Biofuels are fuels derived from biological carbon fixation. There are several types and generations of biofuels. First generation biofuels are made from food crops like corn and sugarcane, while second generation are made from non-food sources like grass and municipal solid waste. Third generation use algae as a feedstock. Common biofuels include bioethanol, biodiesel, biogas, and biohydrogen. Ethanol is produced through fermentation and distillation of sugars from crops. Biodiesel is made through transesterification of vegetable oils. Biogas is a product of anaerobic digestion of organic materials. Biohydrogen can be produced through dark fermentation or photobiological methods.

1. ANJANA PRASAD

2. INTRODUCTION
Biofuel is a type of fuel whose energy is derived
from biological carbon fixation.
Biofuels include fuels derived
from biomass conversion, as well as solid
biomass, liquid fuels and various biogases.
Although fossil fuels have their origin in
ancient carbon fixation, they are not considered
biofuels by the generally accepted definition
because they contain carbon that has been "out"
of the carbon cycle for a very long time.

3. WHAT IS A BIOFUEL?
• Layman’s Definition:
– “A fuel that gains its’ energy through the use of
already existing carbon in the atmosphere.”
• One legal definition of biofuel is "any fuel
with an 80% minimum content by volume of
materials derived from living organisms
harvested within the ten years preceding its
manufacture".

4. HISTORY OF BIOFUELS
• Biofuels in the solid form (wood) has been in use ever
since man discovered fire.
• In 1890s Rudolf Diesel, inventor of the diesel engine,
was the first person who made biodiesel from
vegetable oil (peanut).
• Henry Ford designed the model T car to run on ethanol.
• During World war ll the demand for biofuel increased
as fossil fuel became less abundant.
• Biofuels surged in popularity during energy crisis of the
1970s
• The 21th century came with the attention of the people
towards the use of biofuels in response to the
increasing demands and tougher emission standards.

5. CLASSIFICATION OF BIOFUELS
• It is related to the method of preparation that
inturn is related to the starting material of the
agent by which the biomass is converted to
biofuels.
First Generation
Second Generation
Third Generation
Fourth Generation

6. FIRST GENERATION BIOFUELS
• Prepared from food crops
• If used in large quantity would have large
impact on the food supply
• Feedstock: corn, sugarcane, wheat

7. CORN
ADVANTAGES DISADVANTAGES
Infrastructure for planting,
harvesting, and processing is
already in place
Relatively high requirement for
pesticide and fertilizer. Not only
is this expensive, but it leads to
soil and water contamination
Relatively simple conversion of
corn starch to ethanol
It is a food staple and use in
biofuel has increased food prices
worldwide, leading to hunger
Potential to use the rest of the
plant (stalk, cob, etc.) to produce
ethanol as well
Energy yield is about 1.2, which is
just barely positive at 20% net
yield

8. SUGARCANE
ADVANTAGES DISADVANTAGES
Infrastructure for planting,
harvesting, and processing
that is already in place
Despite having a higher
yield than corn, it is still
relatively low
The yield is higher than that
of corn at an average of 650
gallons per acre
Few regions are suitable to
cultivation
Carbon dioxide emissions
can be 90% lower than for
conventional gasoline when
land use changes do not
occur.
Sugar cane is a food staple
in countries of South and
Central America

9. SECOND GENERATION BIOFUELS
• Prepared from non-food crops
• Also known as advanced biofuels
• Feedstock: cellulosic sources from urban
(MSW), forestry and agricultural wastes.
Hence also known as cellulosic biofuels

10. GRASS
ADVANTAGES DISADVANTAGES
They are perennial and so
energy for planting need
only be invested once
They are not suitable for
producing biodiesel
They are fast growing and
can usually be harvested a
few times per year
They require moist soil and
do not do well in arid
climates
They have a high net energy
yield of about 540%
They require extensive
processing to made into
ethanol

11. MUNICIPAL SOLID WASTES
• Refers to things like landfill gas, human waste,
and grass and yard clippings
• Though not as clean as solar and wind, the
carbon footprint of these fuels is much less
than that of traditionally derived fossil fuels
• It is burned to produce both heat and
electricity

12. SECOND GENERATION EXTRACTION
TECHNOLOGIES
• Requires several processing steps prior to
being fermented (1st gen technology) into
ethanol

13. THIRD GENERATION BIOFUELS
• Also known as oilgae since they are derived
from algae
• Harvested algal oil is converted into biodiesel
• Algal carbohydrate content can be fermented
to produce bioalcohols

14. CULTIVATION OF ALGAE
1. Open pond system
• Algae is cultivated in ponds exposed to open air
• Ponds can be planned, unplanned, natural or artificial
• Most efficient and low cost method
• Mostly uses environmental CO2

15. 2. Closed loop system
• Closed system, not exposed to air
• Avoid contamination by other organisms
• Highly controlled production
• Widespread mass production of algae
• Most popular method – PHOTOBIOREACTOR
 Uses light source for cultivation
 Made of plastic or borosilicate glass tubes
 Provides higher purity levels than natural habitat

16. 3. Algal Turf Scrubber (ATS)
• System designed primarily for cleaning nutrients and
pollutants out of water using algal turfs
• Imitation of algal turfs of a natural coral reefs
• For a turf, a rough platic membrane coated surface or
screen is used, which allows naturally occuring algal
spores to settle and colonize on the surface
• Once established it can be harvested every 5 – 15 days
• Focus on polycultures of algae

18. FOURTH GENERATION BIOFUELS
• Genetic engineered organisms for efficient
production of biofuels
• Includes altering lipid characteristics and
through lipid excretion pathways
• Aim to be carbon negative by creating artificial
carbon sinks

21. BIOALCOHOLS
• First 4 alcohols are of greatest interest for fuel use
• One advantage that all 4 alcohols sharing is
octane rating: a measure of the resistance of petrol and
other fuels to autoignition in spark ignition internal
combustion engines
• Butanol has the advantage that its energy density is
closer to gasoline than other alcohols
• Chemical formula for alcohol fuel: Cn H2n +1OH
• There is no chemical difference between biologically
produced alcohols and those obtained from other
sources

22. Bioethanol
• It is used as a biofuel alternative to gasoline
• Feedstock: corn, sugarcane, etc
• Ethanol can be mass-produced by
fermentation of sugar or by hydration of
ethylene (ethene CH2=CH2 ) from petroleum
and other sources

23. Bioethanol
• Concerns relate to the large amount of arable
land required for crops, as well as the energy and
pollution balance of the whole cycle of ethanol
production
• Recent developments with cellulosic ethanol
production and commercialization may allay
some of these concerns
• Cellulosic ethanol offers promise as resistant
cellulose fibers, a major component in plant cell
walls, can be used to generate ethanol

24. CHEMISTRY OF BIOETHANOL
• Glucose (a simple sugar) is created in the plant
by photosynthesis.
6CO2 + 6H2O + light → C6H12O6 + 6O2
• During ethanol fermentation, glucose is
decomposed into ethanol and carbon dioxide.
C6H 12O6 → 2C2H6O + 2CO2 + heat
• During combustion ethanol reacts with oxygen
to produce carbon dioxide, water, and heat.
• C2H6O + 3O2 → 2CO2 + 3H2O + heat

25. CHEMISTRY OF BIOETHANOL
• After doubling the ethanol combustion reaction
because two molecules of ethanol are produced for
each glucose molecule, there are equal numbers of
each type of molecule on each side of the equation,
and the net reaction for the overall production and
consumption of ethanol is just: light → heat
• (6CO2 + 6H2O + light → 6CO2 + 6H2O + heat)
• The heat of the combustion of ethanol is used to drive
the piston in the engine by expanding heated gases. It
can be said that sunlight is used to run the engine.
• Air pollutants are also produced when ethanol is
burned in the atmosphere rather than in pure oxygen.
Harmful nitrous oxide gases are produced

26. PRODUCTION PROCESS

27. PRODUCTION PROCESS
• Prior to fermentation, some raw materials
require saccharification or hydrolysis of
carbohydrates such as cellulose and starch
into sugars
• Saccharification of cellulose is called
cellulolysis
• Enzymes are used to convert carbohydrates
into sugar

28. Fermentation
• Ethanol is produced by microbial fermentation of
the sugar
• Two major components of plants, cellulose and
starch, are both made up of sugars, and can in
principle be converted to sugars for fermentation
• Currently, only the sugar (e.g. sugar cane) and
starch (e.g. corn) portions can be economically
converted
• However, there is much activity in the area of
cellulosic ethanol, where the cellulose part of a
plant is broken down to sugars and subsequently
converted to ethanol

29. Distillation
• For the ethanol to be usable as a fuel, water must
be removed
• Most of the water is removed by distillation, but the
purity is limited to 95-96% due to the formation of a
low-boiling waterethanol azeotrope
• The 95.6% m/m (96.5% v/v) ethanol, 4.4% m/m
(3.5% v/v) water mixture may be used as a fuel
alone, but unlike anhydrous ethanol, is immiscible
in gasoline, so the water fraction is typically
removed in further treatment in order to burn with
in combustion with gasoline in gasoline engines

30.  Dehydration
• There are basically five dehydration processes to remove the
water from an azeotropic ethanol/water mixture. –
• The first process, used in many early fuel ethanol plants, is
called “azeotropic distillation“ and consists of adding benzene
or cyclohexane to the mixture. When these components are
added to the mixture, it forms an heterogeneous azeotropic
mixture in vapor-liquid-liquid equilibrium, which when
distillated produces anhydrous ethanol in the column bottom,
and a vapor mixture of water and cyclohexane/benzene.
When condensed, this becomes a twophase liquid mixture. –
• Another early method, called “extractive distillation”, consists
of adding a ternary component which will increase ethanol
relative volatility. When the ternary mixture is distillated, it
will produce anhydrous ethanol on the top steam of the
column

31. • With increasing attention being paid to saving energy,
many methods have been proposed that avoid
distillation all together for dehydration.
• Of these methods, a third method has emerged and
has been adopted by the majority of modern ethanol
plants.
• This new process uses ”molecular sieves” to remove
water from ethanol. In this process, ethanol vapor
under pressure passes through a bed of molecular sieve
beads. The bead’s pores are sized to allow absorption
of water while excluding ethanol. After a period of
time, the bed is regenerated under vacuum to remove
the absorbed water. Two beds are used so that on is
available to absorb water while the other is being
regenerated. This dehydration technology can account
for energy saving of 3,000 BTU/gallon compared to
earlier azeotropic distillation

32. BIOGAS
• A naturally occurring gas formed as a
byproduct of the breakdown of organic
materials in an anaerobic environment
• Marsh gas or swamp gas
• Major components:
methane 60-70%
CO2 30-40%

33. BIOGAS

34. BIOGAS

35. BIOGAS

36. BIODIESEL
• Refers to vegetable oil or animal fat based diesel
fuel consisting of long chain alky( methyl, ethyl,
propyl) esters
• Liquid usually yellow to dark brown and has high
boiling point
• It is a mixture of fatty acid alkyl esters obtained
by transesterification :
triglycerides are converted to diglycerides
diglycerides to monoglycerides
Monoglyceride to esters (biodiesel) and glycerol
(byproduct)

37. PRODUCTION
• The triglycerides, methanol and catalyst are placed in a
controlled reaction chamber to undergo transesterification.
• The initial product is placed in a separator to remove
glycerine byproduct
• The excess methanol is recovered from the methyl esters
through evaporation
• The final biodiesel is rinsed with water and pH neutralised

38. GREEN DIESEL
• Produced by refining process
• Identical to petrol diesel except that it does
not contain sulphur
• Greener than standard diesel because it
reduces particulate emissions as well as odor

39. BIOHYDROGEN
• Highly combustible ,1g of combustion
provides 30000 cals as compared to gasoline
that gives only 11000 cals
• Can be produced from water using biological
agents
• Biologically produced hydrogen is known as
biohydrogen

40. Why biohydrogen not hydrogen.?
• Needs a primary energy source
• If source is fossils then hydrogen is not an
clean energy carrier
• If gas is made from electrolysis of water, again
an energy intensive process
• So thinking about production of hydrogen
from biomass known as BIOHYDROGEN .

41. PRODUCTION

42. DARK FERMENTATION
• Fermentative conversion of organic substrate
to biohydrogen
• This method doesn’t require light energy
• The Gram+ve bacteria of Clostridium genus is
of great potential in biohydrogen production
• Require wet carbohydrate rich biomass as a
substrate
• Produces fermentation end product as organic
acids, CO2 along with biohydrogen

43. • Glu → pyruvate → acetyl coA → fd → H2
• Carbohydrate mainly glucose is preferred
• Pyruvate, the product of glucose catabolism is
oxidized to acetyl-coA requires ferrodoxin
reduction
• Reduced ferrodoxin is oxidized by
hydrogenase which generates ferrodoxin and
release electron as a molecular hydrogen.

45. ADVANTAGES DRAWBACKS
It produces valuable metabolites as a
butyric acid, propionic acid
Relatively lower achievable yield of H2 , as
a portion of substrate is used to produce
organic acids
It is an anaerobic process so no oxygen
limitation
Anaerobes are incapable of further
breakdown of acids
It can produce carbon during day and
night
Accumulation of this acids cause a sharp
drop of culture pH and subsequent
inhibition of bacterial hydrogen
production
Variety of carbon sources can be used as a
substrate
Product gas mixture contains CO2 which
has to be separated

46. PHOTOFERMENTATION
• Light is required as a source of energy for the
production of hydrogen by photosynthetic
bacteria
• Purple non sulphur bacteria genus
Rhodobacter holds significant promise for
production of hydrogen
• Organic acids are preferred as a substrate
• The light energy required in this process is
upto the range of 400nm

47. • CH3COOH + 2H2 + Light → 4H2 + 2CO2
• Production of hydrogen by photosynthetic
bacteria takes place under illumination and in
the presence of inert and anaerobic
atmosphere for the breakdown of organic
substrate to produce hydrogen molecules

48. ADVANTAGES DRAWBACKS
Relatively higher achievable yield of
H2, as a portion of substrate is used
to produce organic acids
It can produce carbon during day
only
Anaerobes are capable of further
breakdown of acids in to
biohydrogen

49. DIRECT PHOTOLYSIS
• Certain green algae produces H2 under anaerobic
condition
• Under deprived of S green algae Chlamydomonas
reinhardtiiin become anaerobic in light & commence
to synthesis of hydrogen.
• Light Absorption by Photosystem II (PSII) Initiates the
Photosynthetic Pathway
• PSII is a large molecular complex that contains several
proteins and light-absorbing pigment molecules like
carotenoids, chlorophylls and phycobilins
• The reaction center strips electrons from two water
molecules, releasing four protons and an oxygen (O2 )
molecule into the thylakoid space

50. • The electron carrier from PSII passes through the
thylakoid membrane and transfers its electrons to
the cytochrome complex, which consists of
several subunits including cytochrome f and
cytochrome b6
• A series of redox reactions within the complex
ultimately transfer the electrons to a second
electron carrier i.e. photosystem I (PSI)
• As electrons are transported through the
complex, protons (H+) outside the thylakoid are
carried to the inner thylakoid space

51. • Light absorption by PSI excites electrons and
facilitates electron transfer to an electron
acceptor outside the thylakoid membrane
• Light absorbed by the PSI reaction center
energizes an electron that is transferred to
ferredoxin (Fd), a molecule that carries electrons
to other reaction pathways outside the thylakoid
• The reaction center replaces the electron
transferred to ferredoxin by accepting an electron
from the electron-carrier molecule that moves
between the cytochrome complex and PSI

52. • Under Certain Conditions, Ferredoxin can Carry
Electrons to Hydrogenase
• Normally, ferredoxin shuttles electrons to an enzyme
that reduces NADP+ to NADPH, an important source of
electrons needed to convert CO2 to carbohydrates in
the carbon-fixing reactions
• Under anaerobic conditions, hydrogenase can accept
electrons from reduced ferredoxin molecules and use
them to reduce protons to molecular hydrogen (H2 )
• 4H++ferredoxin(oxi) ――› ferredoxin(reduced) + 2H2

53. • Dissipation of Proton Gradient is Used to Synthesize
Adenosine Triphosphate (ATP)
• ATP synthase couples the dissipation of the proton
gradient generated in step 2 to the synthesis of ATP.
• Translocation of protons from a region of high
concentration (thylakoid space) to a region of low
concentration (outside thylakoid) releases energy that
can be used to drive the synthesis of ATP from
adenosine diphosphate (ADP) and phosphate (P)
• ATP is a high-energy molecule used to convert CO2 to
carbohydrates in the carbon-fixing reactions

55. INDIRECT BIOPHOTOLYSIS
• Cyanobacteria can also synthesis & evolve H2 through
photosynthesis via the following process
• 12H2O + 6CO2 → C6H12O6 + 6O2
• C6H12O6+ 12H2O → 12H2 + 6CO2
• Cyanobacteria contains photosynthetic pigments such
as chlorophyll & carotenoids and can perform oxygenic
photosynthesis
• Within a bacteria vegetative cell may develop into
structurally modified & functionally specialized cell
(that perform nitrogen fixation)

58. ADVANTAGES OF BIOFUELS
• Abundant
• Less environmental impact
 Spills will not persist in the environment because they
are biodegradable
 Burning fuels causes no sulphur emissions, contain
nitrogen, but net impact on acid rain is less
 Gas produced is same as the gas taken and there is no
net impact on global warming
• Energy dependence: if a country has the land resource
to grow feedstocks, it can produce its own energy

59. DISADVANTAGES OF BIOFUELS
• Regional suitability: depends on water
requirement, invasiveness, fertilizer
• Food security
• Land use changes: destroys local habitat,
animal dwellings
• Monoculture, genetic engineering and
biodiversity: problems caused by pest, use of
pesticides
• Global warming: produce less GHGs emissions

61. REFERENCES
• Speight James G, The Biofuels Handbook,
2012
• http://biofuel.org.uk/html
• Tabak John, biofuels, 2009
• Johanson Paula, Biofuel- sustainable Energy in
21st century, 2010
• Scragg Alan, Biofuels- production, application
and development, 2009