The Tidal Irrigation and Electrical System

renewable energy, carbon dioxide sink, biodiesel, and food from the ocean

Sea Lettuce Farms to Reverse Ocean Acidification

Posted by on Saturday, February 5th, 2011

The growth of homogenic carbon dioxide in the atmosphere since the industrial revolution has convinced the majority of the scientific community that the earth is poised to begin an ever increasing warming trend. It has terrified the most influential scientists and lead to the advanced study of geoengineering schemes. At the cost of billions, if not trillions, of dollars the earth may be shaded by items floating in space or by changing the atmosphere, or some other modification so that less light reaches the ground. A few of these plans attempt to deal with the problem from the other side – by absorbing carbon dioxide directly from the atmosphere in the hope to offset the burning of fossil fuels. Flue filters and artificial trees seem like good ideas, except that the energy cost is very large and there are no storage solutions that can guarantee containment for geologic time. By this reasoning, shading the earth seems like the way to go.

There is, however, a whole different set of problems created by having an excess of CO2 in the air. This is about how the atmosphere and the oceans interact to create carbolic acid and is known as ocean acidification. I blogged about it here. The long and the short of it is that as the ocean becomes more acidic, corals and some planktons find it harder and harder to grow until they die off. As the effect increases, the whole oceanic food web breaks down. The major geologic models we have eventually resulted in extinction events, the largest of which killed off 95% of  the life in the ocean. We are a long way off of that but even a slight change can have remarkably deleterious effects on the ocean’s ability to produce food. Some of the latest horrifying figures can be found in this article, which details a report from the UN and this one about a model of surface uptake.

One biologist, Ronald Osinga, presented an interesting idea at a symposium involving the growing of sea lettuce (ulva lactuca) to combat the acidification of the ocean.  Roelof Kleis wrote an article about the symposium which was held at Wageningen, the Netherlands by the International Society for Reef Studies (ISRS). It had an emphasis on climate change and the deleterious effects it will have on coral reefs. Presented on the last day, Osinga pointed out the pollution caused by current fish farming techniques could be utilised to grow sea weeds for human consumption or for food for fish.

Osinga and his colleagues have calculated that a ‘marine garden’ of 180,000 square kilometres could provide enough protein for the entire world population. A sea lettuce bed of such gigantic proportions would raise the pH (acidity level) of the Mediterranean Sea by one tenth. That may not seem much, but according to Osinga, it would be enough to compensate for the rise in acidity that started with the industrial revolution.

My criticism of the scheme is that it fails to account for the eventual nutrient loss if either the fish or the sea lettuce are taken from the system for consumption by humans. This aside, the proposal does have huge implications for the Tidal Irrigation and Electrical System (TIE System), the subject of this blog. One of the key components of a TIE System is its ability to deliver the nutrients necessary to a lagoon isolated from the surrounding ocean, in order to create a sustainable aquaculture. It does this while producing electrical power.

The TIE System is driven by tidal action and so it is difficult to estimate the amount of power generated by Osinga’s 180,000 square kilometre figure. But, if there was a tidal swing average of 2.33 meters and each TIE System had a diameter of 20 kilometres, the 573 aqua farms should produce about 36.3 TeraWatt Hours every flux. This is on top of producing the sea weeds necessary to change the pH of the oceans to offset the consequences of fossil fuel use AND feed the whole population of the world.

It is worth noting that 36.3 TeraWatt hours per flux is about 23,849 TeraWatt hours per year. In 2007 world consumption of electricity was 17,109.7 TeraWatt hours. The economic and societal imperative to develop the Tidal Irrigation and Electrical System seems to become increasingly evident as time passes.

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