Giant Kelp (Macrocystis pyrifera) is one of the fastest growing producers of biomass.  The open ocean is an immense, untapped region for collecting solar energy.  Giant kelp does not grow naturally in the open ocean because kelp normally needs an attachment at about 10-20 meters of depth and also needs key nutrients that are available in deep ocean water or near shore but not at the surface in the open ocean.  This concept proposes an economical system to provide a grid for attachment and access to nutrients, making it possible to farm kelp in the extensive regions of the open ocean.

If successful, this patented approach will grow kelp attached to large grids in the open ocean, each grid towed by inexpensive underwater drones.  These drones will maintain the grids near the surface during the day to gather sunlight for photosynthesis.  At night, the drones will take the grids down to the deeper, cold water where the kelp can absorb nutrients that are not adequate in the warmer surface waters.  These kelp farms will also be taken to deeper water during storms or to avoid passing ships.  Every three months, the drones will move the kelp farms to scheduled locations to rendezvous with harvesters. 


Giant kelp, Macrocystis pyrifera, native kelp bed at San Clemente Island, California, USA. Licensed from Phillip Colla Photography

Why grow giant kelp on farms in the open ocean guided by robotic submarines?Farm Schematic

  • does not compete with food production for agricultural land.
  • will not harm environmentally-sensitive areas, such as deserts or marine reserves.
  • does not use fresh water, pesticides, or artificial fertilizers (using, instead, abundant nutrients in deep water).
  • stores nutrients when they are available and uses them when needed.1
  • is relatively easy to process into drop-in fuels because it has no lignin and little cellulose.2
  • is one of the fastest-growing primary producers with elongation rates ~30 cm/day,3 and average photosynthetic efficiency in the range of 6-8%, much higher than terrestrial plant production at 1.8-2.2%.4
  • stores over 1 Watt/m2 (averaged 24/7/365) of sunlight as chemical energy (~2.8 kg ash-free, dry weight per m2-year) , as observed in natural beds.5,6
  • continues to grow year round especially if adequate nutrients are available, and the harvest is non-destructive so farms can be productive for years without replanting.

Why grow giant kelp on farms in the open ocean guided by underwater drones?

  • near shore areas with natural upwelling of nutrients won’t produce enough biomass to make a significant impact on the nation’s energy needs.
  • many natural kelp beds are in marine reserves, or in recreational or commercial areas.
  • the production underwater drones will be less expensive than one might expect because they will be made out of reinforced concrete and numerous subsystems are already available in production quantities (automated guidance & control, communications, batteries, pumps, sensors).
  • most importantly, kelp grown in the open ocean can utilize massive open ocean areas to supply an energy feedstock sufficient for the projected peak world population at the current U.S. per capita rate of energy consumption of ~9500W/person.

The Pacific Ocean offshore of the Western U.S. represents an immense, untapped solar collecting area and, if this effort is successful, will be the first deployment region for the commercial farm systems.  Fast-growing kelp produces biomass year round and could provide a transformational solution to the need for millions of tons of feedstock per year.