a. Biofuels
Definition:
Biofuels are renewable fuels produced from biomass—plant material, algae, or animal waste. They are biodegradable and serve as a cleaner alternative to fossil fuels.
Types of Biofuels:
- Biodiesel – Made from vegetable oils or animal fats.
- Bioethanol – Produced by fermenting sugar or starch-based crops.
- Biomethanol – Obtained from wood and agricultural waste.
Generations of Biofuels:
- 1st Generation: Derived from food crops like sugarcane, corn, etc.
- 2nd Generation: Produced from non-edible plants and agricultural waste.
- 3rd Generation: Sourced from algae and microbes; high-yield potential.
Process:
- Crops absorb solar energy.
- Crops are harvested and processed.
- Fermentation or digestion is used to extract fuel.
- Biofuel is collected and utilized.
Sources: Organic matter such as wood, straw, sewage, sludge, and vegetable oils.
b. Global Warming
Definition:
Global warming is the gradual rise in Earth’s average temperature, primarily due to the increase in greenhouse gases (GHGs) like CO₂, CH₄, N₂O, and CFCs.
Causes:
- Burning of fossil fuels.
- Industrial emissions.
- Deforestation.
Greenhouse Effect:
- The troposphere traps heat using GHGs, maintaining a livable global temperature.
- Without GHGs, Earth’s average temperature would be -18°C instead of 15°C.
- CO₂ and water vapor are major contributors to this effect.
Consequences:
- Melting glaciers and rising sea levels.
- More frequent droughts, floods, and storms.
- Threat to biodiversity and agriculture.
- Regions becoming uninhabitable.
c. Ozone Depletion
Definition:
Ozone (O₃) in the stratosphere absorbs harmful UV rays. Ozone depletion refers to the thinning of this protective layer.
Formation of Ozone:
- UV radiation splits O₂ → atomic oxygen (O)
- O + O₂ → O₃ (ozone)
Causes of Depletion:
- Emission of Chlorofluorocarbons (CFCs) and nitrous oxide.
- High-altitude aircraft and fossil fuel combustion.
Effects:
- Increased UV-B radiation on Earth.
- Skin cancers, cataracts, and weakened immune systems.
- Damage to crops, phytoplankton, and aquatic ecosystems.
- Faster degradation of paints and plastics.