Nature's fuel, biomass, leaps into flames within furnaces, a captivating dance of energy release. Each kilogram holds a treasure chest of potential, measured in Joules, with dry wood pellets like seasoned veterans burning fierce and bright. Eager vapors ignite first, rookies on the fiery stage, followed by the steady performance of fixed carbon, veterans ensuring a longer burn. Yet, water plays a mischievous role, dampening the flames. Wet biomass, the newcomer, requires pre-drying before joining the dance. But with careful choreography, minimizing clogging ash and harmful emissions, biomass waltzes towards a sustainable future. This fiery partnership holds the key to a brighter tomorrow, fueled by nature's bounty.

1. By Er. T. AYISHA NAZIBA, Dr. D. RAMESH, Dr.S. PUGALENDHI, Dept. of REE, AEC & RI, TNAU, Coimbatore-03
Lecture 1
Biomass structure – classification and
properties

2. Biomass
Biomass refers to organic matter derived from recently living organisms that
can be used to generate energy. This includes wood, crops, algae, and even
waste materials like animal manure or used cooking oil. The most common
forms of biomass energy are wood pellets, biogas, and biofuels like ethanol
and biodiesel.

3. Structure of biomass
The structure of biomass can be quite diverse, depending on
the type of organism and its function. However, there are
some general features that most biomass share:

4. Cellular level
At the most basic level, biomass is composed of cells. These cells are the
fundamental units of life, containing various organelles that carry out specific
functions. The specific structure of cells within the biomass will vary depending
on the organism, but generally, they include:
◍ Cell membrane: A thin, flexible barrier that surrounds the cell and
controls what enters and leaves.
◍ Cytoplasm: A gel-like substance that contains the cell's organelles and
other components.
◍ Nucleus: The control center of the cell, containing genetic material (DNA).
◍ Organelles: Specialized structures within the cell that perform different
functions, such as energy production, waste removal, and
protNucleus:ein synthesis.

5. Chemical composition
Biomass is primarily composed of organic molecules, meaning they
contain carbon atoms. The main types of organic molecules found in
biomass include:
◍ Carbohydrates: Sugars and starches, formed from chains of
sugar molecules. These provide energy for the organism.
◍ Proteins: Made up of amino acids, responsible for building and
repairing tissues, and carrying out various functions.
◍ Lipids: Fats and oils, used for storing energy and providing
insulation.
◍ Nucleic acids: DNA and RNA, which store and transmit genetic
information.

6. Macromolecular composition
◍ These organic molecules are often linked together to form larger
molecules called macromolecules. Some key macromolecules
found in biomass include:
◍ Cellulose: A complex carbohydrate that forms the walls of plant
cells and provides structural support.
◍ Lignin: A complex polymer that strengthens plant cell walls and
helps them resist water and decay.
◍ Hemicellulose: Another carbohydrate that binds cellulose and
lignin together in plant cell walls.
◍ Proteins: Folded into complex shapes to perform various
functions.

7. Biomass classification
Biomass can be classified in several ways, depending
on the criteria used. Here are some of the most
common classifications:

8. Source
Virgin biomass Waste biomass
This comes from naturally occurring
and untouched sources, such as
forests, agricultural land, and aquatic
ecosystems. Examples include
wood, crops, algae, and seaweed.
This is derived from residual or
waste materials, such as food waste,
wood waste, animal manure, and
sewage sludge.

9. Conversion process
◍ Woody Biomass: Trees, shrubs, and their kin take center stage
here. Their sturdy structures make them ideal for generating
energy through combustion and gasification.
◍ Herbaceous Biomass: Crops, grasses, and their non-woody
brethren shine in this category. They excel in the world of biofuel
production, readily transforming into ethanol and other fuels
through fermentation or anaerobic digestion.
◍ Aquatic Biomass: Dive into the fascinating realm of
algae, seaweed, and marine organisms. Their rapid growth and
sustainable cultivation potential make them promising contenders
for future biofuel production.

10. Moisture content
◍ Dry Biomass: With less than 50% moisture, this type packs a
punch in terms of ease of storage and transport. However, pre-
processing might be needed for some conversion methods.
◍ Wet Biomass: Don't underestimate the power of water! With over
50% moisture, this category might require drying before use, but
its properties can be advantageous for specific conversion
techniques.

11. Energy content
◍ High-Energy Biomass: Think wood pellets or certain types of
algae - these champions boast a high energy density per unit
mass, making them perfect for efficient energy production.
◍ Low-Energy Biomass: Straw and food waste might not win the
energy density race, but their abundance and versatility shouldn't
be underestimated. A larger volume may be needed, but they still
contribute significantly to the energy equation.

12. Environmental impact
◍ Sustainable Biomass: This category champions sources that can
be replenished without harming the environment. Sustainably
managed forests and dedicated energy crops are shining
examples of responsible resource utilization.
◍ Unsustainable Biomass: Deforestation and unsustainable
agricultural practices raise concerns in this category. Choosing
wisely is crucial to ensuring biomass use doesn't come at the cost
of environmental harm.

13. Properties of biomass

14. ◍ Heating Value: Imagine energy crammed into each kilogram of
biomass like treasure in a chest. This "treasure" is quantified by
the heating value, measured in Joules per kilogram (J/kg) or
Megajoules per kilogram (MJ/kg). Higher values signify more
energy packed within, like a tightly stuffed treasure chest. Think
wood pellets holding around 20 MJ/kg compared to straw's half
that bounty.
◍ Moisture Content: Now, picture water as mischievous imps
hiding amongst the energy treasures. Water, or rather its content,
plays a crucial role. Excess water acts like an energy-absorbing
imp, hindering the flame's performance. Dry biomass, with less
than 50% moisture, burns readily, unleashing its full potential.
However, wet biomass might require pre-drying, an extra step in
the dance.

15. ◍ Volatile Matter: Think of volatile matter as eager dancers in the
flame's choreography. These are organic compounds readily
vaporized upon heating, igniting quickly and contributing to the
initial burst of heat. Biomass with high volatile matter, like
sawdust or agricultural residues, burns swiftly and fiercely, like
seasoned veterans joining the dancing newcomers.
◍ Fixed Carbon: Picture the veterans alongside the dancers,
representing the less volatile portion of biomass, the fixed carbon.
This releases its energy through sustained burning, ensuring a
longer and more controlled performance. Woody biomass like
wood chips or pellets exhibits high fixed carbon, a slow and
steady burn.

16. ◍ Combustion Rate: Imagine the tempo of the flame's dance.
Combustion rate determines how quickly biomass releases its
energy. Factors like particle size, oxygen availability, and furnace
design influence this. Optimizing these factors ensures efficient
and complete combustion, minimizing energy waste and harmful
emissions, akin to a well-rehearsed and impactful flame show.
◍ Emissions: Even the most graceful dance can leave traces.
Combustion generates emissions, some beneficial, like heat and
steam, while others pose environmental concerns, like nitrogen
oxides and carbon dioxide. Choosing sustainable biomass
sources and optimizing combustion technology can minimize
these emissions, ensuring a responsible dance with nature's
energy.

17. ◍ Ash Content: Now, imagine the residual embers left after the
fiery performance. Ash content represents the inorganic minerals
remaining after combustion. High ash content can create
problems like slagging and fouling, clogging up furnaces and
reducing efficiency. Selecting biomass with low ash content, like
certain types of wood pellets, minimizes these issues, leaving a
cleaner stage.