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_Biogas .pptx

  1. Biogas ● Biogas is mostly composed of methane (CH4) and carbon dioxide (CO2). ● Biogas production is a multistep anaerobic process in which originally complex organic (liquid or solid) wastes are progressively transformed into low molecular weight products by different bacteria strains. ● Biogas generation using the anaerobic digestion process involves the biological degradation of organic matter. The sequence of reactions in biomass to biogas conversion is as follows: (1) hydrolysis, (2) acidogenesis, (3) acetogenesis, and (4) methanogenesis
  2. Anaerobic digestion in biogas production
  3. Step I: Hydrolysis: Within the first stage, complex organic compounds such as proteins, carbohydrates, and lipids are decomposed into simple soluble products by extracellular enzymes, such as cellulases, amylases, proteases, and lipases, excreted by fermentative bacteria. The main hydrolytic reactions at this stage are as follows:
  4. Step II: Acidogenesis: Acidogenesis is the bioconversion through which simple monomers produced by the hydrolysis are further converted into volatile fatty acids, such as acetic acid, propionic acid, and butyric acid and trace alcohols, ketones, CO2, NH3, H2S, and H2. Step III: Acetogenesis. The hydrogen-producing acetogenic bacteria decompose and convert propionic acid, butyric acid, and alcohols into acetic acid, hydrogen, and carbon dioxide, while the homoacetogenic bacteria convert hydrogen and carbon dioxide into acetic acid.
  5. Step IV: Methanogenesis The acetic acid, hydrogen, and C1 compounds (formic acid, methanol, and methylamine) are converted into the end product, methane by methanogens. Two-thirds of the methane produced comes from acetic acid, while the rest comes from hydrogen and C1 compounds. The energy available in organic substances, except that used for cellular metabolism, is recovered by means of methane.The major reactions at this stage include:
  6. Methanogens ● Methanogens are characterized by high physiological specialization and extremely strict anaerobiosis. They belong to the Euryarchaeota of Archeobacteria, which convert inorganic organic compounds into methane and carbon dioxide. ● Methanogens can be divided into two groups, acetate-consuming and hydrogen- consuming. ● These microorganisms exist widely not only in natural ecosystems, such as swamps, lakes, marine sediments, and gastric juices of ruminant animals, but also in non- natural ecosystems such as wastewater treatment, compost, and sludge digestion systems.
  7. ● Methanogens with various morphologies like, rod, cocci, and spiral. Methanogens share the following characteristics: 1. Extremely low growth rate – for example, the doubling time of Methanosaeta is 4–9 days 2. Strict anaerobiosis – they are sensitive to oxygen and oxidants, and thus cannot survive with exposure to oxygen or air 3. Limited simple compounds as their nutrition sources 4. Living in neutral or weak alkaline environment with suitable temperature (30-40 degrees) 5. Biogas is their major end product, which mainly consists of methane and carbon dioxide.
  8. Organic MSW treatment plant
  9. Eco friendly production of biogas
  10. Envirofriendly Production of biogas
  11. Biogas Utilization
  12. Advantages of biogas ● Biogas is a green energy source in form of electricity and heat for the local grid. ● Environmentally friendly: recirculation of organic waste from industry and households. ● Less odour inconveniences when spreading slurry on the fields - fermented slurry smells considerably less than normal slurry and the smell decreases faster. ● Plants absorb fermented slurry better, increasing the yield on the fields. ● Protection of subsoil water - improved nitrogen exploitation reduces leaching and thereby drinking water contamination. ● Reduced costs for artifical fertilizer.
  13. Reference Biogas, X Liu and Z Yan, Chengdu Institute of Biology, Chengdu, China Z-B Yue, Hefei University of Technology, Hefei, China