Sunday, July 29, 2018

Carbon Capture: Ocean Farming

The ocean has absorbed approximately a third of the extra carbon released since the industrial age. A previous article focused on countering acidification of the ocean either directly by adding massive quantities of alkalines or indirectly by adding minerals to encourage phytoplankton growth. This post discusses a more purposeful effort, using the carbon in the ocean to grow plant life which can be used for other purposes.

Much discussion about ocean farming revolves around kelp, for several reasons:

  1. Kelp propogates amazingly quickly, growing up to a foot in a single day in ideal conditions.
  2. Profitable uses for kelp already exist as a food source for humans and in animal feed. Additional uses by processing kelp into biofuel or as feedstock for other chemical processes appear to be feasible.

Despite its tremendous growth rate, kelp in nature is confined to a relatively small portion of the ocean: it has to anchor itself to the sea floor and take up nutrients present in deeper waters, but must be able to reach the surface to photosynthesize. Therefore, natural kelp only grows near coastlines and islands.

Several startups aim to vastly increase the capacity of the ocean to grow kelp by providing the conditions which the plant requires:

  • The Climate Foundation proposes to build Marine Permaculture Arrays stationed about 25 meters below the surface, to provide a point of attachment for kelp. Pumps powered by solar or wave energy would draw water from the depths, providing an artificial upwelling to provide nutrients for the kelp and plankton.
  • Marine BioEnergy proposes robotic submarine platforms which would descend to depths overnight to allow the kelp to take up minerals and nutrients, then ascend close to the surface during the day to allow the plants access to sunlight. The platforms would also be mobile, periodically returning close to shore to allow harvest of the grown kelp and any needed maintenance and replenishment of the platform.
  • GreenWave has developed a training program, legal permitting assistance, and market development for ocean farmers, along with optimized layout for a kelp farm. The plans appear to be for coastal farms, not involving deep water platforms nor extensive automation like the earlier firms.

The major food crops like soybeans, wheat, corn, and rice have been tremendously modified from their original forms. As we develop uses for kelp as feedstock in the production of fuels or chemicals or other uses, it is likely that the specific kelp population can be bred to better fit the applications.