1. Biomass is organic matter produced by plants, both terrestrial and aquatic and their derivatives. It includes forest crops and residues. crops grown on energy farm and animal manure
   1. it is renewable source of energy
   2. Solar energy is stored in the form of chemical energy
   3. solar energy--photosynthesis--biomass-----energy generation
   4. biomass resource fall in 3 categories
      1. solid mass - wood & agriculture residue
      2. liquid fuels - methanol
      3. gaseous fuel - biogas
2. Biogas generation
   1. biogas is the mixture containing 55 to 65 % of methane, 30-40 % CO2 and rest is H2S and N2
   2. it is produced by digestion, pyrolysis and hydrogasification
   3. Anaerobic digestion----biogas technology is concerned to micro organism. they are basically bacteria, fungi and virus
   4. bacteria can be subdivided based on oxygen requirment
   5. presence of oxy --aerobic
   6. absence of oxy - anaerobic
   7. when organic matter undergoes fermentation through anaerobic digestion , gas is produced known as biogas.
3. Factors affecting Biodigestion or generation of gas
   1. ph or hydrogen ion concentration
   2. temperature
   3. total solid content of feed material
   4. loading rate
   5. seeding
   6. uniform feeding
   7. dia to depth ratio
   8. carbon to nitrogen ratio
   9. nutrients
   10. mixing or stirring
   11. rate of feeding
   12. type of feed stock
   13. toxicity due end product
   14. pressure
   15. acid accumalation inside digester
4. Biomass conversion
   1. thermochemical conversion
   2. this conversion takes two forms
   3. gasification and liquefaction
   4. gasification takes place by heating the biomass with limited oxy or by reacting it with steam and oxy at high temp and pressure to produce medium heating value gas
   5. the latter may be used as fuel directly or used in liqefaction by converting it into methanol or ethanol
   6. fermentation
   7. It is the breakdown of complex molc in organic compounds under the influence of a ferment such as yeast,bacteria and enzymes.
5. Types of biogas plant
   1. mainly the biogas plant is classifies as
      1. fixed type
      2. floating type
   2. KVIC DIGESTER
      1. it is a floating type digester
      2. the KVIC is of steel drum in which digestion takes place in a masonry
      3. the drum floats as the gas collects
      4. the gas is taken out from top
      5. the drum in KVIC is costliest
      6. life is compartely less -- 10 yrs
   3. JANTA model
      1. it is a fixed dome type
      2. the construction is similar to kvic except the drum, which is fixed in this case
      3. The dome roof in the janta model requires high specialised design
      4. a poor roof may lead to leakage
      5. the overall cost of both varies from 5000 to 15000INR
6. Modification of SI engine
   1. SI engine can run completely on biogas, provided the engine are required to start on petrol
   2. conversion includes
      1. provision of biogas
      2. throttling of intake air
      3. advancing ignition timing
   3. can be admitted into stationary SI engine through intake manifold.
   4. the air flow control valve can be provided on the air cleaner pipe connecting the air cleaner and carburettor for throttling the intake air
7. Modification of CI engine
   1. it can operate on dual fuel
   2. conversion requires
      1. entry of biogas fuel with intake air
      2. advance in the injection timing
   3. Subtopic 3
      1. reduce diesal supply
      2. the entry of biogas and mixing of gas with intake air requires mixing chamber
      3. the chamber lies below the air cleaner
      4. largely used in stationary engines commerical available in India
      5. the admittance of biogas at initial stage increses engine speeds
      6. a suitable system to reduce diesel supply by actuating control rack must be incorporated.