🌊 Chapter 6.5: Energy from the Oceans – Powering Our World

Hello Marine Scientists! This chapter is all about how humans use the ocean to meet our massive energy demands. We will look at traditional energy sources (like oil) and exciting new renewable technologies (like wave and tidal power). Understanding this is crucial because our energy choices have huge consequences for the marine environment!


Part 1: Non-Renewable Energy – Oil under the Sea

1.1 The Basics of Oil (Fossil Fuel)

Oil is a type of fossil fuel—meaning it was formed millions of years ago from dead organic matter (like ancient plankton) buried under immense pressure and heat. Since it takes millions of years to form, we classify it as a non-renewable resource, meaning it will eventually run out.

  • Where it is found: Oil is extracted from beneath the seabed (the ocean floor).
  • How it is used: Oil has many uses, including:
  • Combustion: Burned as a fuel (for transport, heating, electricity). This process releases carbon dioxide into the atmosphere.
  • Manufacturing: Used as a raw material to make plastics and other chemicals.
1.2 The Risk of Transporting Oil (Oil Spills)

Oil is extracted from offshore platforms and then transported around the globe by ships, especially massive oil tankers. Any time oil is moved, there is a serious risk of oil spillage (a leak or catastrophic accident).

Did you know? The ocean is the superhighway for global commerce, and billions of barrels of oil are moved across it every year!

1.3 Protecting the Seas: MARPOL Standards

To reduce the risks of major spills, international laws were created, such as the MARPOL Convention (International Convention for the Prevention of Pollution from Ships). Modern ships and tankers must adhere to these standards:

  • Tankers must be fitted with double hulls (an inner and outer layer) to reduce the risk of massive leaks if the ship is involved in a collision. (Think of it like having a buffer zone!)
  • Tankers are restricted on when and where they can wash out their holds (tanks), often requiring them to use special port facilities to handle oily water waste.
  • Sewage release and garbage disposal must also be strictly controlled to prevent general pollution.
1.4 Potential Impacts of Oil Spills on Marine Ecosystems (6.5.5)

Even with careful standards, spills happen, and the impacts are severe and immediate:

  • Coating Organisms: Oil covers the fur of marine mammals (like sea otters) and the feathers of birds. This destroys their natural insulation and buoyancy, leading to hypothermia or drowning.
  • Poisoning: Organisms that accidentally ingest the oil while feeding or grooming become poisoned, damaging their organs.
  • Food Chain Disruption: Oil slicks can block sunlight, affecting producers (like phytoplankton) at the base of the food chain, which then disrupts the entire ecosystem structure.
1.5 Strategies for Cleaning Up Oil Spills (6.5.6)

When a spill occurs, clean-up crews use several methods to minimise the impact (Remember: cleanup is difficult and rarely 100% effective!):

  1. Booms: Floating barriers are placed around the spill to contain the oil and prevent it from spreading to sensitive coastal areas (like estuaries or mangrove forests).
  2. Skimmers: Specialized boats or devices that physically scoop or suck the oil off the surface of the water.
  3. Dispersant Sprays: Chemicals that break the oil down into tiny droplets, allowing it to mix into the water. (Warning: These chemicals can sometimes be toxic to marine life themselves.)
  4. Burning: Controlled burning of the oil on the surface, used only when safe conditions allow.

Quick Review: Fossil Fuel (Oil) Pros and Cons (6.5.7)

When discussing fossil fuels like oil, you must weigh the economic benefits against the environmental costs:


Advantages (Economic/Practical) Disadvantages (Environmental/Sustainability)

✔ Provides a constant energy supply, unaffected by short-term weather changes.

❌ It is non-renewable; stocks will eventually run out.

✔ Is highly energy dense (high energy per gram of fuel).

❌ Produces carbon dioxide and other damaging gases (contributing to global warming).

✔ Relatively cheap (once infrastructure is established).

❌ Causes significant environmental damage during extraction (e.g., deep-sea drilling).

✔ Stable and easy to transport and use.

❌ Deposits are becoming increasingly difficult to extract.

Part 2: Renewable Energy from the Oceans

Renewable energy sources are those that are naturally replenished and will not run out. The ocean offers massive potential for generating clean energy through the power of wind, waves, and tides.

2.1 Sources of Ocean Renewable Energy (6.5.8)
  • Offshore Wind: Turbines built in the sea harness consistent, powerful winds.
  • Wave Energy: Devices that capture the kinetic energy from surface waves.
  • Tidal Energy: Structures (like dams or barrages) built across estuaries or inlets to capture the energy from the rising and falling tides.
2.2 Advantages of Ocean Renewable Energy (6.5.8)

Renewable energy sources offer significant environmental and social benefits:

  • Infinite Supply: They are an infinite energy source that will not run out.
  • Climate Change Mitigation: They reduce the production of carbon dioxide, helping to reduce global warming.
  • Reduced Dependency: They reduce our reliance on finite (running out) fossil fuels.
2.3 Disadvantages of Ocean Renewable Energy (6.5.8)

While great for the environment, these technologies face technical and logistical challenges:

  • High Initial Costs: The technology and construction of offshore farms are expensive (high initial costs).
  • Limited Locations: Effective use often requires specific geographic features (like strong tidal ranges or consistent wave action), meaning limited locations available.
  • Infrastructure: Requires underwater cables to carry the generated energy from the offshore site back to the land-based electricity grid.
  • Environmental Damage: Construction can cause damage to the seabed and associated habitats (like dredging for cables).
  • Wildlife Impact: Marine life can be harmed; for instance, sea mammals and birds can be caught in turbine structures.
  • Maintenance: Equipment is exposed to harsh saltwater and storms, leading to high maintenance costs.
  • Aesthetics/Tourism: If visible from shore, large structures can create a conflict with tourism and the natural scenery.
  • Weather Dependency: While tides are predictable, wind and wave energy can be intermittent (though offshore wind is often more stable than onshore).

🔑 Key Takeaway for Energy from the Oceans

The choice between energy sources involves a critical trade-off: Fossil fuels (oil) are cheap and reliable but cause pollution and climate change. Renewables (wind, wave, tidal) are clean and infinite but are currently expensive and geographically limited. For the exam, ensure you can list and explain at least three pros and three cons for both fossil fuels and ocean renewable energy!


Don't worry if the disadvantages list for renewables seems long. Remember, scientists and engineers are constantly working to solve these problems to make green energy better!