LECTURE TOPIC
• Bioethanol
• Feedstock of bioethanol
• Bioethanol Production
• Benefits of bioethanol
• Applications
• Environmental Impact
• Bioethanol from Algae
Bioethanol Introduction
• The principle fuel used as a petrol substitute for road transport vehicles is bioethanol. Bioethanol fuel is
mainly produced by the sugar fermentation process, although it can also be manufactured by the chemical
process of reacting ethylene with steam.
• The main sources of sugar required to produce ethanol come from fuel or energy crops. These crops are
grown specifically for energy use and include corn, maize and wheat crops, waste straw, willow and popular
trees, sawdust, reed canary grass, cord grasses, jerusalem artichoke, myscanthus and sorghum plants. There
is also ongoing research and development into the use of municipal solid wastes to produce ethanol fuel.
• Ethanol or ethyl alcohol (C2H5OH) is a clear colourless liquid, it is biodegradable, low in toxicity and causes
little environmental pollution if spilt. Ethanol burns to produce carbon dioxide and water. Ethanol is a high
octane fuel and has replaced lead as an octane enhancer in petrol. By blending ethanol with gasoline we can
also oxygenate the fuel mixture so it burns more completely and reduces polluting emissions. Ethanol fuel
blends are widely sold in the United States. The most common blend is 10% ethanol and 90% petrol (E10).
Vehicle engines require no modifications to run on E10 and vehicle warranties are unaffected also. Only
flexible fuel vehicles can run on up to 85% ethanol and 15% petrol blends (E85).
First Generation
Biomass
feedstock
Second Generation
for
bioethanol
production
Bioethanol production process
• Biomass wastes consist of a complex mixture of carbohydrate polymers such as cellulose, hemi cellulose and lignin. Biomass is pre-
treated with acids or allowed to react with enzymes to reduce the size of the feedstock and produce sugars.
• The carbohydrate polymers are broken down with the help of enzymes or dilute acids into sucrose sugar and then fermented into
bioethanol. However, the lignin present in the biomass is used as a fuel for boilers in which bioethanol is produced. Enzymatic
hydrolysis, concentrated acid hydrolysis and dilute acid hydrolysis are the three basic methods for extracting sugar from biomass.
• On the other hand, corn can be processed into ethanol by either dry milling or wet milling. In the dry milling process, the corn
kernel is cleaned and broken down into fine particles through hammer milling. This process creates a powder with a course flour-
type consistency. The wet milling process involves soaking corn kernel in warm water to break down its proteins and release
starch.
Bioethanol production process
• Once the biomass or corn is broken down into sugar via the hydrolysis process, the sugar solution is
ready to be fermented into ethanol. The addition of yeast to the solution followed by rapid heating
converts the sucrose sugars into fructose and glucose with the help of invertase present in the
yeast.
• These sugars further react with another enzyme, zymase, contained in the yeast to yield ethanol
and carbon dioxide. The fermentation process is carried out at temperatures between 250 and
300°C. The ethanol thus produced undergoes the fractional distillation process to remove excess
water produced during the fermentation process.
Benefits of bioethanol…!!
• Bioethanol has a number of advantages over conventional fuels. It comes from a renewable resource
i.e. crops (like cereals, sugar beet and maize).
• Another benefit over fossil fuels is the greenhouse gas emissions. The road transport network
accounts for 22% of all greenhouse gas emissions and through the use of bioethanol, some of these
emissions will be reduced as the fuel crops absorb the CO2 they emit through growing.
• By encouraging bioethanol’s use, the rural economy would also receive a boost from growing the
necessary crops.
• Bioethanol is also biodegradable and far less toxic that fossil fuels. In addition, by using bioethanol in
older engines can help reduce the amount of carbon monoxide produced by the vehicle thus
improving air quality.
• Another advantage of bioethanol is the ease with which it can be easily integrated into the existing
road transport fuel system. In quantities up to 5%, bioethanol can be blended with conventional fuel
without the need of engine modifications.
• The price of bioethanol / petrol fuels will be kept low due to government subsidies and lower rates in
tax. This has shown to encourage the use of a cleaner fuel, assuming public interest is sufficient to
create a significant market in alternatively fueled bioethanol and alcohol cars.
• Bioethanol produces only carbon dioxide and water as the waster products on burning, and the
carbon dioxide released during fermentation and combustion equals the amount removed from the
atmosphere while the crop is growing.
Applications of bioethanol
❖ Bioethanol can be used in petrol engines as an alternative for gasoline. It can be
mixed with gasoline to virtually any percentage. Most of the existing petrol engines
operate on blends of up to 15% bioethanol with petroleum.
❖ The higher octane rating of bioethanol than ethanol-free gasoline increases an
engine's compression ratio giving increased thermal efficiency. It is also used to
fuel bioethanol fireplaces. It is extremely suitable for residential use as it is flueless
and does not require a chimney.
❖ Other major applications of bioethanol include the following:
• Fuel for power generation by thermal combustion
• Fuel in cogeneration systems
• Feedstock in the chemicals industry
• Fuel for fuel cells by thermochemical reactions
Environmental Impacts
❖ Improving the quality of air is one of the most important functions of bioethanol.
When added to fuel, bioethanol reduces the use of cancer-causing gasoline
compounds such as ethylbenzene, xylene, toluene and benzene. It also reduces the
emissions of small particulates and soot from motor fuels, and greenhouse gas
emissions.
❖ Water-saving ethanol plant designs are very common. In addition, the water
discharged from these plants is regulated such that the water is environmentally
neutral when it leaves the plant.
❖ Certain plants manage and reuse the wastewater generated during the ethanol
process. Therefore, it is evident that using bioethanol has a positive effect on
ecology, minimizes exhaust gas emissions and improves energy safety and operation
of transport facilities.
Bioethanol from Algae
• Researchers have recently launched a proposal to cultivate massive amounts of seaweed or
algae. They claims that the project could occupy about ten thousand kilometers of seaweed
farm and they estimated that the farm would be able to produce bioethanol from algae, as
much as 20 million kiloliters or 5.3 billion gallons of bioethanol per year. This amount equal to
a third of Japanese fuel consumption a per year.
• Seaweed / algae has already been proven to be capable of becoming an alternative option
for producing biofuel. Most of the biofuel today is produced from food stock which has
its own disadvantage and the ratio of the crops and the amount of ethanol that it produces is
not balanced. Some suggest that the using of food stock for bioethanol production has
caused food prices to rise.
• This would be then processed by floating bio reactors. Facilities that would use enzyme to
breakdown the seaweed into sugar which would then be processed and be converted to
ethanol. This process will take place on the sea and would be then transported to land by
tankers.
What are the advantages of using algae / seaweed for
bioethanol production?
• It doesn’t need soil or freshwater and other producer substances. It is
naturally occurring in the sea and there would be no imbalance that
would happen when it is harvested.
• We would be able to avoid the food price hike, if we would utilize this
new technology for we will no longer be taking away lands to farm
crops.
• Algae / seaweed grow unbelievably faster. Around 10 times as fast as
sugar cane. It is actually the fastest growing crop known to man.
