BIOMASS ENERGY

OVERVIEW
•Biomass is a renewable energy source that is derived from living or
recently living organisms.
•Biomass includes biological material, not organic material like coal.
•Energy derived from biomass is mostly used to generate electricity
or to produce heat.
•Thermal energy is extracted by means of combustion, torrefaction,
pyrolysis, and gasification.
•Biomass can be chemically and biochemically treated to convert it
to a energy-rich fuel.

ENVIRONMENTAL
ADVANTAGES
• Renewable resource
• Reduces landfills
• Protects clean water supplies
• Reduces acid rain and smog
• Reduces greenhouse gases
– Carbon dioxide
– Methane

BIOMASS AND CARBON
EMMISIONS
• Biomass emits carbon dioxide when it
naturally decays and when it is used as an
energy source
• Living biomass in plants and trees absorbs
carbon dioxide from the atmosphere
through photosynthesis
• Biomass causes a closed cycle with no net
emissions of greenhouse gases

Biomass characteristics
• Heat Value
• The heat value, or amount of heat available in a fuel (kJ/kg), is one of
the most important characteristics of a fuel because it indicates the
total amount of energy that is available in the fuel. The heat value in
a given fuel type is mostly a function of the fuel's chemical
composition.

• Moisture Content
• Fresh, "green" wood is often
about half water, and many
leafy crops are primarily
water. A low moisture level in
the fuel is usually preferable
because high-moisture fuels
burn less readily and provide
less useful heat per unit mass
(much of the energy in wet
fuel is used to heat and
vaporize the water). Extremely
dry fuel, however, can cause
problems such as dust that
fouls equipment or can even
be an explosion hazard.

• Composition
• In addition to heat content, other differences in fuel performance are
related to composition of the various biofuels. The three most
significant compositional properties are (1) ash content, (2)
susceptibility to slagging and fouling, and (3) percent volatiles.

• Fuel Size and Density
• The size and density of the biomass fuel particles is also important. They affect
the burning characteristics of the fuel by affecting the rate of heating and drying
during the combustion process. Fuel size also dictates the type of handling
equipment that is used. The wrong size fuel will have an impact on the
efficiency of the combustion process and may cause jamming or damage to
the handling equipment.

Biomass conversion
• Densification
- Large biomass reduces to
better volume to weight
ratio by compressing in a
die at high temp and
pressure.
- Forms- briquettes or
pellets

• Combustion
- Burning in presence of oxygen to produce
heat.
- Heat utilised for cooking, industrial
purpose, electricity generation
• Incineration
- Completely burning solid masses to ashes
by high temperature oxidation
- Urban waste

• Pyrolysis
- Organic material converted to liquids, solids
and gases by heating to 500°to 900°in
the absence of oxygen.
• Thermo-chemical conversion
- Liquefaction (Methanol)
- Gasification (Producer gas)

• Biochemical conversion
- Anaerobic digestion
- Microbiological digestion of biomass in
absence of oxygen
- Fermentation
- Decomposition of organic matter by
micro organisms specially bacteria and
yeast

Bio methane
• Bio methane or renewable natural gas (RNG) is produced via biogas upgrading.
It can also be used as a renewable fuel in gas engines.
• Bio methane Production
• Bio methane is a sustainable fuel that is produced by biogas upgraders which
remove the CO2 from biogas.
• Bio methane is produced from biogas that is derived from organic matter such
as human waste / sewage, food waste, distillery waste or agricultural materials.
• As the carbon in this material has been recently taken from the atmosphere and
is part of the short-term carbon cycle biogas and bio methane are deemed to be
renewable fuels.

Bio hydrogen
• Meaning of Bio hydrogen
• Bio hydrogen is defined as the biofuel or the source of energy that uses
living microorganisms to convert hydrogen via biological processes like
fermentation and photolysis in a specialized container or a bioreactor.
• Generations of Biofuels
o There are three generations of biofuel, which include:
o Biofuels made from a food crop, and their residues are termed as “First-
generation biofuels”.
o Biofuels made from non-food crops or wastes are termed as “Second-
generation biofuels”.
o And the biofuels made by the use of microorganisms are termed “Third-
generation biofuels” or “Advanced biofuels”.

Production of Bio hydrogen
Through Fermentation
The fermentation of Bio
hydrogen is carried out by the
use of microorganisms like
bacteria. The process is either
carried out in the presence of
light, i.e. photo fermentation or
in the absence of light, i.e. dark
fermentation.
Biophotolysis
It makes the use of photoautotrophic
organisms such as microalgae and
cyanobacteria. These organisms use light
as an energy source and carbon dioxide as
a carbon source for the splitting of
hydrogen.

• Alcoholic fermentation is the anaerobic transformation of fructose
and glucose (sugars) into ethanol and carbon dioxide. The process
is conducted by yeasts and a few bacteria (Zymomonas mobilis).
• Alcoholic fermentation is a process of cellular energy production
without the use of oxygen, taking place in the cytosol of
microorganisms like yeast.
• It is also known as ethanol fermentation, or anaerobic respiration.
The name anaerobic respiration means "without oxygen," and
highlights the notable feature of how the process occurs
independent of oxygen.
• The process of alcoholic fermentation can broadly be divided into
two main parts –
• Glycolysis – glucose is broken down into 2 pyruvate molecules
• Fermentation – pyruvate molecules are converted into 2 molecules
of carbon dioxide and 2 ethanol molecules
Alcoholic Fermentation

Biodiesel
• Biodiesel is a renewable, biodegradable fuel manufactured domestically from
vegetable oils, animal fats, or recycled restaurant grease.
• Biodiesel is produced from vegetable oils, yellow grease, used cooking oils, or
animal fats.
• The fuel is produced by transesterification—a process that converts fats and oils
into biodiesel and glycerin (a coproduct).
• Approximately 100 pounds of oil or fat are reacted with 10 pounds of a short-
chain alcohol (usually methanol) in the presence of a catalyst (usually sodium
hydroxide [NaOH] or potassium hydroxide [KOH]) to form 100 pounds of
biodiesel and 10 pounds of glycerin (or glycerol).
• Glycerin, a co-product, is a sugar commonly used in the manufacture of
pharmaceuticals and cosmetics.

Microbial fuel cell (MFC)
• A microbial fuel cell is a bioreactor that
converts chemical energy in the
chemical bonds in organic compounds
to electrical energy through catalytic
reactions of microorganisms under
anaerobic conditions.
• Microbial fuel cell (MFC) is a type of
bioelectrochemical fuel cell system that
generates electric current by diverting
electrons produced from the microbial
oxidation of reduced compounds (also
known as fuel or electron donor) on the
anode to oxidized compounds such
as oxygen (also known as oxidizing
agent or electron acceptor) on the
cathode through an external electrical
circuit.

Biomass Electrical Power Plants
• Various Biomass Based on Electrical Plants
• Bio-chemical based (i.e. Bio-gas) power plant.
• Thermochemical based (Municipal waste) plant.
• Agro-chemical based (Bio-diesel) plant.

Biomass-fired steam power plant.
• In the mixing tank the water and cattle dung are mixed together thoroughly in the ratio of 1:1 to
form the slurry. This slurry is then transferred to the digester via inlet chamber up to the
cylindrical portion level of the digester.
• The fermentation of slurry starts in the digester and biogas is formed, which is accumulated at
the top of the digester in the dome. Since the outlet gas valve is closed, the bio-gas exerts
pressure on the slurry which starts moving in the inlet and outlet chamber due to which the level
of slurry drops in digester and increases in the outlet chamber.
• If the biogas outlet valve is further kept closed, the level of slurry further drops in the digester.

• Due to gas pressure the slurry reaches to highest possible level in the inlet
and outlet chambers.
• If the gas valve is still kept closed the bio-gas will further get accumulated
in the dome and its pressure increases. Eventually, its pressure becomes
high enough and it starts escaping through the inlet and outlet chambers to
the atmosphere. During its escape the biogas creates bubbles in the slurry in
inlet and outlet chambers and there is also formation of froth.
• The increase in the volume of slurry in the inlet and outlet chambers helps
you calculate the amount of biogas generated within the digester.
• If you want to use the biogas, you can open the valve of the gas pipe and
remove it as per the requirement for various applications. When the gas is
taken out from the dome, the level of slurry in the digester increases while
the level in inlet and outlet valves reduces.

Combined cycle power plant
 Atmospheric air (A) is compressed in compressor and pressurized air (B) enters
into the GT combustor where it mixes with fuel and undergoes combustion.
 The resulting very high temperature gases (C) enter into gas turbine.
 The exhaust gases (D) from gas turbine have temperature of around 500 - 5500C.
Heat recovery steam generator (HRSG) generates steam using water (E) by
utilizing exhaust gases and finally, flue gases from HRSG are sent to stack.
 The generated steam (F) drives steam turbine and exhaust from steam turbine is
fed to the condenser. Condensed water is again pumped back to the HRSG.

Cogeneration plant
• Cogeneration is also called as combined heat and power or combine heat and
power.
• As it name indicates cogeneration works on concept of producing two different
form of energy by using one single source of fuel.
• Out of these two forms one must be heat or thermal energy and other one is
either electrical or mechanical energy.

• The CHP (Combined Heat & Power) definition is given above and is working on the basic
principle to work out two different energies to get useful work from i.e. generation of
electrical energy.
• One is the primary source such as mechanical energy power plant and the second is
secondary source such as a thermal power plant.
• The mechanical energy might be utilized for driving an alternator for the production of
electrical energy or any other equipment such as a pump, motor, or even compressor etc. for
delivering useful services.
• The thermal energy can, however, be used for direct applications or for the production of
steam or hot water for heating purposes.
• The cogeneration is delivering a huge range of technologies for various applications of
different domains.
• The efficacy of cogeneration power plants is more than 80 percent and in some cases, it is
even above 80 percent. The basic need for Cogeneration is to enhance the efficiency of power
plants and to keep the overall cost to a minimum.

BIOMETHANATION
• Biomethanation is anaerobic digestion of organic materials which is converted into biogas. Anaerobic
digestion (AD) is a bacterial fermentation process that operates without free oxygen and results in a
biogas containing mostly methane (~60%), carbon dioxide (~40%) and other gases. Biomethanation has
dual benefits. It gives biogas as well as manure as end product.
• This technology can be conveniently employed in a decentralized manner for biodegradation of
segregated organic wet wastes such as wastes from kitchens, canteens, institutions, hotels, and slaughter
houses and vegetables markets.
• The biogas generated from Biomethanation process can be burned directly in a gas boiler/burner to
produce heat for thermal application industries and cooking or burnt in a gas engine to produce
electricity. Alternatively, the biogas can be cleaned to remove the carbon dioxide and other substances,
to produce BioCNG. This can be injected into the national gas grid to be used in the same way as
natural gas, or used as a vehicle fuel.
• By using Biomethanation process, 20-25kgs of Cattle dung can generate about 1m3 of biogas and
further 1m3 of Biogas has potential to generate 2 units of electricity or 0.4kgs of BioCNG.
INCINERATION:
• Incineration technology is complete combustion of waste (Municipal Solid Waste or Refuse derived
fuel) with the recovery of heat to produce steam that in turn produces power through steam turbines.
• The flue gases produced in the boilers have to be treated by an elaborate air pollution control system.
The resultant ash from incineration of solid waste can be used as construction material after necessary
processing while the residue can be safely disposed of in a landfill.
• This technology is well established technology and has been deployed in many projects successfully at
commercial level in India to treat solid wastes like Municipal Solid Waste and Industrial solid Waste
etc. and generate electricity.

Waste-to-energy
• Waste-to-energy (WtE) or energy-from-waste (EfW) is the process of generating energy in
the form of electricity and/or heat from the primary treatment of waste, or the processing
of waste into a fuel source.
• WtE is a form of energy recovery. Most WtE processes generate electricity and/or heat
directly through combustion, or produce a combustible fuel commodity, such as methane,
methanol, ethanol or synthetic fuels.
• Waste-to-Energy (WTE) technologies to recover the energy from the waste in the form of Electricity and
Biogas/Syngas are given as below:
GASIFICATION
• Gasification is a process that uses high temperatures (500-1800o C) in the presence of limited
amounts of oxygen to decompose materials to produce synthetic gas (a mixture of carbon monoxide
(CO) and hydrogen (H2)). Biomass, agro-residues, Segregated MSW and RDF pellets are used in the
gasifier to produce Syngas. This gas further can be used for thermal or power generation purposes
• The purpose of gasification of waste is to generate power more efficiently at lower power level (<
2MW) and also to minimize emissions and hence it is an attractive alternative for the thermal
treatment of solid waste.
PYROLYSIS
• Pyrolysis uses heat to break down combustible materials in the absence of oxygen, producing a
mixture of combustible gases (primarily methane, complex hydrocarbons, hydrogen, and carbon
monoxide), liquids and solid residues. The products of pyrolysis process are: (i) a gas mixture; (ii) a
liquid (bio-oil/tar); (iii) a solid residue (carbon black). The gas generated by either of these processes
can be used in boilers to provide heat, or it can be cleaned up and used in combustion turbine
generators. The purpose of pyrolysis of waste is to minimize emissions and to maximize the gain.

The process of generating electricity in a mass-burn waste-to-energy plant has
seven stages:
• Waste is dumped from garbage trucks into a large pit.
• A giant claw on a crane grabs waste and dumps it in a combustion chamber.
• The waste (fuel) is burned, releasing heat.
• The heat turns water into steam in a boiler.
• The high-pressure steam turns the blades of a turbine generator to produce electricity.
• An air pollution control system removes pollutants from the combustion gas before it
is released through a smoke stack.
• Ash is collected from the boiler and the air pollution control system.

Biogas Plant
• Converts wet biomass into biogas
(Methane) by the process of anaerobic
fermentation.
• Bacteria called anaerobe carry out
digestion of biomass without oxygen
• Produces methane and carbon dioxide

Raw material used in Biogas plant
• Cow dung
• Human waste (link latrine to the Gas plant)
• Animal waste
• livestock and poultry wastes, night soil,
crop residues, food-processing and paper
wastes, and materials such as aquatic
weeds, water hyacinth, filamentous algae,
and seaweed.

Components required for Biogas plant
• Mixing tank and inlet
• Digester
• Gas holder or gas storage dome
• Outlet and compost pits and
• Gas main outlet and valve, pipeline, water fittings,
gas stoves, lamp and similar appliances run on bio
gas.

Fixed dome type of biogas

• The various forms of biomass are mixed with
an equal quantity of water in the mixing tank.
This forms the slurry.
• The slurry is fed into the digester through the
inlet chamber.
• When the digester is partially filled with the
slurry, the introduction of slurry is stopped and
the plant is left unused for about two months.
• During these two months, anaerobic bacteria
present in the slurry decomposes or ferments
the biomass in the presence of water.
• As a result of anaerobic fermentation, biogas is
formed, which starts collecting in the dome of
the digester.

• As more and more biogas starts collecting, the
pressure exerted by the biogas forces the
spent slurry into the outlet chamber.
• From the outlet chamber, the spent slurry
overflows into the overflow tank.
• The spent slurry is manually removed from the
overflow tank and used as manure for plants.
• The gas valve connected to a system of
pipelines is opened when a supply of biogas is
required.
• To obtain a continuous supply of biogas, a
functioning plant can be fed continuously with
the prepared slurry.

Floating drum type biogas plant

Floating drum type biogas plant

• Khadi village industries commission stand.
Model in 1961
• Slurry (mixture of equal quantities of biomass
and water) is prepared in the mixing tank.
• The prepared slurry is fed into the inlet
chamber of the digester through the inlet pipe.
• The plant is left unused for about two months
and introduction of more slurry is stopped.
• During this period, anaerobic fermentation of
biomass takes place in the presence of water
and produces biogas in the digester.
• Biogas being lighter rises up and starts
collecting in the gas holder. The gas holder
now starts moving up.

• The gas holder cannot rise up beyond a certain
level. As more and more gas starts collecting,
more pressure begins to be exerted on the
slurry.
• The spent slurry is now forced into the outlet
chamber from the top of the inlet chamber.
• When the outlet chamber gets filled with the
spent slurry, the excess is forced out through
the outlet pipe into the overflow tank. This is
later used as manure for plants.
• The gas valve of the gas outlet is opened to get
a supply of biogas.
• Once the production of biogas begins, a
continuous supply of gas can be ensured by
regular removal of spent slurry and introduction
of fresh slurry.