Forestry in the New Millennium
Tropical India, with its adequate sunlight,
rainfall, land and labour, is ideally suitable for
With the enhanced plan outlay for forestry
sector and financial support from donor
agencies, the country is able to march ahead
towards the target of 33 percent forest cover.
What is biomass?
Biomass is plant matter such as trees, grasses,
agricultural crops (residues), tree borne oil seeds or
other biological material. It may be divided into
woody, non-woody and aqueous waste with high
BOD content. Fuels derived from biomass are called
biofuels compared with petroleum based fuels.
It can be used as a solid fuel, or converted into liquid
or gaseous forms for the production of electric power,
heat, chemicals, or fuels.
RURAL DOMESTIC USE: FUEL FOR COOKING
Cooking energy constitutes about 85 percent of our
rural energy demand and has traditionally been met
by biomass fuels such as firewood, agricultural
residues and animal wastes. Under the National
Programme on Improved Cookstoves, about 30
million cookstoves have so far been installed, which
are helping to cut back and conserve fuelwood use.
Can solid biofuels be used in Power
Power generation plants fired solely by biomass are
small compared with conventional coal, gas, oil or nuclear
stations. This size depends on biomass growing capacity and
delivery. Transport of biomass, a material with a low bulk
energy density is expensive when conveyed over the long
distances to larger plants. The traffic involved may also be a
major local concern. Specific capital cost, efficiency and
specific operational cost advantages of larger power plants
are balanced against fuel transport issues.
What inputs are needed to develop biofuels?
Biofuel as energy source of rural poor people
requires social and technical inputs to make
it a modern sustainable system.
Forest wastes _ forest tree twigs, shrubs
Overcome disadvantage of low bulk energy
density of particulate biomass by preparatory
process like briquetting.
Give examples of solid bio-fuels
WOOD [Forestry / agro-forestry based]
BAGASSE [Agro - industry residue]
RICE HUSK [Crop residue]
NEEM ETC.- [Multi-purpose trees]
PROSOPIS ETC.- [Energy crops]
• RURAL DOMESTIC: COOKING
• HEAT & STEAM FOR SMALL SCALE
• COGENERATION / COMBINED CYCLE FOR
ELECTRIC POWER GENERATION
What is the advantage of solid bio-fuel
over coal as fuel for combustion?
For decentralized and small / medium scale
operation where coal mines are remote but forest
resource / woodlands are near.
• Restricts the emission of green house gases and
air pollutants (like SO2).
•Lessens our dependence on imported
hydrocarbon fuels, creates rural employment.
As fuel for combustion, what are the
disadvantages of solid bio-fuel over coal?
• Availability is location specific and limited
• Lower calorific value; variable particle
• Preparation like drying, briquetting etc.
needed for wood /agro-residue
• Price depends on production system like
energy plantation, social forestry, saw
mills, paddy processing etc.
• India‟s Forest resource is highly stressed
Biomass Power Potential (MW):2000
From surplus Biomass 16000
From bagasse based
co-generation in the
existing sugar mills
Ref: MNES Annual Report, 1999
Suitability as fuel
PARTICLE SIZE & DISTRIBUTION
SUITABLE WHERE LOCALLY AVAILABLE
THROGHOUT THE YEAR AND
FOR SMALL & MEDIUM SCALE OPERATION
Proximate and Ultimate Analysis,
Proximate Analysis: (1) Moisture,
(3) Fixed carbon and
(4) Ash. [Wt %]
Ultimate Analysis : C, H, O, N, S. [Wt %]
Higher Heating Value, MJ/Kg
Providing the Draft
P required to make the air flow through the
fuel bed and to the flue gas discharge height
is called draft of air in a furnace and is
expressed in millimeters of water.
Natural: by means of a chimney
Artificial: The fan is used to suck the gases
away from the furnace [induced draft], or to
force the air required [forced draft] through
C6n[H2O]5n = 6nC + 5nH2O
C + O2 + 3.79N2 = 3.79N2 +CO2
EXOTHERMIC, 395400 KJ / KG ATOM
• Combustion: Oxidation of reduced
forms of carbon and hydrogen by free
• Chemical properties determine the
higher heating value & the pathways of
• Bio-fuel: A wet (50% moist), dirty, light
in weight, heterogeneous in particle
size, and quite reactive condition.
COMBUSTION PROCESS continued
fuel of moderate heating value.
Moisture content lowers the combustion efficiency
and affects the economics of the fuel utilization.
• Release of volatiles and
• Formation of char
are followed by
• pre-combustion gas phase reactions
• char oxidation reactions.
Flaming combustion <> Glowing combustion
Requirements of efficient
Sufficient air to provide oxygen needed
for complete burning; higher than
Distribution of air supply: mix with fuel
Secondary air to burn the volatile
Volume of furnace; Flow path for flue
Minimize heat losses
Factors influencing thermal efficiency
in wood combustion
Enthalpy of the fuel
Moisture content of the fuel
Level of excess air employed
Final stack temperature
Note: Theoretical flame temperature
depends on moisture content, %
excess air and preheating of air
Briquetting in India
• Indian briquettes made from: groundnut
shell, cotton stalk, saw dust, coffee husk,
bagasse, mustard stalk and press mud.
• Southern region: groundnut shell and saw
• Western and Northern regions: bagasse,
groundnut shell, cotton stalk, mustard
stalk and press mud briquettes.
A recent addition: Municipal solid waste
densified for use as fuel in process
industries (tea, tobacco, textile,
chemical, paper, starch, tyre retreading, tiles, etc.) for thermal
Screw and Ram Press
• Both the machines give briquettes with a
density of 1-1.2 gm /cc, suitable as industrial
• The screw type machines: briquettes with a
concentric hole-- better combustibility- a
• These briquettes can also be more
conveniently deployed in small furnaces and
even cook-stoves than solid briquettes
generated by a ram press.
FURNACE FOR BIOFUEL
Horizontal grate furnace
Chain grate furnace
Inclined step grate furnace
Suspension burning system
Cyclone firing system
Fluidized bed combustion system
Inclined step grate furnace:
• Fuel is fed to the top of the grate
• heating and drying can occur very near
to the fuel feed shoot.
• Solid phase pyrolysis can occur as the
fuel is sliding down the grate.
Inclined step grate furnace:
• Char oxidation can occur at the base of
the grate and on the dumping grate.
• Gas phase reactions can be controlled
by over-fire air distribution and
separated completely from solid phase
• Fuel particles are fed into the firebox
and flung, mechanically or
pneumatically across the grate
• Some heating and drying and possibly
some pyrolysis occurs while the particle
is in suspension
• Solid phase pyrolysis and char oxidation
occur on the grate.
Spreader stoker …continued
• Pre-combustion gas phase reactions
occur between the grate and the zone
where secondary air is introduced.
• Gas phase oxidation occurs either
throughout the firebox or in the vicinity
of the zone where secondary air is
introduced if the under-grate air is
limited to sub-stoichiometric quantities.
Suspension burning system:
horizontal cyclone furnace
• A horizontal or slightly inclined cylinder lined
with firebricks into which air is ejected
tangentially at a velocity of 6000- 7000 m/min.
• The flame in the furnace revolves at a rpm of
1200 to 1800
• The fuel introduced at the cyclone tip is
entrained by the revolving mass and is thrown
against the cyclone walls where it burns.
Horizontal cyclone furnace
• The flue gases that escape at high
velocities through the aperture at the
other end of the cyclone are substantially
free from fly ash.
• The heat release rate of (2-5 )X 106
kcal/m2-hr can be achieved for
pulverized coal in a cyclone furnace
COMBINED HEAT & POWER
• STEAM INJECTED GAS TURBINE
• INTERCOOLED STEAM INJECTED GAS
• COMBINED CYCLE
biofuel use in
• SUITABLE FOR SMALL SCALE (<10 MW)
• PRODUCES LESS AIR POLLUTANTS AND
• AUGMENTS POWER SUPPLY TO
BIOMASS INTEGRATED GASIFIER /GAS
TURBINE (BIG/ GT) TECHNOLOGY
HIGH THERMODYNAMIC CYCLE
GAS TURBINES TECHNOLOGY IS
MADE AVAILABLE NOW AT REASONABLE
LOW UNIT CAPITAL COST AT
MODEST SCALES FEASIBLE
IT IS EXPECTED THAT THIS
TECHNOLOGY WILL BE COMMERCIALLY
SUCCESSFUL IN THE NEXT FIVE YEARS.
A. Chakraverthy, “Biotechnology and
Alternative Technologies for Utilisation of
Biomass / Agricultural Wastes”, Oxford &
IBH publishing Co., N. Delhi, 1989.
Samir Sarkar, Fuels and Combustion, 2nd
Edition, Orient Longman, 1990
Chapters on Combustion process
Stoichiometry and Thermodynamics,
Combustion Kinetics and Combustion
Appliances. pages 217 to 326
Reference Books / journals
Journal—„Biomass and Bio-energy‟,
a) 1996, 11(4): 271-281 „Biomass Combustion
for power generation‟
b) 1998, 14(1): 33-56 „De-centralized biomass
combustion: state of the art and future
4. Wood Combustion, Tillman, Ch.
production & release from wood combustion‟,
5. Progress in biomass Conversion, vol 3, Edited
by K V Sarkanen, D A Tillman and. E C Jahn,
Academic Press, 1982
Reference Books / journals
6. Solid Fuels Combustion and Gasification,
Marcio L.de Souza-Santos, MARCEL
7. Wood Energy News, October 1999, Vol. 14,
No 9, The Regional Wood Energy
Development Programme in Asia (RWEDP), Email: email@example.com, „Wood energy in India‟