Mineral Resources and Fossil Fuels

Mineral resources are naturally occurring solid substances, such as metal ores, building stone, sand and salt, that are extracted from the ground; fossil fuels, which are coal, oil (petroleum) and natural gas, are energy resources formed from the remains of ancient organisms buried and transformed over millions of years. In brief: minerals are mined by surface (open-pit, quarrying) or underground methods and are concentrated unevenly in the crust. Coal forms from plant material in swamps, while oil and gas form from marine organisms in sedimentary basins and collect in porous reservoir rock under an impermeable cap rock. Fossil fuels supply a large share of the world’s energy, but burning them releases carbon dioxide, the main cause of human-driven climate change.

Minerals and fossil fuels underpin construction, manufacturing, transport and electricity. This guide explains how each type forms, is extracted and is used, compares fossil fuels in a table, works through a power-station fuel and emissions calculation, outlines the history of mining and energy use and corrects common mistakes.

What are mineral resources?

A mineral is a natural inorganic solid with a definite chemical composition; a rock is made of minerals; an ore is a rock that contains enough of a metal to be extracted at a profit. Minerals can be grouped into metallic (iron, copper, aluminum from bauxite, gold, tin, nickel, and lithium and cobalt used in batteries), nonmetallic or industrial (sand and gravel, limestone for cement, clay, gypsum, salt, phosphate and potash for fertilizers), and gemstones. Ores form by processes such as cooling of magma (concentrating metals), hot water flowing through rocks (hydrothermal veins), weathering that leaves residual deposits (bauxite), and sedimentation. The resources are unevenly distributed: Chile and Peru lead in copper, Australia in iron ore and lithium, Indonesia in nickel, and the Democratic Republic of the Congo in cobalt. Extraction methods: surface mining (open-pit, strip mining and quarrying) for deposits near the surface, which is cheaper but disturbs large areas; and underground mining (shafts and tunnels) for deeper deposits, which is more dangerous and costly. Ore is processed by crushing, concentrating and smelting, which uses large amounts of energy and creates waste.

What are fossil fuels?

• Coal: formed from plants buried in swamps about 300 million years ago (the Carboniferous period, for much of the coal) and compressed and heated through the stages peat, lignite, bituminous coal and anthracite, with the carbon content and energy value increasing. It is mined mostly at the surface or underground, and used for electricity, steelmaking and cement. China, India, Indonesia, the United States and Australia are major producers.
• Oil (crude petroleum): formed from the remains of tiny marine organisms (plankton) buried in sediment, which were changed by heat and pressure into liquid hydrocarbons. The oil migrates up through porous rock until it is trapped under an impermeable cap rock, and it is extracted by drilling wells, onshore or offshore. It is refined into petrol (gasoline), diesel, jet fuel, plastics feedstock and other products. A barrel is 159 liters.
• Natural gas: mostly methane, found with oil or alone, extracted by wells and transported by pipeline or as liquefied natural gas (LNG) in ships. It is used for heating, electricity, industry and fertilizer production. Shale gas and tight oil are obtained by hydraulic fracturing (“fracking”) of low-permeability rock.

What are the impacts and uses?

Fossil fuels supplied about 80 percent of the world’s primary energy in recent years (the share is slowly falling). Burning them releases carbon dioxide (about 94.6 kg of CO₂ per gigajoule for bituminous coal, 73.3 for crude oil and 56.1 for natural gas, by the IPCC default factors), and also air pollutants such as sulfur dioxide, nitrogen oxides and particulates. Extraction can cause habitat loss, water pollution, land subsidence, acid mine drainage, oil spills and methane leaks. Mining waste (tailings) can be hazardous. These problems, as well as the finite nature of the resources, are the reasons for the move toward recycling, efficiency, renewable energy and lower-carbon fuels.

Fossil fuels compared

Worked example: fuel use and emissions

1. Electricity produced: a power station of 500 MW operating all day produces 500 × 24 = 12,000 MWh. Since 1 MWh = 3.6 GJ, this is 12,000 × 3.6 = 43,200 GJ = 43.2 TJ.
2. Fuel energy at 38 percent efficiency (coal): 43.2 ÷ 0.38 = 113.7 TJ of fuel energy per day.
3. Coal mass: with a heating value of 24 MJ/kg, the coal needed is 113.7 × 10⁶ MJ ÷ 24 MJ/kg = 4.74 × 10⁶ kg = about 4,740 tonnes per day.
4. CO₂ emissions: 113,700 GJ × 94.6 kg/GJ = 10.76 million kg = about 10,800 tonnes of CO₂ per day.
5. Gas plant for comparison: a combined-cycle gas plant of 55 percent efficiency needs 43.2 ÷ 0.55 = 78.5 TJ of gas, with emissions of 78,500 GJ × 56.1 kg/GJ = 4.40 million kg = about 4,400 tonnes of CO₂ per day, which is 4,406 ÷ 10,755 = 41 percent of the coal plant’s amount.
6. Annual coal: 4,740 tonnes a day × 365 = about 1.73 million tonnes a year, or a train of 100 wagons with 100 tonnes each (10,000 tonnes) arriving every 2 days.

How has the use of minerals and fossil fuels developed?

Humans have mined flint, copper and tin since prehistoric times (the Bronze Age began around 3000 BCE in some regions) and iron from about 1200 BCE. Coal was used in China and Britain for centuries, and the invention of the steam engine by Thomas Newcomen (1712) and its improvement by James Watt made coal central to the Industrial Revolution. The first commercial oil well in the United States was drilled by Edwin Drake in Pennsylvania in 1859, and the internal combustion engine made oil the main transport fuel in the 20th century. Natural gas grew after the Second World War as pipelines and LNG developed. The Paris Agreement (2015) aims to limit global warming, which requires a major reduction in the use of fossil fuels.

Which mistakes are common?

Mistake 1: Thinking that oil is formed from dinosaurs

Most oil comes from microscopic marine organisms. Most coal comes from plants.

Mistake 2: Confusing a mineral with a rock or an ore

A mineral has a definite composition, a rock is a mixture of minerals, and an ore is a rock that can be mined for a metal at a profit.

Mistake 3: Believing that we have “run out” when a reserve number is quoted

The reserve is what is economically recoverable now. It changes with technology and prices.

Mistake 4: Assuming that all fossil fuels have the same emissions

For the same energy, coal emits more CO₂ than oil, and oil more than natural gas, though methane leaks from gas systems also matter.