ENGINEERING TECHNIQUES FOR THE DESIGN OF OPEN OCEAN MACROALGAE FARMING SYSTEMS  

Our future depends upon the development of high value marine products that have positive ecological impacts and macroalgae (kelp) aquaculture has enormous potential for human foods, fuels, feed supplements, fertilizers, hydrocolloids, pharmaceuticals and nutraceuticals.  Evidence also exists that large-scale kelp aquaculture may provide ecosystem services that offset many anthropogenic impacts including bioremediation of excess nutrients and carbon sequestration.   Expanding kelp aquaculture in populated coastal regions will be important, however, large-scale growth will likely be limited by social carrying capacity due to multi-stakeholder issues. Therefore, development is expected to occur in exposed, open ocean regions.  This will require a detailed design approach to ensure system integrity.

The objective of this presentation is to describe engineering techniques necessary for the design of kelp farms in high energy coastal and open ocean areas. We report on our use of numerical models to represent large deformations, compliancy and contact between elements of kelp farms in the ocean. To have confidence with our computer models, input parameters must accurately represent the farm system so our approach incorporates the geometric and material properties of kelp and harvest densities.  Full-scale physical models are then designed and built by matching dimensions, mass densities and flexural rigidity characteristics of a section of long-line at harvest.  We have designed and performed some tow, wave and planar motion experiments in a large tank with full-scale models to obtain drag and inertia coefficients.  Hydrodynamic characteristics can then be incorporated into numerical models so that a wide range of kelp farming systems can be analyzed.