Biomass Technologies
Mohammed. N. Khan
School of Mechanical Engineering
Fiji National University
What is Biomass?
All living and recently living organisms,
animal/plant waste, industrial and municipal
waste
Categories
Biofuels
Bio power
Bio products
Bio refineries
What is Biomass Energy?
Energy derived from living materials
(organic) including plants, animals.
The use of material having a vegetable or
biological origin that is used as a source of
energy.
renewable energy because its energy comes
from the sun
What is Biomass?
Biomass can regrow over a relatively short time
period, and by the process of photosynthesis,
chlorophyll in plants captures the sun’s energy by
utilizing CO2 from the air and H2O from the ground
to produce carbohydrates – complex compounds
composed of carbon, oxygen and hydrogen.
Energy is released when these carbohydrates are
burned, and they turn back into CO2 and H2O.
Biomass acts as an agent for storing the sun’s energy
until it is needed.
Biomass raw materials?
Crop (Agricultural) residues: leaves; corn stalks are
controversial because of ethanol production.
Manure: use anaerobic digesters (biogas), combustion or
gasification.
Woody biomass: bark, sawdust, etc. Burn it.
Forest residues: tree tops, branches, etc. Most should be left in
place, but some can be burned.
Better forest management would allow dead, damaged, smaller
trees for energy.
Urban waste: shipping pallets, leftover construction wood, tree
trimmings, etc. Collect methane from landfills.
Animal wastes: cattle, pig and poultry wastes
Landfill gas: methane from bacterial digestion of organic waste
Composition of Urban Garbage
Waste to Energy Plant
Biomass to Fuel Conversions
Results: Alcohol (Ethanol), Biogas (Methane), Syngas, Gasoline
(Bio crude), Diesel Fuel (Plant Oil)
Conversion Technologies
Biochemical Platform
(Sugar)
Biogas Platform Combined
Biomass (Anaerobic Digestion) Heat & Power,
Feedstock Fuels,
Thermochemical Chemicals,
Platform and Materials
• Pyrolysis
• Gasification
Carbon Rich Chains
Platform (Biodiesel)
Converting biomass to bioenergy
Combustion
Pyrolysis: conversion of biomass to liquid, solid and gaseous
fuels in absence of air at high T.
Torre faction: mild form of pyrolysis at lower T.
Anaerobic digestion: Biochemical process – bacteria digest
biomass in oxygen free environment to produce biogas. Dairy
farms do it, produces heat and electricity. Done in Denmark and
other European countries. Slide.
Gasification: Conversion of biomass to gaseous fuel called
syngas.
Moisture Content of biomass
Wet basis: W’
Dry basis: W
Let m = total mass of material (with moisture) and
mo = dry mass of material
(𝑚−𝑚𝑜 ) ′ (𝑚−𝑚𝑜 )
∴𝑊= and W =
𝑚𝑜 𝑚
Combustion
Combustion: burning of fuel (chemical reaction of
fuel with oxygen)
Biomass + Oxygen products of oxidation + heat
energy
Complete Combustion: supply of enough oxygen
• Biomass + Oxygen CO2, H2O and minor oxides SO2, NOX
Incomplete Combustion: when insufficient supply of
oxygen (fuel/ air mixture insufficient)
• Biomass + Oxygen CO, C as soot and various CX HY
Uses: Cooking
Biochemical Conversion
Plant matter – hemicellulose, cellulose, lignin
Pretreatment
Hydrolysis
Sugar Fermentation
Thermochemical Conversion
Gasification,
Pyrolysis,
Direct
Hydrothermal
Liquefaction
Carbon
monoxide and
Syngas
(Hydrogen)
Gasification process
Degradation of biomass at high temperatures under controlled
conditions of oxygen supply.
End Result: conversion of most biomass into energy rich
gases (CO, H2 and some CH4) and other components.
Gasifiers converts HC feedstock into gaseous components by
applying heat under pressure in the presence of steam.
Unlike a combustor where ample supply of oxygen is
necessary, the amount of air available inside gasifiers is
carefully controlled to only allow small portion of fuel to
burn completely. This partial oxidation process provides the
heat necessary for the chemical breakdown of the rest of the
feedstock eventually producing syngas.
Gasification process
Sugar cane and rice residues are important crop residues. Because of their
high silica content, rice hulls should not be burned or fed to cattle.
However, rice hulls can be used to produce biogas through gasification.
Gasifiers
Pyrolysis
Thermal degradation of biomass in the absence of
oxygen to produce secondary fuels and other
chemical products.
Secondary fuels are combustible substances
produced in the pyrolysis/ gasification process (CO,
H2).
Liquid pyrolysis oil
Anaerobic Digestion
Converts animal or
plant waste into
methane
Decomposition -
microorganisms
Anaerobic Digesters
Four Main Processes
Uses wastes and
turns into valuable
compost
Transesterification
“Biodiesel” Platform
Takes vegetable oil, animal fat, or grease
into biodiesel – fatty acid methyl ester
Base catalyzed of the oil with alcohol,
direct acid catalyzed, and conversion of
the oil to fatty acids and then to alkyl
esters with acid catalysts
Energy Crops
Specific purpose of
producing energy
DOE – switchgrass,
willow, poplar
Selective breeding,
genetic engineering
Biomass Today
Construction of large-scale Biorefineries
Improved Catalysis Technology
High Selectivity
Less Energy Intensive Conditions
Reduction of Unit Operations
Combined Government and Industry
Efforts
Issues/problems
Handling, transport, storage, feedstock.
Low efficiencies
Corrosion
High capital costs
Needs large scale demonstration plants
Competition of biomass with food, animal
feed, electricity generation, and biofuel.
Sustainability (water)
Advantages of bioenergy
Bioenergy is a reliable renewable energy.
Can use organic waste that may be discarded.
Utilization of marginal land to grow
feedstock.
Potential for being less expensive than fossil
fuels.
Can be produced locally.
Creates local jobs.
Disadvantages of bioenergy
Economics, economics, it’s the economy.
Biomass has lower energy content per mass than
fossil fuels.
Labor, transportation, storage costs are high.
Water sustainability.
The competition for biomass between food,
fuel, and electricity generation!
Questions?
References
Energy Efficiency and Renewable Energy, Biomass Program: Biomass Basics,
November 2006, http://www.eere.energy.gov/biomass.
National Renewable Energy Laboratory, Biomass Research, November 2006,
http://www.nrel.gov/biomass.
Energy Information Administration, Biomass, August 2005,
http://www.eia.doe.gov/cneaf/solar.renewables/page/biomass/biomass.html.
Dutton, Gail. Industry Takes Another Look at Biomass: New Policy Encourage
Growth of Technology, Genetic Engineering News v. 21, n. 5. March 1, 2001.
http://www.mindfully.org/GE/Look-At-Biomass-Growth.htm
