OCEAN FORESTS: FEEDING THE WORLD WITH FLOATING ARTIFICIAL REEFS

Kelly Lucas*, Mark E. Capron, Reginald Blaylock, Michael D. Chambers, Jim R. Stewart, Steven F. DiMarco, Kerri Whilden, MH Kim, Zach Moscicki, Corey Sullivan, Igor Tsukrov, M. Robinson Swift, Scott C. James, Maureen Brooks,Stephan Howden, Suzanne Fredericq, Stacy A. Krueger-Hadfield, Antoine De Ramon N'Yeurt, Chris Webb, Don Piper

Thad Cochran Marine Aquaculture Center, School of Ocean Science and Engineering, University of Southern Mississippi, Ocean Springs, MS, USA
mailto:reg.blaylock@usm.eduKelly.Lucas@usm.edu

The U.S. Department of Energy Advanced Research Projects Agency-Energy (ARPA-E) MacroAlgae Research Inspiring Novel Energy Research (MARINER) program retained nine teams to identify ways to grow and harvest macroalgae for less than $85 per dry metric ton (DMT). ARPA-E wants the teams to have a path-to-market, meaning an immediately profitable way to build and operate pilot and then full-scale structures.

The University of Southern Mississippi's (USM) path-to-market uses a new type of aquaculture ecosystem, ocean forestry, where the essential input is ammonia or nitrate and phosphate on a floating artificial reef. Nutrient conversions, per the figure at right, combine with photosynthesis to add carbon to inorganic nutrients as basis for the food chain. As a result, the floating artificial reef can have an optimally balanced suite of products including macroalgae, shellfish, and finfish, without adding fishmeal. Based on natural circulation through the ecosystem, ocean forestry takes Integrated Multi-Trophic Aquaculture to a new level.

When ocean forests are operating at energy scales of a few million hectares, millions of tons of shellfish and finfish can be harvested per year. Lapointe demonstrated in 1978 and 1990 that it is possible to generate yields of Gracilaria tikvahiae near 127 DMT per hectare per year with sufficient nutrients and frequent harvests. (Current macroalgae systems harvest 20 to 40 DMT/ha/yr.)

The shellfish, mollusks, and free-range finfish produced in ocean forests are worth up to $150,000/ha/yr, while the macroalgae might be worth only $10,000/ha/yr as energy feedstock. This value differential drives a path-to-market that starts by building and operating structures that feed the world with high-value seafood. After accessing high-value food market, energy producers can count on a reliable supply of macroalgae. Food co-production is achieved using the same structure as energy production. Nutrients are supplied from food and energy-processing wastes. The USM team has several designs for efficient planting and harvesting systems.