Biogas production

Biogas Production

1. BIOGAS PRODUCTION DILSHANA FATHIMA M.Sc . BIOCHEMISTRY

2. INTRODUCTION Biogas is a mixture of gases composed of CH 4 , CO 2 , N 2 & H 2 S with traces of H 2 , O 2 & 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 CH 4 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. H 2 O 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. CH 3 COOH CH 4 + CO 2 CO 2 + 4 H 2 CH 4 + 2 H 2 O

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 p H - 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.

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