AQUACULTURE: BIOREMEDIATION FOR AGRICULTURE AND

INDUSTRY

Nick C. Parker

Texas Cooperative Fish and Wildlife Research Unit2

Texas Tech University

Lubbock, Texas 79409-2125

Clifford B. Fedler

Department of Civil Engineering

Texas Tech University

Lubbock, Texas 79409-1023

Mark C. Bates

Department of Range & Wildlife Management

Texas Tech University

Lubbock, Texas 79409-2125

Reprinted from: Annual Proceedings of the Texas Chapter American Fisheries Society. (1992) 14:13-21

 

1Publication No. T-9-647 of the College of Agriculture, Texas Tech University.

2Jointly supported by Texas Parks and Wildlife Department, Texas Tech University, The Wildlife Management Institute and the U.S. Fish and Wildlife Service.

 

Abstract - The expanding human population throughout the world places people in competition with fish and wildlife for land, water, and air. Because the urban centers of industrialized nations are dependent on extraction of natural resources from less populated rural areas, habitat loss is a recognized threat to a stable environment. Many natural resources, including marine and freshwater fisheries stocks, are being rapidly depleted, which is stimulating the development of aquiculture. Current agricultural and industrial processes produce or concentrate discharges that degrade the environment. Regulations developed to protect the environment require reduction or total elimination of discharges. To comply with these regulations, aquaculture integrated with agricultural and industrial processes can recycle some waste by-products into valuable products while minimizing environmental degradation. Specifically, the marine microalgae Spirulina can be grown in water too saline for traditional agriculture. In addition, Spirulina can also utilize discarded nutrients from cattle feedlots, CO2 from power plants, and organics from textile mills to produce protein and fine chemicals for use in pharmaceuticals and research. The integration of agriculture, industry, and aquaculture offers the opportunity to build a new environmentally sound agribusiness in Texas.

 

Over $9.6 billion worth of fish and fishery products were imported into the United States in 1989 (National Marine Fisheries Service 1990). However, the global catch of 98.4 million tonnes of fish in 1988 was not adequate to meet current and projected demands (National Marine Fisheries Service 1990). The Food and Agricultural Organization estimates that industrialized nations will need an additional 22.5 million tonnes of fish and fisheries products and non-industrialized nations will need 5.9 million tonnes by the year 2000 (Ratafia and Purinton 1989). Depending on regional fertility rates and other factors, the United Nations estimates the global human population to be from 8.5 to 28 billion by the year 2150. At the current rate of expansion the world's population of 5.2 billion is expected to double by the year 2038 (Ratafia and Purinton 1989). Although aquaculture has been expanding globally, present aquacultural production will not satisfy the projected demands of even the most modest population expansion.

Increasing salinization of freshwater supplies limits traditional agricultural production in many arid and semi-arid regions. Saline water unsuitable for traditional crops can be used to culture marine or brackish water algae and fish. These aquaculture products may be marketed as food, bait, or recreational species or may serve as the source for high value pharmaceutical and other biochemical products. Specifically, production of algae and fish using animal wastes from livestock and poultry production systems, saline water from oil production, and CO2 from power plants can not only provide bioremediation of environmental problems, but also can be the basis for a new agribusiness. In arid and semi-arid regions where intensive solar radiation is conducive to high primary production and other natural resources are available, marine algae has the potential to develop as a new agricultural crop.

Locations in the southwest and especially in the Texas Southern High Plains have the natural resources required to develop efficient, commercial-scale systems for culture of algae and fish using the plentiful livestock waste from feedlots as a nutrient base and saltwater as a culture medium (Parker et. al 1991). Because aquaculture is a form of agriculture, the High Plains area has much of the infrastructure needed to support aquaculture. Potential aquaculture products in such a system include algal protein for direct consumption by fish or zooplankton that are important food organisms for larval fish and several species of adult fish. Other possible products include food fish (Tilacia spp. and red drum Sciaenops ocellatus), caviar from paddlefish Polyodon soathula, and harvested algae. The harvested algae provides products such as animal feeds, health food, and a variety of high value extractable compounds.

The increased demand and declining supply of seafood products worldwide has prompted investors to identify aquaculture as a growing industry. The commercial value of some products (fish and caviar) is known, but the value and identity of other potential products remains unknown. As a food source for livestock and poultry, algal protein will be more expensive than soya protein (Henson 1990). 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).

Algal lipids containing omega-3 fatty acids should be more valuable than fish oils; however, if consumer concern about contaminants in marine fish increases, algal-derived fatty acids could command a higher price. Engineering improvements in the development of water reuse systems to conserve fresh water and development of aguaculture production systems to use saline waters would be a marketable technology of increasing value worldwide.

 

Agricultural and Industrial Problems

A large portion of the earth has an arid or semi-arid climate. In the United States, irrigation technology and development of drought-tolerant crops have resulted in agricultural development of arid and semi-arid lands. Irrigation has been a tremendous boon to our agricultural production and economy, but it is not without drawbacks. Water used for irrigation on U.S. farms was only 269 billion liters annually in 1940 but peaked at 568 billion liters in 1980 (U.S. Bureau of Census 1990). Analysis of these data indicate this increase was not due to population growth alone; daily per capita consumption of water increased from 3,887 liters in 1940 to 7,392 liters in 1989 -- an increase of 90% in 40 years. Withdrawal of ground water from the Ogallala Aquifer, estimated to contain 0.5 x 1012 m3 of drainable water (Weeks and Gutentag 1984), has increased in the High Plains to support population growth and extensive agricultural production (Nativ 1992). In many areas, withdrawal of water for irrigation has been blamed for alarming declines in the level of the Ogallala Aquifer. Due to concern for the increased cost of pumping water, some farmers have ceased irrigation. Irrigated agriculture is responsible for salinization of soils and water (Camp 1963). Some areas of the arid southwest that formally produced agricultural crops are now fallow because of the presence of subsurface saline water and an accumulation of salts at the surface. The relation between these changes and water withdrawal from the Ogallala Aquifer is unclear.

Natural sources of salt water are a liability to traditional agricultural development. Because brine springs are found throughout much of the arid western United States, several retention dams have been built to contain the salt water and protect downstream freshwater supplies. Several other containment dams have been authorized but not yet funded by Congress. The oil industry in Texas, valued at $17 billion in 1988 (Kingston 1989), produces considerable quantities of oil-contaminated brine -- in some cases, one barrel of brine is produced for each barrel of petroleum pumped to the surface. Brine water must be re-injected into deep wells or contained on the surface. Bioremediation to remove the hydrocarbon from the brine (Sims 1991) could condition it for use in aquiculture.

In addition to water consumption by crops, large cattle feedlots that require relatively large amounts of fresh water exist in Texas. Cattle are typically maintained in feedlot pens for 120-150 days while they gain weight from an initial 200-400 kg to about 500 kg at time of slaughter (Bush 1992). In 1989, over five million head of cattle were shipped from feedlots in the southern High Plains (Texas Agricultural Statistics Service 1989). Recent trends have been to develop large feedlots; in 1989, 198 feedlots accounted for 51% of the nation's output of fed cattle. A typical feedlot will have 50,000 to 100,000 head of cattle at one time. Each feedlot steer annually excretes approximately 10 tonnes of waste (88.2% moisture) per 454 kg 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. The Environmental Protection Agency has recently fined dairy farmers for groundwater pollution. Several fines have been in the $10,000 range, and at least one fine was $85,000.

 

Interaction with Migratory Waterfowl

Individual feedlots are frequently sited on sloping land to provide adequate drainage. On the High Plains, much of the surface drainage flows into one of the 20,000 playa lakes. These typically shallow, and often ephemeral, basins are believed to be the predominant recharge zones for the underlying Ogallala Aquifer and exchange rates greater than 30 mm/yr have been reported (Nativ 1992). Playas receiving runoff from cattle feedlots typically contain water throughout the year and often contain open water during the winter when other bodies are covered with ice. During harsh weather, waterfowl actively feed on grain spread throughout the feedlots and occasionally feed directly from cattle feed troughs. Under damp conditions much of this grain may mold and contain levels of alfatoxin or other mycotoxins at levels high enough to stress waterfowl. The population of migratory waterfowl on feedlot playas has been as high as 40,000 geese and 40,000 ducks on an approximately 18-hectare playa in Castro County, Texas (Personal communications, H. Miller, U. S. Fish and Wildlife Service, Lubbock, Texas). This high concentration of birds increases the likelihood of disease; however, avian cholera is not restricted to feedlot playas. Avian cholera is frequently found in birds on playas not associated with feedlots.

The potential effects of waterfowl ingesting organic and inorganic contaminants associated with runoff from cattle feedlots have not been fully explored; however, contaminants are expected in waterfowl. The occurrence of avian cholera has been linked to presence of mycotoxins on moldy waste grains and may be the cause of epizootics (Higgins et. al 1992). Water analyses from sites receiving feedlot runoff were reported to have elevated concentrations of ammonia, calcium, chemical oxygen demand, chlorophyll a, coliform bacteria, conductivity, magnesium, total Kjeldahl nitrogen, sulfates, and volatile suspended solids (Irwin and Dodson 1991).

Playas receiving effluent from feedlots can be protected by incorporating them as the final stage in a wastewater treatment facility. Waste treatment systems for cattle feedlots can be designed to include a series of anaerobic and aerobic oxidation lagoons with either (1) no discharge or (2) discharge of water of quality much greater than that now found in playas associated with feedlots. Adoption of these techniques would allow economical screening of the small, anaerobic, first-stage ponds if exclusion of migratory waterfowl from these ponds were desirable. The second- and third-phase ponds can provide a healthy habitat for migratory waterfowl and the production of economically important fish species, including fish for bait, recreation, and food.

Organic wastes from cattle feedlots provide an untapped nutrient base to support aquacultural operations. Specifically, anaerobically digested nutrients from feedlot wastes can be converted through aquaculture to algal protein for inclusion in animal feeds, including fish feed. A pilot project has been developed to produce freshwater microalgae such as Chlorella and Scenedesmus or to produce marine algae such as Spirulina (Parker et al. 1991; Parker et al. 1992), when using saline water. Manure collected from cattle feedlots and anaerobically digested and combined in a 50:50 ratio with synthetic sea salts (Instant Ocean) supported daily growth of Spirulina up to 785 mg/L (Table 1; Bates 1992). This level of production is far greater than the 60 mg/L considered acceptable on commercial Spirulina farms (Richmond 1986). The microalgae may (1) be harvested and fed without drying to livestock, swine, and fish, (2) be dried to produce a protein rich (65-70%) powder for formulated rations, (3) be harvested directly by phytoplanktivorous fish and molluscs, or (4) serve as the base stock for extraction of pharmaceuticals, fine chemicals, and other bioextracts.

 

Aquaculture: A Bioremediation Alternative

Fish production in ponds is based on surface area and is greatly regulated by ambient temperature. Natural ecological processes in ponds are used to convert waste products to nontoxic forms. To attain high production in limited water volumes in temperate climates, fish can be cultured indoors, where temperature can be controlled to speed up fish growth and degradation of waste metabolites. Control of temperature allows continuous production, thereby increasing total annual production, and allows the culture of warmwater fishes in locations that would otherwise be 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. In arid regions of the world, it may be prudent to rear and sell fry and fingerlings to other fish farmers with more abundant water supplies. Other species could be produced to meet specialty markets such as hobby fish, molluscs, shrimp, bait fish, and aquatic plants. Markets for aquatic plants include sale of cultured plants not only as a protein source, but also as ornamentals, as nursery stock to restore degraded wetlands, as stock to construct wetlands, and as bioaccumulators of toxic metals (Dunbabin and Bowmer 1992; Lan et al. 1992).

 

Summary

Locations in the southwest, and especially in the Texas Southern High Plains, have the natural resources to develop efficient, commercial-scale systems for culture of algae and fish using livestock waste from feedlots as a nutrient base, saltwater as a culture medium, the intense solar irradiation and other associated components. These natural resources, the abundance of level farm land easily modified to support raceways for algae and fish, the presence of farm equipment, labor, natural gas and CO2, and the high production rate of Spirulina grown on a cattle waste medium provide encouragement for development of a new agribusiness in the Southwestern United States. Aquaculture provides an attractive method for bioremediation of feedlot runoff into plays lakes.

Hydrocarbon-degrading microorganisms can detoxify petroleum spills. Phytoplankton can use the degraded petroleum as a source of carbon and, when provided a nitrogen source, grow at a rapid rate. On-site bioremediation of aquatic environments can be combined with aquaculture to improve water quality, not only for fish and wildlife, but also before recharge to underlying aquifers.

The potential of aquaculture seems to be unmatched by any other sector in the agricultural community in Texas. Semi-arid and arid regions can support significant aquacultural operations if approaches are taken to use natural resources available locally, to produce products of special interest and high value, and to develop the infrastructure to become an integral part of agriculture and other industries.

 

Acknowledgments

We thank R. Patino, U.S. Fish and Wildlife Service, Lubbock, Texas; L. Smith, J. Winter, Texas Tech University, Lubbock, Texas; and two anonymous reviewers for constructive criticism of the manuscript.

 

References

Ratafia, M. and T. Purinton. 1989. Emerging aquaculture markets. Aquaculture Magazine 15(4):32-44.

Treatment Concentration Final daily growth rate (ma/L*)

no. (cattle waste:fresh water) Lagoon water Digested Leachate

effluent

1(control) 0:100 61 41aA 235 74aB 157 11abAB

2 12.5:87.5 225 41bA 384 70aB 184 16aA

3 25:75 228 37bA 637 129bB 128 14bA

4 50:50 363 41cA 785 28bB 128 21abA

5 100:0 213 14bA 381 73aB 149 20abA

*All reported values are treatment means standard error (n = 4). Any two means in a column not followed by a common lowercase superscript are significantly different (P < 0.05) as determined by a CRD ANOVA and Fishers protected LSD means separation test. Any two means in a row not followed by a common uppercase superscript are significantly different (P < 0.05) as determined by a CRD ANOVA and Fishers protected LSD means separation test.