Introduction
Plastic is extensively used in aquaculture. Its strength, durability, flexibility, tensile and waterproof properties, in addition to the low cost of this material, make plastic optimal for diverse applications in the industry. However, Scale Aquaculture, as a technological supplier, recognise that marine litter, and especially plastic pollution, is a major environmental problem. It is important for us to work with reducing emissions of plastic in nature and increasing the recycling of our products.
In the aquaculture industry there are about 192,000 tonnes of plastic in use in sea-based aquaculture in Norway. About 16,000-29,000 tonnes of this amount is plastic waste annually (Hognes and Skaar, 2017). There is a need to increase the recycling rate of the plastic equipment and derive the most value from resources during their lifetime Additionally, the Directive (EU) 2019/904 on the reduction of the impact of certain plastic products on the environment includes i.a. requirements for producer responsibility schemes for certain plastic products, including equipment from fisheries and aquaculture industry. The directive requires equipment suppliers to have solutions for collection, reuse and recycling of plastic equipment.
Lost equipment as consequence of storms, wear and tear of plastic materials used in off-shore farms generate large amounts of plastic waste to the surrounding regions of the farm (Lusher et al., 2017). Plastic waste from fish farming has been found along the Norwegian coast. Ropes were the major polluting materials, but parts of other plastic equipment such as feeding pipes, walkways, and floating collars were also found (Vangelsten et al., 2019). In addition, weathering of plastic equipment at the fish farms can release microplastics and contribute, to another extent, to the microplastic pollution in the marine environment. Recent studies have estimated the amount of microplastics released from materials used in fish farming. In 2020, a study assessed the abrasion of feeding pipes caused by the fish feed pellets to analyse the amount of microplastics released (Gomiero et al., 2020). Results showed that aged and curved pipes had higher abrasion rates compared to new and straight pipes. Aged pipes released 2 to 3 times more microplastics than new pipes. In average, abrasion of the feeding pipes was estimated to release 0.24 g of microplastics per meter of feeding pipe and per day. Some reports estimate that up to 200 tons of microplastics per year are release from feeding pipes (Vangelsten et al., 2019).
Small microplastics (< 50 μm) can affect marine organisms like reduced food intake, delayed growth, and decreased efficiency of the immune system of the organisms affected (Abihssira-García et al., 2020). As for other equipment used in fish farming, there is no detailed information about degradation rates or microplastic release as far as we know. Though, it has been roughly estimated that the degradation rates of plastic in the Norwegian marine environment is less than 0.5% per year (Booth et al., 2017).
We will present the work that Scale Aquaculture is doing regards to reduce emissions of plastic in nature from fish farms both regards to micro- and macro-plastic. We will give examples on possible technological solutions. Results from an ongoing project called Circular plastic products for sustainable aquaculture (“SPARE”) will also be presented.
Results
The main objective of the project “SPARE” is to increase the proportion of recycled plastic in several of our products used in the aquaculture industry. In 2021, we mapped out the material flows of plastics in the company’s value chain, all the way to post-use in the fish farm and subsequent recycling. Our estimates show that we currently recycle around 42% of our plastic equipment, an amount we want to increase. As an extension of this study, we conducted a pilot project where we collect one discarded floating collar and produced 17 tons of recycled plastic pellets. After grinding and extrusion, the re-granulated was analysed and characterized to find the most suitable area of application. Relevant analysis like strength calculations, durability, tensile strength was carried out. We are now using these recycled plastic pellets to produce new plastic-based equipment for the aquaculture industry. Testing and documentation of full-scale pilot installation of selected products made from recycled material is now being carried out.
In the aquaculture industry, air-based feeding is typically used, but during the last years water-based feeding is becoming more common. Water-based feeding systems represent a key solution for the reduction of microplastic emissions. At the end of 2021, we developed and launched our new barge with subsea/ water-based feeding technology. After testing subsea/ water feeding through pilots in both Tasmania and Norway, we experienced promising results on several parameters such as no microplastic emissions, less noise, reduced energy consumption and increased feeding capacity.
A more detailed presentations of the results will be given.
Acknowledgement
The project “SPARE” is partly funded by Norwegian Retailers’ Environment Fund. The work in the project “SPARE” is done in collaboration with Norner Research AS and Hallingplast.
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