14 years after Deepwater Horizon, can cork treat oil spills?

It was 14 years ago that the Deepwater Horizon disaster spilled over 130 million gallons of oil into the Gulf of Mexico. It was the largest such spill in history. Since then, scientists have been working on the best way to contain disasters like this. One problem is that chemical dispersants that are often used to break down oil can increase the toxicity in the process. But researchers in Israel and China say they have come up with a clever way around it - which involves using laser-treated cork. To explain more are Chemistry World’s Philip Broadwith and Boston University biologist Robinson - Wally - Fulweiler, who carried out research on the environmental impact of the disaster in the Louisiana wetlands…

Wally - So it was this really intense environment as you would imagine, because there was all of a sudden this huge influx of people trying to work on this problem. We were in and out of boats on salt marshes trying to look for where the oil was coming up on the salt marsh. And so it was really horrifying, to see this like ooky substance <laugh>, for lack of a better word, all over marsh surfaces and beach surfaces and things like that.

Chris - Many people look at the big animals like birds and that's devastating when they get coated. But you were very interested as well in the other things in the environment that often get overlooked. What were you looking at?

Wally - We were really interested in trying to understand how the microbes that live in salt marshes do this process of nitrogen removal. It's an ecosystem service or benefit that salt marshes provide and we were really interested in trying to figure out what could happen when the salt marsh surface was covered with oil and how that would change those microbial dynamics.

Chris - And did it?

Wally - It did. And I think some of the neatest work that's come out of this, if you could say like a silver lining of this awful event, is how much interesting work scientists have done on the microbial communities, that sort of the biodiversity of those microbial communities that are in the environment and how they respond to such an event.

Chris - It was a huge amount of oil that ended up in the sea, wasn't it, Phillip? How did they actually try to deal with it at the time?

Phillip - Yeah, it was huge. It was bigger than any of the sort of spills that we'd seen before and it's coming up from very deep under the water as well. There are various ways that you can try to contain that. You can put physical barriers in the way. But you can also, if you get there in time and under the right conditions, you can apply chemical disbursements. It's a bit like your kind of fairy liquid, it's a surfactant. It's breaking up the oil into smaller droplets and those would be applied at the surface to try and disperse the oil over a bigger area so it can disperse more quickly. But in Deepwater Horizon, they also do this underwater as well and that changes the composition of the oil as it comes up towards the surface, meaning it's in smaller droplets, changing the way some of the different components of the oil go into the atmosphere. So one of the things that was kind of reported later was that there were less volatile things like benzene in the air above the water than there might have been had they not used these disbursements underneath. But the kind of flip side of that is that then the dispersed oil is a mixture of the oil and the disbursements. The disbursements themselves have some toxicity and the mixture itself has different toxicological properties as well. So there can be issues associated with the dispersed oil that are different to if the oil had just been kind of left on its own. It will then spread out over a larger volume of the sea and dispersing the oil doesn't change its chemical composition at all. It's still oil. The only way we kind of eventually get rid of the oil is to have something break it down and that's usually the bacteria. Similarly to what Wally was talking about, there's bacteria in the ocean that will eventually break down the compounds in oil and transport it to the seabed and that kind of thing. So you can contain and collect and pick up a certain amount of the oil, but a lot of it is going to end up in the ocean and it's just going to end up dispersed and over time will be degraded.

Chris - And as Wally was saying, it ended up all over the salt marshes in large amounts didn't it? This paper that's coming out, they say that they've got possibly something else to bring to the party. What are they proposing?

Phillip - It's taking cork, the wood of cork trees, and they are essentially charring it with a laser. It's black, which means it heats up in the sun. That helps to warm it up and make the oil a bit runnier so that it can go into the pores of the material. It's also porous. It also repels water so it can separate the oil from the water and that makes it easier to deal with afterwards.

Chris - Sounds like you'd need a huge amount though, Phillip, and you're back to sort of the problem you were saying where it's still got to go somewhere. So is the idea you come back and scoop the oil soaked cork up later or does it float off and take this toxic cargo onto Wally's salt marshes?

Phillip - My interpretation is that you would have it contained in some kind of matrix material, some kind of blanket. There is a similar material called oleo sponge. It is essentially like a mattress, a polyurethane mattress sponge, that then has a coating of titanium oxide on it, which does the same thing. It makes it attract oil and repel water. And they kind of fashion that into these mats, which you can ring the oil out of. You can put it under the water on the top of the water, it will absorb the oil. You can take that off. You can physically remove the oil by squeezing it out of the pores like a sponge and then you can just go back in and get some more. I would assume that the intention is that this kind of thing is going to work a bit like that. It has the added benefit of this warming in the sun. So if you've got a particularly viscous oil, if it's started to emulsify with the water a bit, if it's heavier oil, some of the lighter fractions have already evaporated off, then you might have problems absorbing it into some kind of material. This kind of thing might help with that. I mean, we're talking about very early stage research. There's a huge difference between doing that and then having a product that will actually be useful in a real life oil spill.

Chris - As we mentioned earlier, Wally, it is 14 years since this all happened. Do we know what the aftermath is now? Has the environment got back together or is there a lasting legacy?

Wally - You know, I've been back to Louisiana. I've been back to some of those areas, but not in a scientific way. Mainly for leisure or conferences or something like that. And so I can't speak directly to what's happening to the places that I looked at, but, from what I know about other places, I would anticipate that most of the visual oily goo is gone, but the residue is probably still hidden and will be for a long time in the sediments as they slowly degrade.