L3: Biofuels Flashcards
Green Energy vs Renewable Energy
- Renewable energy source simply does not deplete (solar, wind)
- “Green” is also good for planet as does not harm ecosystems or environment
- Solar = green and renewable
- All green is renewable, but not all renewable green
- Liquid biofuel is renewable but not green as it produces GHG’s
- H2 from biomass is green as there is no GHG emission.
Applications of biofuels
Transportation
- Vehicles require clean, dense, high power fuel cells in a liquid state
- Liquids can be easily pumped and store
Power generation
- solid biomass fuel like wood
Heat
Biofuel and Fossil Fuel Counterparts
Biofuels are counterparts to traditional fossil fuels
Ethanol : Gasoline/Ethane
Biodiesel : Diesel
Methanol : Methane
Biobutanol : Gasoline/Butane
1st Generation Biofuel
- Conventional biofuels
- Made form sugar, corn etc
- Biofuel made from feedstock that can be consumed as human food
- Threatening food chain
- Intense growth requirements
- Alternatives are being developed
2nd Generation Biofuel
- Produced from sustainable feedstock in terms of its availability, impact on GHG emissions, impact on lad use and potential to affect food supply
- Must not be suitable for human consumption
- Grow on marginal land
- Not require great amount of water or fertilizer
- Waste vegetable oil = food product that can become 2nd generation
- “Advanced biofuels”
- Can be burned directly
2nd Generation Fuel Processing Technologies
Thermochemical conversion
- Gasification
- Pyrolysis
- Torrefaction
Biochemical conversion
- Fermentation with bacteria
- Digestion
Waste Vegetable Oil (WVO) / Advantages
- 2nd generation biofuel as use of food has expired.
- Recycling can help improve overall environmental impact
Advantages
- Does not threaten food chain
- Readily available
- Easy to convert to biodiesel
- Can be burned directly in some engines
- Low S
- No associated land use changes
Disadvantages
- decrease engine life if not refined
Non woody biomasses
- Grasses (Miscanthus)
- Switch grass
- Municipal Solid Waste
- —- landfill gas, human waste, yard clippings
- —- carbon footprint of this fuel less traditionally derived fossil fuels
- Burned to produce heat and electricity in cogeneration plants
3rd Generation Biofuels
- Biofuels derived from algae
- Previously 2nd, but got their own generation because of their higher yields
- Algae-based biofuels required unique production mechanism
- Potentially mitigate drawbacks of 1st and 2nd generation biofuels
Potential of algae-based biofuels
- Algae produce oil that can be refined into diesel or gasoline
- Algae can be genetically manipulated to produce a product
- Nearly identical energy density to gasoline and improved emissions profile
- High yields
Techniques for cultivating algae
Open ponds
- Algae grown in pond in open air
- Simple design, low capital costs
- Less efficient than other systems
- Other organisms can contaminate pond
Closed-loop systems
- Similar to open ponds but not exposed to atmosphere
- Use a sterile source of carbon dioxide
Photobioreactors
- Complex, expensive, closed systems
- Significantly higher yield and better control
Challenges for Algae Production
- ) Algae require large amounts of water, nitrogen and phosphorus to grow
- - GHG emissions to meet these needs can be larger than saved by biofuel
- - High cost
- - Energy into biofuel greater than output
2.) Harvesting and pre-processing are energy intensive
4th Generation Biofuels
- Includes electofuels and solar fuels
- Electrofuels made by storing electrical energy in the chemical bonds of liquids and gases. Primary target is hydrogen
- Solar fuel = synthetic chemical produced from solar energy
- Light converted to chemical energy by reducing protons to hydrogen, or converting CO2 to organic compounds
Advantages of biofuels
- Renewable sources of energy
- Effective way of reducing the emission of GHG’s
- Energy density: enough energy in small space for practical uses
Disadvantages of biofuels
- Regional suitability
- Food security
- Land use changes
- Impact on biodiversity
