In this article

What are fossil fuels

The different types of fossil fuels

What are fossil fuels used for?

Why are fossil fuels bad?

Disadvantages of burning fossil fuels

Do we use fossil fuels to generate electricity in the UK

Renewable electricity

"The best energy is the one you don't use"

We all know that fossil fuels are the bad guys. They damage our planet, contribute to climate change, and energy companies, like Igloo, are trying not to use them. But do you know how fossil fuels are formed? Could you identify one and explain why it’s bad for the planet? If you’re sitting there feeling a little out of your depth, don’t worry. You’re not alone!

Here at Igloo, we believe knowledge is power and the more informed our customers are, the better decisions they make – for themselves and the planet. With this in mind, we’ve put together a quick guide to fossil fuels and how they contribute to climate change.

What are fossil fuels?

Fossil fuels are made of dead plants and animals – in fact any organic matter – that have decayed and decomposed under the Earth’s crust. Over millions of years, heat and pressure force the decomposed matter to take on a new form i.e. coal, oil or natural gas.

Fossil fuels also go by the name of ‘mineral fuels’ and are what’s known as hydrocarbons. As the name suggests, they’re made up of hydrogen and carbon. When fossil fuels are burned, they release carbon dioxide into the atmosphere and that’s where the trouble starts.

Yes, we’re sorry to say that the carbon emissions created by burning fossil fuels are the biggest cause of climate change.

The different types of fossil fuels

Fossil fuels is a broad term that covers several different resources that are burned to create energy. We’ve identified some of the main fossil fuel types below.

Crude oil

This is a type of fossil fuel made up of decomposed plankton and algae. Over a long period, the decomposed matter turns into oil reserves, which are trapped deep inside the Earth.

Crude oil is either found at the bottom of the ocean or in places where there were once ancient seas. The process of extracting crude oil is known as drilling or fracking. Once extracted, crude oil is used to make gasoline, diesel and jet fuel to power our vehicles (amongst other things).


Petroleum or petrol is made of crude oil so it’s also classed as a fossil fuel. Petrol, as you know, is used to power cars and other vehicles but it’s also used to create mass-produced plastics and fabric.

Natural gas

This fossil fuel is primarily made of methane, a compound made up of 1 carbon atom and 4 hydrogen atoms. In the UK, if your home is on mains gas, it’s likely that natural gas is powering your boiler and central heating.

Currently, the energy industry is seeking ways to replace natural gas with a more eco-friendly alternative. The current solution is known as ‘biomethane,’ which is a man-made, renewable version of natural gas produced from food and farm waste.

As well as biomethane, you may have heard of the term biogas, and there are some key differences between the two fuel sources that you should note. Biomethane (also known as “renewable natural gas”) is a near-pure source of methane produced either by “upgrading” biogas (a process that removes any CO² and other contaminants present in biogas) or through the gasification of solid biomass followed by a process called methanation.


Out of all the fossil fuels, coal is the worst offender. It’s the dirtiest of the lot when burned, releasing more carbon dioxide than either gas or oil.

While oil is made up of ancient marine life, coal is made up of the ancient remains of plants and trees. It’s the fuel that powered the Industrial Revolution and transformed society but it’s also killing our planet.

Is wood a fossil fuel?

Like coal, wood comes from trees but it’s not a fossil fuel. This is because it’s taken from growing trees and not decomposed matter extracted from the ground.

In terms of energy production, wood is also referred to as biomass energy. While, technically speaking, it is a renewable resource and low carbon, it’s far from “clean” as it still produces carbon emissions, and there’s still much debate over whether it’s a true green energy source.

Is nuclear energy a fossil fuel?

Nuclear energy is not a fossil fuel but it’s not renewable either. Nuclear energy is made using a process called ‘nuclear fission,’ which involves splitting atoms inside a nuclear reactor.

This type of energy is non-renewable as it uses uranium. This is a resource that will one day run out and cannot be replenished.

What are fossil fuels used for?

Fossil fuels are burned to release the natural energy stored inside.

In the 1880s coal was first used to generate electricity for homes and factories here in Britain. The discovery powered the Industrial Revolution and ever since then, fossil fuels have played a huge role in generating the energy we use daily.

Despite our increasing awareness of their effects on climate change, fossil fuels are still used to supply 84% of the world’s energy.

3 main uses of fossil fuels include:

  • Generating electricity

  • Producing petrol and diesel to power vehicles (crude oil)

  • Generating heating and cooking power in our homes (natural gas)

Why are fossil fuels bad?

As we mentioned at the start of this article, knowledge is power and helps to inform wiser decisions. Back when humans first started burning coal to generate energy, they didn’t know what we now know about fossil fuels.

In their eyes, it was a cheap way to create energy and it was (at least in their eyes) an infinite resource. They didn’t know that it would destroy the planet or one day run out. Fossil fuels were seen as the way forward for society - something that could power industrialisation and inspire innovations.

Thanks to modern-day science, we now understand that while fossil fuels serve a purpose, their detrimental effect on climate change is just too great. We simply can’t carry on burning fossil fuels the way we do. If we don’t cut down our carbon emissions, we’ll destroy our planet and everything living on it.

The Intergovernmental Panel on Climate Change (IPCC) has found that fossil fuel emissions are the dominant cause of global warming. CO² acts as a greenhouse gas, which means it absorbs infrared radiation emitted from the Earth’s surface and radiates it back to the surface. As a result, the amount of CO² in the atmosphere increases, which is a major contributing factor to global warming.

Large amounts of CO² have been added to the atmosphere. We know that CO² concentrations in the atmosphere fluctuated between 275 and 290 parts per million by volume (ppmv) between 1000 CE and the late 18th century. Since then, atmospheric concentrations increased to 316 ppmv by 1959 and rose further to 412 ppmv in 2018. That's a whopping 50% increase.

In 2018 alone, 89% of global CO² emissions came from fossil fuels and industry. As mentioned before, coal is the ‘dirtiest’ type of fossil fuel responsible for more than 0.3 degrees C of the 1 degree C increase in average global temperatures, making it the single largest source of temperature rise. It is followed by oil, which releases approximately a third of the world’s total carbon emissions. And while natural gas is often advertised as one of the cleaner energy sources, it still is responsible for more than a fifth of global carbon emissions.

How much carbon dioxide is produced when different fossil fuels are burned?

The levels of carbon dioxide fossil fuels emit into the atmosphere vary depending on the fuel being burned. In order to calculate emissions released across different fossil fuels, the amount of CO² emitted is compared against each unit of energy output or heat content.

The list below shows the pounds of CO² emitted per million British thermal units (Btu) of energy for various fossil fuels. Again, coal stands out with almost twice as much CO² produced compared to natural gas.

  • Coal (anthracite): 228.6

  • Coal (bituminous): 205.7

  • Coal (lignite): 215.4

  • Coal (subbituminous): 214.3

  • Diesel fuel and heating oil: 161.3

  • Gasoline (without ethanol): 157.2

  • Propane: 139.0

  • Natural gas: 117.0

Disadvantages of burning fossil fuels

Fossil fuels release CO²

Burning fossil fuels releases CO² into the atmosphere, contributing to the greenhouse effect and global warming. It’s reported that half of all carbon emissions in the atmosphere stem from burning fossil fuels over the last 30 years. Scary, isn't it?

Fossil fuels are non-renewable

This means they’re going to run out. If we carry on burning fossil fuels at our current rate, they will likely run out within the next century.

They disrupt the environment

Extracting fossil fuels through mining, drilling and fracking destroys natural habitats. There have also been numerous oil spills and mining disasters with severe consequences.

They cause pollution

Fossil fuels pollute our water and the atmosphere. Ever seen smoke billowing from your chimney? That’s air pollution. Heard reports of oil spills on the news? That’s water contamination and it’s killing our marine life.

Do we use fossil fuels to generate electricity in the UK?

Fossil fuels have long been used to generate electricity in the UK. In fact, most of our infrastructure is designed to run using fossil fuels. Back in the 1970s, a whopping 94% of the UK’s total energy was made using fossil fuels. Problematic? Yes. But thankfully, things are now looking a lot more hopeful.

Today, the use of fossil fuels to generate electricity in the UK is constantly falling, with renewable sources like wind and solar energy taking over. In 2019, coal accounted for just 2.1% of the electricity generated in the UK, and fossil fuels made up less than half (45.5%) of the electricity generated.

And that’s not all! In 2020, it was reported that countries across the EU were using more electricity generated by renewables than by fossil fuels for the first time in history.

It’s certainly progress but we still need to do more.

Renewable electricity

We are classified as 100% renewable electricity through an OFGEM scheme called the Renewable Energy Guarantees of Origin (REGO).

This is a system set up by the industry to use these certificates to offset buying energy generated by fossil fuels & supported by the Government.

Basically, REGO certificates are awarded to generators of renewable energy so they can prove that a certain amount of green electricity has gone into the grid. Energy suppliers can then purchase these certificates to ring-fence the equivalent amount of the UK’s renewable supply for the energy they have sold.

So for every unit of electricity sold, a unit of renewable electricity is added to the national grid, but it does not do enough overall to support the renewables industry when compared to other initiatives.

“The best energy is the one you don’t use”

In addition to REGOs, we’re all for encouraging our customers and providing them with solutions to use less energy. Paradoxically for an energy supplier, we do believe that the best energy is the one you don’t use!

While there isn’t currently a feasible way to offset fossil fuel gas, we are here to support our customers in using less of it to reduce their carbon footprint.

One such way is to switch our fossil-fuel-powered boilers to air source heat pumps. This proven solution provides a clean and low-carbon way to heat your home. Air source heat pumps are up to 4 times more efficient than gas and oil boilers and can help cut your carbon footprint by up to 65%!

Upgrading your heating system doesn’t have to cost the earth either. With the Igloo Clean Heat Switch, you’ll have early access to the Renewable Heating Incentive to help bring down the cost of installation. Chat to our advisors to find out more.

Make the natural choice and switch to an air source heat pump. Enjoy cleaner energy and a cleaner conscience to match.