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Development of a Net Washing Machine for the Scallop Aquaculture Industry
Final Report
Island Scallops Ltd.
AIMAP-2010-P06
Table of contents
- 1.0 Executive Summary
- 2.0 Introduction
- 3.0 Background
- 4.0 Methods
- 5.0 Results
- 6.0 Summary & Conclusion
1.0 Executive Summary
The scallop aquaculture industry in British Columbia is in an expansion phase. The standard material employed in the ocean grow-out stage of farming is the cylindrical “lantern” net, which becomes quite fouled by the time the scallops are harvested. Fouled lantern nets must be washed before re-use, but no equipment is available that is specifically designed for cleaning these nets. The alternative is to manually clean the nets or to purchase new nets for each crop cycle. Neither of these options is economically viable or environmentally sound as the industry expands and the number of nets increases.
The objective of the project was to develop the technology for cleaning lantern nets in an efficient and cost-effective manner. The technical approach was based on the results of prototype testing and consultation with the Japanese manufacturer of major components of the machine. Development focused on increasing operational efficiency and reducing production costs in order to increase sustainable production.
With the support of AIMAP funding, an innovative lantern net washer was successfully developed and tested at Island Scallops’ hatchery and processing facility in Qualicum Beach, BC. The final cost of the machine and accessory components was less than budgeted, the operational efficiency of the machine was greater than expected, and the projected cost savings was exceeded. Consequently, the new technology had a significant economic impact.
Successful development of the new technology also had a significant environmental impact. The machine effectively cleaned nets that were brought directly from the farm, eliminating the need to store fouled nets on land to allow fouling organisms to decay prior to cleaning. This mitigated odour and other environmental issues associated with increasing quantities of fouled nets.
Although further refinements are underway, the new lantern net washer has been incorporated into commercial production at Island Scallops. The machine has already benefited the company and accessibility to the technology will benefit the entire scallop farming industry. The capital cost of the machine may be prohibitive for small farming operations, but the Island Scallops’ net washer is currently under-utilized so available for cleaning nets from other growers.
Overall, the project goals were exceeded. Development of the machine addressed the gap in technology for cleaning lantern nets. It also provided an efficient and economical means of dealing with the increasing number of nets associated with the expanding industry. In addition, development of the technology improved environmental performance of the scallop aquaculture industry.
2.0 Introduction
In the BC scallop farming industry, scallops are typically cultured in cylindrical “lantern” net cages that are suspended in the ocean at deepwater farm sites. By the time the scallops are harvested in about two years, the nets are quite fouled with a myriad of marine organisms.
Lantern nets must be cleaned prior to re-use, but an automated lantern net washer is not available. The primary objective of the project was to develop the technology for cleaning the lantern nets employed in the BC scallop aquaculture industry.
The rationale for developing a lantern net washer at this time is that the BC scallop farming industry is in an expansion phase and increasing number of fouled nets are impacting not only production costs but also the environment. Cleaning the nets manually is not practical or economically feasible on a large scale. The standard practice of storing fouled nets on land to allow fouling organisms to decay creates odour and other environmental issues.
The basic criteria used for developing the net-washing technology were efficiency and cost of operation. The main goal was a machine that could clean lantern nets for a total operating cost of $6 or less per net. Lantern nets retail for about $28 each, so achieving this goal would represent a substantial savings over the cost of purchasing new nets for each crop. Using the nets for more than one harvest cycle would also reduce the environmental impact by decreasing the number of used nets in landfills by at least 50%.
The project was consistent with the following AIMAP innovation priorities:
- Sustainable production
Development of the net washer was an improvement to technology that increased operational efficiency and reduced production costs.
- Green technology
The net washing technology increased environmental performance of the industry by allowing the nets to be re-used. Cleaning the fouled nets also mitigated environmental issues of waste control and odour from decaying organic material.
- Species Diversification
The project involved technological development for farming scallops, identified as an alternate aquaculture species in BC.
3.0 Background
3.1 The Scallop Farming Industry in BC
On Canada’s Pacific Coast, there are no populations of scallops large enough to support a sustainable fishery. In the 1980s the federal and provincial governments conducted research aimed at developing a commercial scallop aquaculture industry in BC, and in 1989 Island Scallops Ltd (ISL) was established to commercialize the results of this research. Currently, ISL is the leading scallop farming company in BC and the sole supplier of scallop seed for the BC industry.
The industry mainly employs the suspended culture technique, whereby scallops are grown in net cages suspended from horizontal “longlines”. Typically, the longlines are submerged about 10 m below the surface in water about 30-40 m deep. In BC and other scallop farming areas of the world, two main types of net cages are utilized in suspended culture: pyramid-shaped “pearl” nets are used to rear scallop seed during the initial ocean nursery phase and cylindrical “lantern” nets are used for the final grow-out stage.
Over the last two decades, ISL has adapted the basic lantern net design to BC conditions. The custom net has more compartments (12) and is constructed of larger diameter mesh and stronger steel than standard nets used elsewhere in the world. This net is not only employed in large numbers at company farms but also supplied to other industry members, so is in widespread use in BC. An estimated 30,000 custom nets are already in BC and a projected 30,000 additional nets are required to meet the demands of the expanding industry.
3.2 Technical Approach
Japan and China are the world leaders in scallop farming. As a result, techniques and equipment specifically adapted to local culture methods and conditions have been developed in these countries. One such piece of equipment is an automated washer for cleaning pearl nets. ISL imported this machine from Japan and successfully utilized it to clean the pearl nets employed in the nursery phase of scallop farming in BC. However, there is no machine available that is specially designed for cleaning the lantern nets. The current project addressed this gap in technology.
The pearl net washer basically consists of a conveyor that moves the nets under a rotating head, where jets of pressurized water remove any debris. This machine did not effectively clean lantern nets for several reasons. The main problem was that the water pressure was insufficient to remove the firmly-attached fouling organisms on the lantern nets. In addition, the water jets did not penetrate all 12 compartments of the lantern nets. ISL subsequently developed a prototype lantern net washer based on modifying the existing pearl net washer. Successful results of prototype testing led to the AIMAP proposal to develop a commercial lantern net washer.
The technical approach of the project was to build on the results of prototype testing with the focus on increasing net washing efficiency and capability. One key issue that remained was cleaning lantern nets that were recently removed from the ocean (“fresh” nets). The prototype net washer did not effectively clean fresh nets, only nets that had been stored on land for a period of time to allow fouling organisms to decay. The practice of storing fouled nets before cleaning is widespread since decayed organic material is more easily removed than fresh material. However, this practice has become a social and environmental issue as the industry expands and the quantity of fouled nets increases. The technical approach to the problem of cleaning fresh nets was to increase pump capacity and water pressure.
Material handling was another key issue that remained after prototype testing. Handling the nets and debris was very inefficient using the prototype. The technical approach to this problem was to develop improvements for loading and unloading the nets, removing debris, etc.
4.0 Methods
Originally, the plan was to assemble the lantern net washer using components sourced from BC suppliers. The proposed design comprised a single power unit consisting of a high pressure pump driven by a diesel engine, a custom stainless steel conveyor, and custom rotating cleaning heads. However, following submission of the proposal, a more economical source of equipment was found in Japan. As a result of ongoing tests with the prototype and discussions with the Japanese manufacturer, the final design of the lantern net washer was altered and the major components were ordered from Japan. As manufacturer of the original pearl net washing technology, the Japanese source also provided valuable technical knowledge and expertise specific to the project.
Due to Japanese safety standards, the Japanese manufacturer would not fabricate the machine as originally proposed using a single large pump/diesel engine unit. Instead, a custom dual-head system comprising two net washing units driven by two smaller pump/engine units was designed. In the new configuration, the two washer units were arranged in series so that the lantern nets would pass through the first with one side up, then through the second with the reverse side up.
The net washer units from Japan were installed adjacent to the Island Scallops processing facility since they required access to three-phase power with inverters to allow variable speed operation. This was a change from the proposed site at the back of the ISL property, which was adjacent to a pond for water supply. Instead, a 20,000-L header tank was provided to supply seawater for operating the machine. Another alteration resulting from the change in design and source of equipment was conversion to hydraulic power. This was required so that the net washer could be used remotely as intended.
Following assembly of the various components, basic operation of the net washer was tested and refined to establish the optimum conveyor belt speed, water pressure, etc. The net washer was then tested using fouled nets. Tests were undertaken with both fresh nets brought from the farm immediately after harvesting the scallops and nets that had been stored long enough to allow the fouling organisms to decay. Testing with the nets was carried out over a period of several weeks in order to optimize performance of the machine under commercial conditions.
5. Results
5.1 Net Washer Design
A header tank provides seawater for two diesel engine/pump units; each of these delivers high pressure water to a separate net washing unit. The washing units are arranged in series so that a fouled net is conveyed through the first with one side up, and then flipped for conveying through the second. Speed and water pressure are adjustable to adapt to the condition of the nets and to optimize water usage, labour force, etc.
The change in set-up location did not impact testing the technology or evaluating the overall design, but it did limit water supply. The header tank was insufficient for operating the net washer for periods longer than an hour at a time. Ideally, the machine will be moved adjacent to a larger source of water for larger-scale commercial use.
5.2 Testing with Fouled Lantern Nets
Overall, the machine proved to be highly efficient and effective despite the fact that it involved passing the nets through two washer units and manually flipping the nets between them. The net washer produced a very clean product within a relatively short time frame. Only broken shells remained in the cleaned nets after washing, which were easily removed through shaking
The new net washer, re-designed with technical advice from the Japanese manufacturer, provided water at significantly higher pressure than that of the original design. Testing with fouled nets demonstrated that the diesel engine/pump units driving each cleaning unit did not need to be operated at maximum rpm or pressure in order to adequately clean the nets. Nevertheless, the technical capability to alter the speed, water pressure, and water volume was a desirable feature of the machine. In project tests, optimum results were achieved at 1500 rpm, 725 psi, and 200L/min. At this setting, the washer could handle approximately four nets per minute.
Several accessory components were necessary to improve operational efficiency when cleaning large quantities of nets. Improvements to the net washing operation included the following:
- conveyors for delivering fouled nets to the washer and unloading cleaned nets from the washer
- racks for final cleaning, inspecting, and stacking the nets
- a bin for moving large quantities of nets
Both “fresh” nets brought directly from the farm and stored nets with decayed fouling organisms were successfully cleaned using new machine. The fresh nets needed to be unbundled and spread open to achieve the best results, but the water pressure did not have to be increased to adequately remove fouling organisms.
The machine was manned by a crew of four for the testing phase: one person to load the fouled nets, a second to flip the nets between cleaning units, and two to unload and stack the cleaned nets. Running the net washer occupied less than 20% of the overall cleaning operation. Following removal from the machine, the nets were shaken to remove any loose shell, then bundled and tied for transport. This occupied a significant portion of the overall cleaning operation. Time was also required for removing cleaned nets and shell debris as they accumulated.
On average, the crew of four was eventually able to clean 200-300 nets per day depending on the time required to set up the machine and the condition of the nets. This encompassed loading the fouled nets onto the machine through stacking the cleaned nets in a cargo net ready for transport. At a basic wage of $15/hr (plus benefits), the cost of labour for this operation was about $2.25 per net. Additional operating costs (trucking nets from the farm, fuel, etc.) were estimated at $0.40 per net, for a total cleaning cost of $2.65 per net. With further refinement of the operation and increased efficiencies, the cost of cleaning the nets will decrease. This represents a significant impact to the cost of production.
Waste from net cleaning operations was combined with waste from processing operations and transported to an off-site location for composting and recycling. Cleaned nets were stored in piles at the rear of the ISL property. Since the new net washer effectively cleaned “fresh” nets, it was no longer necessary to store fouled nets prior to cleaning. Although it was difficult to measure the resulting reduction in smell, eliminating the piles of fouled nets appears to mitigate environmental impacts such as odour.
6.0 Summary & Conclusion
An innovative lantern net washer was successfully developed and tested over the course of the project. The original design was modified using components and technical knowledge obtained from a Japanese manufacturer. AIMAP funds were used judiciously to further refine the new design in order to meet project goals and AIMAP priorities. These changes resulted in improved performance at a significantly lower cost.
Environmental performance of the industry was also improved through successful development of the net washing technology. Reducing the storage of fouled nets mitigates environmental issues of waste control (decomposition and disposal of fouling organisms) and odour from decaying material. Re-use of cleaned lantern nets also impacts the environment by reducing the number of used nets discarded in landfills.
The operational efficiency of the machine was greater than expected. This resulted in reduced production costs and therefore increased sustainable production. The goal of the project was to achieve a cleaning cost of $6 or less per net. The cost of cleaning during the tests was calculated to be $2.65 per net, which far exceeded this goal.
The BC scallop farming industry currently has an estimated 30,000 lantern nets. At a price of $28 each, the cost of replacing these nets for each crop cycle is $840,000. At a cleaning cost of $2.65 each, the cost of re-using the nets is $79,500. This represents a savings of over $750,000. The final cost of the machine and accessory components was under $140,000. Therefore, the savings realized using the new technology is several times the capital cost of the machine. As a result, successful development of the lantern net washer will have a significant economic impact on the company and the industry.
Although the capital cost of new net washer was considerably less than projected, it remains a relatively expensive item for an individual scallop farmer. Moreover, small operations require the machine for only a portion of the time. Consequently, large operations or cooperatives rather than individual growers will ultimately be the target for sales of the machine.
The marketing plan for BC will initially focus on offering a net cleaning service at Island Scallops using experienced company labour. During the project trials, the net washer operated only one to two hours in order to keep the crew of four busy for the entire day. As a result, the availability of the ISL machine immediately benefits other scallop farmers.
Future activities will include moving the net washer to another site on the Island Scallops property in order to deal with issues that arose during the project. Relocating the machine adjacent to an adequate supply of water, such as a pond, is an immediate priority so that that it can be operated full-time if required. Moving the machine to a more remote area of the property will also mitigate the impact of noise.
Future activities should also focus on developing a water recirculation system since the operation uses large volumes of water. Another option that should be pursued is locating the net cleaning operation off-site on a barge. This would address the water supply issue as well as increase efficiency since the nets would not have to be trucked back to ISL for cleaning.
Further modifications to the machine should be made to increase efficiency and reduce costs. For example, a conveyor should be added to automatically flip the nets between cleaning units. Improvements to handling time are also required since material handling still occupies a significant portion of the net washing operation.
Overall, project goals were exceeded. Development of the lantern net cleaning machine met the technological needs of the company as well as the scallop aquaculture industry by providing an efficient and cost-effective means of dealing with the increasing number of nets accompanying the expanding industry. While refinements continue in order to increase operational efficiency, the machine is currently in commercial use at Island Scallops; this is the ultimate indicator of success of the project.
