|Bioconversion of Organic Residues for Rural Communities (UNU, 1979)|
|Micro-organisms as tools for rural processing of organic residues|
For many years algae have been used by the shoreside populations of Lake Chad and Lake Texcoco (Mexico) as a source of food, and one algal species (Spirulina sp.) is now produced commercially in Mexico at the rate of several thousand tons per year.
Certain big-engineers and microbiologists believe that carefully selected genetic strains of algae (Scenedesmus acutus, Spirulina maxima, Cosmarium turpinii), or photosynthetic bacteria (Rhodospirillum sp. or Rhodopseudomonas sp.) are the organisms of choice for the production of single-cell protein (30, 31). Such microbes contain about 65 per cent crude protein of moderately high biological value. The protein appears to be well utilized by animals. In addition, most species are as good a source of the B vitamins as yeast, and they contain ascorbic acid.
In addition to algal biomass having many uses, the process can be used to help purify sewage, livestock manure, and other agricultural wastes. A unique feature proposed by Colombo (31) is the cultivation of the algae in plastic tubes that can be extended for considerable distances in arid regions over land that is not useful for cultivating crops. Such a system takes advantage of solar energy, saves water, requires little capital and labour for development, and can be used either in the rural areas of less developed countries or on a larger industrial scale.