AQA A-Level Environmental Science (7447)

## Learning Outcomes

- Understand how energy links to sustainability in AQA A-Level Environmental Science
- Explain the difference between **renewable**, **low-carbon** and **non-renewable**
- Identify how natural systems and human systems use energy differently
- Explain why **intermittency** affects some renewable energy resources
- Assess the sustainability of biomass, nuclear power and mixed energy strategies
- Evaluate how energy choices affect both environmental sustainability and **energy security**

## AQA A-Level Environmental Science (7447) Syllabus

For the AQA A-Level Environmental Science (7447), you are expected to understand energy within sustainability, with a focus on the following syllabus points:

- Know that future energy supplies are affected by changing availability, new technologies, economic factors and environmental concerns
- Understand that natural systems are driven mainly by renewable energy, especially solar power
- Explain that natural systems use low energy-density processes at relatively low temperatures, unlike many human systems
- Identify the difference between **renewable energy resources** and **non-renewable energy resources**
- Understand that a renewable resource can still be overexploited, such as biomass or geothermal energy
- Explain why **energy security** means reliable, affordable and continuous energy supply
- Assess the role of intermittency, storage, grid balancing and energy mix in sustainable energy strategies
- Distinguish clearly between **renewable** and **low-carbon**, especially for biomass and nuclear power

## Test Your Knowledge

_Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, look more closely at that area during your revision._

1. What is the difference between a renewable energy resource and a low-carbon energy source?
2. Why are natural systems described as being driven by low energy-density processes?
3. How does intermittency limit the use of some renewable energy sources?
4. Why is biomass not automatically carbon neutral?
5. How can an energy source improve energy security but still raise sustainability concerns?

## Introduction

Energy is at the centre of sustainability because it affects resource use, pollution, climate change, transport, food production and living standards. In this topic, AQA wants you to think beyond simply naming energy sources. You need to explain how energy systems work, how they compare with natural systems, and why some choices are more sustainable than others.

A common exam mistake is to assume that renewable means harmless, or that low-carbon means renewable. Neither is true. Good answers define terms precisely, then weigh up advantages, limits and wider environmental impacts.

> **Key Term: sustainability**
> Development that meets present needs without reducing the ability of future generations to meet their own needs.

### Natural systems, anthropogenic systems and energy use

AQA places strong emphasis on the contrast between **natural systems** and **anthropogenic systems**. Natural systems are mainly powered by renewable energy, especially solar radiation. This energy drives major Earth processes such as the hydrological cycle, atmospheric circulation, the carbon cycle, the nitrogen cycle and thermohaline circulation.

These natural processes usually operate at relatively low temperatures and with low energy-density inputs. They are often gradual, distributed over large areas, and linked by feedback mechanisms. Human systems are different. They often depend on concentrated fuels, especially fossil fuels, to release large amounts of energy quickly.

> **Key Term: anthropogenic systems**
> Systems created or strongly altered by human activity.
>
> **Key Term: energy density**
> The amount of energy available from a given quantity of resource.

This contrast matters because a sustainable society is more likely to work with the limits and patterns of natural energy flows, rather than relying entirely on finite, concentrated fuels. Fossil fuels gave rapid industrial growth because they are energy-dense, easy to transport and useful for high-temperature processes. However, they are finite and their combustion releases greenhouse gases.

Natural systems show that long-term stability depends on renewable flows. Human systems do not need to copy nature exactly, but they do need to reduce dependence on non-renewable, high-emission fuels.

> **Test Tip:** If a question asks you to contrast natural and human systems, do not just say “nature uses renewables.” Add the ideas of **low energy density**, **low temperatures** and major natural cycles driven by solar energy.

### Renewable, non-renewable and low-carbon: key distinctions

A renewable energy resource is replenished naturally on a human timescale. Sunlight, wind and tidal movement fit this definition. Biomass can also be renewable, but only if harvesting does not exceed regrowth.

A non-renewable resource is not replaced quickly enough for human use. Fossil fuels and uranium are finite reserves. They may last for a long time, but they are still non-renewable.

> **Key Term: renewable energy resource**
> A resource replenished naturally fast enough to remain available if use is properly managed.
>
> **Key Term: non-renewable energy resource**
> A finite resource that is not replaced on a human timescale.

Students often confuse renewable with low-carbon. These are not the same category. A source may be renewable but still release greenhouse gases or damage habitatss. Biomass is the clearest example. When burned, it releases carbon dioxide. It may still be treated as renewable if new plant growth replaces the carbon store, but this depends on regrowth, land use, transport, fertiliser use and processing.

Nuclear power is the opposite case. It is usually classed as low-carbon in operation because electricity generation releases very little carbon dioxide compared with fossil fuels. However, it is not renewable because uranium fuel is finite.

> **Key Term: low-carbon energy**
> Energy with low greenhouse gas emissions across operation or across its full life cycle compared with fossil fuels.

A strong exam answer uses these distinctions carefully:

- **Fossil fuels**: non-renewable, generally high carbon, usually reliable
- **Wind and solar**: renewable, usually low-carbon, but intermittent
- **Biomass**: can be renewable, but not automatically low-carbon or sustainable
- **Nuclear**: low-carbon, reliable, but non-renewable

### Intermittency, energy security and the energy mix

A major challenge with some renewable resources is **intermittency**. Solar power is unavailable at night and reduced by cloud cover. Wind power depends on wind speed. Tidal power is intermittent too, but unlike wind and solar it is very predictable because tidal cycles can be forecast.

> **Key Term: intermittency**
> The fact that some energy resources are not available all the time.

Intermittency does not mean a source is useless. It means that the energy system must be designed to cope with variation. This is why AQA expects you to understand that sustainable future energy systems are likely to depend on a **mix** of resources rather than one single source.

> **Key Term: energy security**
> Reliable, affordable and continuous access to enough energy to meet demand.

Energy security is wider than installed generating capacity. A country may have a large theoretical energy supply, but still have poor energy security if that supply is too expensive, too variable, import-dependent or easily disrupted.

A more secure low-carbon system usually needs several supporting features:

- a diverse **energy mix**
- storage technologies
- flexible demand
- interconnection between regions
- some dispatchable or controllable generation
  > **Key Term: energy mix**
  > The combination of different energy sources used to meet demand.

Batteries can help with short-term balancing. Pumped storage and other longer-duration options can help when low renewable output lasts longer. Demand-side response can shift electricity use away from peak periods. Interconnection allows electricity imports and exports across wider areas.

This means renewable energy and energy security are not opposites. Wind and solar can support security if the wider system includes flexibility. Equally, a source may improve short-term security but still harm long-term sustainability. For example, coal can be stored and used when needed, but it increases greenhouse gas emissions and air pollution.

> **Test Tip:** In evaluation questions, separate **security** from **sustainability**. A source can score well on one and poorly on the other.

### Biomass, nuclear power and sustainable energy strategies

Biomass is often used in exam questions because it needs careful judgement. Biomass includes wood, straw, sewage gas, dung, crop residues and energy crops. Its main advantage is that it stores chemical energy and can be used when needed, unlike wind or solar. Some biomass fuels can also replace liquid transport fuels.

However, biomass is only sustainable under strict conditions. If forests are cut faster than they regrow, it becomes unsustainable. If land for energy crops replaces food production or natural habitats, the wider environmental cost may be high. Intensive cultivation can also involve fertilisers, machinery and transport, all of which add emissions.

So biomass is not automatically carbon neutral. Carbon released on combustion may be offset by plant growth only if the whole cycle is well managed.

Nuclear power has a different profile. It provides reliable large-scale electricity with low direct carbon emissions. It can support grid stability and reduce dependence on fossil fuels. But it remains non-renewable because uranium is finite. There are also concerns over radioactive waste, decommissioning costs and accident risk, even if routine operation is low-carbon.

A balanced answer on nuclear power would say:

- more sustainable than fossil fuels in terms of carbon emissions
- useful for reliable electricity supply
- not renewable
- associated with waste, high capital cost and long-term management issues

The best long-term strategy is usually a mixed system. This may include renewables such as wind, solar, hydro and sustainably managed biomass, supported by storage, smarter grids and possibly nuclear power. The exact balance depends on geography, technology, cost and environmental priorities.

AQA also expects you to recognise that manufacturing renewable energy technology requires materials and energy, often from fossil-fuelled industry. This does not cancel the benefit, but it means no source is impact-free. The key issue is whether lifetime impacts are lower and whether the system can be maintained without damaging life-support systems.

## Key Point Checklist

_This article has covered the following key knowledge points:_

- Sustainability in energy means meeting present energy needs without damaging future resource availability or life-support systems
- Natural systems are mainly driven by renewable energy, especially solar power
- Natural processes usually use low energy-density inputs at relatively low temperatures
- Human energy systems often rely on concentrated, non-renewable fuels
- Renewable does not mean the same as low-carbon
- Biomass can be renewable only if harvesting does not exceed replacement and wider impacts are controlled
- Nuclear power is low-carbon in operation but non-renewable because uranium is finite
- Intermittency affects wind, solar and tidal energy, but tidal energy is predictable
- Energy security means reliable, affordable and continuous supply, not just enough installed capacity
- A sustainable energy strategy usually depends on a diverse energy mix plus storage, balancing and flexible demand
- Renewable energy sources can still have environmental impacts
- Good exam answers define terms precisely, then assess trade-offs rather than making absolute claims

## Key Terms and Concepts

- sustainability
- anthropogenic systems
- energy density
- renewable energy resource
- non-renewable energy resource
- low-carbon energy
- intermittency
- energy security
- energy mix


Sustainability - Energy