The Promise of OTEC Aquaculture

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Written By: Emma Websdale

In a time of declining wild fish stocks and growing fish demand – which currently over a billion people globally depend upon as their primary source of protein – aquaculture is becoming an important component in helping to improve food security in many parts of the world. 

‘Aquaculture’ refers to the rearing, breeding and harvesting of aquatic animals and plants across a variety of water environments including ponds, rivers, lakes and oceans, primarily for human consumption. Aquaculture practices have also proved important for restoring threatened and endangered aquatic species and providing fish for aquariums.

Need for Aquaculture Industry

A recent collaborative report between the World Bank, Food and Agriculture Agency (FAO) and the International Food Policy Research Institute (IFPRI) has highlighted the urgent need to increase investment into sustainable aquaculture in order to meet growing fish demands.

The report, entitled ‘Fish to 2030: Prospects for Fisheries and Aquaculture’, estimates that by 2030, 62% of all consumed seafood will need to be farmed, including fish for foods and fishmeal, in order to meet demand. Demand is greatest in certain regions, particularly Asia, where approximately 70% of fish will be consumed. The report states that aquaculture will help satisfy the world’s growing appetite for fish as human populations continue to grow.

Investing in aquaculture is not a new notion. In 2007, the United Nations cautioned that without better management of fish production, the rising demand for seafood would lead to a collapse of today’s commercial fish stocks by 2050.

Aquaculture pensFurthermore, the UNEP Global Environment Outlook Year Book 2007 noted that the impact of climate change on the world’s oceans (by increasing ocean acidity and bleaching coral reefs) would further aggravate the fishing dilemma. These projections have since been strongly supported by scientists and organizations. A report released in October 2013 estimated that human-induced greenhouse gases are not only increasing the acidity of our water but are also depleting water oxygen levels -two biochemical changes that are likely to reduce ocean productivity significantly.

Meeting the Rising Appetite for Fish

Fortunately, some organizations and companies are developing sustainable methods and technologies for aquaculture. One recent advance that deserves attention is the water drawn by the pipes of Ocean Thermal Energy Conversion (OTEC) plantsOTEC is a base-load renewable energy production process particularly suited for tropical zones. By using the ocean’s abundant temperature differential between warm surface water and cold deep water, OTEC technology generates both clean energy and fresh drinking water.

Due to the technology’s looped system, under certain conditions the water can be re-used for secondary applications including desalination to create fresh drinking water. One particularly attractive by-product of OTEC plants is nutrient-rich and virtually pathogen-free water from the deep ocean. This water provides an optimal environment for various forms of aquaculture cultivation of both plants and animals. Through open-ocean fish farming (where adequate flushing ensures dilution of waste products), aquaculture can produce sustainable food supplies. Thus, OTEC provides an attractive application to the aquaculture industry, especially in the face of current declines in commercial fishing stocks.

The cold, deep seawater, available as a result of producing renewable energy through OTEC technologyhas numerous advantages for aquaculture systems:

-Rich in dissolved nitrogen, carbon and phosphorus, OTEC’s deep-ocean water contains chemicals that are essential for fish and plant growth.

-The consistent low temperature of OTEC water provides opportunities to culture valuable cold-water organisms both in native environments and in the tropics.

-The virtually pathogen-free water pumped by OTEC allows disease-free cultivation of sensitive organisms.

Aquaculture via deep seawater is not just a theory or hopeful expectation. The Natural Energy Laboratory of Hawaii Authority (NELHA) currently utilizes cold deep seawater for both mature and developing commercial aquaculture applications. NELHA already farms numerous seafood products including shrimp, lobster, oysters, abalone, tilapia, kampachi, flounder and salmon. Additionally, aquaculture at NELHA includes the growing of microalgae for pharmaceuticals or biofuels, thus providing an input for humanitarian and environmentally friendly industries.

Investment Opportunity

Aquaculture is both sustainable and achievable. With wild fish stocks disappearing at an all-time rate, aquaculture provides a solution for replenishing global fish populations and alleviating pressure on intensively over-fished wild stocks.

Moreover, OTEC aquaculture can provide self-sustaining food resources for tropical island communities, helping them to compete with foreign fishing industries.

OTEC aquaculture can also strengthen local economies of small island developing states (SIDS), by creating job opportunities for local island residents. As the global population edges towards nine billion by 2050, the opportunity for jobs in the aquaculture industry will continue to grow. This economic impact doesn’t stop with island communities. Aquaculture can also extend to ‘upstream’ industries including agriculture, hatcheries, feed manufacturers, equipment manufacturers, and veterinary services. ‘Downstream’ industries such as processors, wholesalers, retailers, transportation, and food services are also supported by the aquaculture industry.

Because OTEC plants can incorporate aquaculture services into their design, they will help to meet future fish demands – improving both food security and protection of dwindling wild fish populations. An investment into OTEC facilities is a smart one – it helps reduce the risk of global conflict over depleting food resources and enhances the livelihoods of the millions of people who depend upon our oceans.

Open Cycle OTEC Plant - NELH via PICHTR