Briquetting is a way to make use of biomass residues that would otherwise go to waste, and replace the use of wood and charcoal (often produced unsustainably) as well as fossil fuels, thus cutting greenhouse gas emissions.

2.  80% of the total energy consumption in a village
goes for domestic use
 90% of the domestic energy used goes for cooking
 80% of cooking energy used is from fuel wood i.e.,
approximately 60% of total energy used is from fuel-
wood

3. CROP PRODUCTION
(1000 tonnes)
RESIDUE
(1000 tonnes)
Rice 48,470 77,984
wheat 28,486 50,480
maize 7,256 8,707
Cotton 1,012 3,036
Jute 755 1,510
Barley 3,192 4,788
Sugar cane 1,40,604 28,121
Other minor groups 36,157 28,926

4. RESIDUES ENERGY CONTENT (x 109 MJ)
Rice straw 212.66
Rice husk 58.23
Sorghum stalk 4.63
Sugarcane bagasse 82.00
Saw dust and shavings 0.77
Soybean stalks 1.90
Cassava stalks 39.84
Coconut husks 4.62
Coconut shell 2.91
Cotton stalk 1.37
G.Nut shell 2.03
Maize stalk 33.62
Mungbean stalk 3.94

5. Biomass
Lignin
Content
(%)
Bulk
density
(kg/m3)
Calorific
value
(Kcal/kg)
Ash
content
(%)
Volatile
matter
(%)
Fixed
carbon
(%)
STRAW
Rice 12.60 80.11 3730 15.50 68.30 16.20
Wheat 16.97 80.00 4150 8.00 77.30 14.70
SHELL
Groundnut shell 31.28 165.00 4524 3.80 73.30 22.90
Jatropha shell 11.90 106.18 3168 14.88 68.73 16.38
HUSK
Rice husk 17.20 235.00 3437 16.80 67.80 15.40
BAGASSE
Sugarcane 14.84 133.00 4216 3.00 82.00 15.00
OTHER FEEDSTOCKS
Saw dust 39.00 177.00 4463 1.60 82.90 15.50

6. Sl.N
o
Fuel type
Moistute
content
(%)
Density
(Kg/m3)
Heat of combustion
Mass Energy
Density (MJ/Kg)
Volume Energy
Density
(MJ/m3)
1. Biomass 50 1.0 9.20 9200.00
10 1.25 18.60 11200.00
2. Densified
biomass
10 1.25 18.60 26,100
3. Charcoal - 0.25 3.18 8,000
4. Bituminous coal - 1.30 28.0 36,400
5. Methanol - 0.79 20.10 15,900
6. Gasoline 0.70 44.30 30,900

7. Several of these undesirable attributes result from the low
mass and low volume energy density of biomass
 Relatively low heat value per unit volume
 Variability of quality and heat value
 Difficulty in controlling the rate of burning
 Rapid burning, necessitating frequent refueling
 Difficulty in mechanizing continuous feeding
 Large area required for storage
 Economic problems in transportation and distribution

8.  In its natural form, biomass is often an inefficient fuel because it
is bulky, wet and dispersed
 In bulk form, the density of the biomass is very low and the
efficiency of combustion is also low
 Among the options for conversion of biomass into energy intensive
fuels, densification of biomass is a simple and economic
proposition
 Densification yields an economically viable solution to the storage
volume, handling and transportation problems of different types of
biomass
 These briquettes have proved to be an improved and efficient fuel
which burn with less smoke and leaves low ash content. Hence,
upgrading of biomass is essential to economically exploit its
potential

9. Collection and
Storage Crop
residues
Drying and
pulerization Distribution and
Scheduling
Production
Activities
Domestic
Activities
Gasifier
plant
Hot air/
Steam
Agro
Enterprises
Electricity
generation
Storage
BIOMASS BASED DECENTRALIZED POWER
Briquetting

10.  In the past, the principal form of biomass burned for energy
was wood because of its relatively high density and availability
 Biomass briquetting is the process of compaction of the low bulk
density biomass into a product of high density than the original
raw material
 Biomass residues such as saw dust, straw, etc now wasted are
compressed into pellets, briquettes or logs
 Briquette replaces traditional fuel wood and kerosene both in
domestic use and in small scale industries in developing
countries

11.  Ready availability and renewability of biomass make briquettes
cheaper than coal
 Combustion of biomass briquettes is clean and nearly pollution
free because biomass does not contain sulphur.
 Biomass briquettes have a higher practical thermal value and
much lower ash content (2-10% as compared to 20-40% in coal)
 Combining waste disposal and energy recovery processes offers
recycling opportunities as well as improved disposal technology,
often at low cost
 Low energy and capital requirements for production
 No requirement for special storage facility

12.  There is no fly ash when burning briquettes
 Consistent quality have high burning efficiency and are ideally sized
for complete combustion
 Combustion is more uniform compared to coal
 Rate of combustion is comparable to coal
 Permits burning in grate-fired boilers
 Reduces particulate emission
 Makes transportation, storage and feeding more efficient
 Reduces or eliminates the possibility of spontaneous combustion in
storage
 Significant reduction in biodegradability
 Fuelling wood stoves and firing external combustion engines
 Raw material for pyrolysis and gasification
 Produced near the consumption centres and supplies do not depend
on erratic transport from long distances

13.  High investment cost and energy input to the process
 Undesirable combustion characteristics often observed e.g.
poor ignitability, smoking, etc
 Tendency of briquettes to loosen when exposed to water or
even high humidity weather

14.  The main raw materials comprising of forest and agricultural
wastes are abundantly available in most parts of the country
 The permissible moisture contents in the raw materials are 10-
15%. The following are the lingo-cellulose residues used for making
briquetted fuel
 Saw dust, sugar cane bagasse, cotton stalk, coffee husk, groundnut
shell, wood, wood shavings, sunflower husk, paddy straw, rice
husk, wheat straw, maize stalk, cardboard waste, corncob, palm
fruit bunch, tobacco waste, mustard stalk, jute waste, bamboo
dust, tea waste, soybeans husk

15. OTHER BIOMASS MATERIALS
Groundnut shell: Because of low ash (2-3%) and a moisture content
less than 10%, it is also an excellent material for briquetting
Cotton sticks: This material is required to be chopped and then
stored in dry form. It has a tendency to degrade during storage.
Also, it has a higher content of alkaline minerals and needs to be
used with caution
Bagasse/bagasse pith: These residues have high moisture content of
50% after milling, hence drying is energy intensive. They have low
ash content and a correspondingly high heating value of the order
of 4400 kcal/kg

16. Rice husk
When compared to sawdust, agro-residues have a higher
ash content, higher potash content and have poor flow
characteristics
However, rice husk is an exceptional biomass. It has good
flowability, normally available with 10 percent moisture and
the ash contains fewer alkaline minerals, thereby it has a high
ash sintering temperature. In fact, it makes an excellent fuel
although its calorific value is less than wood and other agro-
residues

17. There are many factors to consider before a biomass
qualifies for use as feedstock for briquetting. Apart from its
availability in large quantities, it should have the following
characteristics
LOW MOISTURE CONTENT
Moisture content should be as low as possible, generally
in the range of 10-15 percent. High moisture content will pose
problems in grinding and excessive energy is required for drying
FLOW CHARACTERISTICS
The material should be granular and uniform so that it can
flow easily in bunkers and storage silos
CHARACTERISTICS OF BIOMASS RESIDUES FOR
BRIQUETTING

18. ASH CONTENT AND COMPOSITION
 Biomass residues normally have much lower ash content
(except for rice husk with 20% ash) but their ashes have a
higher percentage of alkaline minerals, especially potash
 These constituents have a tendency to devolatalise during
combustion and condense on tubes, especially those of super
heaters
 These constituents also lower the sintering temperature of
ash, leading to ash deposition on the boiler’s exposed
surfaces

19.  The densification of biomass may be defined as compression or
compaction to remove inter and intra particle voids
PROCESS OF DENSIFICATION
 It involves compression, deformation and self-bonding
between adjacent particles of biomass
 The mechanical energy of the drive screw is converted into
heat by means of friction and shear as the granular material is
compressed and forced through an orifice
 When heated above the plastic temperature range (1650C for
wood), the agricultural wastes loose their elasticity and are
relatively easily compressed, particle surfaces come into
intimate contact and the thermally softened lignin and other
phenolics allow the creation of adhesion between adjacent
particles

20.  Moisture plays an important role in densification
 It may help in heat transfer and in enhancing the plasticity of the
material. If the feed stock is either too dry or too wet, pressures
required for densification increases dramatically
 Normally moisture content should be in the range of 10-15 per
cent.
 Additional heat is generated from the mechanical work of
densification which requires 32 to 80 MJ/kg with a heat capacity
of about 1.7 J/g0C, the temperature of the densified material is
raised from 20 to 50 0C
 Thus in commercial densification systems, the densified biomass
product emerges with a temperature about 1500C
 The hot biomass is fragile and should be handled carefully until
cooled

21. Binders are substances such as molasses, starch, clay,
resin, cowdung, lime, etc which are used to bind particles of
the primary material
The qualities of good binders include good binding
ability, low cost, good smell while burning ready availability,
etc

22. The briquetting process primarily involves
 Drying
 grinding
 sieving
 Compacting and
 Cooling operations

23. UNIT OPERATIONS INVOLVED IN PREPARATION OF
DIFFERENT FEEDSTOCK FOR BRIQUETTING
Sr.
No.
Feed-stocks Unit operations performed
Sieving Drying Cutting of
branches/chopping
Shredding Grinding
1 Saw Dust √ √ - - -
2 Sugarcane Bagasse - - √ - √
3 Cotton Stalk - - √ √ √
4 Groundnut shell - - - - √
5 Jatropha Shell - - - - √
6 Wheat straw threshed - - - - √
7 Rice straw - - √ - √
8 Pearl millet stalk - - √ - √
9 Mustard stalk - - - - √
10 Dry leaves - - - - √

24. STEPS INVOLVED IN PREPARATION OF
BRIQUETTING
Cutting of
branches
Shredding in a
shredder
Shredded
material
Grinding in a
hammer mill for
powder
making

25. MOISTURE CONTENT
 Moisture content of the feed material should be between 10-12
%. At this moisture content the machine runs smoothly, the
briquettes are strong and without cracks
 At higher moisture content briquettes are weak and machine
operation is erratic
 Excess steam formation also occurs which blocks the flow of
incoming material. If the moisture content of the feed stock is
high, it should be dried using flash dryer or in open sun
 If the moisture content is too low, the power requirement
increases, the output decreases and the quality of briquettes is
also not very good

26. PARTICLE SIZE AND SHAPE
 In small size machines (50 mm dia briquette) for best results,
the particle size of biomass material should be about 6-8 mm
size with 10-20% powdery component
 In bigger size machines (90 mm size briquettes) particle size
even upto 20-25 mm could be used
 Larger size particles are not properly conveyed through the
screw conveyer and start accumulating at entry point,
resulting into jamming of the machine and lump formation
 Grinding of material to smaller sizes is necessary

27. TEMPERATURE OF BIOMASS DURING BRIQUETTING
 Briquette density, crushing strength and moisture stability can be
varied by varying the temperature of biomass
 Heating of biomass makes the lignin softer thereby reducing the
resistance to briquetting, results in decrease in specific power
requirement, higher outputs, less wear and tear of dies
 In commercial machines, the heat is developed due to internal
and external friction. Lignin becomes softer at a temperature of
about 110°c and on applying pressure helps in binderless
briquetting
 The die temperature should be kept between 250-290°c

28. DRYING
OPEN DRYING TUNNEL DRYING
POLYMER BASED TUNNEL DRYING

29. Shredded stalks

33. On the basis of operating condition, the briquetting
technologies can be divided into
 Hot and high pressure compaction
 Medium pressure compaction with a heating device
 Cold and low pressure compaction
 Based on mode of operation, it falls into two categories
 Batch densification
 Continuous densification
 The most important densification process is the hot and
high pressure continuous process

34. Depending on the types of equipment used,it could be
categorized into four main types
• Piston press densification
• Screw press densification
• Roll press densification and
• Pelletizing

35.  The piston presses which are currently operating in India are
also known as ram and die technology
 The biomass is punched into a die by a reciprocating ram with a
very high pressure thereby compressing the mass to obtain a
briquette
 The briquette produced is 60mm in external diameter
 This machine has a 700 kg/h capacity and the power
requirement is 25 kW
 The ram moves approximately 270 times per minute in this
process

36. PISTON PRESS DENSIFICATION

38. HAMMER TYPE SHREDDING
MACHINE
BRIQUETTES
CYCLONE SEPARATOR FEEDING
MECHANISM
PISTON PRESS
PISTON PRESS DENSIFIER

39. Process of briquette making
Collection of raw materials Drying Shredding
Powdered biomass
Briquetting machine
Briquettes

40.  There is less relative motion between the ram and the biomass
hence, the wear and tear of the ram is considerably reduced
 It is the most cost-effective technology currently offered by the
Indian market
 Some operational experience has now been gained using different
types of biomass
 The moisture content of the raw material should be less than 12%
for the best results
 The quality of the briquettes goes down with an increase in
production for the same power
 Carbonization of the outer layer is not possible
 Briquettes are somewhat brittle

42. In a screw extruder press, the biomass from the feed
hopper is conveyed and compressed by a screw through a
heated die
Extrusion uses a screw extruder to force a feed stock
under high pressure into a die thereby forming large cylinders
of 2.5 to 10.0 cm of densified biomass
Screw presses produce denser and stronger briquettes
compared with piston press
o Horizontal screw press
o Conical screw press
o Screw press with heated die

43. RICE HUSK BRIQUETTES FROM
HORIZONTAL SCREW PRESS

46.  The output is continuous and the briquette is uniform in size
 The outer surface of the briquette is partially carbonized
facilitating easy ignition and combustion. This also protects the
briquettes from ambient moisture
 A concentric hole in the briquette helps in combustion because of
sufficient circulation of air
 The machine runs very smoothly without any shock load
 The machine is light compared to the piston press because of the
absence of reciprocating parts and flywheel
 The machine parts and the oil used in the machine are free from
dust or raw material contamination
 The power requirement of the machine is high compared to that
of piston press

47.  In a piston press, the wear and tear of the contact parts (the ram
and die) is less compared to the wear and tear of the screw and
die in a screw extruder press
 The power consumption in the piston press is less than that of the
screw press
 In terms of briquette quality and production procedure, screw
press is definitely superior to the piston press technology
 The central hole incorporated into the briquettes produced by a
screw extruder helps to achieve uniform and efficient combustion
and also these briquettes can be carbonized

49. PELLET PRESS DENSIFICATION
 Pelletizing is closely related to briquetting except that it uses
smaller dies (10-30 mm) so that the smaller products are produced
which is called as pellets
 Pelletizer consists of a matrix and a roller, the pressure between
which causes the frictional heating and forces the material through
the perforations in the matrix plate
 The extruded pellets are cut-off at a specified length by means of
a knife. They are normally 5-15mm diameter with a length below
30 mm. The capacity of these press ranges from slightly below 1 to
30 ton/hr
 The material to be pelletized is fed in the cylinder and when the
rollers ride over this material and rotate, they push the material
through holes in the die against resistance from pellets already
formed in the die holes

50.  Pellets are less harder than briquettes
 The two main types of pellet presses are: flat and ring
 The flat die type features a circular perforated disk on which
two or more rollers rotate
 The ring die press features a rotating perforated ring on
which rollers press onto the inner perimeter
 Thus, pellet press capacity is not restricted by the density of
the raw material as in the case of piston or screw presses
 Power consumption falls within the range of 15-40 kWh/ton

54. PELLETING MACHINE

55. CC = Castor cake, SD + Sawdust, SBP + Sugarcane bagasse powder
Pellets of 10
mm size made
out of Castor
Cake and
Sawdust in the
proportion of
50:50
PELLETS OF 22 MM SIZE MADE WITH DIFFERENT COMBINATIONS OF
CASTOR CAKE WITH SAW DUST AND SUGARCANE BAGASSE

56.  Densification of biomass under high pressure brings
about mechanical interlocking and increased adhesion
between the particles, forming intermolecular bonds
in the contact area
 In the case of biomass, the binding mechanisms under
high pressure can be divided into adhesion and
cohesion forces, attractive forces between solid
particles and interlocking bonds

57.  High viscous bonding media, such as tar and other molecular
weight organic liquids can form bonds very similar to solid
bridges
 Adhesion forces at the solid-fluid interface and cohesion forces
within the solid are used fully for binding
 Lignin in the biomass/wood can also be assumed to help in
binding in this way
 The softening lignin at high temperature and pressure form the
adsorption layer with the solid portion
 The application of external force such as pressure may increase
the contact area causing the molecular forces to transmit high
enough which increases the strength of the bond between the
adhering partners

58. The various processes being adopted for densification of
biomass are
 Baling
 Pelleting
 Cubing
 Briquetting and
 Extrusion
 Compression baling and roll-compression can reduce biomass
volume to one fifth of its loose bulk. These processes are useful
for agricultural wastes and certain type of forest biomass
 Pelleting employs a hard steel die which is perforated frequently
placed holes of 0 to 1.3 cm in diameter. The die rotates against
inner pressure rollers, forcing the biomass through the holes with
pressure of 700 kgf/cm2. As the biomass in extruded through the
die, small dense pellets are broken off at a specified length

59.  Cubing is a modification of pelleting which produces larger
cylinders or cubes, 2.5 to 5.0 cm in diameter
 Briquetting compacts a biomass feed stock between rollers with
cavities, producing forms like charcoal briquettes. In this
process, the raw material is pressed together at an elevated
temperature and forced through an orifice
 The extrusion process that utilizes a conical screw for the
compression and forces the material through a die. A heating
jacket, driven by electricity supplies external heat to the
material, thus helping in the binding process. The extrusion
press unit had good flexibility and fairly low energy
consumption

60. DENSIFIED MATERIAL

62. 1. Briquetting press / pellet press of desired capacity, complete
with feed material conveying screw
2. Biomass grinding unit of matching capacity with feeding screw
3. A dryer for drying the feed material. Normally a flash dryer is
used in which hot gases up to 200-300°c are passed. The
moisture is reduced by 10-12% just in few seconds
4. Sieve shaker for sieving the bigger size feed stocks and
extraneous materials
5. Storage bins or sufficient covered space for keeping the feed
stock and briquettes produced by the machine

64. CONVENTIONAL CHULHA TNAU SINGLE POT CHULHA
EFFICIENCY = 8.85 % EFFICIENCY = 16.5 %

65. COMBUSTION STUDIES OF CROP RESIDUE PELLETS IN
TWO DIFFERENT TYPES OF COOK STOVES

66. TESTING OF BIOMASS BRIQUETTES IN A LAB MODEL
GASIFIER