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The total world reserves of fossil fuels are estimated to be approximately 1,100 billion TCE (tonne of coal equivalent) comprising of 180 billion TCE of natural gas, 300 billion TCE of mineral oil, shale and liquid gas, and 600 billion TCE of coal (all forms). On the other hand, world’s current rate of consumption is estimated to be around 14 billion TCE (RWE -World Energy Report 2005). This essentially means that if the rate of consumption stays at the present level considering no economic development – no population growth, the present reserves would last until the end of this century at the current prices.
At present, world’s conventional fossil fuel reserves i.e. oil, gas and coal combined meet approximately 87% of the world’s energy demand. Rest of the energy demand is met by various other forms of generating energy ” from nuclear to hydro, solar, wind and others which do not contribute much on global terms. In view of the soaring prices of conventional fuels, alternatives liquid fuels such as bio-fuels (mainly ethanol and bio-diesel), shale oil, extra-heavy oil, liquefied coal or gas are expected to become increasingly competitive in the near future.
Their supply is expected to grow from 3 to 10 million barrels per day from 2005 to 2030. The crucial issue with regard to the present energy crisis is not whether the availability of conventional fuels at economically affordable price but how fast and better alternatives becomes available. The usage of biofuels, owing to their more environment friendly nature as compared to conventional fossil and their contributions in greenhouse gas emission reduction, is increasing day by day.
The bio origin fuels are derived from renewable sources. Further, bio origin fuels may be alcohol, vegetable oils, biomass and biogas. Some of these bio origin fuels can either be used directly whereas others need to be alternated with others to meet the required properties near to fossil fuel . According to the present scenario, the diesel engines are highly efficient in comparing to other engines. Hence, it has been used as a leader prime mover of key engineering applications . For diesel engines, numerous analysts have been proposed towards utilizing biofuels and they are essentially gotten from the vegetable oils, despite the fact that non-eatable vegetable oils in their methyl or ethyl esters from recognized as biodiesel. It has been appeared by the analysts that the attributes of the biodiesel fuel are practically identical to the mineral diesel fuel and it tends to be utilized as a feasible alternative option of the traditional diesel fuel. However, there are some problems like lower calorific value and volatility, free fatty acid content, high viscosity, polymerization during storage, and the reactivity of unburned fuel causing fouling of injector nozzles and carbon deposition on cylinder walls, lubricating oil thickening and gum formation in presence of oxygen etc. In view of resolving these hurdles, the vital studies has appeared on a combination of different biofuels or biodiesels having higher calorific value and low viscosity and such as turpentine oil, alcohol, eucalyptus oil and conventional diesel or highly viscous biodiesel like: Cashew Nut Shell, Karanja, Jatropha. In this perspective, Devan et al.  resulted higher brake thermal efficiency, increased NOx emission, and lower HC and CO emission with increasing blend ratio of Paradise-eucalyptus biodiesel with diesel. Dubey et al. [6, 7] uncovered that the impact of higher compression ratio enhanced the performance and emissions with the use of turpentine oil and Jatropha biodiesel. It was seen that at the smoke opacity and NOx, CO2, CO and HC emission diminished while brake thermal efficiency increased by 2.17%, at the compression ratio of 20. Chauhan et al.  observed on mineral diesel and blends of Jatropha biodiesel. The study observed reduction of emissions of HC and CO emissions and higher NOx emission with an increase in blend ratio and an increase in BTE with load increase as compared to mineral diesel fuel. Sivalakshmi  has attempted to study ethanol and blends of neem oil and experienced increase in brake thermal efficiency with increases concentration of the biodiesel in the blend whereas decrease in CO, increase in HC and NOx emission with increase in percentage of ethanol at full load condition. Anand et al.  performed experiments on methanol and Karanja biodiesel and resulted 4.2% increase in BTE by at 80% load, with a reduction in smoke and NOx emission on a diesel engine. Prem Anand et al.  reported that engine operating on blend of diesel and 30% turpentine oil shown lower HC, CO, NOx and smoke. It is shown that turpentine blends of 40% and 50% resulted lower exhaust emission and brake power. Vallinayagam et al.  reported that the use of fuel with low cetane number and viscosity like pine oil is blended with mineral diesel. He resulted lower CO emission than diesel for 50% and 25% blends and higher BTE and HC emission for 100% and 75% blends and lower NOx emission for all other blends compared with diesel fuel. Karthikeyan et al.  demonstrated that engine running on the dual fuel (turpentine and diesel) blend revealed reduction of 40-45% smoke, lower CO and HC emissions.
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