Prof. R. Shanthini 09 Feb 2013 Module 07 Renewable Energy (RE) Technologies & Impacts (continued) - Use of RE sources in electricity generation, in transport,

Prof. R. Shanthini 09 Feb 2013

Module 07

Renewable Energy (RE) Technologies & Impacts

(continued)

- Use of RE sources in electricity generation, in transport, and in other energy consumption modes

- Ecological impacts of RE sources, and mitigation measures


RE technology options:

- Hydroelectric Hydroelectric

- Solar Solar

- Wind Wind

- Geothermal

- Marine (Wave and Tidal)

- BiofuelsBiofuels (Biomass Biomass , BioethanolBioethanol and Biodiesel)


Bioethanol

Bioethanol is simply ethanol.

It is called bioethanol when it is produced from biomass.

Fuel made by blending ethanol with petrol assures that the fuel mixture burns more completely.

Oxygen in the ethanol molecule helps in complete combustion, which means less emissions.


Ethanol is a high-octane fuel, and is widely used as a blending ingredient in petrol.

Bioethanol

The octane rating is a measure of how likely a gasoline or liquid petroleum fuel is to self ignite.

The higher the number, the less likely an engine is to pre-ignite and suffer damage.


Bioethanol

The most common blend is 10% ethanol and 90% petrol (E10), which is also known as gasohol.

Vehicle engines require no modifications to run on E10 and vehicle warranties are unaffected also.

Only flexible-fuel vehicles (FFV) can run on up to 85% ethanol and 15% petrol blends (E85).

Prof. R. Shanthini 09 Feb 2013 Source: http://www.distill.com/World-Fuel-Ethanol-A&O-2004.html

Bioethanol


Bioethanol

C2H5OH 2 CO2 + 3 H2O + heat

ethanol

Heat released is 1020 kJ/mol.

CO2 is also released as when petrol is being burned.

So what is the big deal?

Ethanol combustion:

+ 3 O2


Bioethanol Bioethanol is produced from plants (biomass) that harness the power of the sun to convert water and CO2 to sugars (photosynthesis).

CO2 is reabsorbed by the biomass when growing it.

So it is OK.

CO2 sun light

biomass

ethanol

water


Bioethanol Bioethanol is produced from plants (biomass) that harness the power of the sun to convert water and CO2 to sugars (photosynthesis).

http://wheat.pw.usda.gov/wEST/nsf/nfmain.html


Bioethanol

http://oregonstate.edu/instruct/dce/ans312/one/carbs_story.htm

- The major constituent of biomass is carbohydrates, which are composed of carbon (C), hydrogen (H) and oxygen (O).

- Carbohydrates are represented by Cx(H2O)n.

What is biomass made up of?

Prof. R. Shanthini 09 Feb 2013 http://oregonstate.edu/instruct/dce/ans312/one/carbs_story.htm

Monosaccharide (known as simple sugars) is the simplest form of a carbohydrate.

They have the general formula (CH2O)n where n = 3 to 7 .

Examples: glucose, fructose and galactose (all are n = 6).

(CH2O)6

or C6H12O6

Bioethanol What is biomass made up of?


http://www.tutorvista.com/content/biology/biology-iii/cellular-micromolecules/monosaccharides-and-oligosaccharides.php



Bioethanol

C6H12O6 2 C2H5OH + 2 CO2 + heatYeast

glucose ethanol carbon dioxide

180 g 92 g 88 g 26.4 kcal

1 kg 511 g 489 g 147 kcal

Ethanol formation from glucose:

Bioethanol from glucose:


Bioethanol

Glucose does not exist as glucose in nature.

So, go to sugars that are slightly more complex than the simple sugars considered so far.


Disaccharides are formed by joining 2 monosaccharide molecules.

Examples:

- Maltose is formed by two glucose molecules. It occurs in cells as a breakdown product of starch. It is also formed in the seeds during germination. It is commonly called malt sugar.

- Lactose is found in milk and hence commonly called milk sugar. It is formed by condensation of a glucose molecule and a galactose molecule.

- Sucrose is found extensively in plants. It is commonly called cane sugar. It is formed by condensation of a glucose molecule and a fructose molecule.


C6H12O6 C12H22O11 + C6H12O6 + H2O






Bioethanol from sucrose:

Sugar cane and sugar beets store the energy as sucrose (C12H22O11)

2 C2H5OH + 2 CO2zymase

Impure cultures of yeast produce glycerine and various organic acids

Invertase and zymase are enzymes derived mainly from yeast.

Bioethanol

C6H12O6

2 C6H12O6invertase C12H22O11 + H2O


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

Bioethanol


sugar cane crushed and soluble sugar washed out

sugar cane residue

(bagasse)

can’t be used as petrol additive but as petrol

replacement

can be used as petrol additive

CO2

Bioethanol

distilled to concentrate to 80 – 95% ethanol

5 - 12% ethanol

sugar cane

yeast / bacteria soluble sugar for fermentation

dehydrate to 100% ethanol

Dehydration in an expensive process

Bioethanol from sucrose:


Bioethanol


What about ethanol from corn as it the USA?

Bioethanol


Corn belong to the family of starch.

Starch is a polysaccharide, which is composed of three or more monosaccharides.

The two primary polysaccharides are starch and cellulose.

Both starch and cellulose are composed of glucose molecules.

So it is possible to convert starch (and cellulose) to glucose and then to ethanol.

The primary difference between starch and cellulose is the linkage of their units.


Prof. R. Shanthini 09 Feb 2013 http://www.caister.com/supplementary/acanthamoeba/b7.html

alpha-glucose

beta-glucose



- The glucose molecules in starch are linked via alpha linkages, which may be broken by both mammalian and microbial enzymes.

-The glucose molecules in cellulose are linked via beta linkages, which may be broken by only microbial enzymes.



Corn, wheat and cassava store the energy as starch.

dextrins

alpha-amylase enzyme

Amyloglucosidase enzyme

glucose monomer

} starch(glucose polymer)

Bioethanol Bioethanol from starch:


Liquification Liquification

(at 90 – 95 deg C; (at 90 – 95 deg C;

pH = 4 - 4.5; 400 rpm)pH = 4 - 4.5; 400 rpm)

Saccharification with Saccharification with glucosidase enzymeglucosidase enzyme

(at 55 - 65 deg C, pH = 4 - 4.5)(at 55 - 65 deg C, pH = 4 - 4.5)

Cooling (32 deg C)Cooling (32 deg C)Fermentation Fermentation

(40 – 50 hrs)(40 – 50 hrs)

Dehydration Dehydration

80-95% ethanol 80-95% ethanol 100% ethanol 100% ethanol

corn flour + water + corn flour + water + alpha-amylase enzymealpha-amylase enzyme


Distillation Distillation


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.



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



Rice strawPaddy husksSaw dustGrasses Bagasse

Bioethanol Bioethanol from biomass (other than sugars and starches):

They are rich in cellulose and lignin.


- Cellulose is the major structural material of biomass

- Cellulose is made from several 100s to over 10,000s glucose molecules

- Cellulose has the formula (C6H10O5)n

- Cellulose can be hydrolyzed to glucose molecules

- The crystalline structure of cellulose makes it resistant to hydrolysis

Bioethanol What is it made up of?


- Other carbohydrates include pectins and hemicellulose.

- Pectins and hemicellulose are only digested and utilized by microbes.

http://www.bio.miami.edu/dana/226/226F09_3.html



- Hemicellulose comprise almost 1/3 of the carbohydrates in woody plant tissues.

- It is made mainly from the five-carbon sugar, xylose.

Bioethanol

Xylose

What is biomass made up of?


- Hemicellulose is relatively easy to be hydrolyzed 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 Bioethanol from biomass (other than sugars and starches):


Lignin is an essential part of biomass.

- It is not a carbohydrate.

- Chemically, lignin is a polyphenolic polymer.

- Lignin is associated with fibrous feedstuffs, and is indigestible by both microbial and mammalian enzymes.

- As a plant matures lignin content increases.



- Lignin is 10 to 24% by weight of biomass.

- It 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.




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 genetically modified (GM) microorganisms

Source: DOE's 2006 Annual Energy Outlook

Bioethanol Bioethanol from cellulose:


A cellulosic ethanol plant with 50 million gallons per year capacity and a lignin-fired 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

Bioethanol Bioethanol from cellulose:


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.

Bioethanol


Bioethanol will be used in engines that convert heat into work

Engines that convert heat into work are very inefficient

Bioethanol


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)

Bioethanol


Bioethanol Water Requirements forEnergy Production by different process

Process Litre/MWhpetroleum extraction 10 - 40

oil refining 80 - 150

oil shale surface retort 170 - 681

NGCC power plant, closed loop cooling 230 - 30,300

coal IGCC ≈ 900

nuclear power plant, closed loop cooling ≈ 950

geothermal power plant, closed loop tower 1900 - 4200

Energy Demands on Water Resources; Report to Congress on theInterdependency of Energy and Water; U.S. Department of

Energy: Washington, DC, 2006; p 80.

NGCC: Natural gas combined cycleIGCC: Integrated gasification combined-cycle



Process Litre/MWhEnhanced oil recovery ≈ 7600

NGCC, open loop cooling 28,400 75,700

nuclear power plant, open loop cooling 94,600 - 227,100

corn ethanol irrigation 2,270,000 - 8,670,000

soybean biodiesel irrigation 13,900,000 - 27,900,000



NGCC: Natural gas combined cycleIGCC: Integrated gasification combined-cycle



Process Litre/MWh

petroleum extraction + oil refining 90 - 190

nuclear power plant, closed loop cooling ≈ 950

nuclear power plant, open loop cooling 94,600 - 227,100

corn ethanol irrigation 2,270,000 - 8,670,000

soybean biodiesel irrigation 13,900,000 - 27,900,000



In summary

Documents

Prof. R. Shanthini 09 Feb 2013 Module 07 Renewable Energy (RE) Technologies & Impacts (continued) - Use of RE sources in electricity generation, in transport,