Dossier Océan et énergie - Énergie Thermique des Mers

Sommaire IOA News Letters

ARTIFICIAL UPWELLING FOR ENVIRONMENTAL ENHANCEMENT

Stanley Dunn and Manhar Dhanak
Florida Atlantic University
Boca Raton, Florida
United States

and

Patrick Takahashi and Michelle Teng
University of Hawaii
Honolulu, Hawaii
United States

Introduction

Relative to fossil or nuclear energy, renewable technologies are mostly friendly to the environment. However, very few sustainable systems actually improve the environs. Perhaps some benefit can come from growing more trees for biomass production, but eventually much of this feedstock is utilized, and certainly after several decades or centuries, most trees die, replacing every bit of the carbon dioxide back into the atmosphere.

Notwithstanding many of the previous evils wrought by colonialism, colonization of the open ocean does not clash with cultures, and might well be a respectable option that can someday bring about increased economic productivity and an enhanced environment. With the end of the Cold War, interest in ¡§ colonizing ¡¨ space has significantly diminished. The next true frontier, the ocean around us, holds immense promise and is the next stage for development by humanity.

Through much of the tropical ocean-not owned by any country-nutrient-rich fluids are available a few hundred meters below the surface. At depths of 1000 meters in the tropical belt, the available temperature differential provides a mechanism-called ocean thermal energy conversion, or OTEC-to move this cold, rich, pathogen-free fluid to the surface. Should it prove to be economically attractive to build large floating platforms to tap the combined resources of sunlight, deep ocean water, and seabed resources, the result could be a cornucopia of integrated products, covering the spectrum of seafood, biofuels, clean chemicals, hydrogen, biopharmaceuticals, nutraceuticals, strategic metals, and fresh water(Takahashi, 1994).

An open-ocean artificial upwelled system, however, shows promise for both providing revenues and, possibly, positively impacting the environment. Properly managed, the high-nutrient deep waters can induce growth in the photic zone, on balance, although possibly with the need to add iron, uptaking carbon dioxide from the atmosphere. Much of the CO₂ formed will sink to the bottom of the ocean, where much of it will remain trapped for a long, long period. The carbonate cycle slowly transforms the gas back into the atmosphere, but those bound in silicate compounds remain in place for many millennia(Berner and Lasaga, 1989).

These same marine systems, which would for good reason be placed at the equatorial belt, might also cool the surface of those ocean regions responsible for generating typhoons and hurricanes(Takahashi, 1996). All the hurricanes which visit the Caribbean, Gulf of Mexico, and eastern coastline of the United States form just off Africa, while those that cause havoc in Hawaii come from a relatively small area off the Mexican Coast, although the particularly disastrous Iniki, it is believed, might have had African origins. If the temperature of the ocean surface can be kept below 26.8 ¢J , these storms do not form.

A team from Florida Atlantic University and the University of Hawaii has been discussing the prospects for preventing hurricanes since 1992 when Andrew devastated Florida, resulting in $30 billion in damages, and Iniki hit Hawaii( $2 billion),. A second team involving the University of Hawaii and various partners has been looking at global climate change remediation for at least as long.

Induced Upwelled Systems in the Open Ocean

A grazing ocean thermal energy conversion(OTEC) plantship of several hundred megawatts will produce a cold-water plume that can be engineered to remain in the photic zone so that the surface over several square miles will be cooled. Through a 1000-megawatt OTEC system would flow 1.7 billion cubic meters per day of both warm surface and cold deep waters. The equivalent nitrogen could result in 2 billion dry tons of kelp per year(Takahashi et al., 1993). Several hundred of these energy pods can reduce the temperature of thousands of square miles.

Each plantship, of course, would be a revenue generator, ranging from:

	industrial plantforms refining alumina, processing seabed ores, and converting biomass feedstock into green chemicals and biofuels;
	ocean ranches for next-generation fisheries and marine biomass plantations;
	casino-resort-marine entertainment complexes in partnership with Disney-at-Sea-type theme parks;
	marine utilities(powerplants, waste treatment facilities, and the like);
	military peace-keeping stations;
	to marine cities.

Location of these applications on very large floating structures(VLFS) in the open ocean would be beneficial in numerous ways(Takahashi and Ertekin, 1996), including:

	displacement of air, land, and water pollution away from populated municipalities;
	utilization of the oceans as part of the total system package for waste re-use, for example, smaller amounts of power-plant effluents can be combined with marine biological growth needs, while massive disposal of carbon dioxide from a coal power-plant can be accommodated into the deep ocean through the use of pipes(Masutani 1997); and
	freedom to operate beyond territorial waters, potentially resulting in the formation on VLFS platforms of new nations.

Clearly, these systems would be located in the equatorial belt to obtain maximum temperature differential, and most definitely, planning must this time be smarter than in the past to insure for development in harmony with the natural environment. However, with artificially upwelled systems, the possibility of actually improving the environment also becomes an intriguing prospect.

Society and the Environment

There is an unfortunate tendency for individuals and institutions to treat the symptom and not the root cause. Part of this trait is because it is necessary to fight the brush fire, and decision-making systems can understand the need to provide resources to accomplish this task. Not too long ago, for example, the United States government spent enormous sums of money to build the better iron lung. Then, along came Jonas Salk and Albert Sabin, who developed vaccines to eliminate polio.

Society is again trying to build the better iron lung by enacting regulations to strengthen buildings from hurricane force winds and design walls around coastal cities to accommodate sea level rise. Workshops are provided the world over on these topics, and become politically charged whenever the big one(hurricane or very hot summer) hits. Very little attention is ever given to prevention.

But is it possible to reverse the greenhouse effect? Is it reasonable to even talk about preventing hurricanes? Should we tamper with Mother Nature?

About Mother Nature, nothing wrong with helping her overcome problems she creates. We already wear clothing to shield from severe weather, suntan lotion to minimize skin cancer, and enjoy air-conditioning. But again, this is reacting to the forces and not necessarily test, or improve upon, the basic nature of being.

The U.S. Department of Commerce on May 24 of 1993 hosted a gathering at its headquarters on 14th Street in Washington, D.C., ostensibly to talk about OTEC plant-ships as a major defense conversion or National Institute of Science and Technology advanced technology program initiative. It might be indicated that the National Oceanic and Atmospheric Administration(NOAA), a component of the Commerce Department, has historically been sensitive about hurricanes because of past debacles. Representatives from General Dynamics, Lockheed, various Washington, D.C.-based consulting firms, the University of Hawaii, Florida Atlantic University, Johns Hopkins University, and NOAA surmised that a national program to explore the potential of preventing or ameliorating hurricanes was sensible. Groups were formed to identify realistic mechanisms for hurricane prevention, develop computer models to optimize at-sea experiments, recommend a financing plan to implement the program design, build and operate up to 500 floating plantships, and recommend a financing plan to implement the program. The next two sections touch on the team assigned the basic modeling program.

Hurricane Prevention

In 1992, hurricanes caused more than $30 billion of damage in the United States. The prospect of global climate warming will only mean more intense and frequent hurricanes, as they do not form in the North Atlantic when the monthly mean temperature is less than 26.8¢J over a minimum area of about 10 million square kilometers(approximately 3 square miles).

Hurricanes form in these warmer waters and dissipate when incurring a temperature drop of 2¢J . Thus, if a mechanism can be found to lower the temperature of the ocean surface in those areas of the Atlantic, Pacific, and Indian Oceans where hurricanes/typhoons are normally generated, it is possible that the frequency or severity of them can be minimized, if not entirely eliminated. If prevention is not attainable, then the imposition of a cold band across the path might weaken or divert the storm.

Reversing Global Climate Warming

There is about as much carbon in living plants and animals as there is in the atmosphere. However, there is seven times more each in recoverable fossil fuels and dissolved bicarbonate and carbonate in the ocean ¡K and about 100,000 times more as carbonate in sedimentary rocks, which are the fossil remains of animal skeletons. As relatively insignificant as the carbon in the atmosphere might be, a doubling of the CO₂ and other green house gas level by the next century, which has been predicted by most modellers, will increase global temperatures from 1.5¢J to 4.5 ¢J.

The solution to remediating global warming is relatively simple: reduce greenhouse gas emissions(CO₂ represents about half the effect [Ramanathan 1987]) and enhance the activity of natural sinks. The model is complicated by volcanic dust, severe forest fire seasons, and the like, but less use of fossil fuels, more intelligent land management, and enhancement of carbon dioxide uptake by the oceans are addressable targets. Much of the ocean attention has thus far been restricted to high-latitude productivity and the influence of iron. Among other options are utilization of marine mineral accretion for ocean structures(Hilbertz 1991) and artificial upwelling on grazing platforms along the equatorial belt. The remainder of this paper will summarize this latter alternative.

There have been several important ocean conferences and workshops which have treated the subject of artificial upwelling, including:

	the First National Science Foundation Workshop on Engineering Solutions for the Utilization of Exclusive Economic Zone Resources(Hawaii, October 1986);
	Planning Workshop on Mitigation of Global Climate Change(Hawaii, March 1989), involving representatives from the Environmental Protection Agency, NOAA, Electric Power Research Institute, and academia;
	NSF and Republic of China National Science Council International Workshop on Artificial Upwelling and Mixing in Coastal Waters(Taiwan, June 1989);
	NSF and Japan Science and Technology Agency Workshop on Artificial Upwelling(Hawaii, March 1990);
	NSF First International Workshop on Engineering Research Needs for Off-Shore Mariculture Systems(Hawaii, September 1991);
	NSF Franco-American Program Development Workshop on Ocean Engineering, Marine Biotechnology and Mariculture(Maryland, October 1991); and
	NSF and NOAA National Ocean Resource 2000 Workshop(Hawaii, June 1992).

There have been various other conferences and workshops that have since carried on the thrust of the discussion, but the basic ideas were generated at the sessions above.

Two potential oceanic mechanisms to help mitigate global warming are (Phillips et al., 1991):

	enhanced carbon dioxide uptake via nutrient subsidy to marine algae and subsequent deposition in marine sediments and
	enhanced dimethyl sulfide production via marine algae to increase cloud formation and albedo.

Regarding the carbon uptake hypothesis, the CO₂ concentration of the atmosphere has been increasing at about 1.5 parts per million annually, which accounts for an accumulation of approximately 3 gigatons of carbon/year. If application of nutrient subsidy could enhance phytoplankton productivity such that 10% of the open ocean net primary production is buried in deep-sea sediments(an order of magnitude higher than the 1% deposited under natural conditions), then 2 gigatons carbon/year could be removed to mitigate the greenhouse effect. This amount would decrease atmospheric CO₂ concentration at a rate of about one ppm/year. By controlling the amount of ¡§ fertilizer¡¨ applied to the world ¡¦s oceans, the temperature of the planet could thus be controlled.

With respect to dimethyl sulfide, a metabolic waste product of oceanic phytoplankton and the primary source of sulfate aerosol and cloud condensation nucleii in the remote marine atmosphere, an increase would upgrade cloud formation and subsequent albedo, which would reduce the global temperature. Specifically, the mean temperature might be reduced by 1.3¢J through a 30% increase in albedo resulting from the biogenic sulfate induced cloud formation.

color=#800040 size=4>Conclusion: Project Blue Revolution

An international partnership of industry, government, and academia to design, build and operate a VLFS powered by OTEC and producing the range of co-products while providing environmental benefits would be a magnificent undertaking for the new millennium(Takahashi, 1996). As developed by a 1992 workshop in Hawaii of 50 participants representing six nations(Takahashi and Vadus, 1992), the Blue Revolution plantship would be a 1 hectare(100,000 square feet) grazing structure estimated to cost $500 million for full operation early in the 21st Century to:

	serve as an incubator for new marine industries,
	develop the package of integrated products, and
	test the upwelling concept.

While $500 million might seem staggeringly high, one might consider that this sum represents one tenth of 1% the cost of the 1991 Gulf War and one-fifth the current value of each B-1 bomber. Reports also indicate that the U.S. space station would have cost $50 billion and the Mars Project about $500 billion. Now that dreams have come back down to earth, this pioneering venture to develop next generation marine products for Humanity while, possibly, enhancing the environment, seems like a wise bargain.

References

Avery, W., J.R. Vadus, and P.K. Takahashi, 1994,¡§ The Coming of Ocean Resource Plantship,¡¨ In Proceedings of Oceanology International ¡¦94, Brighton, England.

Berner, R., and A. Lasaga, 1989,¡§ Modelling the Geochemical Carbon Cycle, ¡¨Scientific American, pp 74-81.

Hilbertz, W., 1991,¡§ Towards Sustainable Building: Growing Structures in Sea Water to Mitigate Global Warming,¡¨ Ekistics, v. 348, n. 9.

Masutani, S., 1997,¡§ Scoping and Site Selection Study for an Ocean CO₂ Disposal Field Experiment, Personal communications.

Ramanathan, V. et al, 1987,¡§ Climate-chemical Interactions and Effects of Changing Atmospheric Trace Gases,¡¨ Journal of Geophysical Research, v. 25.

Sabine, C.L., D.W.R. Wallace, and F.J. Millero,¡§2 in the Oceans Reveals Clues About Global Carbon Cycle,¡¨ EOS, v. 78, n. 5, pp. 53-61.