Biofuels
•Biofuelis an alternative
considered to replace petroleum gas (gasolineor petrol).
interest
in biofuel: include
•rising oil prices.
•concerns over the shortage of
oil.
•greenhouse gas
emissions(causing global warmingand climate change.
•pollution and waste management
problems.
Biomass
•Production of energy using
biomass is used as an alternative: •Ethanol can be produced by
growing sugar crops (sugar cane, and sugar beet), or starch(corn/maize), and
then use yeast fermentation to produce ethanol(ethyl alcohol).
•To grow plants that
(naturally) produce oils, such as algae, or jatropha. The oils can also be
chemically processed to produce biodiesel.
•Biogas (methane gas) is
produced by the process of anaerobic digestionof organic materialby anaerobes.
Biofuels
•1stgeneration biofuel:refersto
biofuelsmade from food crop sugar, starch, vegetable oil, or animal fatsusing
conventional technology such as: vegetable oil, ethanol and biogas.
•2ndgeneration biofuel:
including cellulosic biofuels from non food crops. Such as cellulosic ethanol.
•3 rd generation
biofuel:abiofuelfrom algaecalled oilgae.
Ethanol
•In addition to being
renewable, ethanol has a major advantage in that it can
•be easily blended with
gasoline. it is clean burning and readily mixes with gasoline.
•Unlike gasoline, ethanol is
nontoxic (safe to handle) and biodegradable, it quickly breaks down into
harmless substances if spilled.
•When small amounts of ethanol
are added to gasoline, usually less than 10 percent, there are many advantages:
Ethanol reduces carbon monoxide and other toxic pollution making the air
cleaner. It keeps engines running smoothly without the need for lead or other
octane enhancers.
Ethanol
•The largest ethanol program is
in Brazil which produced 15.9 billion litres of bioethanolin 2005, more than
one-third of the world’s supply by fermentation of sugar cane.
•almost half of Brazilian cars
are able to use 100% ethanol as fuel, which includes ethanol-only engines and
flex-fuelengines. Flex-fuel engines in Brazil are able to work with all
ethanol, all gasoline, or any mixture of both (20% ethanol, 80 % gasoline).
•In the United States, ethanol
is most commonly blended with gasoline as a 10% ethanol blend nicknamed
"gasohol".
For successful production of ethanol
•Cost reduction by finding
strains that can utilize waste material
•Tolerate high concentration of
ethanol Traditionally, ethanol has been produced in batch fermentation with
yeast strains that can-not tolerate high concentration of ethanol.
•Reducing the recovery costs.
•Thermoanaerobacter ethanolicus is
a gram-positive anaerobic thermophilethat produces considerable amounts of
ethanol from soluble sugars and polymeric substrates, including starch.
•Zymomonasmobilis
•The advantages of Z.
mobilisover S. cerevisiaewith respect to producing bioethanol:
•higher sugar uptake and
ethanol yield,
•lower biomass production,
•higher ethanol tolerance,
•does not require controlled
addition of oxygen during the fermentation,
•amenability to genetic
manipulations.
However,
it has a severe limitation:
its utilizable substrate range is
restricted to glucose, fructose, and sucrose.
Its inability to convert complex carbohydrate
polymers like cellulose , hemicellulose,and starch to ethanol.
Methane
•Biogas (methane gas) is
produced by the process of anaerobic digestionof organic material(ex: sewage,
manures)by anaerobes.
•Anaerobic digestion is a
complex biochemical process of biologically-mediated reactions by a group of
micro organisms to convert organic compounds into methane and carbon dioxide.