Environmental and Global Issues in Energy Use

Engineers use mitigation strategies to reduce these impacts. Carbon Capture and Storage (CCS) involves capturing $CO_2$ from waste gases, transporting it, and pumping it into old oil fields or porous rock. Sulfur scrubbing uses calcium oxide to remove $SO_2$ from flue gases.

The Impact of Nuclear Power

It might surprise you to learn that nuclear power stations do NOT produce any greenhouse gases or sulfur dioxide during operation. Nuclear fuel is extremely energy-dense; $1\text{ kg}$ of uranium releases approximately $10,000$ times more energy than $1\text{ kg}$ of coal.

However, nuclear power has significant environmental risks. Cooling water released back into rivers causes thermal pollution, reducing oxygen levels and harming aquatic life. Catastrophic accidents (like Chernobyl) cause long-term radioactive land contamination.

Managing radioactive waste is a major challenge because it has a very long half-life. It is sorted into categories:

• High-Level Waste (HLW): Spent fuel rods that are highly radioactive and hot. They are kept in cooling ponds, then undergo vitrification (mixing with molten glass to create stable solid blocks).
• Intermediate-Level Waste (ILW): Reactor components that require encapsulation (sealing in concrete or steel).
• Low-Level Waste (LLW): Protective clothing and tools with short half-lives.
• Long-lived waste eventually requires geological disposal deep underground in stable rock formations with low water flow.

The Impact of Renewable Energy

Why don't we just use wind and solar for everything? While renewable energy resources will not run out and can be replenished quickly, they have their own environmental footprints.

Biofuels are carbon neutral. The plants absorb $CO_2$ via photosynthesis while growing, so burning them releases no net increase in atmospheric $CO_2$. However, growing them causes deforestation and competes with food crops for land.

Other renewables rely on specific environments:

• Hydroelectric: Flooding valleys behind dams causes massive habitat destruction and displaces people.
• Wind: Turbines cause visual pollution, noise pollution, and risk bird/bat strikes.
• Solar: Requires vast areas of land and uses toxic chemicals during manufacture.
• Tidal/Wave: Barrages block fish migration and destroy estuary mudflats.

Worked Example: Replacing Nuclear with Wind

Renewable sources often have a much lower power output than nuclear or fossil fuels. Let's calculate how many wind turbines are needed to replace one nuclear station.

How many $1.6\text{ MW}$ ($1.6 \times 10^6\text{ W}$) wind turbines are required to replace a $2.4\text{ GW}$ ($2.4 \times 10^9\text{ W}$) nuclear power station?

Step 1: Write down the known values in standard units.

• Power of nuclear = $2.4 \times 10^9\text{ W}$
• Power of one turbine = $1.6 \times 10^6\text{ W}$

Step 2: Divide the total power required by the power of one turbine.

$$\text{Number of turbines} = \frac{2.4 \times 10^9}{1.6 \times 10^6}$$

Step 3: Calculate the final answer.

$$\text{Number of turbines} = 1500$$

Patterns and Trends in Energy Use

If you looked at the UK's energy mix fifty years ago, it would look completely different from today. An energy mix is the proportion of different resources a country uses to meet its electricity, transport, and heating needs.

Historically, the UK relied on wood, then shifted entirely to coal during the industrial revolution. In the 1950s to 1980s, nuclear power was introduced. The 1970s saw the discovery of North Sea oil and gas, which rapidly replaced coal because gas is cleaner and has a much shorter start-up time (minutes compared to hours).

Over the past 30 years, fossil fuel use has dropped significantly (from $75\%$ to $38\%$), while renewables have surged (from $2\%$ to $35\%$). Interestingly, overall electricity demand has declined despite population growth, caused by improved energy efficiency (like LED bulbs and better insulation).

Energy demand fluctuates daily, usually peaking around 5 pm. A reliable energy resource must meet this demand:

• Base load (constant minimum demand) is met by nuclear power, which has the longest start-up time (days) but runs continuously.
• Peak demand is met by gas-fired stations because they can be turned on in minutes.
• Wind and solar cannot meet the base load easily because they are intermittent.

Evaluating Limitations of Energy Solutions

Science can identify how to stop climate change, but political, social, and economic factors often prevent immediate action.

• Economic Limitations: Transitioning to new energy involves immense capital costs for building infrastructure. While renewables have zero fuel costs, nuclear power stations face extraordinarily high decommissioning costs when they are dismantled at the end of their life.
• Social and Ethical Limitations: The public often experiences NIMBYism ("Not In My Back Yard") — supporting wind farms in principle but protesting if they are built locally. Ethically, leaving radioactive waste that remains hazardous for thousands of years burdens future generations.
• Political Limitations: Governments are bound by international treaties like the Paris Agreement to reach Net Zero targets. However, they must balance this with energy security, maintaining a diverse energy mix so they do not rely on a single foreign country for fuel.