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2013-12-06 18:33:12

bioenergy topic
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  1. Photosynthesis
    Process used by plants to convert light energy into chemical energy
  2. Photosynthesis equation
    CO2 and water is transformed into carbonhydrates and oxygen

  3. Bioenergy sources (3)
    • Woody crops (forestry)
    • Agricultural crops (sugar cane, maiz)
    • Wastes and residues
  4. Combustion triangle
  5. Biomass composition
    • organic material
    • water
  6. Biomass symbol definitions (m, m0, w, w')
    • m - total mass of material
    • m0 - mass when completely dry
    • w - dry basis moisture content
    • w' - wet basis moisture content
  7. Biomass equations (w and w')

  8. Biomass
    The material of plants and animals including their wastes and residues
  9. Biomass description
    Organic, carbon based, and reacts with O2 in combustion to release heat
  10. Bioenergy is obtained from:
    • Crops
    • Oilseed crops
    • Agricultural residues
    • Wood
    • Municipal solid waste
    • Grasses
    • Methane
    • Biodiesel
    • Algae
  11. Biofuels
    Biomass processed into a more convenient form (liquid) for transportation
  12. Moisture presence consequences
    leads to significant loss in useful thermal output
  13. Combustion temperature consequences
    reduced combustion temperature causes smoke and air pollution
  14. High Heat Value (HHV)
    Takes into account the latent heat of vaporization of water into the combustion products
  15. Low Heat Value (LHV)
    The energy required to vaporize the water is not realized as heat
  16. Biodiesel & Esterification
    • Concentrated vegetable oils may be used directly as fuels in diesel engines
    • Difficulties arise -> high viscosity and combustion deposits
  17. Syngas
    Clear fuel like natural gas used to make fuels, chemicals, fertilizers, and penerate electricity
  18. Straw-fired power station diagram
  19. Biofuel types (6)
    • Bioalcohols (ethanol, propanol, butanol)
    • Biodiesel
    • Vegetable oils
    • Biogas
    • Solid biofuels
    • Microalgea
  20. Ethanol
    • Most common worldwide (especially Brazil)
    • Production methods are enzyme digestion, fermentation, distillation, and drying
  21. FFV Systems
    • Flexible fuel vehicles
    • Safely run on any combination of bioethanol and petrol up to 100% bioethanol
    • Disadvantages : high initial cost, inceased vehicle maintence, complex
  22. Wine production
    The process of fermentation in wine is the catalyst function that turns grape juice into alcohol
  23. Fermentation
    Yeast interacts with sugars in the juice to create ethanol and CO2
  24. Fermentation equation
    yeast + sugar -> ethanol + CO2

  25. Biodiesel
    • Most common in Europe
    • Produced from oils and fats using transesterification
  26. Transesterification
    The process of exchanging the organic group R" of an ester with the organic group R' of an alcohol
  27. Transesterfication Chemical Diagram
  28. Vegetable Oil
    • Fuel injectors must atomize the vegetable oil in the correct pattern
    • Must be heated to reduce its viscosity to that of diesel
  29. Biogas gases (6)
    • CH4
    • CO2
    • N2
    • H2
    • H2S
    • O2
  30. Biogas
    • Anaerobic bacteria produce CH4 from liquid waste and CO2
    • Can be used for heat or electricity
  31. CH4 Combustion Equation
    CH4 + 2O2 -> CO2 + Q
  32. Solid biofuels
    • Can be burned directly (firewood)
    • If in an inconvenient form, will be densified (grinding the raw biomass to the right size)
  33. Solid biofuels (advantage and problem)
    Advantage: It if often a byproduct of other processes

    Problem: It emits pollutants
  34. Microalgea
    • Harvested algea releases CO2 when burnt
    • CO2 is taken from the atmosphere when algea is grown
  35. Microalgea Advantages (5)
    • Rapid growth
    • high yield per land area
    • lack of sulphur in the biofuel produced
    • non toxicity
    • biodegradability
  36. Algea biomass components (3)
    • carbonhydrates
    • proteins
    • lipids/natural oils
  37. 3 ingredients required to grow microalgea
    • High solar radiation
    • CO2
    • Brackish water or water high in salt content
  38. 2 systems for microalgea production
    • Raceway ponds
    • Photo bioreactors
  39. Wastes and Residues
    Unstoppable flows of energy potential in our environment arise from:
    • primary economic activity
    • urban, municipal and domestic refuse
  40. Major wastes are: (3)
    • MSW (municipal solid waste)
    • Landfill
    • Sewage
  41. MSW
    • Loose solid material of variable composition available for combustion or prolysis
    • Usually contains significant amounts of metal, glass, and plastic
  42. MSW Combustion Plant Diagram
  43. Landfill
    waste deposited in large pits
  44. Landfill Gas Collection System Diagram
  45. Aerobic digestion
    In the presence of air, microbial aerobic metabolism of biomass generates heat with the emission of CO2
  46. Anaerobic digestion
    In the absence of oxygen, certain microorganisms can obtain their own energy supply by reacting with C compounds to produce both CO2 and CH4 gases
  47. Direct combustion
    The process that converts biomass to heat energy (through a furnace or boiler)
  48. Co-Firing
    The combustion of 2 different types of materials at the same time
  49. Gasification
    A process that converts organic or fossil fuel based carbonaceous materials into CO, H2, and CO2

    Achieved by reacting the material at high temps without combustion (produces syngas)
  50. Pyrolysis
    A thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen
  51. Biofuels Advantages (7)
    • Cost
    • Source material
    • Renewability
    • Security
    • Economic stimulation
    • Biodegradability
    • Lower carbon emissions
  52. Biofuels Disadvantages (7)
    • Energy output
    • Production carbon emissions
    • High cost
    • Food prices
    • Water use
    • Availability
    • Smell
  53. Biogas production
    The gas produced by the breakdown of organic matter in the absence of oxygen.
  54. Biogas is produced using; (6)
    • Manure
    • Sewage
    • Municipal waste
    • Green waste
    • Plant material
    • Crops
  55. Biogas plant
    • An anaerobic digester that treats farm wastes or energy crops