Planet 4 min
Plastics for the aquaculture of the future
Closely linked to the development of aquaculture, the plastics industry is now at the forefront of recycling of the waste and by-products generated by such activities.
Plastics for the aquaculture of the future
Plastics for the aquaculture of the future

Plastics sell themselves at the fish auction

Sophisticated design for shellfish and crustaceans

First introduced in the 1960s in the specialised fishing and shellfish aquaculture industries, plastics have definitely replaced traditional materials. Even the metal used in the structures of fish pots is coated in plastic. 
Plastics offer many benefits for these difficult activities that are often practiced in hostile environments. Their lightness enables them to be moved around easily. Resistance to abrasion and oxidation also contribute to increased durability for traps and shellfish aquaculture equipment. 

In terms of productivity, the benefits of thermoplastics for potters and shellfish farmers are mainly linked to transformation processes. They make it possible, for instance, to compensate for the disadvantages of the too-smooth surfaces of plastics by moulding profiles into mussel farming equipment. Combined with 3D design, injection-moulding processes can now create increasingly sophisticated pots. The traps are made using various polymers, and are now better adapted to local fishing conditions and techniques, and in particular to the species to be caught.

 

Relaxed crustaceans, thanks to Innopure

Unlike fish catches which are distributed through the cold chain, shellfish and crustaceans, and some fish products, must reach stalls alive. The fishmongers' or restaurants' tanks, now fitted with methacrylate glazing, are not simply decorative showcases, but the end-point of a very special logistics chain in which plastics have a major role: ensuring water-tightness and oxygenation.
It first requires storage equipment: on-board potters, such as watertight polyester storage bins with continuous filling systems, and open landing tanks made from high density polyethylene. 
Upon landing, the shellfish and crustaceans are given specific treatments using equipment ensuring oxygenation at all stages of the distribution circuit.

One of the most innovative of these, is the surprising tanks developed by EMYG Environnement & Aquaculture. The Innopure system uses a filtering micro-bubble generator and a closed, or open, polyester bin, available in various sizes, which can be used for storage or transport. It is able to reproduce the characteristics of the marine environment with astonishing accuracy: water flow, temperature, oxygenation and filtration. It enables shellfish and crustaceans to retain their usual behaviour: absorbing the oxygen from the water, and decontaminating themselves in the best conditions.

The main benefit is the system’s low power consumption: 1.5 watts per hour are required to operate the small electric rotor attached to the Plexiglas cone above the plastic generator. The process is used for large fish farming tanks, but it can also be fitted to smaller tanks, enabling crustaceans to be transported in containers by truck, or by ship, over very large distances

 

Biodegradable plastics to fight "phantom" fishing

The impact of "phantom" fishing equipment at sea is a concern shared, by the stakeholders fighting to protect the environment, and, many professional fishermen. While the former send out warnings, and rightly so, about the destruction of biodiversity, caused by lost or abandoned nets and traps, the latter strive to devise solutions. 
Some fisheries in Canada and New Zealand, for instance, advocate the use of pots and traps with lids, made from biodegradable plastic, which enable the trapped animals to escape in the medium term. 
In France, the Breton Seabird company, specialising in developing and manufacturing products made from bioplastics, is focusing on its slow-biodegradable polyester monofilament.

The polymer can be used in various types of fishing equipment, nets, pots, and others, and enables the equipment to be used normally for at least ten years. After ten years, the polymer only degrades in special conditions of prolonged immersion, under the action of marine microorganisms. Perfectly aware of the limitations of the process as regards quickly curbing the impact of "phantom" fishing, the company aims to further develop the concept. Thanks to a miniature radio-identification device, for instance, which would enable quicker recovery.

Plastics come out of their shell

Shellfish aquaculture generates a large quantity of by-products: waste from cleaning the farms, stillborn shellfish and those that fall victim to predators. Every year, the industry's professionals are faced with the task of eliminating hundreds of thousands of tonnes of waste, which is all the more undesirable, as it also harms the touristy image of coastal areas. 
The Kervellin plant, located in Brittany, had developed various recycling processes to address this problem. 
Specialising in the manufacture of algae and shellfish-based fertilisers since the 1960s, it diversified its business with the help of the Brittany Materials Engineering Laboratory (Laboratoire d’Ingénierie des Matériaux de Bretagne - LIMATB) and several of the region's other manufacturers. Their research programme led to the development of a powder, based on calcium carbonate, the main component of the shells of marine animals, which can be used as a chemical and mechanical reinforcement matrix for various polymers.

Christened Ostrécal, this natural ingredient, derived from the local oyster aquaculture, is a perfect substitute for the mineral filler extracted from quarries and used by paint manufacturers. Starting in 2007, it became the go-to product for road markings thanks to its structuring and whitening properties.
More recently, the product also found success in the plastics market. It was used in the composition of the new biodegradable Istroflex filament for 3D printing developed by the Nanovia company as it provides the polymer with properties suited to manufacturing parts requiring very little elasticity and good flexibility, such as shock absorbers, vibration absorbers and joints. Decathlon was also able to make use of these properties in the walking shoes in its Solognac imprint, whose soles are made from a thermoplastic filled with Ostrécal.

 

A future for crustacean shells ?

Chitin, the main component of insect and crustacean shells, and its derivative chitosan, are, the second most abundant biopolymers on earth after cellulose. These polysaccharides are increasingly used around the world as a result of their antimicrobial and antioxidant properties, and their biodegradability. Used in cosmetics and in the pharmaceutical industry for coating medicine, they are also used in the manufacture of biocompatible medical devices and a textile fibre similar to viscose.
Given its availability, this polymer has been the source of much hope in the bioplastics industry. However, the industry's hopes were somewhat dashed by the environmental impact linked to extracting chitin, which is currently mainly done in China and India. The process works through dissolution in an acid and then in an alkaline solution, and is simple and inexpensive. However, this does not take into account the polluting discharge from the process.

Several alternatives are currently being studied, such as Ifremer in France, and Germany has the European ChiBio project aimed at industrialising the extraction and refining of chitin by enzymatic means, using yeast. The German Evonik Industries company which processes the oils obtained using this process has a demonstration project which has produced a transparent polymer which can be transformed using conventional methods of plastic processing.

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