Wood Plastic Composite Structural Lumber for Aquaculture Net Pens

The purpose of this USDA SBIR Phase I project is to determine the feasibility of a novel wood fiber based composite material for structural elements of marine structures, particularly the structural frame of the aquaculture pens manufactured by InnovaSea Systems.InnovaSea has been manufacturing and marketing the Aquapod spherical geodesic fish pens since 2006 and has learned much in the years since we began, steadily improving the product design and construction. An aquaculture structure operates in the marine environment, one of the most demanding of environments, one in which most affordable materials succumb to environmental degradation quickly. It could be argued that the marine environment, especially in a stationary year round use such as an aquaculture net pen, is the most demanding of all.InnovaSea has spent years searching for structural materials that provide greater strength and stiffness at an affordable price. The Aquapod cages are currently constructed using fiberglass-reinforced High Density Polyethylene (HDPE) plastic for the primary structural plastic lumber. This is the primary commercially available plastic lumber available in the market presently that approaches the structural properties required. The HDPE plastic lumber has a number of merits, but it is difficult to fasten, cannot be coated, and has relatively low strength and stiffness. Using this material, InnovaSea has increased the size of the cage with successive models until we now seem to be near a structural limit of the HDPE materials.We have searched for a better product, reasonably priced, already produced and sold in the market. Price is an issue as the large volume of structural material in Aquapods contributes to our price being near the top end of the market for net pens. We need to use commodity type products and the more exotic but costly materials such as carbon fiber are simply not an option. It appears that we are using the best commercially available plastic lumber already, so we need to consider new materials not yet on the market.SMA-WPC is a thermoplastic composite made by combining engineering plastic SMA (styrene maleic anhydride copolymer) and wood fiber. SMA-WPC plastic lumber shows significant promise as a replacement for the HDPE plastic lumber.The purpose of this Phase 1 project is to test the SMA-WPC in the marine environment, making a side-by-side comparison with other materials. We will use a combination of laboratory testing and field exposure test in the ocean environment. We expect to confirm the durability of the material in the ocean so that we can take advantage of it's known superiority in structural properties.SMA-WPC is not yet a commercial product but InnovaSea will be working with the University of Maine (UMaine) researchers who have developed the production process in their laboratory using their commercial scale production system. If the material properties can be proven for this marine application, it can be brought to commercial production either by InnovaSea or under contract with another company.Changing from HDPE plastic lumber to SMA-WPC would improve the Aquapod structural strength and make it relatively insensitive to heat issues. Using SMA-WPC would enable the company to develop new and superior methods of fastening and fabrication of panels thus enabling the company to increase the durability, size and commercial viability of the Aquapod product line.While InnovaSea has identified the need for this material, it will also be applicable to many other marine structures and projects. The development of a reasonable-cost inert and impervious wood fiber based lumber for use in dynamic marine environments opens up a realm of potential uses in marine applications. The information derived from this project would allow the evaluation of suitability for those projects.