Integrated Aquaculture based on spirulina, livestock wastes, brine and power plant byproducts
Nick C. Parker and Mark C. Bates
Clifford B. Fedler
2.Jointly supported by the Texas Parks and Wildlife department, The U.S. Fish and Wildlife Service and the Wildlife management Institute.
The increasing per capita consumption of fish in the United states is partially due to consumer demand for a healthy diet and the growing recognition that the omega-3 fatty acid content of fish provides health benefits in the human. Traditional agricultural and industrial processes produce numerous waste products such as manure from cattle feedlots, CO2 from power plants and brine water from oilfields. Fish processing plants also use large volumes of water that become nutrient rich and create disposal problems. The integrated aquaculture system would recycle these waste nutrients while producing aquiculture products, such as Spirutina.
The growth of the world's human population has demanded increased harvest of fish and fisheries products from marine and inland waters. Even though the global harvest of fish was a record 101million metric tonnes in 1989, stocks of some species such as striped bass Morone saxatilis and red drum Sciaenops ocellata have been reduced to the point that they are now insignificant in the commercial catch. Both striped bass and red drum are being produced in hatcheries for restocking in coastal areas. Species such as panaoid shrimp, Atlanti.c salmon (Salary_ salar) and channel catfish ( Ictalurus cattish) are reared on farms. These and other aquaculture species collectively accounted for 20% by volume and 30% by value of the world supply of fish and fisheries products in 1989.
Aquaculture, the farming of aquatic species including fish and clams, is an emerging industry in the United States and has tremendous potential in Texas and other Southern states (Joint subcommittee on Aquaculture, 1983a,b). The Department of Commerce estimated that 295 million pounds of farm raised catfish were shipped to processing plants in 1988, but others in the aquiculture industry estimated 400 million pounds. The pond-side value of ese fish was about 5300 million and represented 51% by value of all farm-reared fish in the United States. The 1990 aquiculture production in the U.s. was estimated at about $0.75 billion compared to fish and fisheries products imports of $9.6 billion. Imports of fish into the U.S. expanded at an average rate of $860 million per year from 1982 to 1987 and has continued its upward spiral. The market potential for high quality farm-raised fish appears to be expected to be in high demand and command a premium price (Parker, 1988).
Microalgae, of which SPirulina and Chlorella seem to be most promising, have been commercially produced in several locations throughout the world (Richmond, 1986). The primary market for Suirulina is for specialty items such as vitamins, pigments, pharmaceutical products, the human health food market, and feeds for larval aquatic organisms or ornamental fish of high value (Cohen, 1986). In 1984, the worldwide production of SPirulina for food was 850 metric tonnes produced on 10 farms with a total of 35.6 hectares in cultivation. Spirulina is particularly attractive because of the high protein content (50-70%), lipid content (716%), adaption to brackish water (salt at 20-70 g/L is optimal but 1-270 g/L is tolerated), relative ease of harvest by flotation and filtration, and its ability to use animal waste as a nutrient base.
In 1990, 6 million head of cattle were processed through feedlots on the High Plains of Texas. Animal wastes, presently a liability, associated with these feedlots provide an untapped resource that, coupled with saline water, sunny days (about 300 per year), and the arid climate, make the High Plains an ideal location for culture of microalgae. We estimate that over 2 million tons of dried algal biomass could be produced annually from the wastes of the 6 million head of cattle.
The culture of Spirulina depends on a suitable growth medium such as highly saline water. Oilfield brine, a waste water from the petroleum industry, contains high levels of dissolved salts (salinity values of greater than 200 g/L are common) and residual hydrocarbons, that limit disposal options. A producing oil well can produce up to one barrel of brine for each barrel of oil produced. Treatment of brine with hydrocarbon degrading bacteria and dilution to desired salinity produces a diluent suitable for preparation of a SPirulina growth medium while also recycling the brine wastes.
Algae require CO2 as a carbon source for their photosynthetic metabolism. Exhaust from conventional power plants can supply the needed carbon and in turn decrease the amount of CO2 discharged into the atmosphere. Additionally, if raceways are positioned near powerplants, hot water from the power plant could be used to elevate pond temperature in the winter months, which would prolong the Spirulina growing season.GOALS AND OBJECTIVES The goal of this project is to create a new, environmentally sound, aquiculture industry. Specific objectives are (1) to recycle waste material from cattle feedlots, power plants, oilfields and fish processing plants a nutrients for aquiculture, (2) to grow a process Spirulina as fish feed, (3) to evaluate these Spiruli based.diets on growth end survival of fish, and (4) to evaluates potential for extraction of pharmaceuticals from Spirulina. MATERIALS AND METHODS Laboratory cultures of spirulina have been established and a pilotscale algae production plant has been constructed in Lubbock, Texas. The plant consists of four raceways, two under greenhouse cover and two outdoors. All four raceways were built to the same dimensions (16.1 m long x 2.4 m wide x 0.3 m deep) with 10.6 m3 of water and all are circulated by air lift pumps. In addition, three 550-L and two 375-L outdoor fiberglass culture tanks are available.
An anaerobic cattle waste digester system has also been built to provide effluent in sufficient amounts for research purposes. The digester system consists of eight 500-L fiberglass silos, four of which will be used as "open" anaerobic digesters with the remaining four serving as sealed anaerobic digesters. The four sealed digesters are equipped with a gas circulating system to agitate the digester contents.
Fluid will be stored or prepared in three 2,000-L fiberglass tanks. One tank will be used to prepare a slurry cattle manure to be used in the digester silos. The remaining two tanks will be effluent receiving and clarification tanks. The pilot-scale and laboratory cultures of Spirulina will be used to develop design criteria for automated production in a commercial-size plant. Spirulina will be produced in the raceways both outdoors (ambient conditions) and indoors (in the greenhouse to minimize evaporation during the summer and retain heat during the winter). Effluent from the digesters will be passed across vibrating screen filters to remove solids before adding the liquid fraction to the raceways as the nutrient base for Spirulina. Oilfield brine will be mixed with the digester effluent to provide the desired salinity for Spirulina growth. The biomass will be continuously harvested through vibrating screens, moved to a drying belt and then processed into fish feed. Algae, associated bacteria, fungi, yeast, zooplankton, and detritus will be analyzed for content of protein, lipids, carbohydrates and ash and evaluated as feed supplements for warmwater fish.PRELIMINARY RESULTS Preliminary laboratory results are promising and include:
INTERDISCIPLINARY TEAM This research and development project is made possible by the following interdisciplinary team of researchers, local (L), state (s), and federal (F) agencies, Texas Tech University (TTU) and private sector supporters (P):
(1) Demonstration of spirulina growth up to 800 mg/L when grown in a medium containing anaerobically digested cattle waste.
(2) Demonstration of suitability of diluted oilfield brine as a diluent after renovation with hydrocarbon degrading bacteria.
(3) Demonstration of growth of Spirulina in brine from three different oilfield wells in West Texas.
(4) Demonstration of Spirulina to effectively remove odor and color from textile dye wash.
(5) Demonstration of airlift pumps for circulation of raceway water.
Joint Subcommittee on Aquaculture. 1983a. National aquiculture development plan. Volume I, Washington, D.C. 67 pages.
Joint Subcommittee on Aquaculture. 1983b. National aquiculture development plan. Volume II, Washington, D.C. 196 pages.
Parker, N.C. 1988. Aquaculture - natural resource managers' ally? Transactions North American Wildlife and Natural Resources Conference 54:584-593.
Richmond, A., (Ed.) 1986. CRC handbook of microalgal mass culture CRC Press, Boca Raton, FL.