Energy from organic waste The utility of biological sources

by Alessandro Gatto

Among the so-called “alternative energies” there is also that which can be obtained from biological sources such as organic waste. It nevertheless has to be remembered that, producing energy from the biomass implies integration within the biological cycle; in order to avoid upsetting the delicate balance of living systems one has to be competent in the fields of biology, mechanics and engineering, and act with interdisciplinary awareness and extreme caution. Digester of the Chinese type (from “Renewable energies” Clup Edizioni, Milan) Bioconversion can be effected on vegetables and vegetable waste, as occurs in Brazil for the production of alcohol for automotive fuel, but also on recuperated waste products such as sawdust, straw and refuse. At present the energy production is only certain in small plants which can produce biogas through methanogen fermentation, and plants which can produce ethyl alcohol through alcoholic fermentation. Nevertheless there is also the possibility of producing gas and vegetable carbon through pyrolysis. Biogas It was Dr. Ram Bux Singh, an Indian scientist who studied the system for producing energy from organic waste, who coined the word “biogas”. In the 60s in India, at the Gobar Gas Research Station in Ajitmal, the scientist started work on the construction of plants for the production of this gas. The combustible is produced by the activity of bacteria which decompose organic material in the absence of air, and it is composed of a combination of 50-70% methane, 35-40% carbon dioxide and the remainder of other gases. The most widely-used systems for the production of biogas are the Indian and Chinese types, which operate on animal and human excrement, organic domestic waste both liquid and solid, and vegetable waste of varied kinds, such as grass, leaves, straw, algae and aquatic vegetables. To get a clearer idea: the daily dung output of an average cow produces about 1 cubic metre of biogas per day, equivalent to 0.7 litres of petrol, or 0.8 kg of wood carbon, 2kg of wood or 1.3 litres of ethanol.

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