Any body of water when it is warmed by the sun at the surface will tend to separate itself into thermocline gradients. The sharply defined layers prevents the mixing of the waters inside them. This leads to a leaching of nutrients needed for plant growth and so by mid spring in places like the north sea primary biological production has for the most part stopped. Deep Ocean Water (DOW), where these nutrients abound, represents 99% of the volume of the ocean and are just out of the reach of marine plants, separated by a thin skin. This is why the tropical oceans are crystal clear. There are almost no microscopic plants (micro algae) in the water to turn it green.

That is not to say that that the potential of seaweed isn’t huge. A company called Bio Architecture Lab based in Berkeley California has perfected an enzyme and process which liberates the sugar from alginate. This single substance represents 30% of the dry mass of seaweed. BAL’s method has an 80% efficiency rate of the theoretical yield. This is a huge advance and by their figures the harvesting of seaweed from 3% of costal waters would generate 60 billion gallons of biofuel.

The Tidal Irrigation and Electrical System opens up large areas of coastal ocean to macroscopic algae cultivation that would not normally grow commercially harvestable amounts of seaweed.  It does this by using tidal forces to syphon DOW into a lagoon where it is isolated from the surrounding ocean and creates a large bioreactor. It does this while producing food and gigawatts of electricity. (Please see the links on the right of this page for further details of the products of the system)

The new increase in efficiency in the processing of seaweed by BOL will result in a huge gain in production for the TIE System. The two technologies are made for one another.

There are advantages to both systems but now a detailed analysis by Anna Stephenson at the University of cambridge has compared them and found that open air ponds are 16.8 times more efficient than perspex tubing (Energy and Fuels, DOI: 10.1021/ef1003123). In an article published in the New Scientist, it is pointed out that pumping through plastic tubes results in a higher energy cost per unit than traditionally sourced fossil diesel. However, this is not the case for open air ponds.

As Ms. Stephenson says, the major drawback to open air ponds is evaporation. So much water can be needed that ponds in many countries would be in direct conflict with traditional demands for water, if they want to produce enough biofuel to replace their domestic consumption. This is not an issue for the Tidal Irrigation and Electrical system because it does not use fresh water, it uses the ocean. Also, the tidal flux is being harnessed in a TIE System to do the pumping and deep ocean water is used as the both the fertilizer and source water for the open air pond, making it much more efficient than the land based ponds envisioned by Ms. Stephenson.

The New Scientist reports in its June 12th 2008 issue that it now seems the UN Convention on Biological Diversity also has deep concerns about the process and has banned it until more research has been done. At the same time Mary Silver of the University of California, Santa Cruz has presented her findings to the American Geophysical Union in Fort Lauderdale, Florida. She has results that indicate that iron encourages the growth of particular algal populations that produce domoic acid – a potent neurotoxin. Domoic acid can sicken or kill animals and people who eat contaminated shellfish.

Hopefully this will encourage those who see the potential in marine algal growth schemes to look more closely at the full life cycle of what they produce and to instead consider the TIE System. The TIE System uses DOW, which is the ideal fertilizer for algae, and it contains the biomass so the open ocean isn’t shocked and methane pollution can be limited.