Production and Nutritive Value of Arthrospira Platensis, a Spiral Blue-Green Alga Grown on Swine Wastes

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Abstract
Methane generation has been proposed as a means of swine waste disposal. As a secondary treatment to recover nitrogen, carbon and other nutrients from the effluent of a methane generator, Arthrospira platensis (a blue-green alga also known as Spirulina) was grown and its nutritive value determined. This alga contained 55 to 61% crude protein and was easy to harvest. Three indoor culture ponds of .65 M2 were designed and built. The ponds consisted of a bottomless wooden frame lined with a polyethylene sheet resting on a table top. Culture medium was kept circulating by a special aerator. An inorganic medium was evaluated. When algal growth reached a saturation point, there was still 70% of N03— and 11% of HCO3— left unused in the medium. Swine waste fermented at a hydraulic retention time of 10 days gave the highest ratio (2.3:1) of NH3-N to TKN (about 70% NH3-N). NH3 seemed to support best the growth of algae, when the effluent was slowly infused. Organic acids in the effluent also provided a good source of carbon, a limiting factor when algae were intensively grown. Under the light intensity of 500 footcandles, Arthrospira yielded about 5 g/M2/day. A sample containing 2,038 mg of NH3-N produced 16,250 mg of dry algae, containing 9,750 mg protein or 1,560 mg N, giving an efficiency of nitrogen recovery of 76%. The protein of Arthrospira platensis showed a PER of 2.25, apparent nitrogen digestibility of 76.7% and biological value of 67.7%; no toxic effects were noted. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.