Production of Biofuels by Sewage Sludge
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Abstract
Globally, biofuels are produced from the agricultural sources or biomass which contains higher feed stock material and agricultural component. These sources are used as a good source for the good yield of biofuels that results to higher energy production. These biomasses comprised of various organic chemicals which are processed for production like sugars, starch and hydrocarbons components. Industrial, agricultural and domestic wastes are treated and converted to biosolids or sewage sludge, which contains a diversity of organic chemicals in different ranges. Organic chemicals like hydrocarbons, alkanes, alcohols, esters, ethers, various amines, and isomers of compounds were studied in the sewage sludge. As with the variety of sewage sludge it might be used for the production of fuels for energy production. Studies and discussions in the way to use sewage sludge give the assumption for the alternative’s sources or biomass for the production of biofuel. the conventual fuel such as petrol and diesel as these fuels increasing the risk factors that influenced the pollution. Most of the researches for the biofuels are going in the way for leading to liquid biofuel production. A recent classification for biofuel includes 'First generation' and 'second generation' biofuels (4) and the distinction between them is the feed stock used. Some work is also under the progress for production of 'third generation' of biofuels. (5). Carbon dioxide can be fixed by microalgae from three different sources, viz. atmosphere, discharge gases and soluble carbonates. (31). Under natural growth conditions, assimilations of carbon dioxide by microalgae from the air and can tolerate and utilize high level of carbon dioxide. (32). In common production units, carbon dioxide is fed to algal growth medium either from external sources such as power plants or in the form of soluble carbonates. (33). For algal production, other inorganic nutrients are required includes nitrogen, phosphorus and silicon. (34). Fixation of carbon dioxide by algae has been proposed as a method of removing carbon dioxide from flue gases from power plants and used to reduce emission of greenhouse gases. Many algae or rich in oil, as algal cells found to be enriched with oil globules, which can be converted to biodiesel. (5). Algae production mechanism phototrophic, heterotrophic and mixotrophic are in use, which all follow the natural growth processes. Photoautotrophic production is autotrophic photosynthetic processes, heterotrophic production requires organic substances e.g., glucose to stimulate growth, and some algae can combine both autotrophic and heterotrophic assimilations of organic compounds in mixotrophic processes. (35). Many microalgae strains have high lipid content and it can be enhanced by optimization of growth determining factor. (32). Studies demonstrated that algae, when starved forms a suitable source of nitrogen, that produced mainly oil, and in the presence of sunlight algae produces sugars and proteins from carbon dioxide sources. Chlorella prototheorids microalgae when grown under autotrophic and heterotrophic conditions leads to accumulations of lipids, which can be used for production of biodiesel. Nitrogen limitation is most effective method of improving microalgae lipid accumulation of lipids, but results in change of lipid composition from free fatty acid to triacylglycerol (TAG) and these TAG useful for conversion to biodiesel. (36). Instead of using feed stocks or agricultural products, treated sewage sludge will be used for the production of biofuel. As sewage sludge contains a high amount of organic chemicals. These chemicals might be taken in use for production of biofuels and syngas. By the use of various chemical processing techniques or chemical reaction these organic chemicals processed for the production of fuel component. This article gives the future aspect for the production of biofuel from the organic chemical of sewage sludge. Sewage sludge uses, will help in reduction of waste product and advancement in the biofuel production. Challenges reducing the use of feed stocks may reduce from the use of sewage sludge material. Uses of sewage sludge foe biofuel production will makes a new way for development and technology in the field of fuels.