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How do humans use fossil fuels?

Coal, oil and gas have fueled industrial development – and rapid climate change.

We call coal, oil and gas fossil fuels because they derive from the remains of ancient plants and animals in the Earth’s crust. In essence, they are the energy of the sun harvested by plants through photosynthesis and locked up into carbon compounds. From the moment coal was discovered by early humans, fossil fuels served as a source of light, heat and eventually electricity. They are much more energy dense – meaning they contain more energy for every unit of mass, than wood, for example, and are convenient to store, transport and use.

As humans learned more about physics and chemistry, we discovered more and more ways to use fossil fuels to power our homes, our transport and industry, as well as how to transform these fuels into various handy chemicals. At a certain point in the late twentieth century, however, we also learned that burning fossil fuels and releasing ancient carbon into the atmosphere interfered with the climate system, causing global warming and other symptoms of rapid climate change. Climate change was and continues to be mostly a fossil fuel problem, as the vast majority of CO2 emissions come from burning coal, oil and gas. This is why breaking free from our unnecessary dependence on these fuels is so crucial to addressing the problem. In 2021, the International Energy Agency (IEA) supported the findings of the IPCC when it called for no new fossil fuel development as a key strategy for staying within the safe limits of global temperature rise.

Powering our economies with fossil fuels also causes local pollution wherever they are used: oil spills and waste from coal mines poison water and soil, methane leaks from pipelines, nitrogen oxides released from burning contribute to smog and acid rain, and fine particles cause lung damage and even premature death. This means the issue of fossil fuel use is not just about the long-term influence on the climate system, but about the more immediate and tangible consequences for nature and humans as well.

Fortunately, as we learn more about physics and chemistry, we discover new ways to produce energy without relying on non-renewable fossil resources that also heat and pollute the Earth. In fact, renewable energy sources, such as wind and solar power, continue to get cheaper and more accessible, meaning fossil fuels can now be replaced by low- and zero-carbon options.

Where do we use oil and its products?

Stéphane M. Grueso

Kerosene produced from oil was initially marketed in the nineteenth century as one of the alternatives to whale oil for lamps. But people soon realised that oil’s other energy dense derivatives, such as diesel or petrol, could be used in internal combustion engines and in particular for transportation. As these fuel types are liquid they were easier to use than solids (like coal) or gases, and ideal for vehicles. Their energy density made them particularly suitable for cars, allowing these to be lighter and travel longer distances, which soon meant that oil products would come to dominate the transportation sector. Today, efforts to decarbonise this sector include advances in battery technology, where costs have been falling dramatically, and a vast infrastructure for electric vehicles is being built. We are also finding new approaches to fueling aviation, shipping and heavy-duty vehicles.

Some oil products are also used to produce heat and electricity, but this has also begun to change – their share in electricity generation has been steadily declining and is now below 3%, according to the IEA. Solving the challenges of the transport sector will be difficult, but we already have plenty of ways to generate heat and electricity that are much better and far cleaner than fossil fuels.

Besides transport, heat and energy, a variety of oil refining processes gives rise to a whole family of products called petrochemicals. These are widely used in making plastics, fibres and synthetic rubber, as well as a range of industrial chemicals such as solvents, detergents and dyes. Petrochemicals production accounts for about 12% of global oil demand, according to the IEA. They are used in everyday items like clothes and packaging, and also “in many parts of the modern energy system, including solar panels, wind turbine blades, batteries, thermal insulation for buildings, and electric vehicle parts.” While researchers are working on cleaner alternatives to these oil-derived products, it’s also worth noting that their environmental footprint can and should be reduced significantly through better recycling and waste management, energy efficiency and pollution control. 

Where do we use coal?

The IEA states that coal is the largest energy source used globally for electricity generation and the single largest source of CO2 emissions. According to the IPCC, to reach net zero in CO2 emissions by 2050 we need to stop burning coal without capturing emissions – and these technologies are not yet available at the needed scale. At the recent UN climate change conferences, a shift of attitude along these lines was noticeable in talks of phasing down coal and capitalising on the momentum in renewable energy. Furthermore, from production and transportation through to coal-fired power plants, coal is a major source of dangerous air pollution – getting rid of coal-powered generation will have major additional benefits for human health.

The steel and cement industries burn coal to power production processes, which require some truly high temperatures to be maintained – over 1000°C. Electrification of these and similar industrial processes is difficult and even sometimes impossible, making it likely that zero-carbon combustible fuels, such as biofuels or hydrogen produced with renewable electricity, will be developed for this limited range of uses. 

It is also possible to convert coal to syngas, a mix of carbon monoxide and hydrogen that can then be used to make liquid synthetic fuels. While these fuels are cleaner to burn, coal is still the primary resource meaning they remain finite carbon-based fuels despite the shift. An alternative, if it is necessary, is to make similar synthetic fuels via ‘greener’ means while keeping coal in the ground, for instance, to replace oil products in marine and air transport. Similarly, where hydrogen might be needed, there are ways to produce using renewable energy rather than the ‘black’ and ‘brown’ hydrogen fuel made from coal.

Where do we use gas?

What we call gas is a mixture of hydrocarbons that primarily consists of methane – the most potent greenhouse gas after CO2. The carbon footprint of gas therefore includes the CO2 emissions from burning it to generate heat and electricity, and also methane leaks from pipelines and other infrastructure. Gas-supportive governments and industry state that gas is a clean energy fuel, but it can be as bad for the climate as coal because it is often shipped overseas in liquefied form, and methane leaks out at every stage of that process.  

Gas is used for electricity generation and industry processes like making cement. In many Global North countries people also still use gas stoves for cooking, even though there are more efficient and faster electric alternatives. Recent research has shown that using gas stoves is harmful for human health. According to one estimate, gas stoves leak about 1% of the fuel they use as unburned methane, produce fine particulate matter that irritates lungs and airways, and can break safe exposure limits for nitrous oxides emissions.

Just like oil, gas can be used to produce chemicals, as well as being used in the production of nitrogen fertilisers and also ‘blue’ hydrogen. New technologies like green ammonia, which is produced using renewable energy, are beginning to make it possible for the chemical industry to wean itself off gas. Decarbonising fertiliser production will bring a decrease in emissions and could mean our food system and food prices will be less sensitive to fossil fuel prices. 

Useful resources

  • United Nations Secretary-General outlines five critical actions the world needs to prioritize now to transform our energy systems and speed up the shift to renewable energy
  • A BBC report talks about the Secretary-General’s call for a tax on fossil fuel profits