Washed up at sea but not wasted

Materials World magazine
30 Apr 2017

Ian Falconer looks at both sides of the coin when it comes to recycling plastics from the sea and how new work could turn recycled marine plastics into consumables for 3D printing. 

When we think of plastics in the marine environment, perception seems to divide along well defined lines. The undoubted value to a myriad of different plastics used in fishing equipment, boat-building and ocean-based structures from piers to oil rigs and wind turbines is sometimes seen as being in direct opposition to obvious damage to marine ecosytems attributed to loose plastics within the natural environment. Rather than dividing opinion, new business models built on the circular economy concept could help to clean oceans and provide a safe, reliable income for coastal communities.

It’s hard for anyone to ignore pictures of a turtle or seal wrapped in a piece of marine litter. Unsightly slicks of plastic litter are drawing increased attention from coastal communities and global non-governmental organisations. But damage to macrofauna isn’t the biggest problem with a growing amount of plastic that is finding its way into the oceans.

The majority of polymers with neutral or positive buoyancy will be subject to UV, physical and chemical degradation, gradually breaking them down into smaller pieces until they reach microplastic size. As they approach this size, ingestion by fauna near the base of the food chain results in well recorded accumulation in higher organisms, such as seabirds or predatory fish. Prolonged exposure to degraded plastics can cause both physical and biochemical damage to the internal organs of sea life. But the long-term impact of microplastics on ocean ecosystems is less understood and is an ongoing area of research.

Polymers and other pieces of marine litter with negative buoyancy are making their way to the sea floor and being included in the sediment column. Very little is known about their impact in this context, positive or negative. Evidence from the JPI Oceans research programme in 2016 measured the potential impact of deep ocean mining, suggesting that metallic nodules can provide for an increased density of ecological activity. 

JPI Oceans, an intergovernmental EU intiative, conducted a species count of undisturbed sea life fauna (no flora at this depth). They then removed sea floor metal nodules that occur naturally in the area and left the area undisturbed for a decade before repeating the survey. The density of sessile organisms was far reduced. The only difference was the lack of solid metallic nodules located at the surface. Sessile organisms require a solid substrate to grip onto in shallow high-energy environments. The deep ocean is not a high-energy environment but the requirement for a solid grip on something does seem to be a recurring requirement for similar types of organisms, irrespective of whether they are shallow or deep. To further control the experiment, deep-sea critters would need to be analysed. However, because they are specialised to live in the deep sea and tend to die if brought to the surface, this cannot be done easily. So, while the data suggests that these organisms require a solid surface to grip onto and thrive, their real-world location means it is really difficult to prove a causal relationship. This is not an argument to throw dense plastics into the deep ocean, but rather a comment on the complexity of living relationships across a vast volume of the Earth’s living space.

Public coasts

The greatest portion of the environmental side of the marine plastics argument, by volume, covers areas of deep ocean where the recovery of plastics isn’t and probably never will be economic. Retrieving litter with a remotely operated underwater vehicle can require a support team of up to 30 people. This is the case for the vast majority of plastics currently situated in the water column and the shallow sediment, and makes it all the more important to prevent litter from entering these areas in an uncontrolled manner. There are ongoing initiatives attempting to address marine plastics at or close to the surface. 

The UK Government has opened a consultation on microplastics as well as proposing a ban on the sale and manufacture of products containing microbeads that classify as rinse-off items, such as shower gel, face scrubs and toothpaste. The proposed bans on cosmetic products including microbeads is certainly one approach welcomed by campaigners and the fishing industry alike. Officials from the Cosmetic Toiletry and Perfumery Association have called for microbeads to be removed from cosmetics by 2020 under voluntary agreements.

In February, a search of 279 beaches around the UK found that 73% were littered with tiny plastic pellets known as ‘nurdles’. The term covers both the raw granular material used by industry to make new plastic products and plastics that have reached a similar size having fragmented in the environment. The largest number recorded in the Great Winter Nurdle Hunt weekend were found at Widemouth Bay in Cornwall, where 33 volunteers from the Widemouth Task Force collected about 127,500 pellets on a 100-metre stretch of beach. Results from the hunt will be fed into the Government’s consultation on microplastics.

Another effort made by The Ocean Cleanup Project, funded by the Dutch Government, aims to deploy oceanic booms and supporting technologies to find and gather floating litter. This is also an area where private businesses and the circular economy concept start to have some potential. 

Unknown sources

The complicating issues for business, as with all plastics recycling, are consistency and quality. Consistency because ocean processes both mix and sort plastics on a physical, chemical and temporal basis. Quality because there is no means to control the external source of the plastic items, the time or type of environmental exposure, or in some cases the exact collection location. These factors are especially problematic where plastics meet the coastal environment itself. Sources of marine plastics are highly variable and closely linked to immediate and identifiable human behaviours or weather conditions. A beach that catches a tide of pink plastic bottles after one winter storm, as was experienced by Poldhu, Cornwall in early 2016, might only do so for one season or a flood of cheap polystyrene bodyboards might only happen in a few weeks of each year. In both cases, the polymers come from known sources and the company whose pink bottles were washed up contributed to the costs of cleanup, but not all plastics are so easily attributable.

A ten-year study, Marine anthropogenic litter on British beaches: A ten-year nationwide assessment using citizen science data of coastal litter collected from beaches around the UK by Plymouth Marine Laboratory, UK, showed that 42% of attributable items came from land-based sources, mainly public littering, and 18% from marine-based sources including fishing. Public littering is already a focus of significant funding and activity by local authorities and public campaigns, but industry is also engaged. Initiatives such as Fishing for Litter are designed to reduce the amount of marine rubbish in the sea by working with fishermen to remove litter caught during commercial activity, and industry participants such as Newlyn Harbour are working to collect and recycle marine plastics. 

The study reports that the cost to the UK fishery from damaged equipment and lost time incurred by dealing with marine litter is around £10m a year, and removing beach litter costs £15m a year. These figures do not include a significant amount of volunteer beach cleaning that happens around the UK coast under initiatives such as the Two Minute Beach Clean or by local groups caring for specific stretches of coastline, including Rame Penninsular Beach Care.

Fishy filaments 

What none of those organisations and individuals can do is embed the recycling of marine plastics that they collect within the local economy. Only an economically viable recycling business can do that, and the economic part of that equation has been problematic. Technically, we could build a highly capable, multi-material recycling plant optimised for marine plastics, but the recyclate arising from such a plant would be variable in both quantity and quality, limiting its value in the global recycling trade. Even if it were practical to operate and maintain the monolithic super-plant, it would struggle to make a profit when competing against new raw plastics.

However, if you turn the paradigm around, away from global flows of standardised recyclate and competition with the global oil price and towards localised production of end-user items that can either be used in the local economy or exported as a finished product, then the economics of the recycling operation itself changes substantially. Smaller modular plants that tackle a specific waste stream at a local or regional level start to look more attractive.

A new business model developed under the Creative Metallurgy concept, the Fishy Filaments project, is designed to take used fishing nets collected from the Cornish inshore fishery, the Newlyn Harbour and Pier Commissioner’s Office and Fishing for Litter. The process is simple – the nets are sorted and components separated to remove non-recyclable portions. The material is then shredded, washed to remove excess salt and biofouling, dried and finally thermally reformed into a larger diameter filament that 3D printers can use. Other parts of the fishing equipment can be used in packaging, but the relatively high value of the 3D printer filament pays for its processing costs and the end wastage is minimal. 

Looking further into the possibilities of recycling lower-value marine plastics – perhaps those already highly degraded by time and tide – operation at a local scale becomes increasingly important as transportation and administration costs start to take an economic toll. But even then, as long as the end product meets or exceeds minimum design standards, there is no reason to avoid recycling marine plastics. The challenge posed by any new plastics economy is not so much in the recycling and its technology but the location of suitable markets to serve at appropriate scales.

Ian Falconer is Vice President of the Cornish Institute of Engineers at IOM3 and founder of Fishy Filaments, UK.