Cleaning up plastic litter in remote, open ocean areas: Guidance for prospective inventors of plastic-capture systems

Read the Press Release, Scientists provide first public guidance on array of challenges in cleaning up plastic litter from oceans successfully here.

Distributed by MarineDebris.Info

Introduction
Marine debris, and particularly plastic marine debris, poses a significant global threat to marine life. Growing public awareness of this threat, including the recognition that floating ocean plastics tend to congregate in remote areas of the open ocean (the so-called “garbage patches”), has inspired some individuals and groups to conceive of systems for cleaning up debris at sea. These systems have ranged from simple net-based methods to ambitious giant filtering systems that would stretch hundreds of kilometers across the sea surface, among other ideas.

These ideas are laudable for their goal of removing plastics from the sea. However, the proposed systems typically fail to account for real-world ocean conditions and/or the many ecological and engineering-related challenges that would face any cleanup effort on the open ocean. In fact, the array and scale of challenges involved in any realistic cleanup of remote ocean areas have been cited often by experts as evidence that marine debris management should focus on preventing new litter from entering the ocean, rather than attempting to remove the litter that is already there.1

Still, many seemingly intractable challenges faced by humans over time have been solved by bright ideas. And as long as people are aware of and moved by the problem of ocean plastic debris, there will be attempts to solve it. In this light, we do not want to dissuade potential innovators from examining the issue of marine debris cleanup. Rather, we want to inform and channel their innovation.

Guidance
This document presents general guidance for the cleanup of floating plastic debris in the open ocean. This guidance was produced and edited in June-July 2013 by a team of experienced marine debris researchers (see “Background on this document”) and was shared in July with the global MarineDebris.Info community of marine debris managers, researchers, and conservationists for additional input. This list is intended to evolve and improve over time as further knowledge is gained. We also strongly recommend that all prospective inventors of cleanup systems consult experienced ocean engineers early in their development processes.

Systems for open ocean cleanup of marine plastics should account for, and overcome, the following challenges:

1. The size and depth of the ocean gyres within which floating marine plastics tend to gather. The North Pacific Subtropical Gyre, the best-known location of a “garbage patch” or trash vortex, has a surface area of approximately 20,000,000 km² — more than twice the size of the U.S. Thus any system that would tow nets through the gyre to capture debris, for example, must either factor that surface area into its design or determine a way to avoid having to transit the whole area. In addition, in even the most densely polluted regions of the subtropical gyres, microplastics (particles smaller than 5 mm in size) are frequently present at concentrations of less than one piece per square meter, requiring extensive areal coverage to recover just one kilogram of plastic. Furthermore, average water depth of the open ocean is 4,000 meters (2.5 miles); therefore, any cleanup system relying upon moored structures must account for this extreme depth. 
   
2. Depth and concentration of microplastics. Floating plastic debris, and particularly microplastics, can be mixed below the surface in even light winds. The depth of the mixing depends on the strength of the wind and the physical structure of the ocean in that particular area. It may range from a few meters depth during typical low wind conditions in summer months to 100-150 meters depth during stormier winter months. Any cleanup system, particularly one that relies on surface-floating mechanisms, must account for subsurface mixing of debris. 
   
3. Capturing plastics while not harming marine life that is co-located with the plastics. The goal of ocean plastic removal is ultimately to help sea life. If cleanup systems hurt or kill sea life in the process — such as fish or even plankton — they are counterproductive. Most zooplankton, for example, do not survive being caught in a standard net, never mind spun in a centrifuge where they lose critical appendages like their antennae and feeding apparatus. A system that relies on nets or centrifuges will require engineered solutions to avoid or minimize these effects. In addition, indirect environmental impacts of cleanup systems — such as from fuel use by cleanup vessels scouring the ocean, or from incineration of collected plastics at sea — should be considered and mitigated.  
   
4. Potential for entanglement of marine life in the systems. Similar to the above guideline, any cleanup system that poses an indirect entanglement threat to wildlife, such as seabirds or cetaceans, must be reengineered. In the U.S., any activity that might harm protected species is illegal without a permit.  
   
5. Strength and stability in extreme sea conditions. Any cleanup system is in danger of becoming marine debris itself if it breaks up, such as from storm action, high waves, or ship collisions. A successful system must be able to avoid extreme weather or be sturdy enough to withstand such conditions, and must be detectable by fast-moving vessels. 
   
6. Maintenance and fouling. The reality of operating equipment in extreme environments, of which the open ocean is an example, is that equipment breaks down. There must be a cost-effective means to maintain and repair the cleanup system over time, particularly for systems that involve long-term deployment. Furthermore, there must be a way to account for, and address, the rapid biofouling that occurs when any equipment is placed in the ocean. 
   
7. The physical properties of ocean-weathered plastic. Floating marine debris is largely composed of polyethylene and polypropylene — common plastic types with a density less than that of seawater. (Polystyrene, which has a density roughly equal to that of seawater, may also be present but is much less abundant in floating debris.) Ultraviolet light degrades these plastic polymers, making them brittle and difficult to recycle. Cleanup schemes that propose to recycle and/or market the plastic they collect should be aware of the technical issues, and of the actual market value of the plastic they collect, which may be low. Recyclers with the technology to “upcycle” mixed ocean plastic into consumer-quality polymers remain very few (Envision Plastics, which partners with home products manufacturer Method on a recycled ocean plastic bottle, is one). As a result, the market for collected ocean plastic is underdeveloped at best. 
   
8. Legal issues. There are extensive laws and regulations governing the deployment of equipment at sea. For example, structures cannot be a hazard to navigation or a threat to protected species. In the U.S., multiple permits from state and/or federal agencies may be required for cleanup devices. The permitting process is lengthy, onerous, and expensive, and may require specialized legal consultation. On the high seas — marine areas beyond national jurisdiction — the applicability and relevance of the United Nations Convention on the Law of the Sea must be evaluated in each case.

Background on this document
This guidance was drafted by:

• John Davis, M.M.A., of MARE
• Miriam Goldstein, Ph.D., of California Sea Grant and Scripps Institution of Oceanography at UC San Diego

Editors and contributors included:

• Courtney Arthur, M.S., Research Specialist, NOAA Marine Debris Program
• Pete Davison, Ph.D., Postdoctoral Scholar, Scripps Institution of Oceanography
• Kara Lavender Law, Ph.D., Research Professor, Sea Education Association (SEA)
• Chelsea Rochman, Ph.D., Aquatic Health Program, School of Veterinary Medicine, University of California, Davis

The guidance was submitted for additional review to the MarineDebris.Info community.
We welcome additional editors and contributors; this guidance is intended to be a living document. To provide input, please contact John Davis, project supervisor of MarineDebris.Info, at jdavis@marineaffairs.org.

Media
For interviews, please contact:

• John Davis, jdavis@marineaffairs.org
• Miriam Goldstein, miriam.goldstein@gmail.com

About MarineDebris.Info
MarineDebris.Info is the global knowledge-sharing community for marine debris management and research, with members representing government agencies, research institutions, conservation organizations, industry, and more (www.marinedebris.info).  It consists of a listserv, website, and live chat events allowing members of the MarineDebris.Info community to interact with leaders in the field.

MarineDebris.Info is a project of Marine Affairs Research and Education (MARE), a Seattle-based organization that provides a range of knowledge-sharing services to ocean managers and conservationists worldwide.  These services include the OpenChannels forum on ocean planning (openchannels.org), the MPA News service on marine protected areas (mpanews.org), and the Marine Ecosystems and Management information service (meam.net). MARE collaborates on several of its projects, including MarineDebris.Info, with the University of Washington.

The Hazards of Plastic Waste

Posted in Living On Earth, March 8, 2013

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Plastic debris in the Tijuana River Valley in San Diego (photo: Chelsea Rochman)

In a recent piece in Nature, a group of scientists called for reclassifying plastic as a hazardous waste. This would give environmental agencies more tools and funding to clean up plastic in ecosystems around the world. One of the authors, Chelsea Rochman, an marine ecologist at the University of California at Davis, tells host Steve Curwood about the dangerous pollutants inside many plastic products.

Transcript

CURWOOD: Every year, humans produce nearly 280 million tons of plastic. And much of that plastic ends up in the environment, harming marine life and other ecosystems. Now a group of scientists has a potential solution. Writing in Nature magazine, they argue that reclassifying plastics as hazardous waste would give regulators more tools and funding to clean the place up. One of the authors, Chelsea Rochman, a marine ecologist at the University of California at Davis, says it’s clear that plastics need a new label.

ROCHMAN: Waste is basically separated into two categories, those that are non-hazardous like grass clippings, and those that are considered a hazard, which are often based upon this long list of priority pollutants, or substances that the government deems are hazardous to organisms. And we found that plastics are associated with 78 percent of these priority pollutants listed by the US EPA and 61 percent listed by the European Union, either as a chemical ingredient of the plastic itself or when the plastic ends up in the aquatic environment; they absorb these contaminants from the water. And so from that perspective we thought maybe plastic as a waste product should also be considered as a hazardous substance.

CURWOOD: What's the danger?

ROCHMAN: We don't know an awful lot about the ecological hazards of plastics themselves. But we know a lot about the hazards associated with these priority pollutants. There's a vast amount of peer-reviewed literature on this. And so we know that these priority pollutants, when they get into food webs and into ecosystems, that they can cause harm at organism level, population level and so we’re concerned that if these plastics are another vessel for these priority pollutants to be getting into habitat, that they also may cause harm.

CURWOOD: Quickly, list for me the priority pollutants.

Chelsea Rochman looking for plastic at sea (photo: Stiv Wilson)

ROCHMAN: So, for the ones that are ingredients of plastics themselves...so styrene, which is the monomer for Styrofoam, vinyl chloride which is the monomer, the building block, for PVC, polyvinyl chloride, those are both considered priority pollutants. And they’re flagged as being carcinogenic - or potentially estrogenic for styrene. Some of the ones that are absorbing from the environment are things like toxic metals, like copper or lead, and pesticides such as DDT, that a lot of us are familiar with from the work of Rachel Carson. And PAHs which are maybe less familiar, but they’re an industrial byproduct that come from the combustion of oil, and a lot of them are considered either carcinogenic or they can cause harm to the reproduction system - depends on the chemical what their hazard is.

CURWOOD: So what are you recommending?

ROCHMAN: So what we’re recommending is to start off with a policy change that will enable a domino effect. So what we’re expecting first is that if we consider these plastics as a hazardous substance or hazardous once they end up in the environment, certain policies like in the US, for instance, CERCLA or Superfund, would be able to actually use funding to go in there and clean it up. So, for example, let's take the Hawaiian Islands where a lot of the plastic from the middle of the gyres, of the garbage patches are washing up. And so we know there’s large accumulations of plastic items on the beaches there. If plastics are considered a hazardous substance, the EPA then has legislation to go in and clean up that area and use funding and litigation to prevent further debris from accumulating.

CURWOOD: Let’s talk some numbers of plastics. How much plastic do we produce every year, and how much of it is not taken care of?

ROCHMAN: So at the moment, in 2011, we produced 280 million tons of plastic, and that’s globally. That same year, the World Bank reported that they collected in the waste stream, so they accounted for either in landfills or recycling, 130 million tons of plastic. So that leaves 150 million tons unaccounted for. Now obviously, some of that plastic is still on our feet as shoes or on our computers, in our houses, but not all of it can still be in use. So if you wonder where is that 150 million tons of plastic...and so we know there’s large accumulations in the environment. So I think that's troublesome because how much are we adding every year, and that’s the question we don’t know the answer to yet.

CURWOOD: Where is this worst? What ecosystems are being threatened by this?

More plastic debris in the Tijuana River Valley (photo: Chelsea Rochman)

ROCHMAN: Unfortunately at the moment we don't know. We still need a lot of research to determine this. The areas where we find a lot of plastic debris are, of course, we hear a lot about it in the middle of the open ocean; but there’s a lot of it near the coasts. So what I would argue is that your coastal ecosystems is probably where we want to concentrate because that's where we have the largest accumulations of these pollutants in the water which could potentially store to this plastic as it enters the water. And so we find plastics in these coastal ecosystems that are near urban areas that are gonna be associated with large concentrations, of say pesticides and the PAHs I talked about earlier and toxic metals.

CURWOOD: So you remember famously in the movie The Graduate, Dustin Hoffman is told, “Plastics, young man, plastics.” So what would we tell Dustin Hoffman today, his character? What would we replace plastic with?

ROCHMAN: I am so happy that you asked that question. It used to be how we began and ended the paper. So there’s a famous line in that movie that says, “plastics are the future”, right, or “the future is plastics”? And I would say that that’s not necessarily untrue. I still think there is a great future in plastics. And I don’t think plastics are evil and that we should ban them all, but I think we should start thinking about making plastic materials that are benign by design, and use our innovation strategies to make products that are recyclable, reusable and durable, and that are safe for people and the planet.

CURWOOD: Chelsea Rochman is a marine ecologist who studies toxicology at the University of California at Davis. Thank you so much.

ROCHMAN: Thank you.

Links
The original commentary article
Chelsea Rochman’s webpage at SDSU