6.8 - Fossil Fuels: Alternatives
The need for energy transition
As fossil fuels become scarcer, societies must shift towards more sustainable energy sources. This shift is called energy transition, which involves reducing reliance on fossil fuels.
A key aspect of energy transition is decoupling, where economic growth is separated from fossil fuel use. This means finding ways to maintain or increase economic activity without increasing fossil fuel consumption. Decoupling often involves moving towards renewable energy sources, which can be replenished naturally and produce fewer greenhouse gas emissions compared to fossil fuels.
Types of renewable energy sources
Renewable energy comes from natural processes that are constantly replenished, unlike finite fossil fuels. These sources harness environmental forces to generate power, often with lower long-term environmental impacts.
Main renewable energy sources
| Source | Description |
|---|---|
| Solar | Captures energy from the Sun to heat water, power solar cookers, or generate electricity through photovoltaic (PV) cells, which convert sunlight directly into electrical energy. |
| Wind | Uses wind turbines to convert kinetic energy from wind into electricity; turbines can be placed on land or offshore in wind farms, producing no greenhouse gas emissions during operation after construction. |
| Hydroelectric | Relies on the energy of falling water; dams store water in reservoirs, releasing it through tunnels to spin turbines and generate electricity. |
| Tidal | Harnesses the movement of ocean tides or currents to drive turbines and produce electricity. |
| Wave | Converts the motion of ocean waves, created by wind blowing over water, into electrical energy via turbines. |
| Geothermal | Involves pumping water underground where it is heated by the Earth's crust to produce steam; this steam then powers turbines for electricity or is used directly for heating and hot water. |
These sources form part of a diverse energy mix, allowing countries to adapt based on their geography and resources.
Nuclear power as an alternative
Nuclear power provides another option beyond renewables, generating large amounts of energy from small quantities of fuel. It works by splitting atoms of uranium, which releases energy used to generate electricity.
Nuclear power is considered a recyclable energy source because its waste products can sometimes be reprocessed to create new fuel.
Costs and benefits of alternative energy sources
While alternatives to fossil fuels offer sustainability, they come with trade-offs. These include environmental, economic, and location-specific factors that influence their viability.
Challenges and location-specific factors
The effectiveness of renewables depends on local conditions, such as climate, geology, and terrain. This leads to different energy mixes across countries. For example, sunny regions favour solar, while windy areas suit wind power.
Large-scale projects like wind or solar farms can raise local concerns about their impact on quality of life or property values.
Costs and benefits of wind power
- Costs - Requires average wind speeds over 5.5 metres per second (m/s) for efficiency; turbines shut down in winds above 25 m/s to avoid damage, limiting reliability in variable conditions.
Costs and benefits of nuclear power
- Costs - High construction and decommissioning expenses; radioactive waste needs secure storage for thousands of years; accidents, though rare, can have severe consequences.
Costs and benefits of hydroelectric power
- Costs:
- Depends on high water flow, making it unreliable in low-rainfall or drought-prone areas.
- Requires building dams, which can flood land, displace communities, and destroy ecosystems.
- Best suited to basins with large rivers and steep terrain, but construction can be costly or challenging.
- Influenced by drainage density (the network of rivers in an area) and local geology.
Costs and benefits of solar power
- Benefits - Works in many countries, including developing ones, and can be installed on rooftops.
- Costs:
- Most effective in low-cloud areas.
- Output varies by season, with longer summer days producing more energy when demand is often lower.
- Large solar farms may compete for rural land.
Shifting to these alternatives can affect fossil fuel prices, which may decrease as demand falls but fluctuate due to geopolitical factors.
The changing energy mix in the UK
The UK's energy sources have evolved significantly, moving away from coal towards cleaner options. This reflects efforts to reduce emissions and improve sustainability.
Trends in UK primary energy sources
Since 1990, coal use has declined sharply, while natural gas, nuclear, and renewables have grown. Investment in wind power and nuclear stations has driven this change.
UK energy mix by percentage:
| Year | Coal | Oil | Natural Gas | Nuclear | Renewables and Biofuels |
|---|---|---|---|---|---|
| 1990 | 37.3 | 30.8 | 23.0 | 8.4 | 0.5 |
| 2000 | 16.5 | 33.0 | 39.4 | 10.0 | 1.1 |
| 2010 | 15.2 | 31.3 | 41.7 | 8.0 | 3.8 |
| 2020 | 3.3 | 31.9 | 41.2 | 8.4 | 15.1 |
These shifts support policies for energy efficiency, such as requiring efficient appliances in homes and businesses. The UK aims for all electricity from clean sources by 2035.
Biofuels as an alternative energy source
Biofuels offer another path away from fossil fuels, derived from organic materials. Biomass (organic matter like wood, plants, or animal waste) can be burned for heat or processed into biofuels such as bioethanol (from sugary crops) and biodiesel (from oil-based crops).
These fuels can replace petrol and diesel, with lower particulate emissions. Production involves growing crops like grass, sugar cane, wheat, rapeseed, or linseed.
Costs and benefits of biofuels
| Costs | Benefits |
|---|---|
| Growing crops can reduce biodiversity by clearing land, including sensitive areas like rainforests. | Relies on simple crop-growing processes, accessible to countries at all economic levels. |
| Heavy use of fertilisers and pesticides may pollute water sources. | Can be cheaper than petrol on a large scale; brings income to rural areas with low investment. |
| Competes for land and water needed for food crops, potentially affecting food security. | Biodegradable and less harmful if spilled, causing minimal long-term damage. |
| Releases less carbon dioxide than fossil fuels when burned. |
Biofuels in Brazil
Brazil produces about 34 billion litres of bioethanol annually from sugar cane, used for vehicle fuel and home energy. It is mixed with petrol to create flex-fuel for compatible car engines.
Production has expanded with economic growth, using cleared land for intensive farming. The industry peaked in 2005 with over 500,000 jobs. Government policies, like mandating 27% bioethanol in fuel and removing petrochemical subsidies, boosted profitability.
Despite a dip after the 2008 economic crash, production is recovering. In 2022, bioethanol cost US$0.84 per litre, compared to US$1.02 for petrol.