The document discusses the production of biogas and biofuels from waste. It defines biogas and biofuels, describes various types of biofuels like biodiesel produced from lipids, bioethanol produced from carbohydrates, and biobutanol and syngas produced via microbial fermentation. The mechanisms of biogas production from organic waste via anaerobic digestion and the advantages of biogas are also summarized. Biomethane can be produced by upgrading biogas to remove impurities and increase methane concentration.

1. PRODUCTION OF BIOGAS AND BIO-FUEL
FROM WASTE
SUBMITTEDBY
SAKSHI
AEM-PB1-03
SUBMITTEDTO
Dr. NEELAMSAHARAN&
Dr. RATHI BHUVNESWARIG.
SCIENTIST,AEHMDIVISION

2. INTRODUCTION
 Two of the main environmental problems of today’s society are the continuously increasing
production of organic wastes as well as the increase of carbon dioxide in the atmosphere and the
related green house effect.
 Biofuels can reduce the consumption of fossil fuels and thus reduce carbon dioxide emissions,
because biofuels are carbon neutral.
 The carbon dioxide that is emitted when a biofuel is burned merely returns to the atmospheric
carbon dioxide that was taken into plants from the atmosphere by photosynthesis.
 Global biofuel consumption rose from about 1000 Tg in1850 to 2460 Tg in 2000, an increase of
140%.
 Today biofuels represent around 3% of road transport fuels used in the world.

3. BIOFUEL
 Any fuel that is derived from biomass (Plant and animal waste).
 They are one of the largest sources of renewable energy in use.
 Biofuel production widely varies depends on the type of raw material, efficiency level, production
volume, surrounding situation and end-users requirement.
 Biomass converted into biofuels using conversion processes (Carlos and Khang 2008).
 The major conversion technologies can be grouped as biochemical and thermochemical (Anex et
al. 2010)
 Biofuels produced and used in solid, liquid and gaseous forms.

5. IMPORTANCE OF BIOFUEL
 Sustainability - Biofuels have the considerable potential to reduce the ecological footprint by
factors between 8 and 16 compared to fossil fuels. Therefore, from an ecological footprint
perspective they are more sustainable than the existing energy supplies.
 Less Polluting - Since biofuels can be made from renewable resources, they cause less pollution
to the planet. They release lower levels of carbon dioxide and other emissions when burnt
compared to standard diesel.
 Biodegradability - Domestic origin (non- toxic)

6. FEEDSTOCK
The biofuels can be classified according to their feedstock -

7. BIOFUEL TYPES
1. Gaseous biofuel
• Biogas
• Syngas
2. Liquid biofuel
• Biodiesel
• Bioethanol
• Biobutanol
• Biohydrogen
• Biomethane

8. BIODIESEL
 Biodiesel is a very good replacement fuel for
petroleum diesel.
 Biodiesel is produced from vegetable oils, yellow
grease, used cooking oils, or animal fats. (Lipids)
 The fuel is produced by transesterification—a
process that converts fats and oils into biodiesel
and glycerin (a coproduct).
 Oil or fat are react with short-chain alcohol
(methanol) in the presence of a catalyst (NaOH
or KOH) to form biodiesel and glycerin.
 Glycerin, a co-product, is a sugar commonly used
in the manufacture of pharmaceuticals and
cosmetics.
 The main advantages of biodiesel are its cleaner
production strategies, lesser amount of
environment harmful emissions and its ease of
degradability.

9. BIOETHANOL
 Bioethanol is a clean gas produced through fermentation
technology.
 It is used for power generation and transportation.
 Bioethanol is obtained mainly from lignocellulosic materials,
which are highly abundant and renewable. (Carbohydrate)
 The dominant components found in lignocellulosic feedstocks
are lignin, cellulose and hemicellulose.
 The major steps involved in the biochemical method for
ethanol production are
1. Crushing of the feedstock and pretreatment
2. Enzymatic hydrolysis
3. Fermentation
4. Distillation

10. CONTD…
1. PRETREATMENT
 Crushing or milling of the feedstock allows reduction of the size and crystallinity of the prime
matter. This reduces the particle size and the degree of polymerization, which increases the
accessibility for subsequent pretreatments and improves the efficiency of hydrolysis stage and to
allow more efficient cellulose digestion.
 Besides mechanical treatments, thermal pretreatments can be applied as well, such as pyrolysis
and different types of irradiation processes, e.g. electron-beam irradiation, gamma-ray irradiation
or microwave irradiation
 These treatment mainly degrades lignin and the removal of lignin will enhance enzymatic
hydrolysis.

11. CONTD…
2. HYDROLYSIS /SACCHARIFICATION
 It aims at converting cellulose and hemicellulose polymers into
fermentable monosaccharides.
 Either acid or enzymatic treatments may be used to hydrolyze
polysaccaharides, where cellulase enzyme degrade the
cellulose to sugar.
 Cellulase producing common fungi are Aspergillus niger ,
Trichoderma reseesi used for cellulose degradation
 Breaking down cellulose and hemicellulose will result in the
production of mainly hexoses and pentoses, respectively,
although some hexoses (glucose) may be obtained from
hemicellulose as well.

12. CONTD…
3. FERMENTATION PROCESS
 Sugars are fermented to ethanol by the use of different microorganisms.
 The microorganisms are selected based on their efficiency for ethanol productivity and higher
product and inhibitors tolerance. Yeast Saccharomyces cerevisiae is used commercially to
produce the ethanol from sucrose, other species such as Zymomonas mobilis.
 The yeast contains an enzyme called invertase, which acts as a catalyst and helps to convert the
sucrose sugars into glucose and fructose.
4. Fractional Distillation Process
 The ethanol, which is produced from the fermentation process, still contains a significant quantity
of water, which must be removed.
 The distillation process works by boiling the water and ethanol mixture. Since ethanol has a lower
boiling point (78.3°C) compared to that of water (100°C), the ethanol turns into the vapour state
before the water and can be condensed and separated.

13. BIOBUTANOL
 Biobutanol is produced by microbial fermentation, similar to bioethanol, and can be made from
the same range of sugar, starch or cellulosic feedstocks..
 The main steps, viz., drying, Pretreatment, acid hydrolysis, detoxification, and fermentation.
 The pretreatment method is used to break down the complex structure (lignocellulosic biomass)
into fermentable sugars. During this process, numerous inhibitors are known to be formed which
are lethal to microorganisms, affecting the fermentation process, and can be removed by
detoxification.
+

14. CONTD...
 The most commonly
used microorganisms are
strains of Clostridium
acetobutylicum and Clos
tridium beijerinckii.
 The fermentation step is
commonly called as
Acetone-Butanol-
Ethanol (ABE)
fermentation, In addition
to butanol, these
organisms also produce
acetone and ethanol.

15. CONTD…
 This anaerobic fermentation consists of two stages: first the acidogenic phase where Clostridial
bacteria produce acetic and butyric acids, carbon dioxide (CO2) and hydrogen (H2) from sugars,
followed by the solventogenic phase where acids are converted into acetone, butanol and ethanol,
typically in the ratio of 3:6:1.
 After the fermentation, final products are recovered and purified in downstream processing.
Adsorption, gas stripping, liquid-liquid extraction, pervaporation, reverse osmosis are the most
used separation methods.
*Biobutanol is preferred over bioethanol due to several advantages, including its high energy density,
low volatile nature, high boiling point, and hydroscopicity (Ndaba et al., 2015).

16. SYNGAS
• The synthesis gas is defined as a gas with
H2 and CO as the main components of fuel.
Carbon dioxide (CO2) and other
components such as water (H2O) may also
be present in syngas.
• Biomass-derived syngas can typically be
obtained from gasification of agricultural
and forestry residues, along with industrial
wastes
• The biomass gasification technology
involves partial oxidation of biomass in the
presence of a gasifying agent (for instance
air, oxygen, steam, CO2 or mixtures of these
components)

17. CONTD…
o
 Pyrolysis is the thermal decomposition of the
biomass feedstock into gaseous, liquid, and solid
products without any oxidizing agent .

18. CONTD…
• Reaction conditions:
High temperature (800–1000°C),
low pressure (1–20 bar)
H2/CO ratio within 0.5 and 1.8
resulting in the production of a low-to-
medium heating value fuel gas called syngas
or producer gas that contains CO, H2 , CO2 ,
CH4 , and N2 in various proportions
 Secondary by-products: tar, char, ashes.
 Syngas is obtained after suitable
purification and conditioning stages.
o
Partial oxidation processes use less than the
stoichiometric amount of oxygen required for complete
combustion.

19. BIOGAS
 Biogas is one of the most promising renewable energy sources in the world.
 Biogas is naturally formed in landfills, for example, but in biogas plants it is produced under
controlled conditions from organic waste.
 Since the useful gas originates from biological process, it has been termed as bio-gas
 Biogas is an important source of heat and electricity generation, for use in engines and offers a
natural fertiliser for agriculture.
• Biogas can also be upgraded into biomethane, also called renewable natural gas or RNG, and
injected into natural gas pipelines or used as a vehicle fuel.

20. BIOGAS COMPOSITION
*Regardless of the substrate, it has two major components: methane and carbon dioxide

21. BIOGAS FEEDSTOCK
Biogas can be produced from all kinds of organic wastes -
 Food Waste
 Livestock Waste
 Municipal waste
 Agricultural waste
 Green waste
 Manure

22. COMPONENTS OF BIOGAS PLANT
• Inlet pipe - The substrate is discharged into the digester through the inlet pipe/tank.
• Mixing tank - The feed material (dung) is collected in the mixing tank. Sufficient water is added
and the material is thoroughly mixed till a homogeneous slurry is formed.
• Digester - The slurry is fermented inside the digester and biogas is produced through bacterial
action.
• Gas holder or gas storage dome - The biogas gets collected in the gas holder, which holds the gas
until the time of consumption.
• Outlet pipe - The digested slurry is discharged into the outlet tank through the outlet pipe. The
effluents are removed from the outlet tank in a regular interval and are used as fertilizer.
• Gas pipeline - The gas pipeline carries the gas to the point of utilization, such as a stove or lamp.

23. BIOGAS PLANT
 Biogas plant consists of an airtight
underground digester tank, a gas holder,
mixing devices, and gas regulator valves
 Digesters receives dumped wastes in a regular
interval
 Digester performance will also depend on the
microbial population in the digester.
 Organic materials (plant and animal products)
are broken down by bacteria in an oxygen-free
environment, a process called anaerobic
digestion, place in reactors.
 Bio-gas is produced through a bio-chemical
process in which certain types of bacteria
convert the biological wastes into useful bio-
gas.

24. CONTD…
 The installed capacity of biogas plant is determined by the amount of biogas a plant produces (in
m3) within 24 hours.
 In average, 25 kg of fresh cattle dung produce 1 m3 of biogas through digestion in biogas plants .
Biogas burns with blue flames without or with very little smokes which results in almost CO2
neutral combustion.

26. MECHANISMS OF BIOGAS PRODUCTION
1. Hydrolysis
2. Acidogenesis
3. Acetogenesis
4. Methanogenesis

27. 1. HYDROLYSIS
 The very first step of AD is very important as large organic molecules are not readily absorbable.
 Several pretreatments that can be used to increase the process efficiency and reduce digestion
times.
Biological pretreatments - several microbes secrete different enzymes, which cleave the complex
macromolecules into simpler forms
Chemical Pretreatments – acidic, alkaline
Mechanical Pretreatments - The principal objective of mechanical pretreatment is the reduction
of the particle size in wastes, thereby increasing the surface area of particles
Thermal Pretreatments - Thermal pretreatment involves exposing wastes to high temperatures to
induce hydrolysis.
 Organisms that are active in a biogas process during the hydrolysis of polysaccharides include
various bacterial groups such as Bacteriodes, Clostridium, and Acetivibrio.

28. ACIDOGENESIS/FERMENTATION
 The diversity of the microbial consortium involved in AD reaches its peak during this stage.
 Most of the microbes involved in hydrolysis step are also involved in fermentation.
 Along with them, microbes belonging to the genera like Enterobacterium, Acetobacterium and
Eubacterium also carry out the process of fermentation (Schnurer and Jarvis 2010).
 Through various fermentation reactions, the products from hydrolysis are converted mainly into
various organic acids (acetic, propionic acid, butyric acid, succinic acid, lactic acid, etc.), alcohols,
ammonia (from amino acids), carbon dioxide and hydrogen.

29. ACETOGENESIS
 In this step, the fermented products are oxidized into simpler forms.
 Substrates for acetogenesis consist of various fatty acids, alcohols, some amino acids and
aromatics.
 Syntrophomonas, Syntrophus, Clostridium, and Syntrobacter are organisms that can perform
acetogenesis.
 In addition to hydrogen gas, these compounds primarily form acetate and carbon dioxide (Heeg et
al. 2014).

30. METHANOGENESIS
 Methanogenesis is the methane production pathway .
 The pathway which leads to the methane production solely depends on the methanogenic
consortia and the availability of the suitable substrates that favors the digestion process.
1. Methylotrophic methanogenesis, i.e., production of methane by decarboxylation of methyl
alcohols/methyl amines/methyl sulfides, etc.
2. Hydrogenotrophic methanogenesis, i.e., production of methane by the reduction of H2/CO2
3. Acetoclastic methanogenesis, i.e., production of methane by acetate decarboxylation.
 It has been reported that Acetoclastic methanogenesis is the major pathway of methane
production in anaerobic digestion as 70 % of the total methane generated during AD of domestic
sewage is via this pathway (Lettinga 1995; Merlino et al. 2013).

32. ADVANTAGES OF BIOGAS PRODUCTION
 It is a eco-friendly fuel.
 The required raw materials for biogas production are available abundantly in villages.
 It not only produces biogas, but also gives us nutrient rich slurry that can be used for crop
production.
 It prevents the health hazards of smoke in poorly ventilated rural households that use dung cake
and fire-wood for cooking.
 It helps to keep the environment clean, as there would be no open heap of dung or other waste
materials that attract flies, insects and infections
 Availability of biogas would reduce the use of firewood and hence trees could be saved.

33. BIOMETHANE
 Biomethane production involves upgrading, or ‘cleaning-up’ of raw biogas to a higher-quality gas
containing primarily biomethane.
 Biogas upgrading involves removal of carbon dioxide, hydrogen sulphide, water vapour as well as
trace gases.
 The resulting biomethane usually have a higher content of methane and a higher energy content
making it essentially identical to conventional natural gas.
 There are number of different upgrading method which can be used to increase CH4
concentration (Wellinger and Lindberg 1999 ; Ryckebosch et al. 2011 ) .
Membrane separation- A membrane is used from which water, O2 and CO2 are able to permeate
through while a very limited amount of CH4 and nitrogen is able to pass (Wellinger and Lindberg
1999)

34. CONTD..
Water scrubbing – It is used to increase CH4 by removing CO2 from biogas (Wellinger and
Lindberg 1999 ). Scrubbing with water is one of the cheapest and most common techniques for
this purpose
H2S is also a common contaminant present in biogas, which can be removed by in situ reduction
of H2S within the digester vessel by adding metal ions.
 In addition to H2S, H2O and CO2 , there may be other trace contaminants present in the biogas
which are potentially harmful to equipment and/or people and must therefore be removed or
reduced to acceptable levels.
 There have also been new developments in upgrading process of biogas such as cryogenic
separation which is based on the sublimation points of different gases.

35. CONTD…

36. REFERENCES
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37. REFERENCES
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38. THANK YOU !