Written for presentation at the 1995 International Summer Meeting

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THE AMERICAN SOCIETY OF AGRICULTURAL ENGINEERS

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1Funding provided by the U.S. Department of Commerce Economic Development Administration Project No. 08 06-02714, the Texas Higher Education Coordinating Board Advanced Technology Program, Project No. 003644- 064, and the Texas Tech University Water Resources Center. Publication number T-9-710 of the College of Agricuttural Sciences and Matural Resources.

Engineering improvements in the development of water reuse systems to conserve fresh water and development of aquaculture production systems to use non-potable water would be marketable technology of increasing value worldwide. Many regions of the world already have the resources available to support integrated operations if approaches are taken to use natural resources locally available, to produce products of special interest and high value, and to develop the infrastructure as an integral part of agriculture and other industries. A ponding system that utilizes known technologies in a new way for the treatment of wastewater integrating by-product development is one alternative to providing wasete treatment for the 21st century.

Since a large portion of the earth has an arid or semi-arid climate, irrigation technology and development of drought-tolerant crops has resulted in continued development of these lands. Irrigation has provided a tremendous benefit to our agricultural production and economy, but not without drawbacks. Water used for irrigation on U.S. farms was only 0.27x109 m' (71 billion gallons) annually in 1940 but peaked at 0.57x109 m' (150 billion gallons) in 1980 (U.S. Bureau of Census, 1990). This increase was not due to irrigation growth alone; daily per capita consumption of water increased from 3.9 m' (1027 gallons) in 1940 to 7.4 m' (1953 gallons) in 1989-an increase of 90% in 40 gears. Withdrawal of ground water has increased to meet the greater demands for fresh water to support the population growth and extensive agricultural production. Some farmers have ceased irrigation, not only because of the high cost of pumping but the fact that irrigation is responsible for salinization of soils and water (Camp, 1963).

In addition to water consumptions by crops, large animal feedling operations that also require relatively large amounts of fresh water have been developed in this mosaic of rangelands and row crop agriculture. Cattle, for example, are usually maintained in feedlot pens for about 5 months while they gain weight from an initial 200400 kg (400 800 lb) to about 500 kg (1100 lb) at the time of slaughter. Recent trends have been to develop large feedlots; in 1989, 198 feedlots accounted for 51% of the nation's output of fed cattle (Texas Agricultural Statistics Service, 1989). A typical feedlot will have 50,000 to 100,000 head at one time. Each feedlot steer annually excretes 10 tonnes (9 tons) of waste (88.2% moisture) per 1,000 units of live weight (Midwest Plan Service, 1975). The concentration of waste resulting from these and other intensive agricultural operations, such as swine, poultry, and dairy, creates severe waste management problems. In addition to potential environmental damage, there are economic aspects associated with disposal of this waste, such as fines for non-compliance with current regulations.

Elements of wastewater treatment systems of Oswald (1988) and Hammer (1989) have been incorporated to develop an integrated system to treat effluent from animal production units while producing biomass-based energy and agricultural products. This treatment system consists of a 4-stage system (Figure 1), beginning with the separation of solids from the waste. The second stage is an anaerobic pit incorporated into a facultative lagoon (called an advanced facultative lagoon, AFL) (Figure 2). The third stage consists of an aquatic plant production pond (for production of algae, duckweeds, or macrophytes). The final effluent could then be used to raise fish. This effluent with the algae phormidium boneri, can contain ammonia levels at less than 1 ppm which is necessary for raising most species of fish. Another type of system, currently being designed to reduce the nutrient discharge from secondary treated municipal we will consist of constructed wetlands with the option of producing native macrophytes, duckweed, microalgae, ornamental plants or alternately flooded and dried grasslands using knotgrass, Components of these two systems are under construction at the Texas Tech University animal science demonstration site near New Deal, Texas. This system provides three options for the third stage of the process - production of algae, duckweeds, or macrophytes (Figure 1). ibis demonstration treatment system will accept both swine and cattle waste that is screened to separate some of the heavy solid material in the waste. Water will pass sequentially through the units shown in Figure 1 and be recycled back to the swine and cattle operations for flush water or discharged as water for irrigation of crops.

Another potential product from this type of integrated waste treatment system is the production of water lilies, Louisiana irises, and other ornamental aquatic plants. This system is the most labor and capital intensive, however, it provides the greatest potential for economic return. Aquatic plants grown in Texas are now being shipped throughout the country and also to foreign markets, including Germany and Japan. Some of these ornamental plants are produced in open outdoor ponds, others in ponds covered with greenhouse structures. Selected individual plants have sold for $69.95 for a 10-15 cm (4-6 inch) pot. Returns for some ornamental plant crops have been as high as $80,000/A in one year. Of course the average return is much lower, but the potential for managing a nutrient reduction system as a business does exist.

Production and sale of fish will generate additional funds. Bait fish commonly sell for $22-33/kg (($10-15/lb)) and other high-value fish include fingerlings of sport fish such as bass and bluegill; fingerlings of foodfish such as red drum and channel catfish to be stocked and reared in other facilities; and ornamental fish such as swordtails and mollies. Lower value fish, such as carp, can be processed as fish meal and incorporated into feeds for swine, poultry and other fish.

Although 60% by weight of the fish harvested from the oceans is consumed directly by man, fish and fish by-products have other important uses. One such use is production of fish meal, which provides a large part of the protein formulated into feeds for livestock and poultry. The demand for fish meal increased in the Far East, China, the Scandinavian countries, and the United Kingdom in 1988 as a result of expansion of the aquaculture and poultry industries. As demands increased in other parts of the world, not to the cost of fish meal increased. United States' imports of fish meal decreased by 30% between 1987 and 1988 as the cost increased and the value of the U.S. dollar in the world market declined (Ratafia and Purinton, 1989). As a result, animal producers in the United States were forced to feed feeds formulated with higher levels of plant protein.

Figure 2.  Simplified schematic of the advanced facultative pond used in the integrated wasterwater treatment system (not to scale).

For current land-based animal production methods and technologies, the net effect of a limited global fish supply is a limited global protein supply. Not only will the oceans' fishery products be insufficient to provide needed protein for human consumption, they will be insufficient to provide the feeds necessary for intensive production of animals in confinement.

Economic incentives exist for further development of aquaculture. One percent of the United States' fish supply was farm-reared in 1970; by 1987, 7% of the fish consumed in the United States were produced by aquaculture. In 1989, fish reared on American far were valued at about $750 million (National Marine Fisheries Service, 1990). However, imports of fish and fishery products into the United States were valued at $9.6 billion in the same year. Exports of seafood products are about S2 billion less than imports (Smith, 1995). Clearly, economics alone are not sufficient to increase aquacultural production in the United States.

Commonly, fish reared on fish farms, particularly in the United States, are those that are economically desirable for fish farmers. Rearing fish for stocking recreational fisheries (sportfish) or for aquarists (hobby fish) can be lucrative; however, rearing sportfish and hobby fish does little to satisfy the need for protein. For the many farmers producing food fish that are "economically desirable. means rearing high-value fish that typically require large quantities of expensive protein in their diets. Recycling plant and animal protein into high-value fish does little to reduce world-wide protein needs.

Marine algae, the predominant synthesizers of omega-3 fatty acids, are at the base of the marine food chain through which these nutritionally important lipids enter fish and, ultimately, the human diet. Recent studies have suggested various benefits of omega-3 fatty acids to human health (Stansby, 1990; Land, 1986). The National Institute of Health and other health organizations have shown that omega-3 fatty acids are essential in the human health (Hunter, 1987, 1988; Lees and Karel, 1990). The effects of dietary omega-3 fatty acids on farm raised fish is now being investigated at several locations including Texas A&M University, Mississippi State University and on fish farms in Japan.

The increased demand and declining supply of seafood products world wide identify aquaculture as a growing industry. The commercial value of some products (fish and caviar) are known but the value and identity of other potential products remains unknown. In many arid and semi-arid regions in particular, attaining a high level of production in limited water volumes means that fish culture must move indoors where temperature and water loss can be controlled. Control of temperature allows continuous production, thereby increasing total annual production, and allows the culture of warmwater fishes in locations that would otherwise be climatically unsuitable.

Environmental control in water reuse systems allows great flexibility in the types of fish that can be produced However, there are two constraints: (1) the products must be sufficiently high in value to compensate for the additional costs of construction and operation of the facility and (2) the animals reared must tolerate high-density crowding. For example, in arid regions of the world it may be prudent to rear and sell fry and fingerlings to be stocked and grown by other fish farmers with more abundant water supplies. Other species could be produced to meet specialty markets and could include hobby fish, mollusc, shrimp, and bait fish.

As a food source for livestock and poultry, algal protein is valued in comparison to the cost of soya protein when produced in integrated ponding systems. The cost of algal protein would be lowered by the scale of the production system and the high value of products extracted from the algae (e.g., pigments, pharmaceuticals, reagents, etc.). Processing of the algae to obtain the high-value products leaves algal protein as a value-added protein by-product.

Algal lipids containing omega-3 fatty acids will be valued in comparison to fish oils; however, algal-derived fatty acids could command a higher price if consumer concern about contaminants in marine fish increases. Engineering improvements in the development of water reuse systems to conserve fresh water and development of aquaculture production systems that use waste nutrient resources would be marketable technology of increasing value worldwide. Many regions can support significant aquaculture operations if approaches are taken to use natural resources locally available, to produce products of special interest and high value, and to develop the infrastructure as an integral part of agriculture and other industries.

Camp, T. R. 1963. Water and its impurities. Reinhold Publishing Corp., New York.

Cohen, Z. 1986. Products from microalgae. Pages 421-454 in Richmond, A. (Ed.) 1986. CRC handbook of microalgal mass culture. CRC Press, Boca Raton, Florida.

Fedler, C. B. and N. C. Parker. 1993. High-Value Product Development Potential From Biomass. Paper No. 936056 presented at the International Summer Meeting of the ASAE/CSAE. Spokane, Washington. June 20-23, 1993.

Fedler, C. B., N. C. Parker, H. L. Schramm, Jr., and J. Borrelli. 1991. Integrated production of algal protein, omega-3 fatty acids, and fish in West Texas. Final Report to the U.S. Department of Commerce, Economic Development Administration, Project No. 08-06-02714. Austin, Texas.

Hammer, D. A. (ed.). 1989. Constructed wetlands for wastewater treatment - municipal, industrial and agricultural. Lewis Publishers, Inc. Chelsea, Michigan.

Hunter, J. E. 1987. Fish oil and other omega-3 sources. Journal of the American Oil Chemists Society 64(12):1592-1594, 1596.

Lees, R. S. and M. Karel. 1990. Omega-3 fatty acids in health and disease. Marcel Dekker, Inc. New York.

Midwest Plan Service 1975. Livestock waste facilities handbook. Iowa State University, Ames, Iowa.

National Marine Fisheries Service. 1988. Aquaculture and captive fisheries: impacts in U.S. seafood markets. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Washington, D.C.