Biomass Energy
Reza Toossi
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Energy from vegetable matter, produced
through processes of photosynthesis
Non fossil fuel organic matters
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Foodstuff, rice husks, peanut shells, and fruit pits
Energy crops (willow, alfalfa, etc.)
Papers, pulps, wooden products
Municipal wastes
Yard waste
Tires and sewage sludge are sometimes
included as biomass fuels.
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Photosynthesis is the process of removal
of carbon dioxide from atmosphere by
plants, in the presence of sunlight, and
combining it with water to form
carbohydrates.
CO2  H 2O  CH 2O  O2
Sunlight
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The reverse process is called respiration,
i.e. when biomass is burned in air to
carbon dioxide and water.
CH 2O  O2 
 CO2  H 2O  Energy
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Occurs in:
◦ Air (Chlorophyll absorbs red, another pigment
absorbs the blue but reflects the green. The light
absorbed is responsible for formation of
adenosine triphosphate (ATP) which is a catalyst
for formation of carbon dioxide to carbohydrate)
◦ Water (different set of pigments results in red
algae)
Common carbohydrates are:
◦ Glucose (C6H12O6)
◦ Sucrose (C12H22O11)
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Food production depends on the
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Amount of the land
The productivity of the land
 Sunlight (112 kcal of light energy per mole of CH2O)
 Temperature
 Water (about a 1000 tons of water for each ton of
biomass)
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Food Pyramid
◦ Autotrophs (self feeders) – plants, algae, bacteria
◦ Heterotrophs (other feeders)
 Primary consumers (herbivores) – vegetarians
 Secondary consumers (carnivores) – meat eaters
 Grass  sheep  wolf
 Plant  insect  frog  man
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Energy needed for own
growth (A)
Energy needed to feed
others (B)
Gross (A+B)
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Chemical energy in food  Mechanical energy in muscles
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M kg
BMI  2 2
h m
19<BMI<25
Height,
cm
Healthy
Mass,
kg
Height,
feet
Healthy
Mass,
lbs
150
43-56
5’ 0”
97-128
155
46-60
5’ 2”
104-136
160
49-64
5’ 4”
110-145
165
52-68
5’ 6”
117-155
170
55-72
5’ 8”
125-164
175
58-77
5’ 10”
132-174
180
62-81
6’ 0”
140-184
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1 Calorie = 1 kcal = 1,000 calories
1 Cal/h = kcal/h = 1.16 watts
1 MET = kcal/h/kg (of body mass)
Example: A 110-lb woman is biking for
20 minutes @ 20 km/h (13 mph)
◦ Burn rate = 450 Cal/h = 522 W
◦ Total burned: 150 Cal = 626 kJ (muscle
energy)
◦ MET = 450/50=9
◦ With metabolic efficiency of 20%, we need
750 Cal of food energy
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Aerobic (Direct burning)
◦ Incinerators
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Anaerobic
◦ Thermochemical conversion (intense heat and
pressure in absence of oxygen)
 Fisher-Tropsch (gasifying biomass in an oxygenstarved environment to produce syngas)
◦ Biochemical conversion (decay by microorganisms)
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US: Corn Ethanol (only 13% effective in reducing CO2)
Brazil: Sugarcane Ethanol (90% efficient)
Europe: Miscanthus Giganteus
◦ 1150 vs. 350 gallons of ethanol per acre of corn
◦ Need 100 million acres of miscanthus to meet all US demand
for transportation.
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85% of the cars sold in Brazil are “fuel-flex,”
replacing 40% of their petroleum
consumption.
Officially became energy independent in
2006, i.e. its ethanol exports equal to its
petroleum imports.
But
Half of the sugar crop goes to make fuel
(food scarcity)
Rainforests are cleared to plant soy
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Sugar: 8 times the energy put into it
Corn: Only 1.3 times
Cellulose (hard fibrous stuff making up
stalks, husks, and cobs and tree trunks and
branches): 36 Btu for every Btu put in
◦ Cellulose is best because it gives the most energy and at
the same time is not suited for food
◦ The problem is crystalline structure (long chains of sixcarbon glucose molecules  require expensive enzymes
(proteins that catalyzes the chemical reaction)
◦ Termites make good enzymes (turn 95% of what they eat
(wood) into energy (methane and hydrogen)
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Poplars and willows (Miscanthus grows up to
thirteen feet with no need for fertilizers
Jatropha (Very rich in inedible oil content,
grows anywhere)
Tall-grass prairie
Algae (microscopic single-cell capable to
survive in the harshest of environments)
◦ Acre of soybean  60 gallons of biofuel
◦ Acre of palm  600 gallons
◦ Acre of algae  6,000 gallons
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Modern landfills use plastic liners to prevent leachate
and prevent it from draining deep into water
supplies.
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Paper
Other
Glass
Yard wastes
Metals
Paper
Plastics
RLT
Food wastes
Wood
Wood
Food wastes
RLT
Plastics
Metals
Yard wastes
Glass
Other
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Biomass energy is renewable, but not clean
◦ Sewage Sludge (household chemicals)
◦ Tires (when burned produce dioxins and PCBs, and toxic metals
such as mercury, lead and arsenic)
◦ Wood Waste
(Construction debris and paper pulp wastes may
contain nails, metal staples and PVC contamination from electrical
wires and other sources, glues, plastic laminates, phenol and
formaldehyde resins)
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