⏳ Estimated Reading Time: 7 - 9 minutes

Identify types of fuels and their uses.

Humans use a variety of energy sources to fuel society. Traditional fuel sources such as coal, petroleum, natural gas, and even wood can be considered a finite resource, as each can be used up faster than natural processes can replace them. To that end, finding more reliable, longer-lasting, cleaner energy in the form of renewable energy becomes even more important to the future of society.

Fuel Types

Explore the tabs below. Which type of fuel do you use at your house? At our house, we have natural gas for heat, our stove, and the dryer. The rest of our house uses electricity, but the electricity is also powered by natural gas. Our vehicles use oil. Some of our neighbors have wood-burning fireplaces, but we do not.

Wood
Peat
Coal
Natural Gas
Oil

Wood

a wood stove — **Wood is easy to access and produces a large amount of heat when burned.**

Wood as an energy source was widely used world-wide until coal became more desired. Wood is heavily used in developing nations, but has led to widespread deforestation, especially in some of the poorest places on Earth.

Benefits:

✅ relatively cheap

✅ relatively easy to access

✅ can be renewable if managed correctly

✅ low carbon footprint compared to fossil fuels

Drawbacks:

❌ low energy content

❌ deforestation

❌ biodiversity loss

❌ burning wood produces smoke, releases particulates and greenhouse gases

❌ requires more storage space and transportation than other fuels

Peat

Peat logs burning — **Peat can be used as a fuel for domestic heating, cooking, and electricity generation, especially in regions where other fuels are scarce or expensive.**

Peat is a dark brown or black substance that is formed by the partial decomposition of organic matter, mostly plants, in wetlands such as bogs, fens, and swamps. Peat is the first step in the formation of coal, but it has a lower carbon content and a higher moisture content than coal.

Benefits:

✅ relatively cheap

✅ relatively easy to access

✅ can be renewable if managed correctly

✅ low sulfur content so it does not produce acid rain when burned

Drawbacks:

❌ low energy content

❌ high ash content

❌ deforestation

❌ increased erosion

❌ can cause water pollution

❌ biodiversity loss

❌ burning peat releases more carbon dioxide than natural gas and coal

Coal

Coal is formed when dead plant matter is buried under high pressure and temperature for millions of years. — **Coal formation typically occurs when dead plants are buried for millions of years and requires high temperatures and pressure to form.**

The formation of coal produces methane, nitrogen, carbon dioxide, and other gases. The pressure pushing down on the coal keeps the methane underground with the coal. Natural gas is methane and small amounts of carbon dioxide and nitrogen and is found in coal.

Coal is ranked based on carbon content, heat value, and hardness with anthracite being highest ranked, followed by bituminous coal, then subbituminous coal, with lignite ending the list on the lowest-ranked end.

Explore the interactive below to learn more about each type of coal, just tap on the white dots at the bottom to uncover all the details!

Benefits:

red hot coals — **Coal is abundant and** **cheap, but it** **produces significant air pollution when burned for energy.**

✅ abundant and widely available in many countries

✅ cheap

✅ easy to use

✅ high energy density

Drawbacks:

❌ mining and burning can cause air pollution

❌ mining and burning can cause water pollution

❌ habitat loss

❌ increased erosion

❌ mining and burning can cause health problems

❌ biodiversity loss

❌ major source of greenhouse gas emissions

❌ nonrenewable resources

❌ produces a lot of ash, waste, and impurities

Coal continues to be used as an energy source, especially in developing countries. Developed countries continue to move away from relying on coal for electricity production due to pollution associated with it.

Natural Gas

Oil and natural gas are formed when dead organic matter, such as plankton, is buried under high pressure and temperature for millions of years. — **Oil and natural gas are formed when organic matter (usually oceanic) is buried for millions of years and require high temperatures and pressure to form.**

Natural gas is composed mostly of methane gas (CH₄) and is formed over long periods of time, from organic matter in marine sediments. Microscopic organisms die and settle to the sea floor and accumulate in the sediment. These organisms partially decompose, using dissolved oxygen in the sediments.

The heat and pressure change the organic matter into concentrated coal, petroleum, and natural gas. Some of the gas collects near the original deposits of organic matter and some of the gas works its way out into surrounding rock and soil layers.

Benefits:

✅ abundant and widely available in many countries

✅ cheaper than coal and oil

✅ easy to use

✅ power plants are highly efficient

✅ cleanest burning fossil fuel - does not produce any of the hydrocarbons or sulfur dioxides that are produced when other fossil fuels are burned

Drawbacks:

an offshore oil drilling rig in calm waters under a clear blue sky — **Natural gas must be stored and transported in its liquid form.**

❌ combustible and can explode easily

❌ fracking process can cause earthquakes and contaminate groundwater

❌ habitat loss

❌ increased erosion

❌ expensive to store and transport

❌ biodiversity loss

❌ major source of greenhouse gas emissions, especially carbon dioxide

❌ nonrenewable resources

❌ has a long processing process

Natural gas is supplanting coal as the fuel of choice for electrical power plants, especially in developed nations.

Oil

a gas station during nighttime — **Oil produces abundant air pollution when burned, but it is convenient since it works with our existing infrastructure.**

Petroleum (oil) and natural gas typically form in concert as the remains of plants and animals decay under anaerobic (without oxygen) conditions. When the oxygen is gone from the areas that form natural gas, decay slows. The remaining organic matter is preserved and trapped within sediment. Over time, this mud is buried deeper and deeper. This forms oil shale, which becomes the source of petroleum. Above or below the oil shale, either limestone or sandstone allows the flow and storage of petroleum. To form pools of petroleum, however there must be an impervious layer of rock that keeps the oil from escaping. Because oil and natural gas are less dense than water, they tend to rise upward through water-saturated rock and sediments and accumulate in areas above the groundwater.

Benefits:

✅ high-density fuel

✅ easy to extract and transport

✅ reliable and works with existing infrastructure (e.g. gas stations)

✅ helps create solar and wind products

Drawbacks:

❌ drilling disrupts habitats

❌ subject to price fluctuations and geopolitical conflicts

❌ drilling can cause increased erosion

❌ can cause oil spills and fires

❌ drilling can cause biodiversity loss

❌ major source of greenhouse gas emissions, especially carbon dioxide and carbon monoxide

❌ major source of air pollutants, including those that cause acid rain

❌ nonrenewable resources

As awareness has risen about the problem above, the search for alternative, renewable energy to power society has accelerated. This awareness, combined with the rising costs of petroleum products has opened the door for other energy sources to find their place in society.

Essential Knowledge

Wood is commonly used as a fuel in the forms of firewood and charcoal. It is often used in developing countries because it is easily accessible.

Peat is partially decomposed organic material that can be burned for fuel.

Three types of coal used for fuel are lignite, bituminous, and anthracite. Heat, pressure, and depth of burial contribute to the development of various coal types and qualities.

Natural gas, the cleanest of the fossil fuels, is mostly methane.

Crude oil can be recovered from tar sands, which are a combination of clay, sand, water, and bitumen.

Uses

Flip the cards below to learn about the uses for oil/petroleum, coal, and natural gas:

Essential Knowledge

Fossil fuels can be made into specific fuel types for specialized uses (e.g. in motor vehicles).

Cogeneration

a comparative diagram contrasting a Traditional System with Cogeneration for producing electricity and heat. — **Cogeneration plants are more efficient than traditional power generation systems.**

More recently, the efficiency of traditional power plants has been increased by moving towards Combined Heat and Power (CHP) designs, also known as cogeneration. In a CHP system, heat is produced by burning fuel to make electricity, but the thermal heat is also used for industrial processes, thereby increasing the overall efficiency of the plant.

Benefits:

✅ decreased air pollution

✅ increased power plant efficiencies

✅ enhanced grid reliability

✅ reduced energy costs

✅ reduced infrastructure costs

Cogeneration simply makes use of what used to be “waste heat” and incorporates this thermal energy source into industrial use.

Essential Knowledge

Cogeneration occurs when a fuel source is used to generate both useful heat and electricity.

AP Exam Tip

You should know some benefits and drawbacks of each type of fuel.

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