialed in the balance of elements until it herded just as fast as the chemical versions. Maldarelli says they looked closely at both biodegradability and toxicity, and at what they might need to source the new herder commercially.

“The commercial ones, they’re fairly non toxic—some are more than others," says Maldarelli. "But our claim is that if you start with natural products you’re ahead of the game."

The researchers are testing the natural herder in wave tanks and monitoring how long it takes to break down, as they think about scaling up and using it in emergency situations. They're still unsure if the lipid they're using is the best option, so they're testing other options for binders.

The natural herder can be sprayed from a plane, so Maldarelli says it’s best use case will be in calm waters where it’s hard to navigate a boat. "The Arctic seas are usually calmer and have icebergs floating, so chemical herding works there," he says.

On July 22, President Obama approved two of Royal Dutch Shell's permits for drilling in the Chukchi Sea, off the coast of northern Alaska. Shell had an accident the first time they tried to drill in the Arctic, in 2012, so having multiple cleanup methods could be a boon.