A guide to fossil fuels: what are they, and what do they have to do with climate change?

27 January 2021 | Aimee Tweedale

Unless you’ve had your head buried under a rock, you’ve probably heard a lot of talk about fossil fuels in recent years. You might have noticed the phrase come up a lot in conversations about climate change, and heard companies like OVO talking about why we’re moving away from fossil fuels.

But what exactly are fossil fuels, where do they come from, and how do they contribute to climate change? Here’s everything you need to know. 

Fossil fuels: what are they, and what do they have to do with climate change?

What are fossil fuels?: a definition

As the name suggests, fossil fuels are made up of dead plants and animals. Just like a fossil you might see in a museum, they’ve taken millions of years to form, from once-living things that have decayed and decomposed under the Earth’s surface.

Those living things eventually become fossil fuels – mainly taking the form of coal, oil, or natural gas. You might sometimes see them referred to as “mineral fuels”.

Now for a bit of science: fossil fuels are what’s known as hydrocarbons. This means they’re made up of hydrogen and carbon. When they’re burned, they release carbon dioxide into the atmosphere.

Carbon emissions created by burning fossil fuels are the biggest cause of climate change. Keep reading to find out why. 

Are fossil fuels renewable?

Fossil fuels are not a renewable source of energy. They take millions of years to form under the Earth’s crust, or at the bottom of the ocean. And that means we can’t simply replace what we use. Once they’re gone, they’re gone.

To find out more about renewable sources of energy, read our guides to wind energy, geothermal energy, solar energy, and tidal energy.

When will fossil fuels run out?

It’s estimated that we have enough coal left to last us another 114 years, while oil and natural gas may run out in around 50 years1

This is based on the assumption that we’ll continue to burn up all the remaining fossil fuels in the world at our current rate. But to avoid climate catastrophe, we need to leave most of those remaining fossil fuels where they are – in the ground. 

Examples of fossil fuels

Is oil a fossil fuel?

Yes, crude oil is a type of fossil fuel. It’s mainly made up of the remains of plankton and algae that died a very long time ago, which eventually become oil reserves, trapped deep inside the Earth. They’re usually found either at the bottom of the ocean, or in places where there used to be ancient seas.

We get crude oil from the ground by drilling or fracking. It’s then used to make things like gasoline, diesel, and jet fuel.

Is natural gas a fossil fuel?

Natural gas is a fossil fuel. It’s made mainly of methane, which is a compound that’s one carbon atom and four hydrogen atoms. In the UK, it’s pumped directly into most homes via the mains. You’ll be pretty familiar with it, if you’ve ever used it to light your hob – and it’s quite possibly powering your boiler and your central heating right now!

These days, you can get a more eco-friendly alternative to natural gas, in the form of green gas. Also known as “biomethane”, green gas is a man-made and renewable version of natural gas. It’s usually made using food or farm waste. 

On the OVO Beyond tariff, our members use 15% green gas, and we offset the rest to make sure that your energy is carbon-neutral. Find out more about our fuel mix.

Is coal a fossil fuel?

Not only is coal a fossil fuel, it’s also the dirtiest of the bunch. It releases more carbon dioxide when you burn it than either oil or gas2.

Made up of the ancient remains of plants and trees, coal is the fuel that drove the Industrial Revolution – and we need to urgently stop burning it, to curb the risks of climate change.

Is petroleum a fossil fuel?

Petroleum, or petrol, is made from crude oil. So yes, it’s a fossil fuel! Not only does it power cars and other vehicles, but it also forms the basis of lots of mass-produced plastics and fabrics.

Is wood a fossil fuel?

Wood, on the other hand, is not a fossil fuel. It comes from trees that have taken tens or hundreds of years to grow, while fossil fuels come from trees (and other living things) that have decomposed underground for millions of years.

Wood can also, of course, be burned for energy – and it produces carbon when it is. When wood and other organic matter is burned to generate energy, this is known as biomass energy. It’s technically a renewable source of energy – but there’s a lot of debate about how green it really is. 

You can read more about biomass energy and its advantages and disadvantages, in our guide.

Is nuclear energy a fossil fuel?

Nuclear energy is not a fossil fuel. It’s the energy generated by splitting atoms – a process called “nuclear fission”, which usually happens inside a nuclear reactor. 

Although it doesn’t make use of fossil fuels, nuclear energy is non-renewable. This is because it uses uranium, which is another finite resource that will one day run out. 

Find out more, by reading our complete guide to nuclear energy.

A man filling his car with petrol

How are fossil fuels formed?

All fossil fuels are created from the fossilised remains of plants and creatures that roamed the Earth millions of years ago. 

Once the remains were underground, under new layers of rock, pressure and heat caused them to turn into coal, oil, and natural gas. 

Coal is mostly made from trees and other dead plants, while oil and natural gas tends to be made from ancient marine life. 

How long does it take for fossil fuels to form? You won’t be surprised to hear that the natural processes that create fossil fuels take millions (sometimes, hundreds of millions) of years. Different types of fossil fuels in different places can take varying amounts of time – but it’s safe to say that it’s always in the millions.

What are fossil fuels used for?

Burning fossil fuels releases the natural energy that’s stored inside them. This discovery powered the Industrial Revolution, which happened here in Britain in the late 18th Century. Since then, fossil fuels have been used for the energy that powers much of our society. 

Today, fossil fuels give us a whopping 80% of all the energy consumed by industrially developed countries of the world3. These are 3 common uses of fossil fuels:

  • Fossil fuels are burned to generate electricity
  • Crude oil is used to make the petrol and other types of fuel that powers most transportation, from cars to planes
  • Natural gas is supplied to over 21 million homes in the UK4, to power heating and cooking

So, why are fossil fuels so bad?

When humans first started burning coal and other natural resources, we didn’t realise we were playing with fire. The advantages of fossil fuels were that they were relatively cheap – and at the time, we believed that there were infinite amounts of the stuff. Because of this, fossil fuels powered industrialisation, leading to many innovations that make our society what it is today.

Now that science has moved on, we know that we can’t keep burning fossil fuels in the way we currently are. Unless we cut down our carbon emissions, we’re heading for the disastrous effects of climate change. Keep reading to find out all the reasons why we’re fighting for a greener, fossil fuel-free future.

Disadvantages of fossil fuels

  • Burning fossil fuels releases a lot of CO2, which is the biggest cause of the climate crisis. Despite this, fossil fuels are still powering much of our society today. In fact, half of all the carbon emissions in the atmosphere have been put there in the last 30 years alone5. We need to stop burning fossil fuels to make a real change. Read our full guide to climate change for more on this subject.
  • Fossil fuels are non-renewable. In other words: they’re going to run out. We need to drastically cut down on the use of fossil fuels, if we want to avoid climate devastation – but if we were to burn them all at the rate we’re currently going, they’d run out entirely in the next century.
  • Mining, drilling, and fracking for fossil fuels is dangerous and disruptive to the environment. Natural habitats are often destroyed by these practices. At the extreme end of the spectrum, oil spills, mining disasters, and other catastrophic accidents can have terrible consequences, for people and the Earth. Gas and oil are also volatile, flammable substances, leading to explosions and fires.
  • Fossil fuels pollute our water and our atmosphere. We’re all familiar with the sight of smoke pouring from a chimney – that’s air pollution in action. Burning fossil fuels releases a huge amount of pollutants into the atmosphere. These pollutants cause smog and acid rain, and can lead to respiratory illness. Drilling for oil can also lead to oil spills and leaks, which have terrible effects on wildlife, and contaminate our water.

How much electricity in the UK is generated using fossil fuels?

The use of fossil fuels to generate electricity in the UK is falling, as new renewable sources of energy like wind and solar take centre-stage. Back in the 1970s, 94% of the UK’s total energy was made using fossil fuels6. Today, things are looking a lot more hopeful: in 2020, countries across the EU used more electricity generated by renewables than by fossil fuels for the first time ever.

In 2019, coal accounted for just 2.1% of the electricity generated in the UK. Meanwhile, oil accounted for 2.8%, while natural gas was 40.6%. Altogether, fossil fuels were behind 45.5% of electricity generated in the UK in 20197.

If you want to cut back on carbon, read more on how to reduce the carbon footprint of your home, and the low-carbon home heating options paving the way for a more sustainable future.

Choosing a new heating system for your home? Compare natural gas, electricity, solar power, and other options for heating fuel.

OVO’s plans for renewable electricity

Here at OVO, we’re on a mission to green up the grid. Since 2020, we’ve supplied our members with 100% renewable electricity as standard8.

We’ve been on this journey for a while. In 2015, we were one of the first UK suppliers to cut coal (as well as nuclear) out of our fuel mix. This decision was made because of the huge cost to our planet from burning coal. 

The renewable electricity we sell is backed by Renewable Energy Guarantee of Origin certificates (or REGOs). We buy these certificates to prove that for every unit of electricity we sell, a unit of renewable electricity has been added to the national grid. But in the future, we’re planning to go further, by sourcing our energy directly from solar and wind generators here in the UK. 

To do our bit to take carbon out of the atmosphere, we’ve also been planting trees all over the UK since 2015. More than a million of them, in fact. Together with our partners at The Woodland Trust and I Dig Trees, we’re planting 1 tree for every OVO member (and 5 for every OVO Beyond member) per year.

Find out more about OVO’s renewable journey here. 

Ready to make the switch to renewable energy?

If you want to power your home with 100% carbon-neutral energy, and get 5 trees planted for you per year, take a look at our OVO Beyond tariff

Not only are our prices competitive, but we’ll also give you an Interest Reward (between 3-5%) when your account is in credit, to say thanks!

Join us on our journey to zero carbon, by getting a quote in less than 2 minutes today. 

Sources and references

8 The renewable electricity we sell is backed by renewable certificates (Renewable Energy Guarantee of Origin certificates (REGOs)). See here for details on REGO certificates and how these work.

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