1. The document compares the calorific values of various biofuels including charcoal, producer gas, biogas, methane, ethanol, and methanol. Ethanol has one of the higher calorific values at 30 MJ/kg. 2. There are two main routes for converting biomass to fuel: biochemical processes using biological processes, and thermochemical processes using thermal energy. Some processing of biomass is required to produce the desired fuel. 3. Ethanol can be produced from biomass containing sugar, starch, or cellulose. The production process involves hydrolysis, fermentation, and distillation. Hydrolysis breaks down the complex molecules while fermentation involves microorganisms to produce

1. 1
Calorific values of biofuels
Type of fuel Calorific value Comments
Charcoal 23 - 33 MJ/kg depending on carbon
percentage
Producer gas 3.5 – 5.5 MJ/m3
Biogas 21 – 23 MJ/ m3 @60% methane
Methane 36 MJ/ m3
Ethanol 30 MJ/kg
Methanol 23 MJ/kg

2. 2
Route for fuel conversion
Route for conversion
Bio-chemical Thermo-chemical
Biological processes are
used for conversion of
biomass to fuel
Thermal energy is used
for conversion of
biomass into fuel
• Some processing of biomass is required in order to
convert it into a desired fuel

3. 3
Bio-ethanol
production

4. 4
Ethanol
Ethanol can be produced from biomass containing
sugar (sugar cane, molasses),
starch (corn, cassava) and
cellulose (wood, agricultural residue)
• Biomass can be converted into ethanol using aerobic
digestion
•Production of ethanol is more suitable from a sugar
containing biomass directly fermentable
•Higher size molecules (starch and cellulose) require
hydrolysis  additional step and cost

5. 5
Ethanol production
Cellulosic
biomass
Hydrolysis
- Enzymatic
- Mineral Acid
Distillation
Ethanol
Carbohydrates
Pre-
treatment
Fermentation
- Bacteria
-Yeast
- Fungi
8 to 10%
Ethanol
• Fermentation is a process of breaking of sugar and other
carbohydrates into alcohols and acids by micro-organisms
•Hydrolysis is a chemical process in which chemical compounds are
broken down by water reaction, water is added in the process

6. 6
Ethanol formation

7. 7
Biogas
production

8. 8
Anaerobic decomposition
• Decomposition of biomass in absence of oxygen, bacteria
called aerobes are used.
• The retention period of biomass inside a biogas chamber
varies between 20 to 50 days
• Cow dung, night soil and pig dung feedstock retention
period is 50 days, 30 days and 20 days respectively

9. 9
Biogas production
• Hydrolysis : Complex organic matter is decomposed into
simple soluble organic molecules
• Fermentation or Acidogenesis: The chemical
decomposition of carbohydrates by enzymes, bacteria,
yeasts, or molds in the absence of oxygen.
• Acetogenesis: The fermentation products are converted
into acetate, hydrogen and carbon dioxide
• Methanogenesis: Is formed from acetate and
hydrogen/carbon dioxide by methanogenic bacteria.
• Anaerobic digestion is complex process

10. 10
(C5H10O5)n + H2O  n(C5H12O6)
n(C5H12O6)CH3CH(OH)COOH
4H2 +CO2  2 H2O + CH4
CH3CH(OH)COOH + H2O + CO2 CH3COOH +CH4
Overall process C6H12O6 → 3CO2 + 3CH4
Processes
in
anaerobic
digestion
Reactions at
each step of
conversion

11. 11
Biogas formation
• All three processes runs parallel and should be in equal
magnitude
• Ph values of the slurry should be 6.8 and 7.2, slightly
basic is more optimal
•Mesophilic & thermophilic digestion

12. 12
Biogas plant
gas
holder
tank
slurry
outlet
slurry
inlet
gas
tank support
digester
tank
• Fixed
dome
•
Floating
dome
Dome

13. 13
Biogas plant