Presentation on theme: "R. Shanthini 06 Feb 2010 Ethanol as an alternative source of energy Bioethanol is produced from plants that harness the power of the sun to convert water."— Presentation transcript:
R. Shanthini 06 Feb 2010 Ethanol as an alternative source of energy Bioethanol is produced from plants that harness the power of the sun to convert water and CO 2 to sugars (photosynthesis), therefore it is a renewable fuel. Bio
R. Shanthini 06 Feb 2010 Bioethanol is produced from plants that harness the power of the sun to convert water and CO 2 to sugars (photosynthesis), therefore it is a renewable fuel. Ethanol as an alternative source of energy Bio
R. Shanthini 06 Feb 2010 Ethanol as an alternative source of energy oxygen in the ethanol molecule helps in complete combustion, which means less emissions Bio
Ethanol is a high-octane fuel, and is widely used as a blending ingredient in petrol. A growing number of cars and trucks designated as FlexFuel Vehicles (FFV) can use ethanol blended up to 85% with petrol (E85 fuel). Today there are more than 6 million FFV's on U.S. roads alone.
R. Shanthini 06 Feb 2010 Source: http://www.distill.com/World-Fuel-Ethanol-A&O-2004.html
R. Shanthini 06 Feb 2010 glucose molecule Bioethanol from simple sugars: Sugar cane and sugar beets store the energy as simple sugars, glucose (C 6 H 12 O 6 ) 2 CH 3 CH 2 OH + 2 CO 2 yeast impure cultures of yeast produce glycerine and various organic acids this simple-looking reaction is a bioreaction and thus very complex
R. Shanthini 06 Feb 2010 Yeast can be replaced by the bacterium Zymomonas mobilis - gives up to 98% yields - minimal by-products - simple fermentation requirements - several-fold the production rates of yeast Z. mobilis industrial strain CP4, originating from Brazil, vigorously fermenting glucose. Photo courtesy Katherine M. Pappas
R. Shanthini 06 Feb 2010 sugar cane sugar cane crushed and soluble sugar washed out sugar cane residue fermentation of sugars produces 5 - 12% ethanol yeast distilled to concentrate to 80 – 95% ethanol used as a petrol replacement dehydrate to 100% ethanol used as a petrol additive CO 2 wet solids
R. Shanthini 06 Feb 2010 Bioethanol from starch: Corn, wheat and cassava store the energy as more complex sugars, called starch dextrins α-amylase amyloglucosidase glucose monomer } starch (glucose polymer)
R. Shanthini 06 Feb 2010 Liquification (at 90 – 95 deg C; pH = 4 - 4.5; 400 rpm) Saccharification with glucosidase enzyme (at 55 - 65 deg C, pH = 4 - 4.5) Cooling (32 deg C) Fermentation with yeast (40 – 50 hrs) Distillation Dehydration 80-95% ethanol 100% ethanol cassava flour + water + alpha-amylase enzyme
R. Shanthini 06 Feb 2010 Dry grind process is the most common method used to make fuel grade ethanol. The whole corn kernel is ground and converted into ethanol. It is relatively cost effective and requires less equipment, but is not ideal for mass producing.
R. Shanthini 06 Feb 2010 In the wet milling process, corn is separated into its four basic components: starch, germ, fiber, and protein, which are each made into different products. Advantage: valuable co-products such as corn oil Disadvantages: equipment is expensive and the process uses hazardous sulfur dioxide
R. Shanthini 06 Feb 2010 Bioethanol from Biomass (except sugars and starches): Rice straw Paddy husks Saw dust Grasses Bagasse
R. Shanthini 06 Feb 2010 Cellulose (40 to 60% by weight of the biomass) made from the six-carbon sugar, glucose. Its crystalline structure makes it resistant to hydrolysis (the chemical reaction that releases simple, fermentable sugars). Bioethanol from Biomass (except sugars and starches):
R. Shanthini 06 Feb 2010 Hemicellulose (20 to 40% by weight) made mainly from the five-carbon sugar, xylose. Its relatively easy to hydrolyze hemicellulose into simple sugars but normal yeast can't ferment xylose. Celunol Corp. has acquired genetically engineered E. coli bacteria which can turn almost all xylose into ethanol. Bioethanol from Biomass (except sugars and starches):
R. Shanthini 06 Feb 2010 Lignin (10 to 24% by weight of biomass) is a complex polymer, which provides structural integrity in plants. It remains as residual material after the sugars in the biomass have been converted to ethanol. It contains a lot of energy and can be burned to produce steam and electricity for the biomass-to- ethanol process. Bioethanol from Biomass (except sugars and starches):
Obstacles to commercial production of cellulosic ethanol: Accelerating the breakdown of cellulose fibers Research on acid / enzymatic hydrolysis is ongoing. Lignin waste problem Lignin can fuel Combined Heat and Power plants, however, CHP plants are expensive. Use of GM microorganisms Source: DOE's 2006 Annual Energy Outlook
R. Shanthini 06 Feb 2010 A cellulosic ethanol plant with 50 million gallons per year capacity and a lignin-fired CHP will cost about $300 million to build. A corn ethanol plant with the same capacity could be built for about $65 million. Source: DOE's 2006 Annual Energy Outlook
R. Shanthini 06 Feb 2010 Currently, ethanol yields 25% more energy output than input to produce it. Research is on for less costly ways of producing ethanol, and better ways to blend it with petrol.
R. Shanthini 06 Feb 2010 Is bioethanol a sustainable energy source?
R. Shanthini 06 Feb 2010 Bioethanol will be used in engines that convert heat into work Engines that convert heat into work are very inefficient Take a look at some examples
R. Shanthini 06 Feb 2010 According to the 2 nd Law of Thermodynamics when heat is converted into work, part of the heat energy must be wasted Power generation type Unit size (MW) Energy wasted (MW) Diesel engine10 - 307 – 22 Gas Turbine50 - 10036 – 78 Steam Turbine200 - 800120 – 560 Combined (ST & GT)300 - 600150 – 380 Nuclear (BWR & PWR)500 - 1100330 – 760
R. Shanthini 06 Feb 2010 We throwaway energy that rightfully belong to the future generations “Development that meets the needs of the present without compromising the ability of future generations to meet their own needs." Our Common Future (1987)
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