This document discusses biogas production. It begins by defining biogas as a mixture of gases including methane, carbon dioxide, and hydrogen sulfide that can be used as an energy source. Common substrates used for biogas production include animal and agricultural waste. The process of biogas production occurs anaerobically in sealed digesters through four microbial phases that ultimately produce methane. Key factors that affect biogas production are temperature, pH, substrate composition, inhibitors, and maintaining anaerobic conditions. The advantages are that wastes are converted to a biofuel and fertilizer while preventing environmental pollution.

1. BIOGAS PRODUCTION
DILSHANA FATHIMA
M.Sc. BIOCHEMISTRY

2. INTRODUCTION
• Biogas is a mixture of gases composed of CH4, CO2, N2 &
H2S with traces of H2, O2 & CO.
• There are many other common names for biogas – gobar gas,
sewage gas, klar gas & sludge gas.
• Biogas is a gaseous fuel & serve as a good source of energy for
various purpose
▫ Can be used for cooking purpose
▫ Gobar gas can generate electricity
▫ Can be purified to yield good grade CH4
• Biogas production significantly contributes to world’s energy
source.

3. SUBSTRATE FOR BIOGAS
• The usual substrates for biogas production are the waste products
of animal husbandry, industries, agriculture, muncipalities & house
hold wastes.
• In India & other developing countries, cow dung is most
commonly used.
• Solid/high grade waste are preferred as substrates for biogas
production.
• In general, most of the substrate used for biogas plants contain
adequate quantities of almost all essential nutrients required for
microbial growth.
• H2O hyacinth, an aquatic weed with huge biomass is a good source
of methane production.

4. • Methane is the most abundant constituent of biogas.
• Can be directly used for various domestic & industrial
purposes.
• The microbial generation of methane – methanogenesis
from biomass occurs in 4 phases
1. Hydrolytic phase
▫ Certain facultative anaerobic bacteria hydrolyse the complex
organic materials of biomass to low mol.wt soluble products
& some organic acid.
MICROBIAL PRODUCTION OF METHANE

5. 2. Acidifying phase
▫ More formation of organic acid besides hydrogen, carbon dioxide &
alcohol.
3. Acetogenic phase
▫ Acetogenic bacteria convert alcohol into acetate & also generate acetate
from hydrogen & carbon dioxide.
4. Methanogenic phase
▫ Actual phase of methane gas formation.
▫ Methanogenic bacteria convert acetate and hydrogen & carbon dioxide into
methane.
CH3COOH CH4 + CO2
CO2 + 4 H2 CH4 + 2 H2O

6. PROCESS OF BIOGAS PRODUCTION
• Biogas production from biomass is an anaerobic process.
• The anaerobic digestion is usually carried out by using air tight
cylindrical tanks referred to as anaerobic digesters.
• A digester may be made up of concrete bricks & cement/steel, usually
built underground.
• The digester has an inlet attached to a mixing tank for feeding cow dung.
• The methanogenic bacteria are also added with cow dung.
• The digester is attached to a movable gas holding/storage tank with a gas
outlet.

7. • The used slurry comes out from the digester through an outlet, this can
be used as a manure.
• The process of digestion usually takes 2-3 weeks when cow dung is used
as substrate.

8. FACTORS AFFECTING BIOGAS PRODUCTION
• Temperature & pH
▫ Ideal temperature – 30-40̊c
▫ pH - 6-8
• Slurry composition
▫ Ratio b/w solid & water composition in the slurry should be around
1:1
▫ C-N ratio is 30:1 in the slurry
▫ Good mixing & solubilization of organic constituents

9. • Presence of inhibitors
▫ Ammonium sulfate & antibiotics inhibit methane production.
▫ Agricultural wastes, pig & chicken manure generating ammonia &
wastes from paper (rich in sulfates) will inhibit biogas production
• Anaerobic condition
▫ Digester should be completely air tight

10. ADVANTAGES OF BIOGAS PRODUCTION
• Agricultural, industrial & muncipal wastes can be converted into a
biofuel.
• Left over residue of biogas formation can be used as biofertilizer.
• Thus the waste materials that would cause environmental pollution are
fruitfully utilized for biogas & fertilizer production.