Seeding the Sea: D.O.E. Efforts in Offshore Seaweed Culture

Offshore aquaculture is a realm of farmland with fathoms full of potential.

While seaweed farming is not a new industry, its production has increased six-fold world-wide over the last 25 years. As we look for potential ways to help feed and fuel ourselves amid a growing population and dwindling natural resources, seaweed biomass production reveals many opportunities.

 Seaweed mariculture does not use earth’s arable land, freshwater, or artificial nutrients, and can potentially help absorb excess nutrients and carbon from the ocean, thereby possibly countering so-called “dead-zones” from eutrophication, and ocean acidification. If the U.S. wants to become a global leader in marine biomass production, there are some knowledge gaps to fill. This is the goal of the Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E) and their Macroalgae Research Inspiring Novel Energy Resources (MARINER) program.

ARPA-E estimates that the U.S. is capable of producing at least 500 million dry metric tons of seaweed annually. Seaweed biomass could be applied for human consumption, feedstock for fuels and chemicals, and animal feed. This level of production could yield enough liquid fuel energy to meet nearly 10% of the nation’s annual transportation energy demand. Domestic biofuel production from seaweed could also lessen the dependence on foreign oil, while boosting our own energy security.

Kelp bed. Photo credit: Oliver Dodd, Flickr.

As is, the seaweed mariculture industry cannot reach the scale, efficiency, or production costs required for a seaweed-to-fuels trade. The ARPA-E MARINER program’s approach to reaching the scale, efficiency, and production costs is through technology—developing innovative engineering, and systems level solutions for offshore seaweed culture systems.

The MARINER program is supporting projects in five areas: 1) integrated cultivation and harvest system design, 2) critical enabling components, 3) computational modeling, 4) monitoring tools, and 5) breeding and genomic tools. Currently, 18 teams are working on developing the tools, technologies, and protocols for their respective project areas.

Gracilaria parvispora, a smaller, tropical species. Photo credit: Keelee Martin, Kampachi Farms.

Some teams are refining system designs to grow kelp while others are working with smaller tropical species and starting from scratch. Novel technologies in seeding, feeding, and harvesting are critical to reach the production scale needed to support a seaweed-to-fuels industry.  A few teams are looking into using binders to attach small propagules to lines, while others are developing sewing methods for larger pieces. Nutrient-rich deep sea water is being tested as a way to achieve high growth rates with no additional external fertilizers. Modeling teams and engineers are designing ways of pumping this nutrient-rich water from under the farm, using renewable energy in “goldilocks” doses (just the right amount). Specialized autonomous ROV concepts are being formulated, to minimize production and energy costs for harvesting seaweed, with some systems looking to perform more than one task: seeding, trimming, harvesting, and transport all in a single vehicle. Farm systems will allow for deeper submersion during storms, and will be designed in ways to minimize the risks of marine mammal entanglement.

Next year, three to four teams will deploy demonstration system farms to bring the modeled data to life. As the MARINER projects move forward, and our gaps in knowledge begin to be filled, the future of aquaculture is looking greener—in the ocean with seaweed farms, and on land with cleaner biofuels.