COMMENTARY The Technological Challenges of Dealing With Plastics in the Environment

AUTHORS tem functions, the effects of micro- the Ellen McArthur Foundation push- Sarah-Jeanne Royer plastics are still not fully understood, ing for new plastic economy (https:// Scripps Institution of Oceanography, although they are widely accepted to www.ellenmacarthurfoundation.org/ University of California, San Diego be negative. This is exacerbated by our-work/activities/new-plastics- and The Ocean Cleanup Foundation, the fact that it is difficult (if not im- economy) and global commitments Delft, The possible) to remove such from a list of countries to manage the from the environment. Or, at least, Dimitri D. Deheyn balance between environmental health the technology of today to do so at Scripps Institution of Oceanography, and the plastic economy (https:// such a large scale is still not ready. University of California, San Diego www.ellenmacarthurfoundation. Hence, most of the technological in- org/news/a-line-in-the-sand-ellen- novations related to plastic targets macarthur-foundation-launch-global- lastic pollution has been at the the macroplastics only; even though commitment-to-eliminate-plastic- forefront of national news and social P this size fraction might not be the pollution-at-the-source). media with shocking images of wild- most abundant or damaging, at life impacted with plastics. Plastics least, it can be removed and hence are found in remote places, from prevent its further fragmentation in Plastics: Impact on Society mountain tops to the bottom of the the environment. and Public Health Still oceans and from the North Pole to fl In this article, we brie yidentify a Well-Kept Mystery Antarctica, and are a sign of the wide- the technologies that are proposed to Despite being one of the most spread impact of human activities. address the issues of macroplastics in pervasive materials on the planet, Plastics that are the most known to the oceans, while addressing the re- the public are the macroplastics (in plastic and its impact on human search and policy framework of this other words, “the ones we can easily health is poorly understood. Yet, ex- global issue in human society. see”); because we use them on a posure to plastic is expanding into daily basis, they are an integrative new areas of the environment and part of our life (from the grocery plas- Plastics: Issue at Large, food chain as existing plastic prod- tic bag to the water bottle or the parts ucts fragment into smaller particles of car or furniture) and are the ones Making All of and concentrate toxic chemicals. As that we consider “disposable” and of Us Responsible plastic production increases, this ex- single use (like straws and plastic has reached some posure under different forms will utensils or cups). dimensions that have gone out of only grow, and the impacts can only “And so what?” one might ask. control. It became one of the most be speculative at this stage. The problem with these plastics is pressing environmental issues, as rap- Indeed, currently, uncertainties that they were made to last “forever,” idly increasing production of dispos- and knowledge gaps undermine the meaning that their degradation in the able plastic products overwhelms the full evaluation of health impacts but environment is slow, although over world’s ability to deal with them. Plas- also limit the ability of consumers, the years, these macroplastics undergo tic debris has become such a ubiqui- communities, and regulators to weathering and break down in smaller tous material used daily by people make informed choices and heighten and smaller pieces (called microplastics) from all over the world that it recently both acute and long-term health that are easier to enter the foodweb. prompted efforts to write a global treaty risks at all stages of the plastic lifecycle Once in these biological processes that negotiated by the United Nations and and for all stages of the lifespan of liv- are critical for the well-being of ecosys- is the focus of key foundations such as ing creatures.

September/October 2019 Volume 53 Number 5 13 Plastics: What Do We FIGURE 1 Know, and What Should Macroplastic debris at Unalau Bay, Kauai, Hawaii. Photo credit: S.J. Royer. We Know? Plastic research has been booming over the past decades, and more infor- mation is now available spanning from the sources, the distribution in the environment, and also the tech- niques developed to assess the emerg- ing contaminants adsorbed, leached, or produced from the polymer com- pounds. However, there are still some important gaps that need to be addressed to understand the global impact of this major anthropogenic pollutant. Clearly, the techniques and envi- ronmental processes driving these contaminants depend on their size. The smaller the polymer fractions are, the more difficult it becomes to detect, extract, quantify, and qualify Single-use plastics (SUPs), durable Microfibers: Anthropogenic them. Processing time also increases goods, and fishing material are the cate- Material Coming From Clothing as the samples get smaller. gories of macroplastic mostly found in A microfiber can be considered as In order, to discriminate the differ- the environment (Figure 1). averyfine yarn that has a diameter ent detection and removal techniques, that varies between 3.4 and 36.2 μm we make the distinction between three (ca. 1/5 the diameter of a human hair; types of polymers: macroplastics, mi- Microplastic: The Ones That Are Figure 3). Microfibers are often dis- croplastics, and microfibers. Difficult to See cussed as being under the umbrella of As of now, there is no legally inter- microplastics; however, it is important Macroplastics: The “Popular nationally standardized definition for to recognize that microfibers are not ex- Ones” You Can See microplastics in terms of size and com- clusively plastic-based material and can Large visible plastic debris (>5 mm position. Generally, it summarizes as be of natural origin (e.g., cellulose- in diameter) is defined as macroplastic. being plastic particles that are small based compounds, cotton, hemp, Macroplastic debris can be degraded plastic debris of less than 5 mm in linen, wool) as well as modified natural and broken down into smaller particles, size. Microplastics encountered in the material (semisynthetic), mixed (i.e., named microplastic debris, through environment (Figure 2) can be of pri- polyester and cotton), and fully synthet- different degradation processes such as mary or secondary origin. Primary par- ic (polyester, nylon, lycra, polypro- photodegradation (ultraviolet radia- ticles are purposefully designated pylene). Overall, synthetic fibers tions), mechanical degradation (i.e., as manufactured granules for further account for approximately 60% of physical stress, action of waves), oxida- conversion processes as well as fine the total global fiber production with tion, and biodegradation. Their sources powders for technical applications or polyamide (nylon) and polyester (poly- are wide and include the mismanage- for addition to cosmetics. Secondary ethylene terephthalate) as dominating ment of plastic waste on land, sewer particles are derived from the disposal fibers (McArthur Foundation; https:// (sewage and storm water), beachgoers, of macroplastic items and its subse- www.ellenmacarthurfoundation. boaters, landfills, commercial fisher- quent breakdown mostly occurring in org/our-work/activities/make- men, vessels, and industrial products. the environment. fashion-circular; https://www.

14 Marine Technology Society Journal FIGURE 2 ellenmacarthurfoundation.org/ publications/the-new-plastics- Microplastic debris at James Campbell National Wildlife, O’ahu, Hawaii. Photo credit: S.J. Royer. economy-rethinking-the-future-of- plastics-catalysing-action). Microfibers are mostly generated from apparels and textiles and, there- fore, as opposed to other plastics, originate in majority from land with access to the ocean via two routes: wa- terborne and airborne. The main source of microfibers released to the environment is through the washing of clothes. Indeed, washing synthetic textiles in industrial laundries and households creates primary microplas- tics through abrasion and shedding of fibers. A recent publication indicated that the number of fibers released from washing 6 kg of laundry could reach more than 700,000 fibers (Napper & Thompson, 2016). The fibers are then discharged in sewage FIGURE 3 water and potentially end up in the ocean (Magnusson & Norén, 2014). Images of microfibers in fluorescence after sample filtration on glass fiber filter and imaged fl Given that the majority of clothing under stereoscope uorescence microscopy (excitation 390 nm, emission >420 nm with fi Nikon Long Pass Filter). Stereoscope is a Nikon SMZ1500 model, equipped with a digital bers are synthetic, their degradation camera (MicroPublisher 6, Photometrics/Q-Imaging), fluorescence filter cubes setups, and adds to the sources of (macro) plastics Bright Field imaging settings with white light LEDs light source, as well as optical zooming. (that can degrade into microplastics) Images were acquired and managed with the QCapture-Pro software interface and not exposed into the marine environment. Other to any postprocessing (images were taken at a magnification of 6×zoom). Photo credit: Deheyn Lab. nonpoint sources of microfibers relat- ed to the shedding of our clothing is while wearing and drying clothes in a dryer. Indeed, these microfibers are smaller than the lint retained on a dryer filter and are released directly into the atmosphere. Once airborne, these microfibers can travel worldwide until settling in remote terrestrial or aquatic environments, exposing isolat- ed organisms to man-made synthetic materials produced far away. Because these three categories of anthropogenic materials (macro- plastics, microplastics, microfibers) are different in size, shape, material composition, and abundance, their detection and possible removal tech- niques need to be addressed separately

September/October 2019 Volume 53 Number 5 15 for each material type. In parallel, there FIGURE 4 is also an urgent need to find alterna- fi Manta trawl used for scooping the ocean surface and collecting plastic debris in the North tive materials to plastics and nd mate- Pacific . Photo credit: University of Hawaii. rials with similar properties that can fully degrade in the environment in a timely manner.

Detection of Plastics in the Environment Detection techniques in the field of polymer are still embryonic com- pared to other fields of scientificre- search, and the technology used for the various types of anthropogenic materials differs depending on the na- ture, size, and geographical location (terrestrial vs. marine/aquatic environ- ments) of the polymer. are submerged in water and/or covered the seafloor level. Multilevel trawls Macroplastic items are visible to by a biofilm that may alter the detec- (Figure 5) were designed to sample the naked eye and the easiest form tion signal. polymer debris in the first 5 m of the to detect. The most common ways Given that a large fraction of the water column (Kooi et al., 2016) to of monitoring macroplastics under polymer debris discarded into the obtain a better understanding of the oceanic conditions for polymer debris environment has a density greater buoyancy of plastic particles and floating at the sea surface are from a than seawater and sinks, new tech- the effect on its distribution. An under- research vessel through visual surveys nologies are needed to get a better water camera allows scientists to profile and through the use of a manta assessment of the concentrations the water column and conduct image trawl.Visualsurveysarecommonly found in the water column and at analysis for polymer quantification. conducted from designated locations onboard vessels using binoculars and FIGURE 5 for a set period of time on a daily Multilevel trawl collecting plastic in the water column in the North Pacific Garbage Patch. Photo basis. Tows using a manta trawl (Fig- credit: The Ocean Cleanup. ure 4) scoop the surface water and typ- ically last between 20 and 30 min at an average speed of 1–3 knots depending on the mesh size that varies between 100 and 500 μm (most common size mesh is 333 μm). Unmanned aerial vehicles are becoming common for surveying water surface and coastal regions to estimate debris concentra- tion through imagery analysis. At a broader scale, satellite detection imag- ery would be the most efficient way of covering greater distances, but many challenges remain for detecting debris from space, especially when the debris

16 Marine Technology Society Journal Similarly, a remotely operated vehicle FIGURE 6 can capture images across the water fi fl Coriolis bio-aerosol sampler from Bertin Technology collecting aerosols and micro bers in the column but also of the sea oor with air in Austria. Photo credit: S.J. Royer. the possibility of sampling. Finally, sediment cores (traditionally used by geologists or scientists studying the seafloor/benthos fauna) allow the col- lection of a large volume of sediments, sometimes combining surface layers or keeping the sediment layering in- tact with core depth that may con- tain different polymer size fractions spread across different sediment layers. Microplastics, although smaller in size compared to macroplastics, can still be collected using a manta trawl, a multilevel trawl, a sediment grabber, captured using an underwater camera and a remotely operated vehi- cle, but will not be observed using visu- al and unmanned aerial vehicle surveys. Along the coastlines, the most common sampling technique is through sifting for debris collected in the sand using a density separation technique and high- vacuum system to discriminate organic matter from the polymers. Microfibers are the most challeng- ing types of anthropogenic debris have microfibers in solution and to multiple hours of analysis for one to detect given their small size and filter the solution for the quantification single sample as opposed to a couple the facility in contaminating the of the fibers retained by the filter of minutes for the fluorescence samples. Water, rain, and snow sam- (usually a 0.45 μmGFF).Thiscan counterpart method. Ultimately, the ples can be filtered using glass fiber be done optically in fluorescence choice of the analytical method used filters (GFF) and nonsynthetic mate- (excitation 390 nm, emission >420 depends on the questions asked and rials followed by stereomicroscopy nm) to help detecting and quantifying the time and resources available for for quantification. Given the ubiqui- the fibers (Figure 3). This is a “fast and the analyses. tous nature of microfibers in air, the easy” method used in the laboratory, Coriolis bio-aerosol sampler (Bertin which, however, lacks the details Technology; https://www.bertin- of providing information about the instruments.com/; Figure 6) shows to plastics material being analyzed Removal of Plastics From be the current method for quantifying (the chemical nature of the plastic the Environment airborne particles, which works for and thus its identity). Alternatively, In use, plastic does not pose a sig- microfibers as well. Sediment/soil optical methods providing the poly- nificant threat; rather, the issue arises collection and extraction is the most mer identification include Fourier- from the by-products created from tedious methodology of all where the transform infrared (FTIR) and Raman the fabrication and the disposal and extraction process takes many hours spectroscopy imaging, but process- degradation of plastic. Given that plas- per sample. Ultimately, the goal is to ing time is lengthy and may take tic debris has been accumulating in the

September/October 2019 Volume 53 Number 5 17 environment since the 1950s (Geyer (https://oceanconservancy.org/trash- org/) develops a Floating Robot for et al., 2017) and degrading due to free-seas/international-coastal-cleanup/ Eliminating Debris. In contrast, weathering processes, its removal to volunteer/) occurring every year in Resynergi (http://www.resynergi. avoid further negative effects is a high September began more than 30 years com/), together with the Ocean Legacy priority. Indeed, large efforts from all ago, when communities rallied Foundation (https://oceanlegacy.ca/), over the globe are focusing to find together with the common goal of developed a system where plastics can ways of removing plastic debris from collecting and documenting the trash be converted into fuel (oil) by chemical the environment; but again, the size, littering their coastline, and is a microwave-assisted pyrolysis directly the location, and the type of debris platform that can regroup all NGOs on the collecting vessel. will drive the technique used. worldwide. These are few of the many projects River/stream cleanups (targeting Ocean cleanup projects, although entrepreneurs and philanthropic and mainly macroplastics) are a removal logistically more complex, are getting environmental foundations are brain- technique adopted by different non- more prevalent since a large part of storming about, giving hope that a governmental organizations (NGOs) the debris is found in the ocean. collective effort can be coordinated that intend to stop the debris from The large-scale project “The Ocean to clean up our oceans of macroplastics. reaching water systems and eventually Cleanup” (https://theoceancleanup. As for the microplastics, although make their way to the ocean. The River com/) consists of a floating screen most of the above-mentioned projects Cleanup, (https://www.river-cleanup. that sits at the surface of the water could include their removal as well, org/en), the Plastic Soup Foundation and traps and concentrates marine most systems are not exclusively de- (https://www.plasticsoupfoundation. debris. The floater provides buoyancy signed for it. Microplastic-targeted org/en/psf-in-action/clean-rivers/), to the system and prevents plastic from projects are less common given the the Royal Ecosystem (https:// flowing over it, whereas the 3-m-deep increase in technical and instrumental wasteecosystem.com/river-cleanup- skirt stops debris from escaping difficulties given the small size of the processor.html), and several other underneath. Many other ongoing plastic objects. In addition, microplas- NGOs also include river cleanups in projects intend to create devices to tics do not necessarily float and can their agenda. Engineering projects such remove plastic from the open ocean, sink to the seafloor sometimes more as Mr. Trash Wheel (https://www. such as The Seacleaner (https:// rapidly than macroplastics, making baltimorewaterfront.com/healthy- seacleaners.com/) and Ocean United the collection of microplastics from harbor/water-wheel/) in Baltimore (https://oceansunited.org/). These sediment (instead of water) the focal ef- also designed a device to harness the projects are usually a two-way fort of new technologies. Projects such power of water and sunlight to collect approach, where the Phase 1 of most as Hoola One (https://hoolaone.ageg. litter and debris flowing down of these projects is to remove the ca/en/the-project-2/) and, on a smaller the river and prevent this debris debris from the ocean and the Phase 2 scale, Seeds (https://seed.world/ from reaching the ocean. Smaller is to reuse this plastic, using, for educating) are specifically designed to devices are also designed to be left example, pyrolysis technique onboard use the buoyancy of the floating passively in rivers and harbor to the vessels to create biofuel, or to plastic to separate microplastic from trap trash floating downstream ship the material to the closest organic matter and collect only (https://seabinproject.com/, https:// recycling facilities on land. Effort on anthropogenic material. rivercleaning.com/). new technology is to minimize the Regarding microfibers, fashion Beach cleanups are the most com- transfer back to land and perform and textile industries are important mon technique for removing plastic direct recycling on board of the polluters, and given that 60% of debris that are either discarded from collecting vessels, such as proposed our clothes are synthetic, it accounts the local community or redeposited by Freylit (http://www.freylit.com/), for a major fraction of plastic found and from oceanic origin. NGOs con- which consists in a Catamaran with in the environment. However, the re- ducting such activities are numerous floating flap skimmer system to moval of the current microfibers worldwide and the list would be too ex- remove and compact plastic waste found in the environment is practi- tensive to be presented here. However, from the sea. Similarly, Clear Blue cally impossible given their small the International Coastal Cleanup Day Sea (https://www.clearbluesea. size and the limitation in terms of

18 Marine Technology Society Journal in situ detection techniques. So far, it with the loss of certain performances and consisting in a water bubble made seems technologically impossible to (in exchange to degradability). How- of seaweed. Shower-friendly paper is remove microfibers from air, water, ever, these innovations are poorly outer recyclable, card recyclable, com- or sediment on a large-scale effort, talked about, often because they are postable, glue free, and water resistant. leaving thus the idea that the focus confined to local/regional interests The inner liner is made with recyclable should be rather on limiting the and/or because the dominant plastic plastic and uses 60% less material than input of new microfibers in the envi- industry still has the cutting edge on regular plastic bottles. Stone paper and ronment. To that extent, Filtrol the public use of plastics for comfort plastic is an innovation that has several (https://filtrol.net/) has developed values that have been set by the high possible packaging applications and a filter for washing machines that performance of the material. Never- can be used as a paper or plastic alter- has proven to capture >90% of micro- theless, the alternative innovations native, being printable, recyclable, and fibers from the washing process. More keep on growing. waterproof. It is made from calcium technologies will probably emerge to In relation to macroplastics, SUP is carbonate that has a production pro- expand further the idea that each often the first behavioral change that cess using less water, has a lower car- household should reduce its impact comes to the mind of consumer to bon footprint, and is more energy on the environment as opposed to eliminate plastic from our daily life. efficient than regular paper produc- reply on larger public systems (i.e., SUP is an easy fixsincetheseitems tion. This can be used for making waste water plants) that get over- can easily be replaced by alternative paper (supermarket singlet) bags, take- whelmed by numerous kinds of items. However, when it comes to away food cartons, greaseproof paper contaminants and cannot single out durable goods, the alternatives are wraps, as well as Ziplock® bags. Palm macroplastics, microplastics, and very limited, and also the price is leaves use areca palm to create the oys- microfibers from flowing into our often too high for the average consumer. ter-like cases for handmade soaps. The coastal waters. Similarly, an increasing For SUP, there are now many plastic leaves fall naturally from the areca number of industries have started to alternatives being developed, and the palm and then are collected and work on alternative materials to following innovations are the most molded into the desired shape with a plastics that show similar material common plastic replacement materials. final biodegradable packaging. Corn properties but are fully degradable Plant-based plastics, also commonly starch and sorghum loose fill is made and clearly have less environmental referred to as bioplastics, are made from corn starch or sorghum (a crop impact by the simple fact of decaying from a variety of sources such as similar to popcorn) and can be used well into nonhazardous structures or corn, which is broken down into poly- the same way as regular polystyrene molecules. lactic acid (PLA). PLA can be used to loose fill. Edible six-pack ring is biode- make drinking bottles, various food- gradable, compostable, and edible and grade containers, as well as films (plas- made of barley and wheat remnants, tic wrap for food). Mushroom root which are a by-product of the brewing Is There an Earth-Friendly (Mycelium) is also used for alternative process. Silberboard-metalized paper is Alternative to Plastics? packaging items and to gather agricul- developed as a sustainable alternative This might be the Gold Rush to tural waste, which is mixed with the to traditional composite metalized pa- plastic research: Can we synthesize mycelium in molds. Bagasse is a by- pers and boards and both recyclable or find in nature a material that product of sugarcane processing, and and compostable. Wood pulp cello- could have properties close to those due to its malleability and stickiness, phane is the sustainable younger brother of plastics, yet showing complete deg- it can be easily molded into packaging of cellophane, which is made from radation in the environment and suitable for food delivery and food ser- Forest Stewardship Council-certified therefore having lesser impact on the vice, similar to polystyrene. Most ba- wood pulp and certified biodegrad- wildlife and humans? There are many gasse items are certified biodegradable able. It can be used for fresh produce innovations being put forward, some and compostable. Seaweed water bubbles and dairy, snacks, coffee, tea, choco- more disruptive than others, showing have been created to provide the conve- late, confectionery, as well as home that there are material solutions, but nience of plastic bottles while limiting and personal care items. Prawn shell that there needs to be compromise the environmental impact, being edible, plastic bags are made from chitosan

September/October 2019 Volume 53 Number 5 19 from prawn and crab shells, which are relatively independent from any cycle Authors: usually a waste product. Although not of the plant source is in the cellulose- Sarah-Jeanne Royer and commercialized, the material has the based materials, such as Tencel® or Dimitri D. Deheyn potential to replace plastic in packag- Veocel® from the Austrian company Marine Biology Research Division ing for food and drinks. Finally, milk Lenzing (https://www.lenzing.com/). Scripps Institution of Oceanography plastic is made from casein, the protein The products from this company are University of California, found in milk, and combines the pro- made entirely of cellulose (extracted San Diego tein with clay and a reactive molecule from trees) and show biodegradability 9500 Gilman Drive, (glyceraldehyde), which makes the properties, while still showing La Jolla, CA 92093-0202 plastic much stronger but still bio- attractive material properties closer to Email: [email protected]; degradable. Further options to those of synthetic fibers in terms of [email protected] macroplastics are probably found performance, although with the added elsewhere or will probably emerge side to being natural and hence likely soon. The remaining issue is to be degradable in nonharmful products. References able to scale up these innovations for The ability of mass production seems Geyer, R., Jambeck, J.R., & Law, K.L. 2017. the world market. to become a selective criterion for any Production, use, and fate of all plastics ever made. As for microplastics, especially pri- eco-friendly alternative to plastic, SciAdv. 3(7):25-9. https://doi.org/10.1126/ mary origin ones (i.e., microbeads in considering the size of the market to science.1252826. cosmetic products), these materials be able to supply. Kooi, M., Reisser, J., Slat, B., Ferrari, F.F., can be completely removed or, for ex- Schmid, M.S., Cunsolo, S., … Koelmans, A. ample, other natural material such as A. 2016. The effect of particle properties on fine grain of sand (silica), sugar, or Conclusion the depth profile of buoyant plastics in the other “natural crystals” can be used as The science of plastic is booming, ocean. Sci Rep. 6(October):33882. https:// areplacement.Preproductionplastic and although there are many aspects doi.org/10.1038/srep33882. pellets are one of the main concerns currently being developed and imple- Magnusson, K., & Norén, F. 2014. Screening fi in terms of primary microplastics, mented for detection, analysis, and nd- of microplastic particles in and down-stream and alternative products are similar to ing solutions for alternative materials, it a wastewater treatment plant. IVL Swedish the ones above mentioned in regard to is widely accepted that we are just at the Environmental Research Institute, Report No. macroplastics. onset of the plastic science and many C 55, 22 pp. https://doi.org/naturvardsverket- With regard to microfibers, the sit- more innovations are still to come. 2226. uation is different, because microfibers fi This eld of science is starting to identify Napper, I.E., & Thompson, R.C. 2016. fi have been generated for centuries as a itself and to nd its own set of stan- Release of synthetic microplastic plastic fibres natural product from animal fur and dards and parameters, but more im- from domestic washing machines: Effects plant products (e.g., cotton, hemp, portantly its own instrumentation for of fabric type and washing conditions. Mar silk, plant fibers) and only recently (in fieldwork as well as laboratory analyses. Pollut Bull. 112(1-2):39-45. https://doi. the past 40–50 years) been replaced by org/10.1016/j.marpolbul.2016.09.025. synthetic fibers. The production of nat- ural fibers is still ongoing but, of course, Acknowledgments is more limited because it depends on This work is being supported by plant resources as opposed to synthetic the BEST Initiative (Biomimicry for fibers that rely solely on oil-based source Emerging Science and Technology and associated chemistry. Initiative), which is a platform facili- One “innovation” that is several tating the interaction between acade- decades old already but that is gaining mia and industry (https://deheynlab. momentum because it is associated to ucsd.edu/best-2/) for fundamental the possibility of “mass production” research on nature-inspired solutions.

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