This presentation summarizes ways to convert waste into bioenergy and biofuels. It discusses how biogas is produced from organic waste through anaerobic digestion, with a typical biogas composition provided. A fixed dome type biogas plant is described that continuously converts waste slurry into biogas. Biofuels from biomass are also covered, including how landfill gas captures methane to generate renewable energy. The advantages of biofuels in reducing pollution and foreign oil dependence are balanced with potential high costs and impacts on food and water.

1. Welcome
To
Our Presentation
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2. Waste to Bioenergy
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Presented By
Rabiul Hasan
Submitted To,
Dr. Muhammad Aslam Ali
Professor
Department of Environmental Science
Bangladesh Agricultural University
Mymensingh-2202

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Waste
to
Bioenergy

4. Waste
Waste is unwanted or undesirable materials left over after the
completion of process.
Examples:
 Municipal solid waste (household trash/refuse)
 Hazardous waste
 Waste water (such as sewage,which contains bodily
wastes (feces and urine) and surface runoff)
 Radioactive waste and others.
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5. Bioenergy
Bioenergy is the energy which is stored in
biological matter or “biomass”.
This can be anything from plants to straw to slurry
to food waste and even sewage.
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6. Prevention
Preparing for Re-use
Recycle
Disposal
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Principle of Waste Management

7. Waste to Bioenergy : Biogas
Biogas: Biogas refers to a mixture of different
gases produced by the breakdown of organic
matter in the absence of oxygen.
It is a renewable energy source.
It can be produced from raw materials such as
agricultural waste, manure, municipal waste, plant
material, sewage, green waste, or food waste.
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Typical composition of biogas
Compound Formula %
Methane CH4 50–75
Carbon dioxide CO2 25–50
Nitrogen N2 0–10
Hydrogen H2 0–1
Hydrogen sulfide H2S 0–3
Oxygen O2 0–0.5
Source: www.kolumbus.fi, 2007[12]

9. Production of Biogas
• The various forms of waste
(agricultural waste, manure,
municipal waste, plant
material, sewage, green
waste, & food waste ) 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.
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Fig. Fixed Dome type Biogas Plant

10. Contd.
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 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.

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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.
Contd.

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Advantages of fixed dome type of
biogas plant
 Requires only locally and easily available
materials for construction.
 Inexpensive.
 Easy to construct.

13. Waste to Bioenergy : Biofuel
Biofuel also called as agrofuel and is derived
from biomass and may be in solid, liquid or
gaseous form. The use of waste biomass to
generate energy can decrease waste
management problems, pollution, greenhouse
gaseous emissions and the use of fossil fuels.
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The waste buried in landfill site undergoes
anaerobic digestion and generates gases. The
gases so produced are called landfill gases
(LFG). These gases can be burned and looked up
to as a source of renewable energy. The LFG
comprises of almost 50% methane, which is the
same gas found in natural gas. This LFG can be
used to generate electricity for public
consumption or can be burned for heat.

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• Conventional wood
and forest wastes
• Woody and
herbaceous energy
crops
• Agricultural crops
and wastes
• Municipal waste
Biochemical
Thermochemical
Alcohol
fuels
Feedstock
production
Conversion process biofuels
Fig. Biofuel pathways for renewable alcohol fuels

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Advantages of Biofuels
 Cost Benefit
 Easy To Source
 Renewable
 Reduce Greenhouse Gases
 Economic Security
 Reduce Dependence on Foreign Oil
 Lower Levels of Pollution

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Disadvantages of Biofuels
 High Cost of Production
 Shortage of Food
 Water Use
 Use of Fertilizers

18. Thank You All
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