фев 16, 2011 | 09:02

It is believed that majority of oil and natural gas originates from algae in ancient oceans. Oil (petroleum) consists of liquid hydrocarbons which arc compounds composed of carbon and hydrogen. At least 80% w/w of oil is carbon. The remainder is principally hydrogen, but sulfur and oxygen may each account for up to 5% of the weight of oil. The burning heating volume of oil is relatively high owing to its liquid state, and is comparable to that of coal. Total proven oil reserves worldwide are estimated to be worth the equivalent of 40 years of consumable oil, based on a 1988 worldwide oil production rate of 64.2 million barrels per day. Proven oil reserves include residual oil in oil fields where production drilling has already begun. Projected oil reserves are slightly greater than proven oil reserves, but are not however infinite. Furthermore, oil reserves are not equally distributed globally. The Middle East has by far the world's greatest proven oil reserves. Oil production in other nations will decrease as their reserves decline, putting the Middle East in a dominant position in the oil market. The Organization of Petroleum Exporting Countries (OPEC) is in control of approximately 60% of the world's oil, and exercises a strong influence on oil prices worldwide. The lack of stability of future energy supplies has motivated the development of alternative energy sources in order to eliminate the possibility of a future energy shortage. Microalgae as biological sources of lipids and hydrocarbons Microalgae contain lipids and fatty acids as membrane components, storage products, metabolites and sources of energy. The chemical compositions of various microalgae are shown in.Algal fatty acids and oils have a range of potential applications. Algal oils posses characteristics similar to those offish and vegetable oils, and can thus be considered as potential substitutes for the products of fossil oil. Direct extraction of microalgal lipids appears to be a more efficient methodology for obtaining energy from these organisms, than is the fermentation of algal biomass to produce either methane or ethanol. The lipid and fatty acid contents of microalgae vary in accordance with culture conditions In some cases, lipid content can be enhanced by the imposition of nitrogen starvation or other stress factors. In the late 1940s, lipid fractions as high as 70 to 85% on a dry weight basis were reported in microalgae. Such high lipid contents, exceed that of most terrestrial plants. The effect of nitrogen on the lipid fraction and on cell growth of the strain Nannochlolis cultured under saline conditions is summarized in. Nutrient deficiencies (other than nitrogen deficiency) may also lead to an increase in cellular lipid content.A report came that the lipid content of the diatom Navioua pelliculosa increased by about 60% during a 14-hour silicon starvation period. *Chemical Composition of Algae Expressed on A Dry Matter Basis (%)) Strain Protein Carbohydrates Lipids Nucleic acid Scenedesmus obliquus 50-56 10-17 12-14 3-6 Scenedesmus quadricauda 47 - 1.9 - Scenedesmus dimorphus 8-18 21-52 16-40 - Chlamydomonas rheinhardii 48 17 21 - Chlorella vulgaris 51-58 12-17 14-22 4-5 Chlorella pyrenoidosa 57 26 2 - Spirogyra sp. 6-20 33-64 11-21 - Dunaliella bioculata 49 4 8 - Dunaliella salina 57 32 6 - Euglena gracilis 39-61 14-18 14-20 - Prymnesium parvum 28-45 25-33 22-38 1-2 Tetraselmis maculata 52 15 3 - Porphyridium cruentum 28-39 40-57 9-14 - Spirulina platensis 46-63 8-14 4--9 2-5 Spirulina maxima 60-71 13-16 6-7 3-4.5 Synechoccus sp. 63 15 11 5 Anabaena cylindrica 43-56 25-30 4-7 - Liquid fuels from microalgal biomass It is well known that microalgae is able to assimilate CO2 gas as a carbon source for growth. However, if the resulting cell mass is not suitably treated, CO2 will be evolved and diluted into the environment by decomposition, thus preventing CO2 fixation from contributing to a reduction in atmospheric CO2. Petroleum is widely believed to have its origins in kerogen, which can be easily converted to an oily substance under conditions of high pressure and temperature (15-17). Kerogen has formed from algae, biodegraded organic compounds, plankton, bacteria, plant material, etc., by biochemical and/or chemical reactions such as diagenesis and catagenesis. Several studies have been conducted to simulate petroleum formation by pyrolysis, some of which used the marine alga Fucus sp. as the base material. Recently, activated sludge and fungi were converted to oily substances at relatively low temperatures as compared with those used in previous experimental simulations. On the basis of these findings, it is assumed that algae grown in CO2-enriched air can be converted to oily substances, and that such an approach can contribute to solving two major problems: air pollution resulting from CO2 evolution, and future crises due to a shortage of energy sources. Use of thermochemical liquefaction of organisms in the production of alternative fuels, would reduce CO2 evolution into the atmosphere since such fuels would indeed be produced from CO2. Apart from the experimental simulation discussed above, other work has also been conducted with the objective of producing fuel from microalgae. Feinberg (18) reported that diesel fuel and gasoline were produced through the transesterification and catalytic cracking of lipids accumulated in algal cells. However, the raw material utilized in their work was restricted to microalgae of high lipid content. A process for the production of fuel oil from microalgae by pyrolysis has been proposed. The pyrolysis usually requires a drying procedure in which large amounts of energy are required to vaporize water. An alternative technique involving the direct thermochemical liquefaction of biomass of high moisture content, such as wood and sewage sludge, has been proposed and applied to the production of fuel oils from microalgae. This liquefaction is carried out in an aqueous solution of either alkali or NaCl at a temperature of about 300 C and pressure of 10 MPa in the absence of reducing gases such as hydrogen and/or carbon monoxide. Since drying is not required, energy consumption for water vaporization is avoided. Microalgal cell precipitates derived from centrifugation, which are of a high moisture content, are thus good raw materials for liquefaction. WORK IS ON ……………….. WANT MORE DETAILS THEN WRITE TO US.. Or Visit www.instituteofinnovations.com