Introduction, energy plantation, biomass conversion technologies, photosynthesis, biogas generation, factors affecting biogas generation, classification of biogas plants & their comparisons, types of biogas plants , biogas from plant wastes, community plants & site selection, digester design considerations, design calculations, methods of maintaining & starting biogas plants, properties & utilisation of biogas, thermal gasification of biomass, pyrolysis, alternative liquid fuels

1. DEPARTMENT OF CHEMICALENGINEERING
CHAPTER-7
“Energy From Biomass”
PROF. DEVARSHI P. TADVI
ASSISTANT PROFESSOR
CHEMICAL ENGINEERING
DEPARTMENT
S S AGRAWAL INSTITUTE OF
ENGINEERING & TECHNOLOGY,
NAVSARI

2. Importance of non-conventional sources of
energy:
1.The non-conventional sources of energy are abundant in nature.
According to energy experts the non-conventional energy potential of
India is estimated at about 95,000 MW.
2.These are renewable resources. The non-conventional sources of energy
can be renewed with minimum effort and money.
3.Non-conventional sources of energy are pollution-free and eco-friendly

3. GENERATION AND UTILIZATION OF BIOMASS

4. Biomass is organic matter produced by plants, both terrestrial, aquatic and
their derivatives.
Biomass can be considered a renewable energy source because plant life renews &
adds to itself every year.
Solar energy ->Photosynthesis –>Biomass- Energy conversion

6. BIOMASS SOURCES

7. 1. Field and plantationbiomass
Agricultural crop residues- Cobs, stalks, Straw, Cane thrashes and etc
Edible matters from crops-Environmentally spoiled grains, pulses, fruits, nuts, spices,
seeds and lint etc
Dedicated energy crops- Bamboo
Plantation debris-Leaves, barks and trunks
Livestock wastes from fields
2. Urban waste biomass
Municipal solid wastes
Sewage sludges
Kitchen and canteen wastes
3.Industrial biomass
Agro-industrial processed biomass and their wastes – Husk
Oil cake
Sugar molasses
Hides and skin wastes
Fruit and pulp debris Sawdust
Wood pulp and paper shavings
Fermented microbial mass etc

8. 4. Forest biomass
Log residues
Timber
Forest floor debris
Animal carcass
5. Aquatic biomass
Sea weeds (E.g. Kelp)
Fresh water weeds (E.g. Water Hyacinth)
Dead fishes
Microalgae blooms

9. Utilization of Biomass

10. Properties of Biomass
Physical Properties
Following are important for solid fuels for combustion / thermal processing:
 Moisture Content
 Particle Size and Size distribution
 Bulk Density & Specific gravity
 Higher Heating/Calorific Value

11. Properties of Biomass
• Chemical Compotion
 TotalAsh %,
 Solvent soluble %,
 Water Soluble %,
 Lignin %,
 Cellulose %,
 Hemi-cellulose %

12. Elemental Composition
 • Carbon
 • Hydrogen
 • Oxygen
 • Nitrogen
 • Sulphur
Properties of Biomass

13. How is Biomass Converted toEnergy?
Biomass power is simply carbon neutral electricity produced from renewable
organic waste products, which could have been openly burned, dumped in
landfills or just left in the forest to causefires.
1. Energy from the sun is transferred and stored in plants in the form of
chemical energy. When the plants are cut or die, wood chips, straw and
other plant matter is delivered to biogas plant.When biomass is burnt, it
releases energy in the formof heat.
2. The biomass plants burn wood or other forms of waste to generate
steam. The energy from the steam is directed via pipes to runturbines.
3. The steam rises up to run turbines that produce electricity or generate
heat for homes and industries.
4. In most countries, biomass plants have been built in the countryside to
provide electricity to the local population. There are waste-to-energy
plants that burn trash to produce electricity and power millions of
homes. Energy can also be used by burning the scrap wood or wood
chips that are left over after trees have been trimmed.

15. A wide verity of conversion technologies is available for manufacturing premium
fuels from biomass.
Each biomass resources-wood, dung, vegetable waste can be treated in many
different ways to provide a widespectrum of usefulproducts.
The choice of the process is determined by a number of facts- the location of the
resources & its physical conditions, the economics of competing process &
availability of a suitable market for the

16. Biomass Conversion
Thermo chemical
Conversion
Biochemical
conversion
Gasification
Anaerobic
Digestion
Fermentation
Pyrolysis
Direct
Combustion

18. Direct Combustion
In a direct combustion system, biomass is burned in a combustor or furnace
to generate hot gas, which is fed into a boiler to generate steam, which is
expanded through a steam turbine or steam engine to produce mechanical
or electrical energy.

19. • The direct combustion of biomass in presence of oxygen/air to produce heat
and by products is called direct combustion.
• The complete combustion of biomass into ash is called incineration.
• This heat energy in the product gases or in the form of steam can be used for
various applications like space heating or cooling, power generation process
heating in industries or any other application.
• However, if biomass energy by combustion is used as co generation with
conventional fuels, the utilization of biomass energy makes it an attractive
proposition.
Direct Combustion

20. Direct Combustion
A simple biomass electric generation system is made up of several key
components. For a steam cycle, this includes some combination of the
following items:
• Fuel storage and handling equipment
• Combustor / furnace
• Boiler
• Pumps
• Fans
• Steam turbine
• Generator
• Condenser
• Cooling tower
• Exhaust / emissions controls
• System controls (automated).

21. Direct Combustion
Direct combustion systems feed a biomass feedstock into a combustor or
furnace, where the biomass is burned with excess air to heat water in a boiler
to create steam.
Steam from the boiler is then expanded through a steam turbine,
which runs a generator and produces electricity.
In general, all biomass systems require fuel storage space and some type of
fuel handling equipment and controls. A system using wood chips, sawdust, or
pellets typically use a bunker or silo for short-term storage and an outside fuel
yard for larger storage. An automated control system conveys the fuel from the
outside storage area using some combination of cranes, stackers, reclaimers,
front-end loaders, belts, augers, and pneumatic transport.

22. Thermo-Chemical Conversion

23. Gasification-
takes place by heating the
biomass with limited oxygen
/ Air (deficient O2 and Air)
to produce low heating value
gas or by reacting it with
steam & oxygen at high
pressure & temperature to
produce medium heating
value gas like H2,CO,CH4,N2

25. Pyrolysis
It is the heating of biomass in a closed vessel at temperatures in the range
500oC- 900oC in absence of O2/air or with steam. It produces solid, liquid
and gases.
The pyrolysis process can use all type of organic materials including plastic
and rubeers.
Pyrolysis is the decomposing of
biomass (fresh or fossil) by the
heat of anaerobic (reduced air)
combustion whic converts
organic material into gases
and/or fuel oils.

26. Biochemical Conversion
In biochemical processes the bacteria and micro organisms are used to
transform the raw biomass into useful energy like methane and ethane gas.
Following organic treatments are given to the biomass:
1) Fermentation of biomass (Aerobic digestion)
2) Anaerobic digestion of biomass

27. Fermentation

28. Anaerobic Digestion

30. What is biomass?
• Biomass is rubbish or garbage.
• It includes dead trees , livestock manure, garden waste, bark,
left overcrops, sawdust, paper and kitchen rubbish.
• Biomass is organic matter produced by plants – terrestrial and aquatic
and their derivatives. It includes
1. Forest crops and residues
2. Crops specially grown in ‘energy farms’ for their energy content
3. Animal manure

32.  Biomass resources fall into three categories
 Biomass in its traditional solid mass (wood and agriculture residue)
 Biomass in non traditional form (converted into liquid fuels)
 The frist category is to burn the biomass directly and get the energy . In
the second category , the biomass is converted into ethanol (ethyl
alcohol) and methanol (methyl-acohol) to be used as liquid fuels in
engines.
 The third category is to ferment the biomass anaerobically to obtain a
gaseous fuel called bio- gas

33.  DIGESTION Decomposition of organic matter by anaerobic
bacteria in an oxygen-starved
environment
Anaerobic digesters compost (or
"digest") organic waste in a machine
That limits access to oxygen
encouraging
methane and
the
carbon
generation of
dioxide by
microbes in the waste. This digester
gas is then burned as fuel to make
electricity

34. 3

35.  The energy stored in dry biomass like wood and straw is most easily
released by direct combustion – although dry materials can also be
converted into liquid and gaseous fuels by variety of techniques.
 three biofuels – wood , straw and refuse are being burnt on an increasing
scale in many countries to provide useful heat.

36.  A wide variety of conversion technologiesis avaliable for manufacturing
premium fuels from biomass.
 Some are simple and well understood like digestion and fermentation ;
others like gasification have been tested in large pilot plants and are
now being commercialised

37.  Takes two forms
 Gasification
 Liquefaction
 Gasification- take place by heating the biomass with limited oxygen to
produce low heating value gas or by reacting it with steam and oxygen at
high pressure and temperature to produce medium heating value gas.
 The later may be used as fuel directly or used in liquefication by converting
it to methanol (methyl alcohol CH3OH) or ethnol (ethyl alcohol
CH3CH2OH) or it may be converted to high heating value gas.

38.  Takes two forms
 Anaerobic digestion
 Fermentation
 Anaerobic digestion involves the microbial digestion of biomass. (an
anarebic is a micro organism that can live and grow without air or
oxygen by the decomposition of matter containing it)
 The process take place at low temprature upto 65 degree celsius , and
requires a moisture content of at least 80 percent.
 It generates a gas consisting mostly of CO2 and methane (CH4) with
mimimum impurities such as hydrogen sulfide
 Fermentation is the breakdown of complex molecules in organic
compound under the influence of a ferment such as yeast , bacteria,
enzymes , etc.
 Fermentation is a well established and widely used technology for the
conversion of grains and crops into ethnol.

39.  Anaerobic Digestion
 Fermentation
 Anaerobic digestion or simply digestion consist broadly of three phases :
 Enzymatic hydrolysis : where the fats , starches and proteins contained in
cellulosic biomass are broken broken down into simple compound
 Acid formation: where the micro organisms of facultative and anaerobic
group collectively called as acid farmers, hydrolyse and ferment, are broken
to simple compounds into acids and volatile solids.
 As a result complex organic compounds are broken down to short chemical
simple organic acids.
 Methane formation : when organic acids as formed above are then
converted into methane (CH4) and CO2 by the bacteria which are strictly
anarobs. These bacteria are called methane fermentors. For efficient
digestion these acid formers and methane fermentors must remain in a state
of dynamic equilibrium.

40.  Caloric value of gas :one of the main be nefits is the production of a
biproduct the biogas which has a calorific value and can therefore,
be used as an energy source to produce steam or hot water.
 New sludge production : the conversion of organic matter to methane and
carbon dioxide results in a similar quantity of excess sludge.
 Low running cost : there is no airation in the anaerobic treatment
naturally in this digestion , running costs are quarter of the equivalent
aerobic system.

41.  Pyrolysis – A wide range of energy rich fuels can be produced by
roasting dry woody matter like straw and wood chips.
 The materials is fed into reactor vessel or retort in a pulverised or
shredded form and heated in the absence of air.
 As the temprature rises the cellulose and lignin breakdown to simpler
substance which are driven off leaving a char residue behind.
 This method has been used for centuries to produce charcoal.

42.  Liquid yeilds are maximized by rapid heating of the feedstock to
comparetively low tempratures.
 The vapours are condensed from the gas stream and these seprate into two
phase liquor: the aqueous phase contains a soup of water soluable organic
materials like acetic acid , acetone and methanol
 The non aqueous phase consists of oils and tars.
 These crude oil can be burnt , but it is usually more profitable to up-grade
them to premium fuels by conventional refining technique.
 Pyrolysis of wet biomass produces fuel gas and very little liquid.
 An alternative technique for maximum gas yeilds is to blow small quantities
of air or oxygen into reactor vessel and to increase the temprature to over
1000 degree celsius.
 This causes part of the feed to burn. Fuel gas from air blown gasifiers has a
low calorific values and may contain upto 40% inert nitrogen gas overall
yeilds of 80-85% can be expected.

43.  Methane is produced directly from woody matter by treatment at high
temprature and pressure with hydrogen gas.
 The hydrogen can be added or , more commonly , generated in the reactor
vessel from carbon monooxide and steam.
 Recent analysis suggest that steam gasification is the most efficient route
to methanol .
 Net energy yeilds 55% can be achieved although higher yeilds are likely
in the future as the technology is developed.
 Under less severe conditions of temperature and pressure (300 – 400
degree Celsius and 100 atmospheres) , carbon monooxide and steam react
with cellulose to produce heavy oils which can be seperated and refined to
premium fuels.

44.  Biogas plants are mainly classified as :
 Continuous and batch types
 The dome and the drum types.
 Different variation in the drum type.

45.  Continuous plant – here is a single digester in which raw material are
charged regularly and the process goes on without interruption except for
repair and cleaning etc.
 In this case the raw material is self buffered or otherwise thoroughly
mixed with the digesting mass where dilution prevents souring and
the biogas production is maintained. The countinous process may be
completed in a single stage or separated into two stages
 Single stages process
 the entire process of conversion of complex organic compound into
biogas in completed in a single chamber.
 This chamber is regularly fed with raw materials while the spent residue
keeps moving out.

47.  Double stage process
 The acidogenic stage and methanogenic stage are physically separeted
into two chambers.
 Thus the first stage of acid production is carried out in a separate chamber
and only the diluted acids are fed into the second chamber where bio-
methanation take place and the biogas can be collected from the second
chamber.
 The main features of countinous plants are
 It will produce gas continously;
 It requires small digestion chambers;
 It needs lesser periods for digestion;
 It has less problems compared to batch type and it is easier in operation.

49.  The feeding is between intervals, the plant is emptied once the process of
digestion is complete.
 In this type, a battery of digesters are charged along with lime ,urea etc and
allowed to produce gas 40-50 days. These are charged and emptied one by
one in a synchronous manner which maintains a regular supply of the gas
through a common gas holder.
 The biogas supply may be utilised after 8-10 days.
 Such a plant would be expensive to install and unless operated on large
scale it would not be economical.

50.  There are numerous models of a biogas plant mainly two main types are
usually used:
 The floating gas holder plant and other is
 Fixed dome digester.
 The floating gas holder digester which is used in india is known as KVIC
plant. The fixed dome digester is called the chinese plant.
 There are different shapes in both the designs
 ,cylindrical rectangular , spherical etc.
 The floating gas holder digester developed in india is of mansory
construction with the gas holder. The gas holder is separated from the
digester.
 In the fixed dome digester the gas holder and the digester are combined.
 The fixed dome is the best suited for batch process.

51.  Biogas plant can be grouped under two broad heads
 Floating Gas Holder
 Fixed dome digester
o The family size biogas plants available today in india are broadly of two
types.
 KVIC model (Khadi Village Industries Commission)
 Janta Model

55.  The KVIC plant is of steel drum type or floating gas holder design, in which the
digestion take place in a masonry well and the drum floats as the gas collects and
is taken out from the top
 The janta model or fixed dome digester (also called chinese plant) is a drumless
type similar in construction to the KVIC model except that the steel drum is
replaced by a fixed dome roof of masonry construction.
 The different design variation of family type biogas plants avaliable at present in
our country includes:
 KVIC (khadi and village industries commission) design
 PRAD (Planning , Research and Action division) design (modification of chinese
design)
 ASTRA (Application of science and technology to rural area) design
 Murugappa chettiar Research centre design
 Tamil Nadu Agriculture University dome type design
 Himachal Pradesh capsule design
 Kuccha-Pucca Model of Punjab agriculture University Ludhiana.
 Deen Bandu Design
 Plug flow design
 Roorkee Design
 Ganesh Model etc…

56.  Distance : the distance between the plant and the site of gas consumption
should be less in order to achieve economy in pumping of gas and minimizing
gas leakage. For the plant of capacity 2 cubic meter , the optimum distance is
10m
 Minimum gradient: for conveying the gas a minimum gradient of 1% must
be made avaliable for the line.
 Open space : the sunlight should fall on the plant as temperature between 15
degree Celsius is essential for gas generation at good rate.
 Water table: the Plant is normally comstructed underground for ease of
changing the feed and unloading slurry require less labour.
 Seasonal run off : proper care has to be taken to prevent the interfere of run
off water during monsoon.
 Distance from wells : the seepage of fermented slurry may pollute the well
water. Hence a minimum of 15 m should be maintained from wells.
 Space requirement : sufficient space must be avaliable for day to day
operation and maintenance. As a guide line 10 to 12 cubic meter is needed per
cubic meter of the gas.

57. How does this power generator work?
You could draw a diagram.
 Methane gas is made.
 Then the gas goes along the pipes. When the gas comes out it is like
the gas that is on your barbeque .The steam turns the turbine round to
boil the water . All rubbish is then put into a big tank or pit.

58. Deenabandhu Biogas Project Model

59. Present State of Biomass Energy in India
3,500 MW of power generation through biogases based co- generation in
sugar mills.
537 MW has so far been commissioned
536 MW is under installation
Anaerobic digestion & Regenerative Thermal Oxidiser component of Lubeck
Mechanical Biological Treatment plant in Germany, 2007

60. Typical composition of biogas
Matter %
Methane, CH4 50-75
Carbon dioxide, CO2 25-50
Nitrogen, N2 0-10
Hydrogen, H2 0-1
Hydrogen Sulfide, H2S 0-3
Oxygen, O2 0

61. MUNICIPAL SOLID WASTE (MSW) TO ENERGY INCINERATION PLANT
SHREDDER
AIR
CLASSIFIER
Dry duly treated biomass
HRSG
BOILER
FURNACE
Stack
Heat Recovery Steam Generator
HRSG
Removal of pollutants
Superheated
output
Boiler
Feed
water
Cooling
Tower
Pre-heated
Feed water
Refuse derived
fuel
Aux fuelMetal Glass
Recycled
Thermal Output
Electrical
Output
Ash to landfill
Condenser
Pre-heated
air

62. Main Advantages of Biomass Energy
• Indigenous source
 Economic development opportunities in rural areas
 The pollutant emissions from combustion of biomass are usually lower than
those from fossil fuels
 Commercial use of biomass
 Improve fertility of soil
• Environmental Advantages
 Renewable resource
 Reduces landfills
 Protects clean water supplies
 Reduces acid rain and smog
 Reduces greenhouse gases
 Carbon dioxide
 Methane

63. Disadvantages of Biomass Energy
 It is dispersed and land intensive as a source
 It is often of low energy density
 It is labour intensive and the cost of collecting large quantities for
commercial application is significant

64. Fuel Properties of Biogas
Calorific Value
60% Methane : 22.350 to 24.22 MJ/m3. Without CO2 : 33.525 to 35.390
MJ/m3. Octane rating without CO2 : 130 Octane rating with CO2 : 110
Ignition temperature : 6500 C Air to methane ratio for complete
Combustion (by volume) : 10 to 1
Explosive limits to air (by volume) : 5 to 15

65. Applications
• Anaerobic digestion is used for effluent and sewage treatment.
• Anaerobic digestion is a simple process that can greatly reduce the amount
of organic matter which might otherwise be destined to be landfilled or
burnt in an incinerator.
• Almost any organic material can be processed with anaerobic digestion. This
includes biodegradable waste materials such as waste paper, grass clippings,
leftover food, sewage and animal waste.
• Anaerobic digesters can also be fed with specially grown energy crops
such as silage for dedicated biogas production.