R. Shanthini Bioethanol as an alternative source of energy

What is the problem with petroleum derivatives as the energy source? Petroleum supply has peaked 24 Jan 2008 R. Shanthini

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Petroleum supply peaking is however not the only problem with the conventional fossil fuel energy sources! Fossil fuels releases CO 2 that is not part of the carbon cycle 24 Jan 2008 R. Shanthini Carbon balance is upset and the excess CO 2 accumulates in the environment

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CO2 concentration in the atmosphere Unit: ppmv Source: Jan 2008 R. Shanthini

To stabilize the atmospheric CO 2 concentration below 550 ppmv by 2100 (climate change concern), global anthropogenic CO 2 emissions must be limited to about 7 to 8 GTC (= giga tonne C) per year. - IPCC, 1996

Global CO 2 emissions from the burning of fossil fuels & the manufacture of cement Unit: GTC per year 24 Jan 2008 R. Shanthini Source: at 7.9 GTC in 2004

Therefore, we need urgently to switch to energy sources that are not upsetting the carbon balance 24 Jan 2008 R. Shanthini

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 24 Jan 2008 R. Shanthini

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 24 Jan 2008 R. Shanthini

Ethanol as an alternative source of energy oxygen in the ethanol molecule helps in complete combustion, which means less emissions 24 Jan 2008 R. Shanthini Bio

24 Jan 2008 R. Shanthini

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 percent with petrol (E85 fuel) Today there are more than 6 million FFV's on U.S. roads alone 24 Jan 2008 R. Shanthini

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glucose molecule Bioethanol from simple sugars: Sugar cane and sugar beets store the energy as simple sugars, glucose (C 6 H 12 O 6 ) 24 Jan 2008 R. Shanthini 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

24 Jan 2008 R. Shanthini 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

sugar cane sugar cane crushed and soluble sugar washed out sugar cane residue fermentation of sugars produces % 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

Bioethanol from starch: Corn, wheat and cassava store the energy as more complex sugars, called starch 24 Jan 2008 R. Shanthini dextrins α-amylase amyloglucosidase glucose monomer } starch (glucose polymer)

Liquification (at 90 – 95 deg C; pH = ; 400 rpm) Saccharification with glucosidase enzyme (at deg C, pH = ) Cooling (32 deg C) Fermentation with yeast (40 – 50 hrs) Distillation Dehydration 80-95% ethanol 100% ethanol 24 Jan 2008 R. Shanthini cassava flour + water + alpha-amylase enzyme

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. 24 Jan 2008 R. Shanthini

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 24 Jan 2008 R. Shanthini

Bioethanol from Biomass (except sugars and starches): Rice straw Paddy husks Saw dust Grasses Bagasse 24 Jan 2008 R. Shanthini

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): 24 Jan 2008 R. Shanthini

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): 24 Jan 2008 R. Shanthini

Bioethanol from Biomass (except sugars and starches): 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.

24 Jan 2008 R. Shanthini

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 24 Jan 2008 R. Shanthini

A cellulosic ethanol plant with 50 million gallons per year capacity and a lignin-fired CHP will cost about $300 million to build 24 Jan 2008 R. Shanthini A corn ethanol plant with the same capacity could be built for about $65 million Source: DOE's 2006 Annual Energy Outlook

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. 24 Jan 2008 R. Shanthini

Is bioethanol a sustainable energy source? No, it is not Why do I say that? 24 Jan 2008 R. Shanthini

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 24 Jan 2008 R. Shanthini

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 engine – 22 Gas Turbine – 78 Steam Turbine – 560 Combined (ST & GT) – 380 Nuclear (BWR & PWR) – Jan 2008 R. Shanthini

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)

Recently, Scientists at the Virginia state Polytechnic Institute have developed a breakthrough method of ethanol production method called Advanced Bioethanol Technology (ABT) which lets producers create ethanol from any biological feedstock that contain enough sugars or materials that can be converted into sugar such as starch or cellulose. ABT breaks long chains of sugars down to be fermented.