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Prosjektnummer: 901658
Status: Pågår
Startdato: 15.01.2021
Sluttdato: 15.01.2023

Reduction of Microplastic Emission through System optimisation of Feed Pellet Conveying Pipelines (MICRORED)

The fisheries and aquaculture industry contribute to emissions of microplastics into the sea, which may potentially have negative consequences for the marine environment and living organisms. The release of microplastics from the fish feeding pipes has been recognized as one of the contributing factors to the pollution of the sea water, with implications for seafood safety and potentially human health, lowering the consumer confidence in seafood products.

In larger fish farms, the fish feed is typically transported by means of compressed air from the storage point to several fish cages through a network of transportation pipes that are typically made of plastic, mainly HDPE (high-density polyethylene). The use of unnecessarily high air flow volume rates accelerates the pellets to a high velocity, causing hard impacts with the internal wall of the pipe, especially in bends and curved sections, with directional change of pellet conveying path. Depending on the fish feed properties (hardness, shape, size, surface texture), this can result in potential problems with negative economic and environmental consequences:
1) excessive erosion (abrasion) of the pipe surface and faster wear that lead to more frequent replacement of the pipeline;
2) significant breakage of the pellets leading to local pollution and loss of valuable and costly feed; and
3) higher rates of microplastic release into aquaculture facilities and further into the wider environment.

On the other hand, use of too low air velocity may lead to pipe blockages and pellet breakage due to compressive stress. Optimization of feeding system operating parameters is therefore key for ensuring minimal release of microplastics from the feeding pipes, maximising the lifetime of the pipeline and for delivering intact, undamaged pellets to the fish.

This project is directed towards the FHF 2020 call Tiltak for å redusere utslipp av plast fra sjømatnæringen (‘Measures to reduce emissions of plastic from the seafood industry’). The aim of the call is to gain knowledge on measures and best practices that the industry can implement to reduce emissions of nano- and microplastics from fish feeding pipes.
Main objective
To optimise the feed pellet conveying systems, technology and costs in fish farms to minimise microplastic emissions and maximise pipeline lifetime and pellet integrity.

A. To evaluate the effect of air velocity and pipeline configuration (bend radius) on pipe wall erosion for selected fish feed qualities.
B. To quantify the amount of micro- and nanoplastic (MNP) fragments from objective A and characterize their physical properties (size, shape).
C. To map the erosion pattern and evaluate the evolution of erosion with application time.
D. To implement the results in a simulation software for a selected industrial site to demonstrate how the feeding system can be optimized.
E. To disseminate the learning from the project and present the methodology for optimization of the feed pellet conveying systems to the fish farming community.
Expected project impact
With optimization of the fish feeding systems, the conveying system providers will be able assure significantly reduced emission of microplastics from the fish feeding pipes into the marine environment while at the same time, additional cost savings to the fish farming industry will be achieved due to less frequent pipe replacement, lower degree of fish feed pellet breakage, and less energy used for pellet conveying. Deeper understanding of the chemical and conformational change of the pipeline material in the presence of residual feed ingredients will provide insights in the design of more wear resistant materials, which is especially important for the pipe material producers. A reduction in the levels of microplastic exposure have the potential to reduce contamination and therefore increase both the quality of products and consumer confidence in them.

Project design and implementation
The project work will be divided into four work packages (WP's):

WP1 – Conveying pilot tests
Work package leader: SINTEF Industry (SINTEF Tel-Tek group)

Under WP1, it is proposed to carry out pneumatic conveying tests in the pilot-scale test set-up at SINTEF Tel-Tek, implementing HDPE pipes and testing selected fish feed qualities. Based on recommendation from the industry (e.g., Skretting), and their information on the physical and mechanical properties of the pellets, two fish feed pellet qualities with low and high erosion potential will be selected for the conveying pilot tests. The tests will be performed under different conveying conditions and the amount of erosion will be evaluated for each test by:
1) quantifying the weight loss in pipeline material by weighing selected pipe segments inserted in the straight and bend sections before and after each test; and
2) characterizing the microplastic fragments (described in more detail under WP2).

The eroded pipe surface retrieved from the experiments will be further analyzed by microscopic techniques in WP3. This will not only provide a realistic picture of the amount of microplastics potentially released into the environment from the feeding pipes of an industrial scale fish farm but also identify optimal conditions for pneumatic transport with minimized erosion, including minimum and maximum air velocities to be used with different types of feed and recommendations on the bend radius (linked to A. under Objectives). The test data, such as pressure drops, air volume flow rate, solids flow rate, etc., for different flow conditions, will be used to make a simple calculation/simulation program, which can be used to design a reliable full-scale conveying system and to optimize its performance in terms of conveying parameters and reduced erosion. This will be described in more detail under WP4.

Milestone: M1.1 – Input to final report on the flow behaviour of fish feed pellets and the pneumatic conveying parameters (M14)
Deliverable: D1.1 – Calculation program to optimize system performance (M14)

WP2 – Quantification and characterization of eroded pipe fragments
Work package leader: NORCE
Other contributing partners: SINTEF Ocean (Environment and New Resources), SINTEF Industry

Microscopy visualization of the MP and the mass estimation of NP fragments are especially important because the plastic fragments removed from the surface of the pipe are invisible to the naked eye making it difficult to estimate the degree of microplastic contamination of the pellets in the pilot-scale pneumatic conveying tests performed in WP1. Applied methods within the WP2 will foster the knowledge of the total amount, particle size distribution and morphology of the generated plastic particles in simulated feeding pipes abrasion tests performed in WP1 considering different scenarios (i.e., alternative pipe configurations, pellet velocity, type of food pellet used). The outcomes of the particle quantification and characterization performed in WP2 will support the implementation of the abrasion model (WP4) and will directly contribute to optimization of the feed hoses (configuration, composition) and feed delivery parameters to minimize particle generation and emissions in the aquaculture production process. Furthermore, the outcomes of WP2 will provide additional insights into the character of the MP fragments the fish are potentially exposed to during seafood production activities.

Task 2.1 – Samples preparation to analysis targeting fat removal, isolation, and fractionation
Samples provided by WP1 will be processed and split into microplastic and nanoplastic fractions prior to further dedicated sample preparation and analysis approaches. In the first step, the whole sample will be treated with surfactants (e.g., SDS, Triton X-100, Tween-20) in a water based dense solution to help extracting the plastic particles present in the fat layer present in the fish feed pellets. The dense solution will help separating plastic particles from the pellets. The obtained supernatant fraction will be collected and treated through a sequence of enzymatic and strong oxidizing treatments to reduce the presence of interferences hampering the sample's chemical and physical characterization. The obtained digestates, will be subjected to filtration using a combination of two certified stainless sieves having a mesh size of 300 µm and 20 µm to generate two microplastic fractions (D1 >300µm, 300µm >D2 >20µm) and a nanoplastic fraction (D3 <20µm). To QA/QC assess the efficiency of the sample's preparation procedure, samples will be spiked with fixed amounts of micron sized plastics fluorescent beads and the recovery rates in the final extracts from D1 and D2 fractions will be estimated by florescence microscopy. Furthermore, procedural controls consisting of all reagents used within the sample preparation and analysis phases will be analyzed for plastics contamination. The three fractions will then be processed as described in Tasks 2.2 and 2.3 below.

Task 2.2 – Quantification and characterization of eroded microplastic fragments
The assessment of the micron-sized plastic particles (MPs) will be characterized by a vibrational spectroscopy oriented analytical method. D1 represents a fraction with large fragments and will be quantified by Attenuated Total Reflectance (ATR-FTIR). While the fraction of the finer particles still in the micrometric range (D2) will be analysed through µ-FTIR imaging microscope. Obtained spectra will be compared with commercially and non-commercially available infrared spectra to identify the occurrence of plastic polymers and other organic material fragments in the sample. The combination of the introduced techniques will allow to gain accurate knowledge about shape and size of plastic particles in the range of >300µm to 20 µm as well as the total plastic fragments quantity and the relative abundance of each of the most environmentally relevant polymer types in the investigated samples. The results from this task will feed directly into optimising the configuration and composition of the feeding system (WP1), as well as model development (WP4).

Task 2.3 – Qualification of eroded nanoplastic fragments
There are currently no validated methods for the analysis of nanoplastic particles, especially in complex samples such as those that will be produced in MICRORED. During the project proposal preparation phase, several approaches have been considered for qualifying the presence of nanoplastics and achieving a degree of semi-quantification. After careful consideration, the project team believe that an approach focused on using HDPE additive chemical markers has the highest chance of providing meaningful data 18. In the first step of this task, the additive chemical profile of the HDPE feeding pipes will be determined using a combination of solvent extraction followed by gas chromatography (GC) and liquid chromatography (LC) instrumentation fitted with mass spectrometers (MS). The HDPE material will then be subjected to leaching assessment in water and surfactant to identify which of the additive chemicals leach and which are retained in the polymer matrix. From those retained in the polymer matrix (i.e., no detectable leaching observed) a small number will be selected and their concentration in the pristine HDPE pipe material determined. This data will then be used to quantify the amount of plastic present in the nanoplastic fraction of the samples produced in Task 2.1. To do this, the nano-fraction samples from Task 2.1 will be solvent extracted, cleaned up and analyzed using either GC-MS or LC-MS (depending on the target analytes). Standard in-house QA/QC approaches will be employd at SINTEF Ocean for general chemical extraction and analysis. This will include running a blank sample to check for contamination of the target chemicals to be measured. A reference chemical will also be spiked into the sample (D3) prior to any extractions so that extraction efficiency can be monitored and an estimate of potential losses of the target analytes during the sample handling process. A scanning electron microscope (SEM) will be used to examine the nanoplastic fraction produced in Task 2.1, and images will be recorded that provide information of size and shape of the nanoplastic fragments. The results from this Task will feed directly into optimising the configuration and composition of the feeding system (WP1), as well as model development (WP4).

Milestone: M1.2 – Input to final project report on quantification and characterization of micro- and nanoplastic (M17)

WP3 – Morphological investigation of erosion on pipeline surface and erosion evolution of pipelines
Work package leader: SINTEF Industry's Materials and Nanotechnology

The assessment of erosion of pipeline will include both microscopic morphology investigation and macroscopic physical property measurement (linked to C. under Objectives).

Task 3.1 Surface detection of eroded pipeline
The eroded pipelines that experienced different conveying conditions in the pilot-scale set-up (WP1) will be examined at selected sampling spots (bend and straight pipe). The samples will be treated with surfactant solutions using the same detergent as in WP2 to remove the accumulated feed residual. The surface topography of the inner wall of the pipelines will be investigated by white-light interferometry (WLI) and scanning electron microscopy (SEM) to map the roughness and erosion pattern of the surface. The acquired data will be used to visualize the erosion pattern of the pipeline under selected conveying conditions in WP1. Advanced microscopic techniques are a valuable tool providing additional information about the character of the surface damage on the pipe wall surface (e.g., depth of penetration, localized grooves or dispersed erosion) and thereby, complementing the results on weight loss obtained in WP1 and quantification of MP in WP2. Deeper understanding about how the surface erodes when a pellet collides with the surface at high velocity at different impact angles is needed for identification of the wear erosion mechanisms. The results of this task will feed directly into optimization of the fish feeding systems in WP4.

Task 3.2 Evolution of erosion in the pipelines
The deterioration of the surface smoothness in the eroded pipeline will lead to higher accumulation of the broken feed pellet residues on the pipe surface. The ingredients in the feed pellets that slowly permeate through the eroded layer will impose impact on the conformation of the pipeline materials and potentially react with some of the additives in the pipeline, which may accelerate the aging of pipelines and lead to the worsening of erosion. Deeper understanding of the chemical and conformational change of the pipeline material in the presence of residual feed ingredients will provide insights in the design of more wear resistant materials, which is especially important for the pipe material producers. Furthermore, the surface unevenness and material deprivation (weight loss determined in WP1 and quantification of MP in WP2) of the eroded pipeline induced by the mechanical erosion will lead to the stress concentration in certain spots along the pipeline under high pressure and intense impact of pneumatic transport, which results in the weakness of pipeline. The microscopic conformation change and mechanical erosion will be reflected on the macroscopically physical properties (e.g., tensile strength, elongation at break, and impact strength). The physical properties will be measured for both virgin and eroded pipelines to set up an initial correlation between the conveying parameters and the evolution of erosion and physical steadiness of worn pipes in WP1, which can be valuable for predicting the erosion crack propagation and potential lifetime of the pipelines. The results of this task will feed directly into optimization of the fish feeding systems in WP4.

Milestone: M1.3 – Input to final report on the erosion pattern and evolution of erosion with application time (M18)

WP4 – Implementation in fish farms (case study) and recommendations
Work package leader: SINTEF Industry (SINTEF Tel-Tek group)
Other contributing partners: all

From the results of the pilot-scale pneumatic conveying tests (WP1), a simulation software (in a LabVIEW executable file) will be developed based on the scaling-up technique. This software will allow prediction of the air conveying velocity and pressure profile along the pipeline with given input parameters for a given fish production facility (i.e., required transport capacity, available pressure and air volume flow rate, pipeline configuration, diameter and length). The resulting prediction of the pressure and velocity profile along the pipeline will be valid for the specific site, however, the methodology and the underlying calculations in the simulation software are generic and can be adopted to another site with a change of input parameters. The simulation software will act as a tool for the fish farming facilities to optimize the operating conditions while keeping the air conveying velocity within acceptable limits, i.e., below the maximum threshold to avoid excessive erosion and pellet degradation and above the minimum limit to avoid pipe blockage.

In collaboration with the reference group, a suitable full-scale feeding system will be selected in one fish production facility which will serve as a case study to demonstrate the feasibility of system's optimization for operation with minimized erosion (linked to D. under Objectives). The results of the case study together with additional findings from WP2 and WP3 will be presented to the industrial community through a workshop together with further recommendations for best practice (linked to E. under Objectives).

Milestone: M1.4 – Input to final report on optimization of full-scale feeding system - case study (M20)​
Dissemination of project results
Dissemination and communication of the results shall be carried out according to the FHF's guidelines described in the call. The results of the project will be presented at meetings with the reference group, two workshops and through scientific 
articles in peer-reviewed journal and/or popular science magazines. The aim of the workshops will be to share the knowledge gained through the project with the stakeholders from the fish farming sector (fish farmers, feed pellet handling system providers, plastic pipeline manufactures, feed pellet producers, etc.) and the same time, to get the feedback from industry in relation to the research plan and project findings. Information about the project and the main findings will be published on SINTEF's website and through FHF channels. The presentations and reports from the project will be open to the public and available for the use of FHF.