Biofuels, Photosynthesis, and Energy Sources
Specification Reference R1.3.4
Quick Notes:
- Biofuels come from biological materials, such as plants, which fix carbon via photosynthesis.
- Photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2
- Biofuels are considered renewable because they can be replenished over short (human) time scales.
- Fossil fuels are non-renewable – they take millions of years to form.
- Examples of biofuels include bioethanol, biodiesel, and biogas.
- Advantages of biofuels:
- Renewable
- Lower net CO2 emissions
- Disadvantages of biofuels:
- Use of land for fuel vs food
- Energy inputs in production
- May not be carbon-neutral
Full Notes:
What Are Biofuels?
Biofuels are fuels derived from recently living organisms or their by-products. They are formed from plants, which absorb carbon dioxide from the atmosphere through photosynthesis.
The Role of Photosynthesis
Photosynthesis is the process by which green plants convert sunlight into chemical energy:
Equation:
6CO2 + 6H2O → C6H12O6 + 6O2
(in the presence of sunlight and chlorophyll)
This process captures CO2 in the air and converts it into glucose, which can then be used to produce biofuels.
Renewable vs Non-Renewable Energy Sources
A renewable resource is replenished naturally in a short time.
- Examples: biofuels, solar, wind, hydro
A non-renewable resource takes millions of years to form and exists in finite quantities.
- Examples: coal, crude oil, natural gas
Biofuels are renewable, while fossil fuels are non-renewable.
Common Examples of Biofuels
- Bioethanol – from fermenting sugars (e.g., sugarcane, corn)
- Biodiesel – from vegetable oils or animal fats
- Biogas – methane from decomposition of organic matter
Advantages of Biofuels
- Renewable and can be replenished annually.
- Lower net carbon emissions: CO2 released during combustion was recently absorbed from the atmosphere.
- Biodegradable and less toxic than fossil fuels.
- Can be produced locally, reducing reliance on imports.
Disadvantages of Biofuels
- Land use: May compete with food production.
- Deforestation to grow biofuel crops can reduce biodiversity.
- Energy input: Fuel needed to grow, harvest, and process crops may offset environmental benefits.
- Not always carbon-neutral if unsustainable farming or processing is involved.
Key Considerations
- Evaluate net energy gain (energy output – energy input).
- Consider lifecycle CO2 emissions, including production and transport.
- Promote sustainable sourcing and responsible land management.
Summary
- Biofuels are renewable fuels made from biological material through photosynthesis.
- Photosynthesis fixes CO2 into glucose, which can be used to produce biofuels.
- Advantages: renewable, biodegradable, lower net CO2 emissions.
- Disadvantages: land use issues, energy costs, potential unsustainable sourcing.